Electric Heat Load Questions

[Bull]

I have decided to go with electric heat for my 24x32 (2 story) detached, insulated garage.

I have a 60 amp sub-panel out there. I have been looking at a few heaters that are very well-reviewed on Amazon and elsewhere by folks using them for garages both smaller and larger, less well and better insulated than mine.

I am wondering about how my 60 amp panel can supply these? Can I wire up two outlets to be used by two heaters, one upstairs and one downstairs, but with the understanding that ONLY ONE would ever be in operation at any given moment?

My usage pattern would be to use the heater before going out to the garage to work in order to get it up to whatever temperature was appropriate for the activity: lower temps for just basic wrenching/puttering around, higher temps for things like painting or playing with the kids. Then it would just be an issue of maintaining that temp during the activity. I don't need 24-7 heat, just on evenings and weekends when I have stuff to do in the garage.

My power usage is otherwise modest. I have a few fluorescent lighting circuits, a few 15 and 20 Amp outlet circuits, and a 20 Amp circuit for my 220v air compressor. But, I would avoid using the compressor while the heaters were going, and I'd rarely have more on than some fluoro lights, a stereo, and maybe one corded power tool in use any given time. What I am trying to say is that I want heat more than I need to be doing all kinds of other power-hungry stuff.

So, given that, can my 60amp panel power these in the way that I want?

Also, quite a few reviews suggest that the 5600 Watt heaters are plenty strong. That's good, since they are only rated at a little over 20 Amps. There are some 7500 Watt models, too, but they are rated for over 30 Amps. I'm tempted to go with the biggest unit I can, but with the concerns about my panel I am not sure if this is even an option.

Any helpful guidance will be appreciated. Thank you.

Here is what I am looking at.

7500 Watt
http://www.amazon.com/dp/B000A6H1IS/?tag=atomicindus08-20

5700 Watt (am partial to this unit)
http://www.amazon.com/dp/B000PSFRTG/?tag=atomicindus08-20

5600 Watt (attractive price, but Chinese)
http://www.amazon.com/dp/B003XOZN7A/?tag=atomicindus08-20

 

[ishiboo]

Yes, you can wire up two outlets on one circuit... breakered for the wire size, you will just blow the breaker if you tried to turn both on at once.

Your 60 amp panel is fine for what you want to do, but as you already know you will have restrictions.

Personally, I would go with the largest heater - these are still VERY small BTU ratings and it will take a while to get up to temp... HOWEVER, given your power requirements, I would make sure that the heat settings are ones that are acceptable - ie turn the 7500W on full blast when you need to warm it up or open a door, but on "low" you should be able to run a lot of the tools you need without blowing your main breaker.

 

[Bull]

Whew. I was really sweating whether what I wanted was possible. This is good news.

I don't mind ponying up the extra dough for the 7500W vs. the 5700W if it is really going to make a big difference. What's curious to me is that the 7500W is advertised as being capable of heating 600 sq. ft. but the King 5700W is rated for 720 sq. ft. I don't understand that.

 

[jcar302]

Most heaters rarely draw maximum amperage.
A 60amp subpanel should be capable 13,200 watts running at 220v (i usually calculate at 220v when i'm not there to physically check voltage, it could vary from 208v to 250v)

With that said, I would NOT put both on them on the same circuit. Honestly, why would you? You are already buying the wire, only difference is that you will need another breaker, and most 2 pole breakers are only around $15.

For the largest heater you list there, it says 31 amps, which means you will likely need #8, the nameplate on it probably calls for a minimum circuit ampacity of 40amps. Furthermore they probably calculated the amps at the 240v it lists in the specs, if you only have say 220v (which is very possible) it will draw more amperage, when the voltage goes down the amperage goes up.

I speak as someone with an electrical license.

With all that said, rarely have i installed an electric heater in a garage and been impressed. The electric bill won't be something you love either.
I'd save some money and buy a bullet kerosene or propane heater.

 

[Bull]

Thank you for the reply. I am learning here.

What if my sub-panel out in the barn doesn't have any more knockouts to add breakers? If I need two for two electric heaters (and are these breakers going to take up two slots in the panel, each?) then what am I to do? Add a sub-panel to my sub-panel, or buy a bigger panel altogether?

What dictates whether I have 208, 200, or 240 out there? I have a 220 volt welder hooked up, but what the "actual" voltage to it is, I have no idea!

