Hydrotherm HC-100 Pilot On, No Heat

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Old 03-21-20, 08:09 PM
J
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Question Hydrotherm HC-100 Pilot On, No Heat

Hi,

I have a Hydrotherm HC-100 Nat Gas Boiler that is not igniting the burner. The thermostat shows that the house is at 60f and is set for 68f. If I turn the thermostat down and back up occasionally the burner will ignite and heat the house for a few hours and then cold again. As I mentioned in the subject the standing pilot is on, also when I turn the thermostat down below the room temp and then back up I hear a relay click and the circulation pump appears to be working because I hear the flow of water if I am standing next to the boiler. I can't seem to find a damper switch or/and safety thermostats, where would they be located as I know there needs to be some. I checked for voltage at the gas valve and through the temperature selector and they are not getting power. What should I be looking for and where would these safety thermostats be located so I can check voltage or continuity.
 
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Old 03-21-20, 10:22 PM
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Welcome to the forums.

Look on the service door for a wiring diagram. It will show you all the safety switches.
Do you have a powered vent damper ?
If yes..... try manually setting it to damper open on the damper itself.
 
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Old 03-22-20, 05:48 AM
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Hi, there must be a flame sensor there to prove that the pilot is lite, is it clean and sensing the flame? Post a pic of what you have there.
Geo
 
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Old 03-22-20, 11:03 AM
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I believe with his boiler there is a thermocouple to keep the pilot lit and the main gas valve active. The main gas valve is opened with 24v. There would not be a flame sensor.

There are several editions of the HC-100 boiler. The older ones had standing pilots and the newer ones had an intermittent ignition pilot. It would be helpful to know what your exact model number is.
 
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Old 03-22-20, 12:48 PM
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According to your post you hav a standing pilot. Don't know if you have a book but maybe this might help, especially page 15 which is where your safety switches are located.


https://www.manualslib.com/manual/90...page=22#manual
 
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Old 03-23-20, 07:59 PM
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Thank you all for your quick responses.

My boiler is pretty old, I would guess about 30+ years old. I don't see any service doors that would have a manual or wire diagram hidden behind it. The boiler is tucked into a tight closet and I had to climb to get to the bak side where the pump is and didn't see any doors there either.

Yes this boiler has a standing pilot and I had to change the thermocouple and gas valve a couple of years ago. Its been years since I have worked on appliances that operate with a standing pilot, but if the pilot is lit then the sensors should be operating properly.

spott, the manual you attached is the only one I could find and it is for a new model without a standing pilot and thermostats on the flue.

The model tag only says it is an HC-100, serial number is OX-22810
I have attached a picture of the gas valve and the pilot. is there something else beside the thermocouple that senses the flame to allow power to the gas valve when the thermostat in the house calls for heat?

jeff
 
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Old 03-24-20, 11:50 AM
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You changed the valve. Is it a 24vAC valve ?

The thermocouple only keeps the pilot lit. It has no further control over the main valve as that's opened with 24v.
The circuit should be easy to trace. You'll have a 24v transformer, the gas valve, possibly one safety sensor. You should be able to trace the thermostat wiring to find a safety sensor.

Post a pic of the inside valve and wiring.
 
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Old 03-24-20, 07:30 PM
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Pete,

I will post gas valve pic tomorrow, what is the inside valve you are asking about.
I believe the valve is 24v but it’s been a few years since I replaced that so I will double check.
in my picture of the standing pilot it appears that there are 2 wires running beside the thermocouple, would that be a safety thermostat. I am unable to remove the sides of the boiler because of the tight fit but it also doesn’t appear that it comes apart, any advice on this. If I could get the side(s) of I might be able to get further.

I post pic tomorrow with voltage

jeff
 
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Old 03-25-20, 05:50 AM
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Hi, this system did work at some point after you changed the gas valve, correct? if so I would assume it has the correct voltage, here is a pic of wiring for a basic standing pilot gas valve.
 
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Old 03-25-20, 10:41 AM
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I just want the gas valve. You had mentioned in a previous post that you had posted a picture but you hadn't. From that we can tell the pilot voltage.
 
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Old 04-04-20, 11:33 AM
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Pete,
here is the picture of the gas valve.

also Iíve attach a picture of the pressure gauge. Should the pressure be higher for it to work. Is there a way to check if there is water in the boiler?

the circulation pump is running

jeff
 
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Old 10-21-20, 08:06 PM
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I also have this boiler with a standing pilot. HC-100 - looks exactly the same. The pilot is lit; the thermostat sends / activates when it should; gas actually comes out (you can smell it), but the pilot won't light the gas. What is likely to be the issue? It worked a couple days ago; stopped - and then worked again for a day - and now won't ignite at all. Thank you - Brian
 
 

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