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Old 02-25-2009, 08:41 AM   #1
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Thermostat toubleshooting


My ceiling electrical heating stopped working. I replaced the old Dayton thermostat with a new Dayton specified for electrical heating. Tested line on thermostat - OK. Tested load on thermostat - loaded. Does it mean that the electrical cable is interrupted or did I attached the wires to the thermostat wrong? Please see the diagram.

Milan
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Old 02-25-2009, 10:25 AM   #2
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Thermostat toubleshooting


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Originally Posted by milankalus View Post
My ceiling electrical heating stopped working.
Need more info.

What model Dayton thermostat is it? Is it possible that you have a 120V thermostat (not likely) and your heater is 220V?

What do you have for a "ceiling" heater?

How EXACTLY are your cables (and what colors) coming into and out of the thermostat box, both from your power supply and to the heater.

By black/white and red/red, are you referring to the colors of the pigtails pre-attached to the thermostat? I hope so.

If you have confirmed that the thermostat is operating properly, that is to say you if yours is a 220V heater and have 220 on the line and also 220 on the load, then your next check would be at the heater. Or is your a 120V heater?

What to check there depends on what exactly the heater is.

Also, you can look around and be sure that the load wires are not wired through another thermostat, as is the case sometimes when heating circuits are wired improperly.

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Last edited by williswires; 02-25-2009 at 10:33 AM.
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Old 02-25-2009, 01:45 PM   #3
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Thermostat toubleshooting


If you have power at the load terminals (it looks like you do from the drawing) you have other issues. Bad heater or wiring is possible.

ps.....did you measure the voltage ACROSS the two load and line terminals or to ground? If you measured to ground, go back and measure between the terminals. This is the correct way.

Last edited by J. V.; 02-25-2009 at 01:48 PM.
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Old 02-26-2009, 11:13 AM   #4
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Thermostat toubleshooting


The thermostat is Dayton 4PU48 240V designed for cable electrical ceiling heating. Cable is under the ceiling plaster. It worked for 30 years with old Dayton 240V thermostat.

I wired the new thermostat exactly as the old one. When the old and new thermostat is turned off it shows 200V between the two line points as shown on the diagram. If I turn the thermostat on it shows 200V between the load points. I enclose the diagram again.

My suspicion is, as it is yours, that the heating cable, which is for 240V, is somewhere damaged or interrupted. Is there a way to detect the location of a brake or disconnection? Understandably, I'm not going to remove the plaster from the whole ceiling.

Milan
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Old 02-26-2009, 11:36 AM   #5
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Thermostat toubleshooting


Yeah....you are screwed

Unless you can find a connection between the tstat wires and the cable under the plaster, it's time for baseboard or wall heater.

We don't have that kind of system where I live but it seems like the cable in the plaster wouldn't be line voltage and there would be some kind of something somewhere to transform the voltage. Did they really run line voltage wire imbedded in the plaster?

Even if they did, wouldn't there have to be a junction between the NM and the heating wire??
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Old 02-26-2009, 11:48 AM   #6
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Thermostat toubleshooting


Do you have a meter? If so you could ohm out the cable and see if it's open. Follow the wires (leaving to the heater) from the T-Stat and look for a j-box or connection box for the heater cable. The problem could be in one of these enclosures, if your lucky.
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Old 02-26-2009, 05:28 PM   #7
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Thermostat toubleshooting


I do have meter and I'll try to ohm the red wires going to the thermostat load terminals. The red wires go from the T-box into the wall.

I have no idea where the junction between the heating cable and the red wires going in and out the T-stat is. Probably somewhere in the wall.

Milan
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Old 02-27-2009, 11:29 AM   #8
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Thermostat toubleshooting


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I do have meter and I'll try to ohm the red wires going to the thermostat load terminals. The red wires go from the T-box into the wall.

I have no idea where the junction between the heating cable and the red wires going in and out the T-stat is. Probably somewhere in the wall.

Milan
No, remove the red wires from the T-Stat and ohm the wires. You want to only ohm out the two reds feeding the heating cable. The two wires on the load side of the T-Stat are the heating cables themselves right?
The T-stat you pictured is a line T-Stat. It directly controls the heat. Carries the full current also. Thats why there are no other connection points/boxes except the T-stat itself.

Do you have a similar heat setup in the house? If so, and the heating cable is the same length and size, you could measure the ohms on that one. You then have an idea about what your ohm reading should be on the one in question.
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Old 02-27-2009, 12:18 PM   #9
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Thermostat toubleshooting


Yes, I do have other thermostats in the house. I have connected the new T-stat exactly as the others are connected. I was just assured by Graiger thatt the new thermostat, the way I wired it, is fine and properly wired.

Are you saying that the red, load wires attached to the load terminals on the T-stat are the actual heating cables? I don't think so because they never get hot. There must be somewhere junction to the true heating cable. If they were heating cables why they don't heat up when I measure 240 V between the load terminals?

Milan
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Old 03-01-2009, 12:42 PM   #10
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Thermostat toubleshooting


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Originally Posted by milankalus View Post
Yes, I do have other thermostats in the house. I have connected the new T-stat exactly as the others are connected. I was just assured by Graiger thatt the new thermostat, the way I wired it, is fine and properly wired.

Are you saying that the red, load wires attached to the load terminals on the T-stat are the actual heating cables? I don't think so because they never get hot. There must be somewhere junction to the true heating cable. If they were heating cables why they don't heat up when I measure 240 V between the load terminals?

Milan
Now you are on to something. If the wires in the T-Stat are not the heating cables themselves, then there must be (should be) a connection box somewhere. Unfortunately some wannabe electricians will hide a connection box behind a wall or similar. Some may just connect and use no box.
You are going to have to find a way to follow the load wires and find the transition point. That may be where the issue lies.
Do you get a reading when you ohm the load cables? At least you can tell if it's open or not. This will not tell you if the cable is good though.
Are you absolutely sure you have 240 volts reading across the two wires? Don't measure to ground. Measure across the two line leads and acrossthe two load leads.

Have you measured the ohms of a good heater cable yet? Let us know what the reading is vs the reading at the bad cable. Distance and wire size will make a difference.
Without your readings, we can do nothing for you.
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Old 03-02-2009, 11:42 AM   #11
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Thermostat toubleshooting


The heating circuit is broken and I can't get to it.

The Ohm reading is zero in the defective circuit, 60 Ohm in good circuit elsewhere when T-stats are off. When T-stats on Ohm reading out of scale in both.

I do have 200-220V in all T-stats measured terminal to terminal.

Thanks,

Milan
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Old 03-02-2009, 12:24 PM   #12
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Thermostat toubleshooting


Good job! Now the hard part starts. The repair. Do you plan to try and remove the old one and install a new one yourself? I have no idea how this is set up so I cannot advise you much, unless you can provide more information on how these heater cables are installed, and in your case un-installed. Let us know if we can help. Good luck........John
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Old 03-02-2009, 07:35 PM   #13
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Thermostat toubleshooting


Just a thought, if you have a coat closet or some other closet near the area affected, look up inside to the finished ceiling. I have seen a few junction boxes in those locations where they start the ceiling heat runs. Possibly a bad connection in there. Havent seen much ceiling heat but I have seen connectiions go bad.
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Old 03-03-2009, 12:25 AM   #14
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Thermostat toubleshooting


ceiling heat sucks and goes bad all the time. Do yourself a favor and cut in a picawatt heater under the thermostat

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