Ceiling heating elements (embedded is Sheetrock?) not working

sw_ross

Senior Member
Location
NoDak
This house has ceiling heat. I don't know what the wattage rating is for this particular room (living room).

The t-stat box has 2 sets of lead that come into the top of box. Power comes from the bottom, 10/2 Romex.
Power at box is 244v. OCPD is a 30-amp breaker.

Ohming out the 2 sets of leads show continuity, actually shows about 4-8 Ohm's. I totally bypassed the t-stat to rule that out. Turn on the breaker to check if there was current draw. Nothing.

if I made an assumption that each set of leads represented 2000 watts that would equate to an ohm reading of 28.8 Ohm's.

Given this information, what would you think might be the issue?

originally I expected to find the heating element to have no continuity but was surprised to find 2 sets of leads and had continuity on each set of leads.
 

mopowr steve

Senior Member
Location
NW Ohio
How long did you wait to feel the ceiling? It takes a while to feel warmth, give it 15 minutes to 1/2 hour then see if the ceiling feels warm.
Sounds to me that the ohm reading indicates there is no break in the cable. The last ceiling heat that I looked at actually only had a problem with the crimp connector between the leads that go to thermostat and the actual heating cable, found in the attic just where the heat cable enters the Sheetrock.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
How long did you wait to feel the ceiling? It takes a while to feel warmth, give it 15 minutes to 1/2 hour then see if the ceiling feels warm.
Sounds to me that the ohm reading indicates there is no break in the cable. The last ceiling heat that I looked at actually only had a problem with the crimp connector between the leads that go to thermostat and the actual heating cable, found in the attic just where the heat cable enters the Sheetrock.
He said there was no current so you can wait but there won't be any heat.

You may be getting a bit of reading thru the plaster but it does seem the wire is broken. I have seen these system but I have not worked on them. I suppose I would just tell the home owner that they need a new source of heat
 

StarCat

Senior Member
Location
Moab, UT USA
This house has ceiling heat. I don't know what the wattage rating is for this particular room (living room).

The t-stat box has 2 sets of lead that come into the top of box. Power comes from the bottom, 10/2 Romex.
Power at box is 244v. OCPD is a 30-amp breaker.

Ohming out the 2 sets of leads show continuity, actually shows about 4-8 Ohm's. I totally bypassed the t-stat to rule that out. Turn on the breaker to check if there was current draw. Nothing.

if I made an assumption that each set of leads represented 2000 watts that would equate to an ohm reading of 28.8 Ohm's.

Given this information, what would you think might be the issue?

originally I expected to find the heating element to have no continuity but was surprised to find 2 sets of leads and had continuity on each set of leads.
As you may be describing, many of the line voltage thermostats used are 2 pole switches.. You need to be sure you are not dropping one leg coming into or out of the T-stat and are reading accurate applied voltage to your load.If there are other cable heat zones in the house you can check the resistance on a zone that works and compare it. Also there is a formula for typical resistance for typical wattage of said zones for both 120v and 240 V cable using OHMs law. This is based on the typical wattage per sq. ft, that the system was designed for. I can tell you in my case that when they are running the type of heat thrown off is oppressive.
If you have an open, then the likelihood of repair is low. I have some of this type heat in my house and have replaced several zones with cove heaters because I simply do not like the idea or the feel of sheetrock radiant. It was a bad idea when they came out with it. The Cove heaters are fairly easy to install to replace the cable system. Abandon in place and install something that works.
If you appear to have solid resistance readings, I would be double sure about applied power.
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
He said there was no current so you can wait but there won't be any heat.

You may be getting a bit of reading thru the plaster but it does seem the wire is broken. I have seen these system but I have not worked on them. I suppose I would just tell the home owner that they need a new source of heat
My vote is with reading through plaster...
I have seen these also, mostly in 60-70s houses.
Never worked on one, only saw one that worked in an apartment a friend had years ago.
Always seemed like a fire hazard and backwards to me.

heat rises so let’s put it in the ceiling...:dunce:

BTW. Another post here, could you put up 230.82(11)?
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
My vote is with reading through plaster...
I have seen these also, mostly in 60-70s houses.
Never worked on one, only saw one that worked in an apartment a friend had years ago.
Always seemed like a fire hazard and backwards to me.

heat rises so let’s put it in the ceiling...:dunce:

BTW. Another post here, could you put up 230.82(11)?
230.82 only goes to (9)
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
It goes to 11

