coud use advice on electric heat selection

[Boones]

Hi, been looking over post and on the web. Thought i would check in here for advice

I have a 24x48 garage that has a wall down the middle with a 12' x 8' opening betwen the two sides (so basically 2 24x24 garages). I am going to either use freezer curtain (clear plastic) or sliding doors) to seperate the two at times, one side is a clean side for my finished car and wifes daily and the other is for building my hotrods (grinding, welding etc...) the walls are 10ft. R13 wall insulation and 2" thick 18x8 insulated garage doors. 1152 overall sq ft, each side is about 575 sq ft.

I want to use electric (getting gas to my garage is not going to be easy). Since I plan to be able to seperate the areas, I think I plan to run two units.

I think I need a two unit that are somewhere between a 5kw and 7.5kw in size. I see most of the 5kw are for up to 500 sq ft (is that pushing their limit?)

I live in the Seattle area so most winter days are in the low 40's and nights in the low 30.. we do get days with temps in the low 30 (teens at night). this winter is expected to be colder then normal so more 30 degree days. I would like to be able to maining a 50-55 temp when I am not in the garage but be able to get the room up into the 60 to 65 range when I am in there.

I believe I will have to run 240 and I have a 200amp panel so no problem powering the units

I would like something quiet and not over taxed to maintain the heat.

what are some good products that is not overly priced (not looking for the cheapest unless that happens to be the best choice) that will meet my needs. I am not familar enough with the different brands to know who to keep away from and how is reliable.

thanks in advance

 

[54stude]

If you want quiet, you want electric baseboard heaters with a wall thermostat (and a ceiling fan to circulate the air.). I have a 7.5kw electric modine unit heater in the ceiling of my garage, and it is loud, but it will heat a 22x22 space to 70 degrees when it is 10 degrees f outside.

 

[MikeLawrence]

If it were me I'd be thinking strongly about a multi-zone ductless mini-split system.
Example: www.fujitsugeneral.com/multi.htm

Basically you would have a ~3'x3'x1' box outside which is say a 36k btu compressor and it would have a little copper coming off of it to your two ports (one on each side; a 3" hole for each one) which would be 18k BTU each.

The main advantage to this is that it's going to be the most efficient possible solution at around 16 sEER (as opposed to <13 sEER for other heat pumps or absolute garbage for resistance solutions). As a bonus it would be your cooling solution come spring and would likely be the best at actually keeping the space a set temperature.

The downside is cost. It depends on the area (alot of the price is in the labor) but I can't imagine you're going to get out for under 3k initial. Thing is the cost of heating/cooling a space is not exactly trivial. Saving 50-70% on your cost (for that space) year over year could have it paying the difference very quickly. Then again it may never recoup the difference. You'd just have to run some numbers and see if it is a good solution for you.

Just an opinion,
Michael Lawrence, LISSCO

 

[RAYJAY]

I would look at cost of any other heating you could do, i could not even think of the $$$ to heat a garage with electric, would oil or propane be cheaper ???? you can figure you cost difference on link below

i went from NG to Coal to save $$$$$ on my garage

http://nepacrossroads.com/fuel-comparison-calculator.php

 

[Falcon67]

You can do a search on the Dayton G73 heaters here. I have a 5kW unit in my 20x24x8. The shop is R13 in all directions with a single insulated 8x7 door. The dial rheostat style thermostat is set on LO and it keeps my shop right at the high 60s. Cycles about 3-4 times per hour depending on how cold it's been outside. I would THINK that this unit may do well in your spaces, but not sure. The G73 does move air - you can feel the breeze from the small fan 12' away easy. Most people that have bought one are rather surprised at how well they work for the cost and size. I paid $279 for mine. The Fairenheat units at Northern Tool are similar in size and construction.

 

[Boones]

Thanks for the tips, unfortunately, due to my location, and size of my lot, electric might be my only chose, I was planning to do with gas but to get it from my house out to the garage would be a chore. ( I am about a 100 ft away buts its the forest between the two (lots of old growth cedar trees with large diameters and my lot is very narrow and I plan to run the electricity from the shop to the house eventually (when I rewire the old house) and I have to run in the same location. codes require the distance to be enough that getting through the trees will be almost impossible.

Mike L, had not heard of the system you discribe, will have to research that. (I planned to install the heating system myself (I built and wired the garage myself) so the cost of your system might be more then I can afford right now but if there is a long term savings (and potential cooling) then it might be worth the wait

 

[Boyd Who]

Right now I'm using this 5kw 240V "temporary" heater in my 20x22 garage. The ceiling is uninsulated at the moment and the walls have R-12. The heater easily kept my shop at 50*F even when it was -10*F outside, on a low setting. It cycles on and off about 3 times/hour. It's very quiet, too.

