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a7ecorsair 06-15-2010 09:15 PM

Relay controlled baseboard heaters
I have electric baseboard heat in my cabin but we will be rebuilding it this summer. In the current configuration, all the baseboard is on a separate off-peak panel (240V). The two bedrooms are on a separate circuit and have line voltage thermostats on the the baseboard. The kitchen and dining area are on a separate breaker and the living room is on a separate breaker. These two circuits are controlled by a thermostat that operates two definite purpose 30 amp resistive relays.
Why did the electrician, when this was done, use two double pole relays and then only use one pole on each relay?
The kitchen has its own relay and living room has its own relay. Only one leg of the 240V is interrupted by the each of these relays so it would have worked to use one double pole relay.
Were two relays used because these are two separate 240V circuits even thou the two relays are controlled by a single thermostat?
I will be doing a similar setup in the new house and was wondering if I need a separate relay for each 240V circuit.

LyonsElecSupply 06-16-2010 02:37 PM

I would say not. I dont know why he is only switching ONE leg. Are you sure they are 240?

You only NEED to switch one leg of 240v. Maybe he was allowing for addition of heaters?

My understanding of DP Contactors is that EVERY pole is independent and switched. At least this is the case with Cutler Hammer DP.

You should only worry about switching the load with DP contactors. As each circuit is separate anyways.

frenchelectrican 06-18-2010 02:21 AM

There is the reason why some baseboard electric heaters use relay due the current drawage some of the thermosat will not able handle the load due some of the wall or even baseboard heater thermosat will not handle more than 22 amp the most.

the other reason why that electrician use the two pole relay some are allready wired for 240 volts but the key item is check the coil voltage that will affect the performace { it should have a stamping on it or model numbers one of us can dechiper it }

And also some of the POCO do have off peak electric heater useage load and they will put in couple relays one for electric baseboard heater or a trigger swtich for larger electric heaters and also used on Central air compressor so they can cut out during peak hours.

And finally to answer your last question.,

Yeah I have done this few time use one thermost to handle quite few baseboard heaters just like one thermosat can handle few relays to control large bank of heaters.


a7ecorsair 06-18-2010 08:04 AM

1 Attachment(s)
Thanks for the reply
This panel has a 100 amp mercury rely between the main bus and meter and the POCO controls it.

So this looks OK.

frenchelectrican 06-18-2010 04:54 PM

I have see that set up from time to time and the only gotcha you should make a note that you will have more than one disconneting power source so if you turn off two breakers and the relay power still alive so you have to get third disconnect switch for safety.

Or make a note stated " more than one power source " that is a main item that will make a note in case someone else do the repairs on it.


a7ecorsair 06-18-2010 09:06 PM

The 24VAC transformer for the thermostat will have its own 15A breaker in this panel. Is that what you are referring to?
Thanks again

frenchelectrican 06-20-2010 01:31 AM


Originally Posted by a7ecorsair (Post 458354)
The 24VAC transformer for the thermostat will have its own 15A breaker in this panel. Is that what you are referring to?
Thanks again

Ouais { Yeah }

that what I am refering to this and that the main reason why I have to remind that it have more than one power source or circuits in there.

I have ran into like that pretty often espcally with industrail side if I have to shut down the equiment by LOTO { Lock Out , Tag Out } prodcure so I have to check all soureces like any power sources like Electrical power source, Air power soruce etc etc.


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