Baseboard Heater in low-usage application

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  #1  
Old 11-26-06, 06:50 PM
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Baseboard Heater in low-usage application

Hello,

I will be installing a number of baseboard heaters with a total wattage of 4550W. Going by code I would require a 240V double-pole 30A breaker and 10/2 wiring:
(4550W/240V = ~19A * 125% = ~24A)

However these heaters are only being used to heat a cottage to above freezing (say 5 degrees C) during the winter months.

Is it reasonable and safe to install a 20A breaker and use 12/2 wire instead for this application? The wattage ratings on the heaters are max. output correct? Therefore if I'm not going to be driving the heaters anywhere near this level can I downsize on the breaker and wiring? I realize it is always best to adhere strictly to code but 30A, 10/2 seems overkill for my application.

Thank You
 
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  #2  
Old 11-26-06, 06:56 PM
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No, bad idea. What if in the future someone does use it to full potential? It'll do nothing but trip the breaker and baffle the folks. Besides why limit yourself ? It's alot easier to do it right the first time then re do it a second time.
 
  #3  
Old 11-26-06, 07:00 PM
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Wink

You answerd your own question. Do it right (correctly) or don't do it.

It really doesn't matter what YOU will do.

When the kids come up later, they won't bother doing the math.
With respect... Don't humor yourself. Just do it correctly.
Youll spend no more and your savings will be HUGE.
 
  #4  
Old 11-26-06, 07:13 PM
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Use 12/2 and two 20A circuits.
 
  #5  
Old 11-26-06, 07:15 PM
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Thank you Lectriclee & Burkej62 for your advice.

As an alternative I guess I could divide the heaters between 2 20 A circuits (there are 2 spare dbl-pole 20A breakers in the box) but I wanted to use one thermostat to control all the heaters. Are there such things as "dual" thermostats that allow you to control heaters on 2 separate circuits? If I do go with a single circuit do I need a more heavy-duty thermostat to accomodate the higher amperage? Most thermostat wires seem pretty flimsy and small for even 20A.

Thanks
 
  #6  
Old 11-26-06, 07:19 PM
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Originally Posted by classicsat
Use 12/2 and two 20A circuits.
Thanks Classicsat,

If you read my reply to lectriclee and burkej62 thats probably what I'll end up doing
 
  #7  
Old 11-26-06, 07:25 PM
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Smile

Thanks for thinking,
Someone will never thank you. (Just the way it goes).

Are these two(2) different areas or 1 large area?

This is the beauty of electric heat, Very directed.
 
  #8  
Old 11-26-06, 07:44 PM
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I'm actually heating 3 areas, the living room, bathroom and bedroom. The cottage is only 600 sq-ft but it is very open and high (it has loft) and therefore a lot of volume. I'm using 2 1750W heaters for the living room, 750 W for the bedroom (on main floor) and 300W for the bathroom. There are 2 commercial ceiling fans that run low to help distribute heat.
 
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Old 11-26-06, 08:09 PM
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So 20.68+- amps, #10 220vac will handle it. Place a T-stat for the bathroom, The bed in the loft? Yes, 1 T-stat for this area aswell (split the difference). By all means utilize the ceiling fans. You'll love it!!
 
  #10  
Old 11-26-06, 08:38 PM
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Originally Posted by lectriclee
So 20.68+- amps, #10 220vac will handle it. Place a T-stat for the bathroom, The bed in the loft? Yes, 1 T-stat for this area aswell (split the difference). By all means utilize the ceiling fans. You'll love it!!
Thanks Lectriclee. That sounds like a good idea.

For interests sake, if I went with 2 separate 20A circuits could I control all the heaters with one common thermostat? Technically this should work unless there is a code restriction.
 
  #11  
Old 11-26-06, 08:47 PM
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I would say no. With out some type of relay.
If thats what you want, then 1 ckt and 1 T-stat.

You realy wont save any money either. Some may disagree.
I would go with the 10/2, perhaps another junction box, but then your done.1 breaker,2 T-stats.

If you have the 12/2, then thats a choice aswell. 2-brkrs,2-t-stats.
 
  #12  
Old 11-26-06, 08:57 PM
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Interesting... What function does the relay perform in this instance?

What was your idea for the junction box? To split the wire coming from the T-stat off to the different heater locations? Or would you still wire them in a loop?

