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Electric baseboard heater question
According to KT :
Hi. We've got a couple of electric baseboard heaters that appear to be connected to a relay that apparently runs to a wall mounted thermostat. We're trying to track down a power problem. Service disconnect on the circuit box trips soon after baseboards start heating. _Service_ disconnect? Really? Takes out the whole house? Are you sure you don't mean branch circuit breaker? (probably a pair of breakers tied together). If it's really the service disconnect, we need more detail. Ie: how big are the main breakers? What is the combined wattage of the heaters? Do you have a whole-house ground fault detector? I can't help thinking that you're really going to need an electrician for these. If you have a whole-house ground fault detector, it's probably trying to tell you that one of the baseboards has a wireing fault (short to ground). It could be that you're on a relatively small service, and that running the set of heaters all at once are too much for it. In which case you'll need to upgrade your service (or use something other than electric heat). No trouble when their breakers are turned off. Can anyone tell me what the symptoms of a faulty heater relay would be? Could it allow to much current to pass? Thank you! Unlikely to be the relay. Relays either "doesn't open" (won't stop heating), "doesn't close" (won't start heating) or makes the breaker go "bang" real fast (short). If the relay short is causing the main breaker to trip, you have big problems. If you're getting heat from the heaters, it's probably not the relay. If it's the branch breakers: Two main possibilities: 1) One of the baseboards is going bad and drawing too much current. 2) The breaker is "getting tired" and is tripping at too low a current. If you could borrow an amprobe, that'd be the best way to test the current on each of the heaters. -- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them. |
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Electric baseboard heater question
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#3
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Electric baseboard heater question
Katie - the thermostat circuit is simple, it allows the use of a standard, low
voltage thermostat to control one or more high voltage heater(s) It does this through a relay or contactor which has a low voltage electromagnetic coil which "tells" a high-voltage switch what to do. DO you know where the relay(s) are? |
#4
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Electric baseboard heater question
According to KT :
(Chris Lewis) wrote in message ... According to KT : Hi. We've got a couple of electric baseboard heaters that appear to be connected to a relay that apparently runs to a wall mounted thermostat. We're trying to track down a power problem. Service disconnect on the circuit box trips soon after baseboards start heating. _Service_ disconnect? Really? Takes out the whole house? Are you sure you don't mean branch circuit breaker? (probably a pair of breakers tied together). It is actually the service disconnect, which is a 100 A breaker, and unfortunately does take out the whole house. Let's see if I can cut to the chase he You have a 100A main panel, with a 100A subpanel. The heaters are fed off the 100A subpanel (is the stove, dryer too?). The heaters are on two 20A 240V circuits. When the heaters turn on, the main (not subpanel) breaker (service disconnect) trips. Points to consider: 1) "To code", the maximum current the heater circuits can draw in total is 32A (80% of 2x20). If it's more than 20A apiece the branch breakers should trip (but see below regarding massive shorts). 2) You have a low voltage thermostat circuit. This means: a small transformer converts 220V to 24V. The thermostat (you have only one thermostat, right?) acts as switch to control 24V to the relay. The coil on the relay is 24V. The contacts that the relay opens/closes are 240V driving the heaters. Most furnaces have low voltage or "millivolt" thermostat circuits - the relay is inside the furnace, transformer often mounted nearby. With electric heat, the relay has to switch a lot more current. 3) The thing circuit corresponding to the 'Thermostat Circuit (24V 0.15 Amps/Line Voltage circuit 240 V AC Switched 25A).' powers the transformer (at least). The small box you see is probably the transformer. I'm not an electrician, and I've not worked with a low voltage thermostat system for electric heating since the mid 70's, so, I'm not quite sure of the current practise/hardware is. That "small device" could actually be both the transformer and relay (one thermostat: if there's two 220V circuits going into and out of it - total of four cables _plus_ smaller wires going to the thermostat. If there are two thermostats involved, there are likely two relays hidden somewhere). Or, the relay is parked somewhere else. By code, the relay needs to be "accessible". But that may mean that it's in the wall behind something. [We installed ours in the wall cavity with the in-wall forced air heater. Access by unscrewing the heater from the wall.] There's just about nothing the heaters do on their own that would trip a 100A breaker before their own 20A breakers. That goes for the relay[s], transformer[s] and thermostat[s] too. I can think of two possibilities: 1) "tired" main breaker. But the stove and dryer simultaneously should be able to trip it. Probably not this. 2) One of the heaters has a temperature-induced short. Ie: when it heats up, a hot-ground short occurs and the main breaker simply trips faster than the 20A breaker on a massive short. It's remotely possible this is the relay (or even the transformer connection), but I'd suspect a heater first. You should be able to smell ozone, or hear it go "bang", or find scorch marks in the device that's shorting out. Or all three. 100A+ shorts aren't subtle things. They usually make their presence known. The lights should dim momentarily when this happens for example. If you find burnt contacts on the relay, be aware that they may be the _result_ of a heater problem. So you'll have to check the heaters out too. You're really going to need an amprobe (and someone who knows how to use one) to diagnose this if you can't sniff out the problem directly. Ie: is the main breaker really seeing 100A when it trips? Do any of the heater circuits spike 100A when the main goes? For anything other than a solid diagnosis of a heater/relay/transformer going bad and spiking 100A, you'll need an electrician. [Other highly remote possibilities: temperature-induced short _inside_ panel. Etc. This requires experience to diagnose.] Be _careful_. 100A breakers tripping implies that there's a lot of energy going _somewhere_. Best not to be _you_. Don't be standing around touching the panel or heaters when this thing is likely to trip. -- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them. |