I bought a 75,000-200,000 BTU propane radiant construction heater with a 100lb propane tank from a fellow on here. My very brief experience with it tells me it's not for me. My colon gets clenched up too tight with that tank around the house, and then the soap-bubble ritual before every use (because I am cautious) is also not for me. I know electric heaters will be expensive, but I feel like I am prepared to absorb the cost for heating a building on weekends or occasional weekends for the cold months of the year. Electricity just seems so clean (on my end) and convenient. I also like that they take up zero floor space; my garage is not large.

Also, these models on Amazon that I linked to get consistently excellent reviews. People with insulated and uninsulated shops, in climates similar to mine, with spaces as large as mine report great results with these things. I mean, you cam't believe everything that you read, but at some point the scale seems to tip in one direction with enough surety that you feel it is "worth a shot."

 

[ishiboo]

Most heaters rarely draw maximum amperage.
A 60amp subpanel should be capable 13,200 watts running at 220v (i usually calculate at 220v when i'm not there to physically check voltage, it could vary from 208v to 250v)

Being 240v service, being close to 240v is a better guess than 220v...

With that said, I would NOT put both on them on the same circuit. Honestly, why would you? You are already buying the wire, only difference is that you will need another breaker, and most 2 pole breakers are only around $15.

Since I am recommending two heaters which each use in excess of 30A, and he has a 60A panel, my thought is I'd rather blow the heater breaker if you accidentally turn both on at once, than blow the main breaker and have no lights/etc. while you fix what's wrong. It is very simple and cheap to add a second breaker in the future

For the largest heater you list there, it says 31 amps, which means you will likely need #8, the nameplate on it probably calls for a minimum circuit ampacity of 40amps. Furthermore they probably calculated the amps at the 240v it lists in the specs, if you only have say 220v (which is very possible) it will draw more amperage, when the voltage goes down the amperage goes up.

I speak as someone with an electrical license.

With all that said, rarely have i installed an electric heater in a garage and been impressed. The electric bill won't be something you love either.
I'd save some money and buy a bullet kerosene or propane heater.

Not at all - it would draw less amperage because the voltage is lower while resistance has remained the same. This is one of the things that confuse people - the difference between an electrician versed in code, and an engineer versed in the actual physics of the situation

 

[ishiboo]

Thank you for the reply. I am learning here.

What if my sub-panel out in the barn doesn't have any more knockouts to add breakers? If I need two for two electric heaters (and are these breakers going to take up two slots in the panel, each?) then what am I to do? Add a sub-panel to my sub-panel, or buy a bigger panel altogether?

Yes, each breaker will take up two slots. If you want two circuits and your box supports tandems, you may be able to find a quad breaker which allows two 240v circuits in two spaces.

Given the small size of your panel, IMO if you need the spaces your best bet would be to replace it with a larger panel. Panels themselves are not that expensive.

What dictates whether I have 208, 200, or 240 out there? I have a 220 volt welder hooked up, but what the "actual" voltage to it is, I have no idea!

Single phase electricity in the US is 120/240v, you have 240v out there. Due to delivery there will be fluctuations, but 240 is the supplied voltage and unless there is something wrong or you have a lot of voltage drop, you'll be close.

I bought a 75,000-200,000 BTU propane radiant construction heater with a 100lb propane tank from a fellow on here. My very brief experience with it tells me it's not for me. My colon gets clenched up too tight with that tank around the house, and then the soap-bubble ritual before every use (because I am cautious) is also not for me. I know electric heaters will be expensive, but I feel like I am prepared to absorb the cost for heating a building on weekends or occasional weekends for the cold months of the year. Electricity just seems so clean (on my end) and convenient. I also like that they take up zero floor space; my garage is not large.

Also, these models on Amazon that I linked to get consistently excellent reviews. People with insulated and uninsulated shops, in climates similar to mine, with spaces as large as mine report great results with these things. I mean, you cam't believe everything that you read, but at some point the scale seems to tip in one direction with enough surety that you feel it is "worth a shot."

Electricity is quite expensive in most areas, but not all. Once you have it, you will use the heat more and more. I would look into the costs of getting a propane tank or natural gas to service the garage and a used furnace off Craigslist.

 

[jcar302]

Depending on how old the panel is and the brand, you may or may not be able to use tandem breakers. Which allow two breakers per slot.
But when adding 220 breakers you may need ones like this: http://www.grainger.com/Grainger/SQUARE-D-Circuit-Breaker-2DG49?cm_mmc=CSE:Nextag-_-Electrical-_-Distribution-_-2DG49&srccode=cii_9324560&cpncode=31-61879823-2 To get 220v the outer breakers will be connected by a handle to each other, so will the inners.
Starts to get a little costly.