Thanks
 
  #13  
Old 11-26-06, 09:11 PM
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The junction box: just for added room, to split the ckt.

The relay would allow 1- device to operate 2 ckts for 1 function

2 ckts would require 2 seperate controls.
A relay would be, basicaly, 1 switch running 2 ckts.

Hit 1 switch,2 things happen.
For your application... I don't feel it would be worth the trouble or expence.
 
  #14  
Old 11-26-06, 09:13 PM
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A 220V circuit requires a double pole breaker and double pole switches. So a single double pole thermostat cannot be used to provide disconnect for _two_ separate 220V circuits.

A relay is a device that can control multiple outputs from a single input. You could get a 4 pole relay to control two separate 220V circuits, and then run this relay with a single 120V thermostat.

A heater requires a _disconnect_, which must turn off all hot legs and it requires a thermostat to provide temperature control.

For a 220V heater, this means that you need a double pole switch. A double pole thermostat can serve as the disconnect for a heater. However I believe that you are permitted to use a single pole thermostat for control, along with a separate double pole switch serving as the disconnect.

One thought that I've had, but which I've not checked for code validity: Use a double pole thermostat, but have it control only one of the hot legs for each of two circuits. This double pole thermostat would thus act as the _control_ for the two circuits, but would not be a legal disconnect. Then use separate double pole switches (one per circuit) to act as the required disconnect. This _might_ permit you to use a single standard double pole thermostat to control two separate circuits.

My advice: electric heat is expensive to use, and thermostats are not particularly expensive to install. I would install a thermostat in each separate heated zone, so that you can easily heat only those areas being used.

-Jon
 
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Old 11-26-06, 09:25 PM
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Winnie;
One thought that I've had, but which I've not checked for code validity: Use a double pole thermostat, but have it control only one of the hot legs for each of two circuits. This double pole thermostat would thus act as the _control_ for the two circuits, but would not be a legal disconnect. Then use separate double pole switches (one per circuit) to act as the required disconnect. This _might_ permit you to use a single standard double pole thermostat to control two separate circuits.

Feasable, But legal? I don't know either.
Something to check.

Would you not agree, (based on a 600sq' living area) That single ckt, 2 zone heat would suffice?
 
  #16  
Old 11-26-06, 09:37 PM
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Interesting idea. I wonder if that would be allowed by the code. Too elaborate for my application but very interesting nonetheless!

This may be a little off-topic from my original question but is it always better to wire loads in a loop as opposed to using a junction box to feed wire to different loads? Sometimes using a junction box can save a lot wire but also adds another splice and therefore voltage drop.

What do you guys think?
 
  #17  
Old 11-26-06, 09:51 PM
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Worried too much.

Not to worry about voltage drop. the junction is for your first concern, saving wire.Actualy, utilizing it wisely. If you need more, use it.
The draw back,( minimul, if done correctly), is every junction is a potential point of failure. Again, If done correctly, not a worry.
 
  #18  
Old 11-26-06, 10:33 PM
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Originally Posted by lectriclee
Not to worry about voltage drop. the junction is for your first concern, saving wire.Actualy, utilizing it wisely. If you need more, use it.
The draw back,( minimul, if done correctly), is every junction is a potential point of failure. Again, If done correctly, not a worry.
My plan was to use a junction box (fed from the t-stat(s)) in the crawl space to feed each individual heater instead of wiring in a loop. This would shorten a lot of the cable runs. This is acceptable in your opinion? I had thought that junction boxes were shunned by electricians except when absolutely necessary.
 
  #19  
Old 11-27-06, 08:01 AM
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Alot depends on the logistics of the project.

You don't like to have any more than you need. If done right they are legal,safe and practical.
 
  #20  
Old 11-27-06, 08:44 PM
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Originally Posted by lectriclee
Alot depends on the logistics of the project.

You don't like to have any more than you need. If done right they are legal,safe and practical.
I was going to use one to save about 20 - 25ft of wiring. It seems worth it since I'll probably be using 10/2 wire. Plus there is the added benefit of less energy loss by using shorter cable runs.

Are there any t-stats that you recommend when using 10/2 wire? Most t-stat wiring seems too small for even 12/2.
 
  #21  
Old 11-29-06, 07:15 AM
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220v Line voltage thermostat. At any big box store. This opens both hot legs at set temp.

