Central Boiler OWB Overheat/Not Circulating Troubleshooting Help

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SunHeart

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Dec 29, 2021
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Location
Central NY
Hi All,

I have a Central Boiler Classic, installed in '98 by the previous owner here. It heats two separate spaces, a 1200 sq foot apartment and our main house, with 2 lines coming off of it with 2 different pumps, 1 for each space. Last night I noticed the temp in the house dropping, and the usually hot air from the furnace getting cool.

Went out to check the furnace and realized the fire was smoldering, and it seemed that it had 'shut itself down' a while ago as there was quite a bit of wood for the time. The damper was closed and did not want to open. I then noticed that there is steam coming out of the top of the boiler. It seems that the water in there is hot enough!

But isn't circulating. So I start to check the lines, underneath the boiler and in the different spaces. There are all relatively cool.

Both pumps seem to be working. I can shut them off from electricity and feel in the lines the stopping and then starting again of flowing water, and they sound the same. The previous owner mentioned that he replaced one of them (forgot which on) last year and that I should have one on hand in case the other needs it this year. I did have one. It seems like the one underneath the boiler that goes to the upper apartment was older, so I gave replacing it a try. No change.

The manifold to split the line into two right off the boiler is really hot. Right after that is the pump the goes up to the apartment. After the pump, the water line is a little warm, but should be just as hot I think, and isn't.

The other pump is in the basement of the house. The lines on either side of it are the same temp, kind of warmish, when they should be hot. The return lines are the same temp. The water lines under the boiler for this portion are the same temp, warmish (not cold but should be hot!)

Not sure where else to look to troubleshoot. It seems like a pretty simple set up. Why is it not cycling the hot water? Is there something else to check? The aquastat has never read a temperature since I moved in last year and I have just went with where it was set, and it has seemed to function well until now. Could that have something to do with this issue?

It seems that the water is constantly circulating, and the aquastat mainly controls the air damper, and has nothing to do with choosing when and how to circulate the water, correct?

Thanks for any pointers!
 
How is the water level? Is it possible that there is a flow restriction? It would almost have to be at the manifold with 2 nearly separate circuits as you've described. It sounds like the water at the OWB is up to temperature but that would be nice to know.

The pumps generally do operate independently of the aquastat and circulate water regardless of temperature.
 
I filled the water level a couple months ago. My water gauge is hard to read, I should replace it. When I added water it overflowed. It has been operating fine since.

I believe the water is at temp because the pressure relief valve is letting off lots of steam! My aquastat doesn't display a temp. I'm hoping to make it another month when I have a new system being installed.

Re: flow restriction, it seems like it would have to be at or before the manifold as you mention.It's strange that neither of the pumps is getting hot water through the lines. How would I check for a flow restriction and then relieve it?
 
I would triple check water level. Seems to me Central had an autofill valve that occasionally doesn't work so that may be it.

I'm not familiar with the Central plumbing or what yours looks like without pics. You may have to open up a fitting to check for flow.

Anything else common to the system? Low voltage at pumps, valve turned off, or similar? Heat exchangers in furnaces could be clogged, but seems unlikely both at once - assuming you have forced air for both.
 
Great at a distance diagnosis H-Ranch!

Seems like it was the water level. I added water and after a few minutes the damper opened up and the fire got going. All lines are nice and hot now! Thanks!

A functioning water level gauge would have saved a lot of time! Time to get one installed.

And also seems there is a significant water leak to have lost that much water in a couple months...

When I fill it up with water, it actually overflows from the roofline. I have also seen it dripping from the roofline at times. This isn't normal, is it?
 
As you said, there is not much to the system, so yeah, check the simple stuff first. My next diagnostic check is usually by cost... that does not always get you to the right answer quickly though!

There may be a leak somewhere, but a couple of months is not a terrible thing. Has it boiled over recently (damper stuck open or such)? Been serviced of late? Probably lost some water when you replaced pump as well. A faulty autofill valve/float may be stuck open or closed accounting for the wrong water level in either direction.
 