IMO, just buy a new main lug subpanel rated for 125amps (does not mean you get 125amps), should only be like $50-$75. The wire and breaker in the main panel determine your amperage.

The power company dictates the voltage, there are a few variables, like how far the subpanel is from the main, how far the main is from the transformer, etc... Voltage drops over long runs, it is NOT something you can change, you get what you get.

It really only matters to a homeowner when you are pushing the limits.
I wouldn't worry too much about it. I probably should not have mentioned it.

I think a little of my distaste for the garage electric heaters comes from how much they cost and how much you get. For the money they just aren't a great value. Expensive to buy, setup and run.
I just didn't want you to expect too much. If you shut them down completely they could take hours to bring a detached garage up to working temperature in a northern area.
Where's if a furnace of some sort could do it in just a few minutes.
But if it's what makes you comfortable and the money isn't an issue, you should do it.

 

[jvitez]

Electricity is a great choice for garage heat. Easy to mount anywhere due to no flue requirements, cheaper to buy than fuel burning heaters, clean, easy to maintain. Downside? They produce less heat with the usual ampacity circuit, and electricity often costs quite a big more than NG/propane. Overall though there is nothing wrong with choosing electric!

Bull: your 60 amp panel will allow 60 amps x 240 volts= 14,400 watts of power consumption before popping the 60 amp main breaker. You have 768 sq ft to heat on each level.

A rule of thumb (I know, I know......) is 10 watts/sq ft. I heated our old house's attached insulated garage with 9 watts/sq ft. It worked, but slowly. It took about 2 hours to heat up the garage when thawing washed cars in our winters, but that's at about -20C.

Calculating what you need and what you have is pretty easy. Follow me please:

add up everything you need to have running at the same time, in watts, not amps; eg. fluorescent lights, stereo, compressor, portable drill, etc, whatever you could possibly have running at the same time. Subtract this number from 14,400. The difference is how much capacity you have left for electric heat in total.

Would you ever need to heat both floors at the same time? You said not, but are you really, really sure? If yes, your choices can go up to a 10,000 watt heater assuming you'd have less than 4,400 watts running before heat. 10kW would give you 13 watts/sq ft which would allow for pretty quick warm up. You could actually put a 10kW heater on each floor knowing you can't run both at the same time.

If you think about running heat on both floors simultaneously you're probably stuck with two 5kW heaters, perhaps two 5.6 kW ones. But honestly, for rapid warm up you could easily go with a 10kW heater on each floor as long as you use one at a time. For example:

http://www.ouellet.com/fd.aspx?h=/documents/products/catalog_10_en.pdf

I'd also swap out your panel for a larger one. You could always add a subpanel to the subpanel, no issues here, but for the amount of work for your small panel it would easier and neater to just have one panel with more spaces.

 

[pentavolvo]

I highly recommend this unit over the other 5k watt units you have listed

http://www.air-n-water.com/product/G73.html?utm_medium=affiliate

 

[Bull]

jvitez, that is a very, very helpful post. The prices on those 10kw heaters are higher than I wanted to pay right now...I mean I am looking at these 5-7kw heaters for a few hundred at most. Now, if that is going to get me a product that won't work efficiently, then maybe I need to rethink my approach.

I see this 10kw heater from Ouellet is rated at close to 42 Amps:

http://www.amazon.com/dp/B000NCI8AO/?tag=atomicindus08-20

I still am not comfortable with this idea about my load out there. In a 60 Amp panel to have one heater that is rated at almost 42 amps...it seems like I'd not be able to run much else. But, I have not done the load calculations/Wattage needs that you mentioned.

Now, a 10 kw heater is going to use a lot more power/be more expensive to run, right? Is the tradeoff that it will run for less time before the space is warm, and need to come on for shorter periods to maintain desired temps?

I highly recommend this unit over the other 5k watt units you have listed

http://www.air-n-water.com/product/G73.html?utm_medium=affiliate

How come? That one is rated for 500 square feet and is made in China. The unit I linked to from King is made in USA ad rated to 700 square feet. But, I do know the G73s have very good reviews.