 

[Ocular Engineer]

You can do a search on the Dayton G73 heaters here. I have a 5kW unit in my 20x24x8. The shop is R13 in all directions with a single insulated 8x7 door. The dial rheostat style thermostat is set on LO and it keeps my shop right at the high 60s. Cycles about 3-4 times per hour depending on how cold it's been outside. I would THINK that this unit may do well in your spaces, but not sure. The G73 does move air - you can feel the breeze from the small fan 12' away easy. Most people that have bought one are rather surprised at how well they work for the cost and size. I paid $279 for mine. The Fairenheat units at Northern Tool are similar in size and construction.

I just pulled the pin and ordered one of those yesterday. Here is the link:
http://www.air-n-water.com/product/G73.html

Their discount code changes from day to day. I got 10% off yesterday with the code "DISCOUNT". And you get a free little heater (the kind you might put under a desk) too.

I have a 25' x 25' detached garage (in MN) that I plan to heat so we'll see in a week or so how it does.

 

[Boones]

Ocular, please let me know how that works out

 

[Boones]

one more question, what desired temp rise are you all needing. I figured about 20 degrees (35 to 45 degree with no heat, want it 55 to 65 max heated temp). if I do some calculations for required BTU, it looks like I need around 15,322 (for a 20 degree temp rise)

BTU = sq ft x .133 x desired temp rise

24x24x10' x .133 = 766.08 x 20 desired temp rise = 15,322 BTU requirement

I found a 5000 watt 17065 BTU unit at Northern tool for $249 (that would cover a 23 temp rise)

and a 75000 watt 25,000 BTU for $449. (that would handle more then enough and not max the unit out..

How much margin do you want to ensure you are not taxing the unit..(is 2000 BTU enough)

 

[MikeLawrence]

one more question, what desired temp rise are you all needing. I figured about 20 degrees (35 to 45 degree with no heat, want it 55 to 65 max heated temp). if I do some calculations for required BTU, it looks like I need around 15,322 (for a 20 degree temp rise)

BTU = sq ft x .133 x desired temp rise

24x24x10' x .133 = 766.08 x 20 desired temp rise = 15,322 BTU requirement

I found a 5000 watt 17065 BTU unit at Northern tool for $249 (that would cover a 23 temp rise)

and a 75000 watt 25,000 BTU for $449. (that would handle more then enough and not max the unit out..

How much margin do you want to ensure you are not taxing the unit..(is 2000 BTU enough)

Two 5s should be enough, a 5kw and a 7.5kw would definitely do the trick. One thing I'm a little iffy on is that 7.5kw to my mind means 265/277V (because on 220V you'd be at 34 amps) but I've never really heard of 265V on a residential before.

Just to maybe more clearly illustrate why I was advocating a ~$3,000 minisplit over <$1,000 of strip heat though... You're talking 12.5kw/hr to produce 42.5k heat btu/hour. By comparison a 36k btu minisplit actually produces right at 42k heat btu/hour (The 36k refers to the cooling side) for just a hair under 5kw/hr. Generally you don't get to do a straight up comparison like this but in this case they're so similar you do: You'd save almost exactly 7.5kw for every hour you ran the unit.

You can multiply by the $/kw in your area to get exact figures but it shouldn't be too far out to say that resistance is going to cost you right at $1 extra for every hour you run it over and above the price of heating it with a mini-split. Multiply by 7 years of use and figure the break even point is at around 14 hours a week during the winter. By my rough estimate (based on you wanting a constant ~50 with a 65 operating temp) unless you are VERY well insulated the mini-split is still sounding good to me but as always I would highly advise doing some math yourself and coming to a conclusion that's best for you.

Just an opinion,
Michael Lawrence, LISSCO

Edit: If you're looking for a midway point between resistance and a professional mini-split job (and don't mind the look of motel-style units) two size 15 heat pumps would do the trick for just under 2k.
Example: www.thruwalls.com/units/ptac/az61h15dab
Inside View: http://www.sunroomsbyteam.com/Sunroom Ptac Knotty Pine.JPG

Basically, while in heat pump mode they would be exactly as efficient (same COP) as the minisplit. But when the outside temperature got down below 22F they would switch over to being exactly as efficient as two 5kw resistance heaters until the outside temperature got back up to 22F. They don't look as nice as a mini-split and they're marginally louder. That said, the Zonelines are the cadillac of the thru-wall world so figure they would be at least as nice as the nicest unit you've ever had at a hotel.

 

[Ocular Engineer]

Ocular, please let me know how that works out

I plan on it. I am very hopeful that it will work well after all of the reviews that I read on the company's site and the reviews that I read on Amazon.

 

[Boones]

Mike thanks for the link so I can take a look at what you mentioned. It looks like those are floor mount, since i value all my space, I prefer something that is hanging off the ceiling,. could these be mounted off the ground??

here is a link to the 7500 version I was looking at earlier today. Not sure I would ever need to get the temp up to 65 degrees, I think somewhere near 60 would be comfortable when working out there but its nice to know the system would handle it. When I did a calculation for a unit that would heat it all, it shows I need around 30,000 BTU, which tells me two 5,000 watt (17,000 BTU each) should handle it..

