Shop heater breaker/wire size?

[Simplytodd]

I just received my new electric shop heater but unfortunately the manufacturer didn’t specify what size breaker should be used. It says should be installed by a qualified electrician so I guess they assume he/she should know. So obviously I’m going to do it myself. I do see a sticker on the back listing a few things see below. I guess I’m not sure if it’s asking for a 90amp or an 80amp breaker.

It’s a 15kw 240v all electric system. What size breaker should be installed and the corresponding wire size.






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[mike93lx]

Holy ****, that is a big heater.

How far is the run?

80a breaker with #3 thhn in pipe would work, depending on distance. #4 might be enough

That is going to cost $3-5/hr to run, depending on your electricity costs...

 

[Stuart in MN]

Minimum circuit amps = 80
Maximum overcurrent protection = 90


You need at least an 80 amp circuit, but not more than 90.


The wire size depends on what kind of wire will be used - if it's Romex / NM-B, or individual THHN/THWN conductors in a conduit. Here's a chart showing ampacities: https://www.cerrowire.com/products/resources/tables-calculators/ampacity-charts/


As mentioned above, you also have to take into account the length of the wire, if it's excessive you may have to increase the size to minimize voltage drop.

 

[Simplytodd]

15’ - 20’ if I go with my planned install location. I also won’t be using it to heat the shop to some extreme temperatures. Somewhere in the low to mid 50’s is comfortable for me but mostly it will be used to prevent the wild temperature swings that cause every tool, piece of metal, car, concrete floor to sweat like a ***** in Sunday service every time we have a cold front blow through Texas.

 

[baddriver]

There's a good explanation of MCP and MOP here: titus-hvac.com/softwares/MOPulator/pdf/howwecalculate.pdf

Bottom line, the maximum breaker size you are permitted to use by NEC (US) is 90A. You can use smaller if you like but you increase the risk of nuisance tripping.

The smallest size conductor is one rated for at least 80A which would be #3AWG copper per NEC. You can use larger if you like for reduced voltage drop or if the wire run is particularly long.

 

[MileHighRover]

That is going to cost $3-5/hr to run, depending on your electricity costs...

Not even close. It would be $1.50 or less per hour. Could be free if he has solar.

 

[mike93lx]

Not even close. It would be $1.50 or less per hour. Could be free if he has solar.

15kw @ 0.25/hr is $3.75/hr

Solar isnt free and it would take a huge array to run that thing

That will draw more than my entire house does and I pay 60 to 100/month for electricity at a lower rate than I used above since I am on a Municipal grid

 

[Simplytodd]

Thanks guys looks like I need 80amp double pole with #3 wire

I’m on a co op power I think I’m at .11c a kilowatt hour so it cost what it cost. Better than all my sh*t rusting.

 

[wyliesdiesels]

I just received my new electric shop heater but unfortunately the manufacturer didn’t specify what size breaker should be used. It says should be installed by a qualified electrician so I guess they assume he/she should know. So obviously I’m going to do it myself. I do see a sticker on the back listing a few things see below. I guess I’m not sure if it’s asking for a 90amp or an 80amp breaker.

It’s a 15kw 240v all electric system. What size breaker should be installed and the corresponding wire size.



Sent from my iPhone using Tapatalk

Read the chart closer.

The MCA and MOCP is listed- 80a rated wire and 90a max breaker.

Thats gonna cost a lot to operate.

 

[wyliesdiesels]

Not even close. It would be $1.50 or less per hour. Could be free if he has solar.

15kw @ 0.25/hr is $3.75/hr

Solar isnt free and it would take a huge array to run that thing

That will draw more than my entire house does and I pay 60 to 100/month for electricity at a lower rate than I used above since I am on a Municipal grid

Thanks guys looks like I need 80amp double pole with #3 wire

I’m on a co op power I think I’m at .11c a kilowatt hour so it cost what it cost. Better than all my sh*t rusting.

.11cents KwHr will be $1.65/hr to run the heater.

 

[MileHighRover]

15kw @ 0.25/hr is $3.75/hr

Solar isnt free and it would take a huge array to run that thing

That will draw more than my entire house does and I pay 60 to 100/month for electricity at a lower rate than I used above since I am on a Municipal grid

Houston area is around 10 cent/kw. As the OP stated, he's at 11 cents so nowhere near $3-5/hour like you stated.

The heater isn't going to run 24/7 so the cost to operate it won't be as bad each month.

As far as the solar array requirements, again, the heater isn't running 24/7 so the array wouldn't have to be that big. I have solar. I've been in my home 1.5 years now, haven't had an electric bill yet, and have just under $1,000 in my rollover bank with the power company (the power I generate but don't use, I get credit for). So running a 15KW heater would be free. Since the OP doesn't have solar, none of that matters, though.

 

[Stuart in MN]

The question wasn't about how much it's going to cost to operate.