 

[jvitez]

jvitez, that is a very, very helpful post. The prices on those 10kw heaters are higher than I wanted to pay right now...I mean I am looking at these 5-7kw heaters for a few hundred at most. Now, if that is going to get me a product that won't work efficiently, then maybe I need to rethink my approach.

You're very welcome. I'm glad I can be of some help. Yes the 10kW heater is more expensive, but you get faster warm up. If that's not overly important to you then a smaller, cheaper heater would be just fine.

Fuel burning heaters need to be sized properly. And overly large heater will never achieve maximum combustion efficiency. Not so with electric heaters. They are 99-100% efficient at point of use.

http://www.amazon.com/dp/B000NCI8AO/?tag=atomicindus08-20[/URL]

I still am not comfortable with this idea about my load out there. In a 60 Amp panel to have one heater that is rated at almost 42 amps...it seems like I'd not be able to run much else. But, I have not done the load calculations/Wattage needs that you mentioned.

Don't worry. Even with a 10kW heater, as long as you're not using more than 4,400 additional watts, everything will be fine.

Now, a 10 kw heater is going to use a lot more power/be more expensive to run, right? Is the tradeoff that it will run for less time before the space is warm, and need to come on for shorter periods to maintain desired temps?

Exactly correct. Your cost to heat up the space is the same from a larger heater running less vs a small heater running longer. You need to deliver X-amount of heat to warm it up. That is a fixed value. Your cost is in kW/hr, so 10 kW x 2 hrs= 5 kW x 4 hrs in consumption and therefore cost.

In some ways a smaller heater is better. It's cheaper to buy, the wire to it will be cheaper, and it will run longer which reduces heat stratification. Hot air rises. Therefore the hot air will be at the ceiling and your legs will feel cold if there are long periods where the heater is off. If the fan runs longer it circulates the air keeping more warm air down low. The same effect can be had with slow moving ceiling fans, but that's one more thing to buy and install. Running a ceiling fan too fast during the heating simply makes you feel cold, as moving air removes heat from your skin, your skin temperature receptors register the colder temp and your brain says "I'm cold!" Moving air of the exact same temperature as still air will feel colder to your body, ie wind chill.

One other benefit with smaller heaters is that you can install more than one, which can give more even heat distribution. Depending on the relative cost of wire, two 10/2 NMD runs aren't necessarily that much more than one run of 6/2.

Therefore if you always install one 5 kW heater on each floor and see how it works for you. If warm up from cold is too long, you can always plug in a couple of 1500 watt portable heaters during warm up, then unplug them and keep the heat maintained with the permanently wired heater. Or even better, you can simply install a second 5 kw heater.

 

[Bull]

Your way of explaining things is very effective.

Having these options gives me research paralysis. I have a friend coming here on Saturday and was hoping to have a unit and related supplies ready to rock. Now I don't yet know if I should go with a 10kw right off the bat or try a smaller unit, whether I should replace my panel etc. I need to make up my mind if I hope for a unit to be delivered before Saturday. That Ouelett from Amazon is sold by Northern, and they only seem to offer 3-4 day shipping unless I want to pay over $100 for 2nd day service.

I always feel like whatever choice I make, it's the wrong one lol.

What kinds of loads equal 4400 watts, BTW? I mean, how many watts are six 4' double-tube fluorescent fixtures using?

 

[jvitez]

What kinds of loads equal 4400 watts, BTW? I mean, how many watts are six 4' double-tube fluorescent fixtures using?

The fixture should have an amperage rating on the ballast, but a very close rule of thumb is to simply add the wattages of each bulb. If you're using regular T8's, it should be 6 x 2 x 32 watts or 384 watts. Lighting is a very small load compared to resistance heating.

 

[Bull]

And if I replace the sub-panel with a larger one, is it as simple as buying a larger panel of the same brand I currently have, and that's it? I can buy whatever size I want, as long as it's the same brand? Or is there more to it than that?

 

[ishiboo]

And if I replace the sub-panel with a larger one, is it as simple as buying a larger panel of the same brand I currently have, and that's it? I can buy whatever size I want, as long as it's the same brand? Or is there more to it than that?

You can buy anything... But the same brand/series will allow you to reuse the existing breakers. Not worth it if they are in bad shape and/or crappy also realize the layout of the box can determine how easy it will be to put your existing circuits back - a very different larger Panel you may need to splice a lot of wires to get them to reach.

How about sharing a pic of what you have now and we can further elaborate?

 

[pattenp]

And if I replace the sub-panel with a larger one, is it as simple as buying a larger panel of the same brand I currently have, and that's it? I can buy whatever size I want, as long as it's the same brand? Or is there more to it than that?

