I have the same boiler- will not reliably ignite or stay ignited


Old 01-16-14, 12:13 PM
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I have the same boiler- will not reliably ignite or stay ignited

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I have determined that it is not the thermostat. I have determined that it is not the thermocouple. I can manually make the boiler fire by lifting the plunger in the gas control valve (the black box to the right of the plunger valve that connects to the thermocouple wire) in the original post picture. I think the control valve needs to be replaced... but i am not certain what the copper wire coming out of the top of the box is for. From the postings here, it would appear that is the aqua stat or sensing bulb you all are referring to... i'm just not sure how that would connect to the new control box. I found this response on a website

[NJT edit - which I've removed the link to. Per the rules (please read them) we shouldn't be posting links to other 'blogs' or 'self-help' websites here.]

It would seem removing all of the stuff prior to the valve, since the new control valve makes all the other valves moot, is pretty straight forward. I'm just not certain how to connect that sensor or whatever it is. Unfortunately, I didn't take a picture showing the copper line with the sensor. I put a red arrow in one of the pics indicating the boot where it connects to the control valve. This is clearer in the original post pictures.

Here are some pictures of the valve with the cover removed... it works by running the 24 volts to the two plates to the right of the plunger, the plates rise when heated and open the valve. My problem is the valve doesn't stay open or doesn't come up- presumably because it is getting stuck.

There is proper voltage going to the valve and I do not have a circulating pump...all the radiators are bled and when it does stay on, hot water circulates.
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Last edited by NJT; 01-16-14 at 04:14 PM.
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Old 01-16-14, 01:00 PM
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Moved to own thread with link of thread you posted to....

Welcome to the forums.... You will get a response shortly...
Old 01-16-14, 02:38 PM
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That gas valve is a real antique. I would replace it on general principles.
Old 01-16-14, 07:54 PM
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I agree. I'm up for replacing the valve, I just don't know how that copper tube running out of the top of the valve going to whatever sensor that is would connect to the new valve. Here is a video of the valve and the piece i'm talking about: https://drive.google.com/file/d/0B5uhG66FRpw-OVpoenVyUzJNNkU/edit?usp=sharing It was recommended somewhere to use a Honeywell Standard Pilot Gas Valve - 24V - 3/4" x 3/4" Inlet/Outlet Size SKU:V800A1591
Old 01-17-14, 06:25 AM
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From what I can see in the video it appears that the 'sensor' is in the boiler water and sensing it's temperature.

What I suspect is that it's some form of 'high limit'.

Probably what happens is that when the water reaches a high limit 'setpoint', that bulb over-rides the thermostat input to the valve and cuts off the gas to the burners.

If you do replace the valve, what you will probably have to do is also install some form of electronic high limit control, say an aquastat, in the location of the sensor. This will probably mean that the 'well' that sensor is in will have to be changed out so that you can mount the aquastat. This would require draining the system.

You mentioned a thermocouple 'wire' in your first post, where is that located?

Thermocouples are usually not 'wires', they are a 'capillary tube' similar to the tube that goes to the 'sensor'.

I'm quite sure that along with a new gas valve and some form of high limit control, that you would also need to install a different 'pilot flame assembly'.

It appears to be 'do-able' though... but will require a certain amount of 'engineering' to gitter done.
Old 01-17-14, 06:54 PM
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That's a real oldie and in MA is actually outlawed now because of the manual override. White Rogers made the same type of valve also that is no longer made.
That copper tube that you're concerned about will not be used. It's only part of that control.
You can use a Honeywell combination gas valve and remove everything in your gas train from the valve to the the burner. Turn off yourgas at the meter and replace the shutoff valve also with a regular gas shutoff..
You'll have to get a new pilot assembly that will operate from the new Honeywell.

If that cap tube is actually a limit as Trooper said you'll have to get a high limit like a Honeywell L4006 and put it in series.

That gas valve works when you lift the plunger because your bypassing the control circuit which is why it was outlawed.
When it doesn't come on have you tried jumping 2 terminals on the gas valve to see if that brings it on.
It is safe to do as long as you have a pilot. If it starts with a jump go back and check your controls down the line.
I believe you have more than just a t-stat in that circuit.

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