Here is the 5000 watt

http://www.northerntool.com/shop/tools/product_595_595

here is the 7500 watt version

http://www.northerntool.com/shop/tools/product_200316428_200316428

 

[Falcon67]

FWIW - I seem to like 65ish for working in the shop in winter. I don't mind wearing a sweat shirt out there either. I buy a couple a year on sale just so I have a couple I can trash out. But I have had it in the 70s once in a while, just because I was going to be out there all day.

PS - those Zoneline's look like what the drag strip uses in the tower. If so, they can be mounted low or high - hole is a hole. Not a bad price really for something that efficient. Figure 280 for a heater and 450 for a decent 15K AC unit and you are real close to the Zoneline.

 

[MikeLawrence]

Yeah I still stand by ~35k looking like enough but if you feel comfortable doing the hardwiring the math works out. You'll be over 30amps (to draw that 7500) so you're going to need some special wire and a 35-40amp breaker but it's certainly doable.

Falcon is right, a hole is a hole--technically "window units" are just small form factor ptacs after all. The standard has them at floor height mostly because they're 42"x16", heavy (~100 lb) and historically f-ugly at the bottom (due to how the cord comes out). There are ptac's that have to be on the floor due to special kits they sit on but GE aren't that way so yeah... AFAIK it would work.

I will mention though that unlike a window unit the control systems are top mounted: you'd likely need a step stool or something to set the t-stat. The zonelines use an angled output though so if you're on the tall side you may not even need that. (Take a look at that sunroom photo I posted before and you'll see what I'm talking about. The controls are under a flip top on the right side). On the plus side zonelines have the LEAST ugly bottom of any ptac I know of. They really do just look like a big window unit so it shouldn't look that odd hanging high (other than the slightly weird t-stat access).

Just an opinion,
Michael Lawrence, Lissco.

 

[Boones]

Mike does the one in the sunroom require any fresh air ventilation. (I think not). Also, it is sunk into the wall in that picture?

I wired my garage myself, so I feel comfortable adding another breaker, running the wire and connecting it (as long as there is some basic info that comes with the unit)

I have been looking at my garage the past week at places I might be able to use something like this. I know the clean side has a nice place under the window (dead area anyways) but not sure about the working side (dirty) of the garage.. still putting my plan together on where all my benchs, tools and cabinets are going.


Ocular, I see on the G75 you got it shows two Watts: 5,000 / 3,750 in the details, whats up with the two ratings.. is it how its wired? on whethe it gets 5000 or 3750? or power settings? How many BTU's does it put out. (do not see in their online specs.)

 

[MikeLawrence]

Well a ptac is a ptac. It's basically just a window air conditioner that is 42" wide (so have to cut a "window" especially for it.) Unfortunately they aren't like the mini-splits that hang like a picture on the wall (with a 3" intake hole behind them).

Needing an intake is true of any heat pump/air conditioner as heat can't be destroyed (so cold can't be created). That's actually the single largest "downside" actually to going with the dual ptac solution versus a mini split (if you want to go an A/C / heat pump route) on the outside of your building you'd have two 42"x16" louvers. Some of them are nicer looking than others... but they all look like you have an A/C hanging there. And if you don't have a good place to cut a hole that big on either side the plan wouldn't work.

Mini-split can be much easier in circumstances like that because you can almost always find some place to put a ~3" hole and once you get the copper in the house you've basically got it made.

Just an opinion,
Michael Lawrence, Lissco

EDIT: For ocular's question 20 amp cord will get you a 3.8kw draw and 30 amp cord will get you a 5kw draw. Because resistance is resistance the world around 5kw ~= 17k btu. 3.8 ~= 13k btu.

 

[Boones]

I made a decision on my heaters, I went with two 5000 watt units from Northern Tool. Model FUH54. 17,065 btu. they are 240v 30amp.

I am about to wire the units tonight but I have a question. It said to use 10-2 but I thought we had to use 10-3 per current code for a 240 v. black and red to breaker, white to neutral and copper to ground. On these heaters there is a L1 terminal, L2 terminal and ground screw.

Do I use a 10-2 as they state and put the black and white to the breaker - L1 to black, L2 to white (with black tape to note it as hot), and copper to ground lug. I want to make sure I do not wire it wrong and blow them up right away.

 

[jvitez]

These heaters are 240V, not 120/240V like a clothes dryer, so no need for the neutral wire. Each buss bar on your subpanel supplies 120V, so hot to neutral is 120V. There is no 120V control/lighting circuit needed, so just 240V will do. Therefore, 10/2. Where does the current "return" to complete the circuit? Through the other colored wire.

AC current flows, for example, hot wire "red" to the element, then back through the black wire. Next it goes black to element and back via the red wire. It keeps alternating this way. The ground wire is only protection in case of a short circuit.

Red wire goes to one pole of a 2 pole breaker, it doesn't matter which one. Black wire goes to the other pole of the 2 pole breaker. Ground wire to ground buss. Done.

BTW: 10 watt/sq ft is a good rule of thumb for continues heating, so I'm sure these will work well for you.