Are you asking about larger as in more spaces or more amp capacity? Larger amp capacity may require a new feeder wire to the sub-panel. Sorry if I've missed some detail in previous posts.

 

[jvitez]

What brand of panel do you have? How many spaces are you considering for the new one?

If your breakers are good, then buy the same brand of panel in a larger size. Let's say you're wanting a 24 space panel for lots of future proofing. You can mount it at the same height as the old panel, put the breakers in the same spots at the top of the panel so you won't need to splice wires. Your new circuits will simply go below the current spaces, as the new panel will be longer and closer to the floor.

You feed the new larger panel with same wire as you now have. If you buy a main breaker panel, even one with a 100 amp main breaker, everything is still OK as the main breaker serves as a disconnect. The whole subpanel is still protected by the 60 amp circuit in your main panel.

 

[Bull]

I mean, more amps would be great, but I don't want to run a new feeder out there. That wire is expensive! I'd like to try to work with the existing power supply.

The panel is a Siemens. That means the breakers are Siemens, too?

You can see, only one slot is left. Ideally, if I could take all of the existing circuits and consolidate the single breakers to the double-breakers, or mini-breakers or whatever they are called, that would be great. Well, unless that is more expensive than actually swapping things over to a new, larger panel.

Here is the feeder wire. It's rated for direct burial, I believe, but we ran it through conduit from the barn to the basement of the house, which is some distance away.

 

[pattenp]

The feed cable looks like UF and you can't get anymore than 60A. The panel you have will take tandem breakers. It's an 8 space 16 circuit main lug panel. If you have more than 6 breakers you will need to use a couple slots for a 60A back fed breaker as a main disconnect. With the heating units that you are talking about you are pushing beyond what the 60A service can handle.

 

[Highbeam]

I used a 100 amp panel for my pole barn's subpanel. Fed with by a 60 amp breaker on the main panel in the house with 6 gauge wire. The whole panel, a big one, was really cheap and came with a big box of breakers. It was a siemens and only like 50$. At first I thought it was weird to feed the 100 amp breaker in teh 100 amp panel with a 6 gauge wire but you need to remember that the subpanel's inlet breaker is just an on/off switch. It could be a 200 amp breaker, wouldn't matter.

 

[Bull]

I don't understand the part about needing a back-fed breaker as a disconnect if I have more than 6 breakers. Can you explain that.

Also, which heaters do you think are pushing what the service can handle? I've mentioned 5 kw, 7.5 kw, and 10kw heaters in this thread. So far, everyone is telling me the 60 amps is enough to run any of these sizes one at a time.

 

[walrus]

I don't understand the part about needing a back-fed breaker as a disconnect if I have more than 6 breakers. Can you explain that.

Its a code thing

You need to be able to shut off all electricity in that building with 6 switches, breakers. After that you need a main disconnect, a back fed breaker would serve as that disconnect. I say buy a panel with a main breaker instead, 100 amp GE are less than 100 bucks with a 100amp main, not that expensive.

 

[pattenp]

I don't understand the part about needing a back-fed breaker as a disconnect if I have more than 6 breakers. Can you explain that.

Also, which heaters do you think are pushing what the service can handle? I've mentioned 5 kw, 7.5 kw, and 10kw heaters in this thread. So far, everyone is telling me the 60 amps is enough to run any of these sizes one at a time.

I was going by the 5000W and 7500W being run at the same time. That's 52A and that is exceeding the 80% rule for continuous loads on a 60A circuit. You would need at least 70A. Two 5000W heaters is 42A which needs 53A as the margin, so you don't have any room left to run anything else. You can run the heaters one at a time, but I was thinking you wanted both on at the same time.

 

[Bull]

Its a code thing

You need to be able to shut off all electricity in that building with 6 switches, breakers. After that you need a main disconnect, a back fed breaker would serve as that disconnect. I say buy a panel with a main breaker instead, 100 amp GE are less than 100 bucks with a 100amp main, not that expensive.

Ah, ok, now I understand.

I was going by the 5000W and 7500W being run at the same time. That's 52A and that is exceeding the 80% rule for continuous loads on a 60A circuit. You would need at least 70A. Two 5000W heaters is 42A which needs 53A as the margin, so you don't have any room left to run anything else. You can run the heaters one at a time, but I was thinking you wanted both on at the same time.