230.82 Equipment Connected to the Supply Side of Service Disconnect.

Only the following equipment shall be permitted to be connected to the supply side of the service disconnecting means: (1)Cable limiters.
(2)Meters and meter sockets nominally rated not in excess of 1000 volts, if all metal housings and service enclosures are grounded in accordance with Part VII and bonded in accordance with Part V of Article 250.
(3)Meter disconnect switches nominally rated not in excess of 1000 volts that have a short-circuit current rating equal to or greater than the available fault current, if all metal housings and service enclosures are grounded in accordance with Part VII and bonded in accordance with Part V of Article 250. A meter disconnect switch shall be capable of interrupting the load served. A meter disconnect shall be legibly field marked on its exterior in a manner suitable for the environment as follows:
METER DISCONNECT
NOT SERVICE EQUIPMENT
(4)Instrument transformers (current and voltage), impedance shunts, load management devices, surge arresters, and Type 1 surge-protective devices.
(5)Conductors used to supply load management devices, circuits for standby power systems, fire pump equipment, and fire and sprinkler alarms, if provided with service equipment and installed in accordance with requirements for service-entrance conductors.
(6)Solar photovoltaic systems, fuel cell systems, wind electric systems, energy storage systems, or interconnected electric power production sources, if provided with a disconnecting means listed as suitable for use as service equipment, and overcurrent protection as specified in Part VII of Article 230.
(7)Control circuits for power-operable service disconnecting means, if suitable overcurrent protection and disconnecting means are provided.
(8)Ground-fault protection systems or Type 2 surge-protective devices, where installed as part of listed equipment, if suitable overcurrent protection and disconnecting means are provided.
(9)Connections used only to supply listed communications equipment under the exclusive control of the serving electric utility, if suitable overcurrent protection and disconnecting means are provided. For installations of equipment by the serving electric utility, a disconnecting means is not required if the supply is installed as part of a meter socket, such that access can only be gained with the meter removed.
(10)Emergency disconnects in accordance with 230.85, if all metal housings and service enclosures are grounded in accordance with Part VII and bonded in accordance with Part V of Article 250.
(11)Meter-mounted transfer switches nominally rated not in excess of 1000 volts that have a short-circuit current rating equal to or greater than the available fault current. A meter-mounted transfer switch shall be listed and be capable of transferring the load served. A meter-mounted transfer switch shall be marked on its exterior with both of the following:
a.Meter-mounted transfer switch
b.Not service equipment
 

sw_ross

Senior Member
Location
NoDak
How long did you wait to feel the ceiling? It takes a while to feel warmth, give it 15 minutes to 1/2 hour then see if the ceiling feels warm.
Sounds to me that the ohm reading indicates there is no break in the cable. The last ceiling heat that I looked at actually only had a problem with the crimp connector between the leads that go to thermostat and the actual heating cable, found in the attic just where the heat cable enters the Sheetrock.
Do you have access to the connection between the leads and the actual heating element?
 

sw_ross

Senior Member
Location
NoDak
As you may be describing, many of the line voltage thermostats used are 2 pole switches.. You need to be sure you are not dropping one leg coming into or out of the T-stat and are reading accurate applied voltage to your load.If there are other cable heat zones in the house you can check the resistance on a zone that works and compare it. Also there is a formula for typical resistance for typical wattage of said zones for both 120v and 240 V cable using OHMs law. This is based on the typical wattage per sq. ft, that the system was designed for. I can tell you in my case that when they are running the type of heat thrown off is oppressive.
If you have an open, then the likelihood of repair is low. I have some of this type heat in my house and have replaced several zones with cove heaters because I simply do not like the idea or the feel of sheetrock radiant. It was a bad idea when they came out with it. The Cove heaters are fairly easy to install to replace the cable system. Abandon in place and install something that works.
If you appear to have solid resistance readings, I would be double sure about applied power.
Apparently this heat zone hasn't worked in a couple of years. They tried changing out the t-stat but that didn't make a difference. They were asking me about installing some baseboard heat.

while I was there I was just wanting to confirm that the ceiling heat actually wasn't working. I thought maybe the old t-stat died and when they replaced it maybe they installed it wrong, but the new t-stat install looked fine. The old t-stat and the new one are 1-pole stats.

First thing I did was checked supply voltage. No problem there.
Then I ohm'd out the leads expecting to find no continuity, but was surprised to find a low ohm reading.

In my brain, the confusing thing is that if you have voltage and you have resistance (continuity), you then have a complete circuit, so why don't I have current flow? What am I missing?

If I get there again I will check resistance on a different zone that does work.
 

gar

Senior Member
191006-1945 EDT

sw_ross:

You have provided insufficient information for anyone to give you very useful help.

You have a 240 V resistive ceiling heating system. 240 is supplied to a direct acting thermostat (meaning a thermal sensor directly controls some power switching contacts). We don't know if this is single pole or two pole. The thermostat is in the wall. Output wires from the thermostat go to a heating element or elements in the ceiling. A very simple circuit.

Do you read about 240 V between the two supply leads to the thermostat?
If you close the thermostat does the 240 remain at the thermostat input?
Is there any change in voltage of the 240 between the thermostat open and closed?
At 8 A load you would likely see more than 1 V change.

Assume you see no apparent current flow to the heating element, then what is voltage at the thermostat output going to the heating element?
If this voltage is identical, meaning within possibly 0.1 V of the voltage at the thermostat input, then you can reasonably assume that the thermostat contacts are closed, and there is no load current to the heating element.

Your statement of 4-8 ohms means nothing to me. I don't know where the measurement was made. It certainly is not the heating element. That would be P = (240)^2/(4 or 8) or about 14,400 W or 7200 W. And currents of 60 or 30 A.

So we need to know the resistance of the heating element, as you read it from looking at the leads to the heater at the thermostat output. I would turn the breaker to this circuit off, set the thermostat to open, then measure the heater resistance. If it reads around 30 ohms as someone mentioned, then you are probably seeing the heater element. If there is no current when power is applied, or very little, then you have a connection in the heating circuit somewhere that opens or becomes a high resistance when 240 V is applied.

Do a more thorough analysis of yor circuit. With simple measurements you should find your problem.

.
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
Do you have access to the connection between the leads and the actual heating element?
There's two kinds of ceiling heat. One the heat cable are run on site and are usually continuous for each room. The other kind is embedded in the sheetrock from the factory.

If you have the second kind sometimes you can track down the bad panel and bypass it.
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
Not just a technicality. You can heat a room with the heat source in the ceiling. The house I grew up in had ceiling heat.
The one I grew up in had a fireplace only...
I hated it.
Heat pump and Linear fireplace now.


it would be interesting to know the kWh usage for a season
 
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