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Old January 12th 04, 03:08 AM
Chris Lewis
 
Posts: n/a
Default 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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Old January 12th 04, 06:00 PM
HA HA Budys Here
 
Posts: n/a
Default Electric baseboard heater question

From: (KT)


Hi all,

I'm new here and need some basic info - We've got two electric
baseboards (2500 Watts, 240V) controlled by two 20A breakers, a
'thermostat circuit' (24V 0.15 Amps/Line Voltage circuit 240 V AC
Switched 25A), and a separate Honeywell thermostat. The system has
been in place for over 16 yrs.
Just recently, we started losing power (main 100A service disconnect
gets tripped.) We initially thought it was a load issue with recent
heavy use of an electric dryer, portable electric heaters, baseboards,
etc., but have been able to narrow it down so that we lose service
only when the breakers to the baseboard heaters are on. These are on
a sub-box (100A) off of a main box (100A, I think).
I'm not sure how the baseboards are wired, but shouldn't they trip
their own breakers (or even the breaker on the main for the sub-box)
before tripping the main service? Can you tell me what the symptoms
of a faulty 'thermostat circuit' box would be? Any way to test this?
Our second thought is that the main service disconnect breaker is
faulty, but it seems odd that we only lose power after the heater
breakers are on. We have tried this also with everything off except
for heaters (and lights in one room) - but the main still trips.
Can you shed some light on any of this, mainly what a faulty
thermostat circuit would do? Don't worry - someone more knowledgable
than myself will be carrying out any tests! Thank you!

Katie

Sorry if a similar message shows up twice - I posted yesterday, but
haven't seen it come up yet.


Sometimes, a dead short circuit can cause a backstream overcurrent protection
device to open, rather than the individual specific circuit breaker.

I suspect faulty wiring either inside one of the baseboard heaters, or their
associated circuits somewhere between the panel and the actual baseboard
heaters themselves.

If one heater is butted against the other, and the second heater fed through
the first, I'd look into the wires that run through the "first" baseboard to
see if they're defective - possible an electrician used wire that was handy
instead of wire that could withstand the heat.

Second place I'd look is the connector that the cable which feeds each heater
is connected to - the mechanical clamp where the wire comes out of the wall and
into the heater. Make sure it's not pinching through the wires.

Third - have you done any nailing lately? Hung any pictures, drilled any walls,
nailed any new mouldings around your walls/floors?

I'd also have a look at the circuit breaker which SHOULD be opening upon a
short circuit, and the one that is opening instead and replace them. Breakers
are cheap and every once in a while you get a precarious one.






  #3   Report Post  
Old January 12th 04, 07:20 PM
HA HA Budys Here
 
Posts: n/a
Default 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   Report Post  
Old January 12th 04, 07:36 PM
Chris Lewis
 
Posts: n/a
Default 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   Report Post  
Old January 13th 04, 12:27 PM
CBhvac
 
Posts: n/a
Default 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.





  #7   Report Post  
Old January 13th 04, 06:48 PM
Chris Lewis
 
Posts: n/a
Default Electric baseboard heater question

According to CBhvac [email protected] 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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