Wiring for tstat when line is at the heater.
#1
12-10-08, 11:22 PM
Wiring for tstat when line is at the heater.
Hey all,
Thanks in advance for your help. I am fairly new to electrical but have done some residential lighting branch circuit wiring, but this is my first time dealing with heat and thermostats. In my family room there are two heaters, both 240-volt Cadet ZA-202 wall heaters rated 2000 watts@240-volts. There was a mechanical-style thermostat installed to control both heaters, but the confusing part is how it's connected. SP is the service panel, S is the single-pole thermostat, and H1 and H2 are the heaters:
The circuit uses 10 gauge NM-B 2-wire with both conductors used as ungrounded "hot" conductors and each conductor protected by a 20A CB. Not having a grounded neutral conductor is messing with my head, but that aside, I don't understand how this works. In this scenario, my logic tells me that the thermostat would have no control over the heaters. The heaters would be receiving uninterrupted current from the service panel because the tstat is not in-line with the heaters. I guess I am not understanding the flow of electric current.
I'd like to install a programmable double-pole thermostat to control the circuit, but as far as I can tell, that isn't possible without the line coming into the thermostat, which would dictate either re-wiring or moving the thermostat. I read once somewhere that double-pole thermostats are a code requirement for 240-volt circuits in the U.S. Anyone know if that's true? I live in Oregon.
Thanks,
William
Thanks in advance for your help. I am fairly new to electrical but have done some residential lighting branch circuit wiring, but this is my first time dealing with heat and thermostats. In my family room there are two heaters, both 240-volt Cadet ZA-202 wall heaters rated 2000 watts@240-volts. There was a mechanical-style thermostat installed to control both heaters, but the confusing part is how it's connected. SP is the service panel, S is the single-pole thermostat, and H1 and H2 are the heaters:
The circuit uses 10 gauge NM-B 2-wire with both conductors used as ungrounded "hot" conductors and each conductor protected by a 20A CB. Not having a grounded neutral conductor is messing with my head, but that aside, I don't understand how this works. In this scenario, my logic tells me that the thermostat would have no control over the heaters. The heaters would be receiving uninterrupted current from the service panel because the tstat is not in-line with the heaters. I guess I am not understanding the flow of electric current.
I'd like to install a programmable double-pole thermostat to control the circuit, but as far as I can tell, that isn't possible without the line coming into the thermostat, which would dictate either re-wiring or moving the thermostat. I read once somewhere that double-pole thermostats are a code requirement for 240-volt circuits in the U.S. Anyone know if that's true? I live in Oregon.
Thanks,
William
#2
12-11-08, 06:37 PM
Originally Posted by wmcglass
The circuit uses 10 gauge NM-B 2-wire with both conductors used as ungrounded "hot" conductors and each conductor protected by a 20A CB. Not having a grounded neutral conductor is messing with my head
Originally Posted by wmcglass
but that aside, I don't understand how this works. In this scenario, my logic tells me that the thermostat would have no control over the heaters. The heaters would be receiving uninterrupted current from the service panel because the tstat is not in-line with the heaters. I guess I am not understanding the flow of electric current.
Originally Posted by wmcglass
I'd like to install a programmable double-pole thermostat to control the circuit, but as far as I can tell, that isn't possible without the line coming into the thermostat, which would dictate either re-wiring or moving the thermostat. I read once somewhere that double-pole thermostats are a code requirement for 240-volt circuits in the U.S. Anyone know if that's true? I live in Oregon.
Last edited by doug321; 12-11-08 at 07:05 PM.
#3
12-12-08, 02:43 PM
#4
12-13-08, 12:39 PM
Thank you both tremendously for your help! I haven't read through the article yet, but will certainly make a point to. I went down to Jerry's (a local Oregon hardware store) and got a voltage detector pen so I could come to a better conclusion about how it's wired. Here is how it is actually wired:
So it would appear that the thermostat is only switching one leg of the circuit as Doug suggested. I'll look into installing a double-pole tstat at the first heater. I, too, had a hard time finding a programmable double-pole thermostat. It seems that the selection in the line-voltage arena is slim all around. The one that I found is the Lux ELV4. They don't have it listed on their website, but it was available at Jerry's and Amazon.com.
Thanks again!
William
So it would appear that the thermostat is only switching one leg of the circuit as Doug suggested. I'll look into installing a double-pole tstat at the first heater. I, too, had a hard time finding a programmable double-pole thermostat. It seems that the selection in the line-voltage arena is slim all around. The one that I found is the Lux ELV4. They don't have it listed on their website, but it was available at Jerry's and Amazon.com.
Thanks again!
William