#5
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Electric baseboard heater question
"Chris Lewis" wrote in message ... According to KT : (Chris Lewis) wrote in message ... According to KT : Hi. We've got a couple of electric baseboard heaters that appear to be connected to a relay that apparently runs to a wall mounted thermostat. We're trying to track down a power problem. Service disconnect on the circuit box trips soon after baseboards start heating. _Service_ disconnect? Really? Takes out the whole house? Are you sure you don't mean branch circuit breaker? (probably a pair of breakers tied together). It is actually the service disconnect, which is a 100 A breaker, and unfortunately does take out the whole house. Let's see if I can cut to the chase he You have a 100A main panel, with a 100A subpanel. The heaters are fed off the 100A subpanel (is the stove, dryer too?). The heaters are on two 20A 240V circuits. When the heaters turn on, the main (not subpanel) breaker (service disconnect) trips. Points to consider: 1) "To code", the maximum current the heater circuits can draw in total is 32A (80% of 2x20). If it's more than 20A apiece the branch breakers should trip (but see below regarding massive shorts). 2) You have a low voltage thermostat circuit. This means: a small transformer converts 220V to 24V. The thermostat (you have only one thermostat, right?) acts as switch to control 24V to the relay. The coil on the relay is 24V. The contacts that the relay opens/closes are 240V driving the heaters. Most furnaces have low voltage or "millivolt" thermostat circuits - the relay is inside the furnace, transformer often mounted nearby. With electric heat, the relay has to switch a lot more current. 3) The thing circuit corresponding to the 'Thermostat Circuit (24V 0.15 Amps/Line Voltage circuit 240 V AC Switched 25A).' powers the transformer (at least). The small box you see is probably the transformer. I'm not an electrician, and I've not worked with a low voltage thermostat system for electric heating since the mid 70's, so, I'm not quite sure of the current practise/hardware is. That "small device" could actually be both the transformer and relay (one thermostat: if there's two 220V circuits going into and out of it - total of four cables _plus_ smaller wires going to the thermostat. If there are two thermostats involved, there are likely two relays hidden somewhere). Can tell you right now, the thermostats will be line voltage and NOT 24VAC, but 220VAC...the rating on the stat is all he put up, and most line stats also have the 24VAC rating listed, simply because they can be used in a low voltage setup....I have not seen a baseboard heater that had a 24VAC transformer in it in so long...and the one we DID see had been rigged up that way. The only relay, in a baseboard system like that, is the stat...its either on, or off...thats it. Or, the relay is parked somewhere else. By code, the relay needs to be "accessible". But that may mean that it's in the wall behind something. [We installed ours in the wall cavity with the in-wall forced air heater. Access by unscrewing the heater from the wall.] There's just about nothing the heaters do on their own that would trip a 100A breaker before their own 20A breakers. That goes for the relay[s], transformer[s] and thermostat[s] too. I can think of two possibilities: 1) "tired" main breaker. But the stove and dryer simultaneously should be able to trip it. Probably not this. 2) One of the heaters has a temperature-induced short. Ie: when it heats up, a hot-ground short occurs and the main breaker simply trips faster than the 20A breaker on a massive short. It's remotely possible this is the relay (or even the transformer connection), but I'd suspect a heater first. You should be able to smell ozone, or hear it go "bang", or find scorch marks in the device that's shorting out. Or all three. 100A+ shorts aren't subtle things. They usually make their presence known. The lights should dim momentarily when this happens for example. If you find burnt contacts on the relay, be aware that they may be the _result_ of a heater problem. So you'll have to check the heaters out too. You're really going to need an amprobe (and someone who knows how to use one) to diagnose this if you can't sniff out the problem directly. Ie: is the main breaker really seeing 100A when it trips? Do any of the heater circuits spike 100A when the main goes? For anything other than a solid diagnosis of a heater/relay/transformer going bad and spiking 100A, you'll need an electrician. [Other highly remote possibilities: temperature-induced short _inside_ panel. Etc. This requires experience to diagnose.] Be _careful_. 100A breakers tripping implies that there's a lot of energy going _somewhere_. Best not to be _you_. Don't be standing around touching the panel or heaters when this thing is likely to trip. -- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them. |
#6
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Electric baseboard heater question
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#7
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Electric baseboard heater question
According to CBhvac stephenaddressscfrewedonpurpose@carolinabreezehva c.com:
Can tell you right now, the thermostats will be line voltage and NOT 24VAC, but 220VAC...the rating on the stat is all he put up, and most line stats also have the 24VAC rating listed, simply because they can be used in a low voltage setup....I have not seen a baseboard heater that had a 24VAC transformer in it in so long...and the one we DID see had been rigged up that way. As described, the OP's system appears to have what is likely a 24V transformer on it. It also appears to be _two_ circuits fired off a single T-stat. And note the other posting about "great white north". In the installation I did it had two 2000W baseboards and a 3000W fan heater on a single T-stat - two 240V circuits. The building had approximately 12Kw of electric heat in total (200A service). I assure you, that one T-stat didn't pass 240V ~35A. It was one of those itsy-bitsy round (chromolox if you remember that far back) with a teeny-weenie mercury switch (that could probably safely pass all of about an amp or two) connected to the relay with 18ga wire. AFAIK the relay isn't usually inside the baseboards. The relays go somewhere else (ie: the panel or some other accessible place) to control multiple large loads at once. In ours, the relay went in the cavity behind the wall heater, and controlled two 240V circuits. Please try to trim followups. I know I write good ;-), but wading through pages of my own posting to find a few lines of response is a bit of a PITA. -- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them. |
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