I recognize that two at once might not be possible. If I can have one at a time, to heat the floor I am occupying/using, I will be happy. But are you of the mind that a single Ouellet 10kw heater will be too much to run at all? Because, then you and jvitez will be telling me different things, and research paralysis will set in again!

 

[pattenp]

Ah, ok, now I understand.



I recognize that two at once might not be possible. If I can have one at a time, to heat the floor I am occupying/using, I will be happy. But are you of the mind that a single Ouellet 10kw heater will be too much to run at all? Because, then you and jvitez will be telling me different things, and research paralysis will set in again!

All I can say is 10000W is 42A @ 240V and 42A X 1.25 is 52.5A. So 52.5A is the required circuit size for that heater, so that leaves you with no overhead to run much of anything other than the heater on a 60A circuit. That's my code response. Can you turn on the lights and then power up your circular saw with out tripping the breaker? Maybe, maybe not.

 

[Bull]

Sometimes, I get so depressed. It's like every choice I have made as an adult has some unforeseen consequence that makes stuff difficult. I just want to be warm in my barn in the winter. Through my own ignorance when I built and planned the space, nothing is easy.

Blah.

 

[pattenp]

Bull for what it's worth, I use a 5000W heater in my 30 X 26 garage that has 60A service and have not run into power issues. I just use the heater close to where I'm working.

Edit: Now I'm starting to feel bad for you.

 

[walrus]

Sometimes, I get so depressed. It's like every choice I have made as an adult has some unforeseen consequence that makes stuff difficult. I just want to be warm in my barn in the winter. Through my own ignorance when I built and planned the space, nothing is easy.

Blah.

Bull
Hindsight is supposed to be 20-20, sometimes you learn stuff as you go on in life. Go with the 5000w and save your money for a furnace. A miller gun from a trailer would work great, they can be had pretty cheaply around me, might not be so plentiful down there. You don't have Natural gas do ya?

 

[Bull]

No natural gas, no.

I've been staring at a few web pages for like an hour. Some pages have 5,000 or 5,700 Watt heaters, some have 7500 Watt heaters. I can't make up my damn mind. I think I'm going to have an aneurysm. Total paralysis.

If I have the power for 7500 Watts, isn't it worth it to drop an extra $100 for a unit of that size that will be able to have a better chance of warming my 768 sq. ft lower level? But then again, if I am going to be out there weekends and evenings I will have enough lead time to turn on a smaller heater in advance to get the temps up.

This is stressing me out.

 

[pattenp]

If you go with the 7500W unit you need a 40A circuit for it. It will be pulling 31A when running so in most cases you'll most likely be okay if you are not pulling other heavy loads at the same time. Best of luck.

Edit: What's the length of your service feed to the garage/barn from the house?

Also, have you ever checked your actual voltage at the barn to see what it is?


*

 

[Bull]

I am pretty incapable of estimating distances, and I don't remember from the time of the install what the distance from main panel in house to sub-panel in barn came out to be.

Is it easy to measure voltage out there? I don't even know how to do it.

 

[walrus]

Is it easy to measure voltage out there? I don't even know how to do it.

If you aren't confident in your abilities to work in a panel I wouldn't do it if I were you but if you are.... Be careful you really can hurt not just from a shock but also from arc flash.

Put a voltmeter across the black and red wires coming into the panel from the house. Do the same thing at the breaker in the house. I'd check with a load on it, all the normal stuff on like lights, radio, maybe fire up a table saw if you have one, check it without that stuff running. Not sure what its going to tell you, I doubt it will be low enough to worry about.

 

[Bull]

If you aren't confident in your abilities to work in a panel I wouldn't do it if I were you but if you are.... Be careful you really can hurt not just from a shock but also from arc flash.

Put a voltmeter across the black and red wires coming into the panel from the house. Do the same thing at the breaker in the house. I'd check with a load on it, all the normal stuff on like lights, radio, maybe fire up a table saw if you have one, check it without that stuff running. Not sure what its going to tell you, I doubt it will be low enough to worry about.

Yeah, as you can tell from my posts here, I would be asking for trouble if I started messing around inside a panel: I'm too stupid to be in there! So, that option is out.

I just realized that my dad gave me a Fluke 322 clamp meter for a gift recently. That could tell me what volts and amps I have out at the panel, but again I think I'd have to open the panel to get the clamp around a single strand from the main feeder wire, and I'm not doing that. When my electrician friend comes here, I will ask him to do it.