Run the 220 to the t-stat locaction, then down to the baseboard.They are easy to install, follow the diagram that comes with them.
 
  #22  
Old 11-29-06, 11:55 AM
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Originally Posted by The Gorn View Post
Hello,

Is it reasonable and safe to install a 20A breaker and use 12/2 wire instead for this application? The wattage ratings on the heaters are max. output correct? Therefore if I'm not going to be driving the heaters anywhere near this level can I downsize on the breaker and wiring? I realize it is always best to adhere strictly to code but 30A, 10/2 seems overkill for my application.

Thank You
Heaters are on or off. You are always driving them at max output when you turn them on. It doesn't matter if you turn them on at 30 or 50.
 
  #23  
Old 11-29-06, 08:38 PM
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Originally Posted by lectriclee View Post
220v Line voltage thermostat. At any big box store. This opens both hot legs at set temp.

Run the 220 to the t-stat locaction, then down to the baseboard.They are easy to install, follow the diagram that comes with them.
Most t-stat wires i've seen seem to only be 14 gauge. Don't they need to be thicker to handle the higher amps?
 
  #24  
Old 11-29-06, 09:07 PM
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You will not have seperate T-Stat wires. The wires 10/2 from the ckt breakr are your T-stat wires.

This is why you come from breakr to T-stat to baseboard. Buy a Line voltage (220V AC) T-stat.

If you have done- or plan on something other than this,let us know.



Quickly--- 10/2 From breaker to 1st T-stat. Drop from here to baseboard, then from 1st base to next,to next etc,

Then from 1st T-stat to 2nd T-stat(with 10/2), with the constant 220V. from 2nd stat, drop to the 2nd base heat zone.
 
  #25  
Old 11-29-06, 10:23 PM
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Originally Posted by lectriclee View Post
You will not have seperate T-Stat wires. The wires 10/2 from the ckt breakr are your T-stat wires.
The t-stat I bought is a 2 pole 240V unit but it already has 4 stranded copper wires attached, 2 for line and 2 for load. According to the manual the line and load cables are to be maretted to these wires. The wires though appear to be 12 gauge at most not 10 which i'll probably need. It is a line-voltage unit. I had thought that all t-stats were directly wired as you mentioned but all the ones I've looked at are not like that. Maybe I'm looking in the wrong aisle
 
  #26  
Old 11-29-06, 10:45 PM
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You have the correct T-stat. 240V 2-pole.

These are rated by "UL" (underwriters laboratory) This indicates that the independant testing lab has deemed them suitable for this use.

2- wires will go to the "line" (from breaker) and 2- wires to the load (heater).

There are many types of thermostats. There are many types of heating/cooling systems.
You have the right one as you described.

You do have the ckt. correct...Right?
 
  #27  
Old 12-02-06, 10:34 PM
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[QUOTE=lectriclee;1085175]You have the correct T-stat. 240V 2-pole.

These are rated by "UL" (underwriters laboratory) This indicates that the independant testing lab has deemed them suitable for this use.

QUOTE]

So I don't need to worry that the built-in t-stat wires are of a smaller gauge than the 10/2 line & load wires that are attaching to them? If not, why?
 
  #28  
Old 12-03-06, 06:33 PM
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My understanding is fixture wires often have insulation that can take higher temperature without degrading therefore they can be smaller. Also there is a large safety factor built into wire sizes specified by code because they are used in a variety of situations. It could be testing has shown a smaller wire in this specific use can have a smaller safety factor.
 
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Old 12-03-06, 08:26 PM
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Question

So now the baseboards have built in T-stats? Why didn't you say so.
Just use them or bypass them. WHAT DO YOU WANT TO DO?

The built in T-stats are rated For the load of that 1 (single unit). Thats why the wires are smaller. Your Curcuit, Is rated for ALL of them on together, And that is the way it must be calculated. Unless you want to run a ckt for each unit.

Anything else you forgot? or don't want to tell us?

I'm going back to Telepathy school.
 