 

[alfredeneuman]

#2 Al wire and a 90A c/b

 

[mike93lx]

Houston area is around 10 cent/kw. As the OP stated, he's at 11 cents so nowhere near $3-5/hour like you stated.

The heater isn't going to run 24/7 so the cost to operate it won't be as bad each month.

As far as the solar array requirements, again, the heater isn't running 24/7 so the array wouldn't have to be that big. I have solar. I've been in my home 1.5 years now, haven't had an electric bill yet, and have just under $1,000 in my rollover bank with the power company (the power I generate but don't use, I get credit for). So running a 15KW heater would be free. Since the OP doesn't have solar, none of that matters, though.

0.10 including distribution? The power might be that sheap, but the whole deal?

 

[mike93lx]

The question wasn't about how much it's going to cost to operate.

But the original question has been answered, so we can argue about something else

 

[Simplytodd]

Forgive my ignorance but what is “ The MCA and MOCP” exactly supposed to mean?

 

[wyliesdiesels]

MCA- minimum circuit amps

MOCP- maximum overcurrent protection

 

[mike93lx]

Forgive my ignorance but what is “ The MCA and MOCP” exactly supposed to mean?

The circuit need to be able to supply at least 80a,but not be breakers or fused at above 90 amps.

 

[wyliesdiesels]

The circuit need to be able to supply at least 80a,but not be breakers or fused at above 90 amps.

I think he wanted definitions NOT specs for OPs situation

 

[Simplytodd]

Well I just got back from the electric supply house with a 80amp double pole and two runs of 25’ of #3 with one run of #6 for the ground. Time to mount this thing wire it and watch the meter start to spin.

 

[mike93lx]

I think he wanted definitions NOT specs for OPs situation

It was a way of communicating what the terminology meant. The numbers are irrelevant. My though was just providing a definition didn't make the intent clear

 

[Bert_]

Well I just got back from the electric supply house with a 80amp double pole and two runs of 25’ of #3 with one run of #6 for the ground. Time to mount this thing wire it and watch the meter start to spin.

I'm assuming you got some conduit also?

 

[Bert_]

It blows my mind that anyone pays $0.25/kw. In the Midwest I would call $0.15 high. I'm pay $0.08/kw plus a meter charge of $8.50. Any usage over 1000kw is only about 5.5 cents per kilowatt.

 

[Simplytodd]

I did. 2 sticks of 1” EMT and a 90* sweep as I only have 3/4” bender. Realized I forgot the threaded connector that attaches the conduit to the top of the box. Back to home depot tomorrow before I can wire it.

.25c a kilowatt does seem outrageous. I was mad when I moved up here and could no longer shop for the best provider and it was a few cents higher than what I was paying in the city.
Overall though my bills average like $150 a month so not bad.

 

[mike93lx]

It blows my mind that anyone pays $0.25/kw. In the Midwest I would call $0.15 high. I'm pay $0.08/kw plus a meter charge of $8.50. Any usage over 1000kw is only about 5.5 cents per kilowatt.

The manufacturing plant I work at is 16-21 cents per kwh. We have a large Cogen plant on site so we offset a lot of the cost, but still buy a lot of power at 21

 

[mike93lx]

I did. 2 sticks of 1” EMT and a 90* sweep as I only have 3/4” bender. Realized I forgot the threaded connector that attaches the conduit to the top of the box. Back to home depot tomorrow before I can wire it.

.25c a kilowatt does seem outrageous. I was mad when I moved up here and could no longer shop for the best provider and it was a few cents higher than what I was paying in the city.
Overall though my bills average like $150 a month so not bad.

How big is the service to the building this is going to? Hopefully more than 100a

 

[wyliesdiesels]

Well I just got back from the electric supply house with a 80amp double pole and two runs of 25’ of #3 with one run of #6 for the ground. Time to mount this thing wire it and watch the meter start to spin.

Why did you go with #3 and #6?

#4 and #8 wouldve been fine.

 

[wyliesdiesels]

It blows my mind that anyone pays $0.25/kw. In the Midwest I would call $0.15 high. I'm pay $0.08/kw plus a meter charge of $8.50. Any usage over 1000kw is only about 5.5 cents per kilowatt.

well you havent lived on the edge yet. Almost all california power companies charge a higher rate the more the customer uses...

Have you seen Profit Gouge & Execute's rates lately?

This chart is more than a year old. Profits Gone Elsewhere's current rate is over 21¢/Kwhr for first tier. it goes up to almost 50¢kwhr...

https://www.facebook.com/MIDWatchdo...QaqO-lwEORxuGqiOS8bEcafzvZU5Y1Ya3Dw&__tn__=-R

 

[Simplytodd]

How big is the service to the building this is going to? Hopefully more than 100a

200 amp to the shop.

Why did you go with #3 and #6?

Because I miss read the chart that was provided earlier and looked at the UF-B column.