 

[walrus]

Yeah, as you can tell from my posts here, I would be asking for trouble if I started messing around inside a panel: I'm too stupid to be in there! So, that option is out.

I just realized that my dad gave me a Fluke 322 clamp meter for a gift recently. That could tell me what volts and amps I have out at the panel, but again I think I'd have to open the panel to get the clamp around a single strand from the main feeder wire, and I'm not doing that. When my electrician friend comes here, I will ask him to do it.

The clamp will tell you how any amps you are using on any given wire not the voltage or drop. Knowing the amps might of some interest though, if you were doing what you normally do out there that would give you an indication of whats left for you to use for a heater.

You're not to stupid to be in there. Too stupid would be someone who rips and shreds his way in there and gets hurt.

 

[MoonRise]

Calculated heat-loss calculation from a freebie on-line cal (which is for a single room and not an entire barn, yada yada ):

http://www.shophmac.com/info-center/hvac-calculators/heat-load-calculator.php

24x32, entered 18 ft height (estimated for a two story barn), R6 walls and R12 ceiling, defaults from the page for doors and windows, air infiltration value as "average"

gives an estimated 11,595 watts on a cold winter day (0F outside and 72F inside).

5000 watts in a two story barn is not quite enough to warm it up on a winter day IMHO.

Do you need to try and heat the entire structure, or would you be OK with a more localized 'warm' zone?

If so, look into some radiant heaters. They output IR (radiant) energy. If you are in the zone where the heater is pointed, you absorb the IR energy (heat) and feel warm(er). They are not trying to heat all the air in the space. Just an idea.

Clamp-on ammeter will tell you how many amps are being used through that wire at that time. You still would have to use the test probes (and set the meter in the correct mode of operation) to take a voltage measurement.

A smart person knows what their 'limits' are. An unwise person just goes ahead even if they don't really know what they are doing.

 

[Bull]

Well, with a little encouragement from here, I opened up the panel and very, very carefully used my amp clamp to see what kind of power was being drawn while stuff was on. But, first I have a question. I thought that both the red and black wires of the main feed would have the same amp readings. In my case, the black wire always had a higher (by a couple/few amps) value than the red. Why is this?

With all the lights on downstairs and upstairs, the 220 Volt compressor running to fill the tank, three 18V battery chargers plugged in, and an old corded drill plugged in and running full speed, the highest measurement that I got on the meter was a tad over 20 amps. I realized after the fact that I didn't have a stereo going and didn't have all the outside down-to-dusk lights on, but it seems like even with those things I should have no trouble running a 5.7 Kw heater with a 30 Amp fuse. The biggest power items were the compressor and drill, and I am highly unlikely to be using heat, a corded tool, and the big compressor out there at any given time.

I was too chickenshit to use the meter probes to test the voltage at the main lugs. I will ask my electrician friend to do this. I do want to know what the value is.

MoonRise, I am thinking about adding a ceiling fan downstairs to try and keep the warm air from rising up to the second level. I am also open to the idea of hanging some plastic or blankets or something to separate the front two bays, which have 8' ceilings, from the third bay at the back of the garage with a 12' ceiling. I don't need one small heater to heat the whole shop. I'd like to have one per level, and the only one running would be the one in the space I am using for whatever project or play is at hand.

I have R-19 in my walls and R-30 in most of the second story ceiling, with one section where I think I only had the depth for maybe R-19 in the ceiling, below an attic space. I spent some time with a caulking gun and quality caulk going over as many seams and joints as I could find on the second story of the barn.

 

[ishiboo]

Well, with a little encouragement from here, I opened up the panel and very, very carefully used my amp clamp to see what kind of power was being drawn while stuff was on. But, first I have a question. I thought that both the red and black wires of the main feed would have the same amp readings. In my case, the black wire always had a higher (by a couple/few amps) value than the red. Why is this?

"Single phase" power in the US represents the same AC waveform - shifted 180 degrees. This means each of your "hot" wires is opposite of the other "hot" wire at any given time. Neutral is 0v at all times.

So, each hot phase is 120v/-120v, when you add them you get 240v. 120v to 0v neutral is 120v.

120v circuits are split every other panel slot to each leg - every other breaker goes to every other leg. 240v circuits use BOTH legs EVENLY at all times. (Exception being some dryers/stoves/etc. with a neutral, but it'll be close.) So, depending on which breaker is using more/less, each leg can have different current running through it.