  #30  
Old 12-03-06, 10:21 PM
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Originally Posted by lectriclee View Post
So now the baseboards have built in T-stats? Why didn't you say so.
Just use them or bypass them. WHAT DO YOU WANT TO DO?
I guess I'm not being clear and I apologize for that. Maybe I'm being too concerned with details but I'll try to explain again anyway:

The t-stats are NOT built-in. I am using an EXTERNAL line-voltage 2 pole 240 V t-stat. But the t-stat already has wires hanging off of it (the same as in a light fixture) that are to be attached (maretted) to the 2 poles of the actual line and load wires that I run to the t-stat. My concern is doesn't the gauge of the line/load wires (the ones I'll be running from the breaker and the baseboards) have to match with the gauge of the wires that have been installed on the t-stat by manufacturer.

I hope thats clearer
 
  #31  
Old 12-04-06, 04:29 AM
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You do not need to concern your self with the wire on the thermostat. As long as the thermostat is UL (or equivalent) rated you are fine.

The wires used by manufacturers for fixtures, switches, thermostats, etc. are not governed by the NEC, but rather are determined by the manufacturer and approved by third party testing agencies.

Wires in light, for example, only need to handle the current for the maximum bulb that the fixture is designed for. The same is true for thermostats, the maximum load of the thermostat governs the wire size. Further, "loose" wires in boxes and junction boxes dissipate heat better than wire run in walls in plastic sheaths (NM cable) or in conduit.
 
  #32  
Old 12-04-06, 03:36 PM
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Originally Posted by racraft View Post
The same is true for thermostats, the maximum load of the thermostat governs the wire size.
So wouldn't a t-stat being used in a 30A application require its fixture wires to be at least 10/2? The same as the actual line/load wires. The fixture wires on my t-stat appear to only be 12 gauge at most.
 
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Old 12-04-06, 03:40 PM
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Smile

Please don't think I was scolding..

I just wanted to be on the same page, Then I thought you thru a curve.

Your on the right track. sometimes the deeper you dig, the more confusing it can get. There are many variables to this electric stuff.
You seem to have a good handle on what you need to do.
 
  #34  
Old 12-04-06, 04:27 PM
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Originally Posted by lectriclee View Post
Please don't think I was scolding..
Never thought you were scolding I'm very grateful for all the help you (and others) have given. I know it is difficult to understand someones written explanation when there are no diagrams or pictures.

Was my explanation clearer? I probably should have used the term 'fixture wires' to describe the wires that come already attached to the t-stat. My only question now is does the gauge of the t-stat fixture wires need to match my line/load 10/2 wire? It doesn't make sense to me why they would not have to match.
 
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Old 12-04-06, 05:13 PM
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The wires from the breaker will be bigger.As Racraft explained.(Trust the engineer)
These wires carry the ENTIRE load of both zones, The thermostat carries only the load of the devices connected to it.

Now with that.. Why can't I add a 14/2 to a 20A ckt for a 60 watt light bulb.....I digress.. sorry, Thats part of my previous point, all the variables,theory and code...... Blah..blah..blah.
 
  #36  
Old 12-04-06, 07:24 PM
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The thermostat wires exist only in the junction box where the thermostat is located. They are open wires with no sheath. They can be smaller than the NEC normally requires because they are in the box, and because the NEC does not govern their size.
 
  #37  
Old 12-04-06, 09:30 PM
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So the current-carrying ability of a wire is not completely dependant on its thickness but also on its ability to dissipate heat? I'm sure there are many other factors but heat dissipation seems to be a major one from what you guys are saying.
 
  #38  
Old 12-05-06, 04:23 AM
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Yes. Wires that exist in open air, such as the utility company wires that feed houses, can be smaller that the wires that are required for the same house from the meter to the panel, even though they carry the same current.
 
  #39  
Old 12-05-06, 11:16 PM
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Thanks lectriclee and racraft and anybody else that offered advice. I really appreciate it!
 
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Old 12-06-06, 05:09 AM
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Do it right or not at all

sorry if some one already asked this but whats the amperage rating of the t-stat? If it will handle the load of both heaters, and the directions with the heaters indicate that two heater can be wired togeather on the same circuit then do it using the #10 wire. Be safe follow the code almost all electrical code can be traced back to an accident of some sort.Thats why every 3 years there is a new code book published. Just for pice of mind i would run the 10-2. What if your 20 A breaker sticks the heaters get turned up to high, If the breakers are brand new thats not very likely I know, but Sh%^ happens
why not just do it right the first time, sleep better cause you know you did. Any way thats just my opinion, and my first post on this forum. hope I didnt
offend anyone.
 
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