Maximum watts for a thermostat

[krisway]

Last year I installed and heated my garage (16x36) with 6000watts of baseboard heaters. I used a 1500w, 2000w and 2500w base board heater and two regular (non digital) thermostats. One thermostat controls the 1500w heater and the other thermostat controls the other two heaters (2000w and 2500w).
QUESTION ONE: is this too much on one thermostat? My garage was heated using this method for 5 months straight over last winter.
QUESTION TWO: I want to switch to digital thermostats, yet most I've seen says "maximum 3000 watts". Does this mean I cannot use this type of thermostat on my two heaters which equal 4500w?

 

[nehog]

1. Depends on the thermostat. What were the ratings? (or model so it could be looked up.)

2. Yes you can't use it, that's too much.

 

[Stuff]

You would use a contactor/relay. Take a look at this - http://waterheatertimer.org/H230A.html

 

[DekeT]

I don't get it. My 24 volts boiler thermostats control over 140k btu and that is way more than a 6000 watt heater. Are electric heat thermostats controlled differently than a separate relay and transformer?

 

[n8n]

some of them just act as a switch directly.

 

[krisway]

Is there a thermostat that can control two baseboard heaters totalling 4500w?

 

[dslabuda]

I don't get it. My 24 volts boiler thermostats control over 140k btu and that is way more than a 6000 watt heater. Are electric heat thermostats controlled differently than a separate relay and transformer?

Is the boiler electric or gas? If it's gas you're comparing two different sources of heat.

Sent from my SAMSUNG-SM-N900A using Tapatalk 4

 

[Charles (in GA)]

Are these heaters 120v or 240v?

I don't think you will find a thermostat that will directly control that much current. You get that big, and you need to go to a thermostat/relay combination and let the heavy duty contacts of the relay do the switching, while letting the thermostat control the relay (very low current/voltage).

Charles

 

[krisway]

Are these heaters 120v or 240v?

I don't think you will find a thermostat that will directly control that much current. You get that big, and you need to go to a thermostat/relay combination and let the heavy duty contacts of the relay do the switching, while letting the thermostat control the relay (very low current/voltage).

Charles

It is 240v. Would you say I've been lucky so far? I've used this set up for five months straight last winter.

 

[arsco]

line voltage tstat vs 24v tstat.


if you want to use a 24v tstat you will need a transformer and a contactor

 

[krisway]

Okay so my next question is: what do I need to do with my current setup? It seems that two heaters totalling 4500w is too much for my one thermostat.

 

[nehog]

Either install a contactor (relay) or add another (third) thermostat. A contactor will require a box.

 

[pattenp]

Sounds like a third T-stat may be your best option. There are 3500W T-stats, so you could combine the 1500 and 2000 together and use the 2500 on a second T-stat.

 

[krisway]

Thanks for the help, looks like maybe installing two thermostats side by side might be the best solution.

NEXT QUESTION - At my current thermostat I have one wire from the panel and one from each heater. If I were to hook up two thermostats, naturally one wire from each heater goes to each thermostat. The live wire goes to one thermostat, and can I just join a piece of wire from this wire nut to put power to the second thermostat? Hopefully I'm making sense.

OR is it just as easy and cost effective to use a relay?

 

[yeldogt]

Look on the back of the thermostat -- the rating will be on the switch -- some can switch a lot of baseboard.

The digital ones have to be using a relay of some sort -- so it is just a question of seeing how much and adding a second relay.

You can use a relay to split the load on a manual one -- I would not use two thermostats next to one another.

Are these standard type of electric baseboard? You can get thermostats and relays to mount on the end of some of them

 

[pattenp]

You can split the line wire to the 2 thermostats using a wirenut. Make sure the amp load of the two heaters don't exceed the wire's amp capacity.

 

[krisway]

You can split the line wire to the 2 thermostats using a wirenut. Make sure the amp load of the two heaters don't exceed the wire's amp capacity.

Thanks. I've used the correct wire size and using a dbl pole 30amp breaker.

 

[krisway]

Look on the back of the thermostat -- the rating will be on the switch -- some can switch a lot of baseboard.

The digital ones have to be using a relay of some sort -- so it is just a question of seeing how much and adding a second relay.

You can use a relay to split the load on a manual one -- I would not use two thermostats next to one another.

Are these standard type of electric baseboard? You can get thermostats and relays to mount on the end of some of them

What does a relay look like? Any direction on how these hook up? I'm assuming they work similar to an automotive relay?

 

[wyliesdiesels]

I don't get it. My 24 volts boiler thermostats control over 140k btu and that is way more than a 6000 watt heater. Are electric heat thermostats controlled differently than a separate relay and transformer?

An electric baseboard tstat that switches at line level voltage has the full current load of the heater running through it.

For 4500w this equals 18.75a and the tstat would need to be rated at 125% of that or approx 24a or 5600w. The tstat the OP is using is probably rated at 3000w so this is a major fire hazard! Yes the OP is lucky!

What does a relay look like? Any direction on how these hook up? I'm assuming they work similar to an automotive relay?

Yes a relay is a relay. The difference between the 2 is the rated voltage size of the contacts etc. another name is contactor. Essentially there is a low amp coil that when energized pulls high in amperage contacts that complete/close the circuit.

 

[krisway]

I found this today, looks to be rated for 5280 watts. I'm guessing this single thermostat will safely control my two heaters (2000w and 2500w)?

 

[wyliesdiesels]

How many poles does it have? Looks like it is only 2 wire...

 

[krisway]

How many poles does it have? Looks like it is only 2 wire...

I knew it was too good to be true, yes it just has two wires. What is the advantage of single pole vs dbl pole?

 

[yeldogt]

You will want the "B" -- At one time this must have been code -- all of the baseboard at our old shore house were wired to only disconnect one side of the 220.

I'm sure all the current codes call for a "disconnect" -- so need to cut both.

 

[wyliesdiesels]

I knew it was too good to be true, yes it just has two wires. What is the advantage of 4 pole vs 2 pole?

Its actually only single pole, since the source is one screw and the feed is the other screw. The same concept as a single light switch. 2 pole would have 4 screws and would switch both legs. That would be called double pole single throw because there would be 2 sources of power and the switch mechanism either opens the circuit(off) or closes the circuit(on) which is the single throw. A 4 way switch is an example of a double pole double throw....but i digress....

Im not sure why its rated for 240v when it is only single pole. 240v is not a line to neutral system voltage in the US. Since u would only be interrupting one 120v leg, Im pretty sure youre limited to the 120v rating because only 120v will be running through the tstat.

I have a tstat sitting in front of me from Chicago Electric that is rated 125v/277v @ 22amps....both 120v and 277v are line to neutral system voltages and thus would work with a single pole switch.

 

[APEowner]

I used several of these in my New York house -> http://www.king-electric.com/thermostats/line-voltage-thermostats.html#

You'll have to check with one of the code experts on this board (or look it up) but my understanding was that the breaker is the safety disconnect that breaks both sides and that a single pole t-stat was fine.

 

[krisway]

Here's what it says on the back of the package.




In a nut shell, I have two heaters totalling 4500w and trying to control it with one thermostat. It is 240v, correct size wire, and 30amp breaker.
Turning it off is not really a big deal. The only time these heaters are used is during the winter months in which I leave them on 24hrs a day for about 4-5 months. Electrical panel with the breakers is only about ten feet away, so when the time comes to turn off the heaters I will just turn off the breaker.

 

[yeldogt]

Actually ........I checked .. and you can still use this two wire to control a 240 baseboard heater/s

At 220 volts that will run the watts you have