So to measure power usage, you have to simultaneously measure both hot legs. Obviously you could do one and then the other and then add the two if loads did not change during that time.

With all the lights on downstairs and upstairs, the 220 Volt compressor running to fill the tank, three 18V battery chargers plugged in, and an old corded drill plugged in and running full speed, the highest measurement that I got on the meter was a tad over 20 amps. I realized after the fact that I didn't have a stereo going and didn't have all the outside down-to-dusk lights on, but it seems like even with those things I should have no trouble running a 5.7 Kw heater with a 30 Amp fuse. The biggest power items were the compressor and drill, and I am highly unlikely to be using heat, a corded tool, and the big compressor out there at any given time.

Realize that a 240v compressor will be taking current from BOTH hot legs at once.

 

[frankush]

I may be too late to join this party but I'll jump in anyways. I don't think you'll be happy with those 2-5K heaters once you're done. When I first built my 24X22 garage I ran 2 Fasco 5KW 220v in wall, cabinet heaters. Both were fan forced and they were at opposite ends of the garage on opposing walls. Building is insulated and they couldn't keep up. I have a 60A panel as well and it would handle the load, but it wasn't enough heat. Btu's were too low. I would hate to see you spend all the money and then be unhappy.

I don't remember the rated Btu's of those units, but I sold them both on Craig's and bought a Modine Hot Dawg. I doubt they were much more than 10K Btus each. More expensive? Yes, but I can work in shirt sleeves now. I have 8' ceilings and 45K btus now.

Also I don't think that barn service is going to handle 10K of electric heat, compressor, lights, misc. power items. You're pushing the limits here. Sooner or later, that main will trip, and trip again, and again. Then you'll power off the compressor, so you can stay warm.

I look forward to seeing which way you go and I'll be following this thread.

 

[Bull]

"Single phase" power in the US represents the same AC waveform - shifted 180 degrees. This means each of your "hot" wires is opposite of the other "hot" wire at any given time. Neutral is 0v at all times.

So, each hot phase is 120v/-120v, when you add them you get 240v. 120v to 0v neutral is 120v.

120v circuits are split every other panel slot to each leg - every other breaker goes to every other leg. 240v circuits use BOTH legs EVENLY at all times. (Exception being some dryers/stoves/etc. with a neutral, but it'll be close.) So, depending on which breaker is using more/less, each leg can have different current running through it.

So to measure power usage, you have to simultaneously measure both hot legs. Obviously you could do one and then the other and then add the two if loads did not change during that time.



Realize that a 240v compressor will be taking current from BOTH hot legs at once.

Son of a gosh darn *****. So, I stupidly thought the 20 Amps on the black wire was all I had. I needed to add the 16 or 18 or whatever it was on the red wire to get my total? So it's more like 36-38 Amps with all that stuff cranking? I wonder how much it would be without the compressor going, which I don't plan on ever running when I am heating the space.

I may be too late to join this party but I'll jump in anyways. I don't think you'll be happy with those 2-5K heaters once you're done. When I first built my 24X22 garage I ran 2 Fasco 5KW 220v in wall, cabinet heaters. Both were fan forced and they were at opposite ends of the garage on opposing walls. Building is insulated and they couldn't keep up. I have a 60A panel as well and it would handle the load, but it wasn't enough heat. Btu's were too low. I would hate to see you spend all the money and then be unhappy.

I don't remember the rated Btu's of those units, but I sold them both on Craig's and bought a Modine Hot Dawg. I doubt they were much more than 10K Btus each. More expensive? Yes, but I can work in shirt sleeves now. I have 8' ceilings and 45K btus now.

Also I don't think that barn service is going to handle 10K of electric heat, compressor, lights, misc. power items. You're pushing the limits here. Sooner or later, that main will trip, and trip again, and again. Then you'll power off the compressor, so you can stay warm.

I look forward to seeing which way you go and I'll be following this thread.

I need another beer. My brain just doesn't know what to do after reading so many positive online reviews of heaters in this range, being used in spaces similar to mine, with owners giddy with the results and then to hear from a fellow like yourself with opposite experiences. I am crossing my fingers that the heaters you were using were of an inferior design.

I think I just need to get one of these wired up and see what it does. In no other way am I going to be able to put this to rest. I mean, if I block off the front two bays from the third with some kind of curtain to keep the heat in, then I will only be heating a 24x16 or so space, with R-19 in the walls and insulated garage doors.

If only I had planned this out better back in '06-'07!