I am very happy to hear you found the issue. I struggles with the same issue last year on my Woodmaster OWB. My main issue that was causing the excessive water usage was that the door gasket and fan rubber flap was worn just enough that it allowed just enough air in to make the boiler steam. Visually they did not look bad. Rebuilt all the doors and replaced gastkets, no issues so far this year (knock on wood). Been running since Nov. 14th and water has not dropped.


Sent from my iPhone using Tapatalk
 
Hi All,

I have a Central Boiler Classic, installed in '98 by the previous owner here. It heats two separate spaces, a 1200 sq foot apartment and our main house, with 2 lines coming off of it with 2 different pumps, 1 for each space. Last night I noticed the temp in the house dropping, and the usually hot air from the furnace getting cool.

Went out to check the furnace and realized the fire was smoldering, and it seemed that it had 'shut itself down' a while ago as there was quite a bit of wood for the time. The damper was closed and did not want to open. I then noticed that there is steam coming out of the top of the boiler. It seems that the water in there is hot enough!

But isn't circulating. So I start to check the lines, underneath the boiler and in the different spaces. There are all relatively cool.

Both pumps seem to be working. I can shut them off from electricity and feel in the lines the stopping and then starting again of flowing water, and they sound the same. The previous owner mentioned that he replaced one of them (forgot which on) last year and that I should have one on hand in case the other needs it this year. I did have one. It seems like the one underneath the boiler that goes to the upper apartment was older, so I gave replacing it a try. No change.

The manifold to split the line into two right off the boiler is really hot. Right after that is the pump the goes up to the apartment. After the pump, the water line is a little warm, but should be just as hot I think, and isn't.

The other pump is in the basement of the house. The lines on either side of it are the same temp, kind of warmish, when they should be hot. The return lines are the same temp. The water lines under the boiler for this portion are the same temp, warmish (not cold but should be hot!)

Not sure where else to look to troubleshoot. It seems like a pretty simple set up. Why is it not cycling the hot water? Is there something else to check? The aquastat has never read a temperature since I moved in last year and I have just went with where it was set, and it has seemed to function well until now. Could that have something to do with this issue?

It seems that the water is constantly circulating, and the aquastat mainly controls the air damper, and has nothing to do with choosing when and how to circulate the water, correct?

Thanks for any pointers!
I know if my boiler overhe
Hi All,

I have a Central Boiler Classic, installed in '98 by the previous owner here. It heats two separate spaces, a 1200 sq foot apartment and our main house, with 2 lines coming off of it with 2 different pumps, 1 for each space. Last night I noticed the temp in the house dropping, and the usually hot air from the furnace getting cool.

Went out to check the furnace and realized the fire was smoldering, and it seemed that it had 'shut itself down' a while ago as there was quite a bit of wood for the time. The damper was closed and did not want to open. I then noticed that there is steam coming out of the top of the boiler. It seems that the water in there is hot enough!

But isn't circulating. So I start to check the lines, underneath the boiler and in the different spaces. There are all relatively cool.

Both pumps seem to be working. I can shut them off from electricity and feel in the lines the stopping and then starting again of flowing water, and they sound the same. The previous owner mentioned that he replaced one of them (forgot which on) last year and that I should have one on hand in case the other needs it this year. I did have one. It seems like the one underneath the boiler that goes to the upper apartment was older, so I gave replacing it a try. No change.

The manifold to split the line into two right off the boiler is really hot. Right after that is the pump the goes up to the apartment. After the pump, the water line is a little warm, but should be just as hot I think, and isn't.

The other pump is in the basement of the house. The lines on either side of it are the same temp, kind of warmish, when they should be hot. The return lines are the same temp. The water lines under the boiler for this portion are the same temp, warmish (not cold but should be hot!)

Not sure where else to look to troubleshoot. It seems like a pretty simple set up. Why is it not cycling the hot water? Is there something else to check? The aquastat has never read a temperature since I moved in last year and I have just went with where it was set, and it has seemed to function well until now. Could that have something to do with this issue?

It seems that the water is constantly circulating, and the aquastat mainly controls the air damper, and has nothing to do with choosing when and how to circulate the water, correct?

Thanks for any pointers!
I know if my CB 6048 overheats, it stops circulating and has steam coming out the top. I have had to take the control cover off on the boiler side, not the door and cool off the thermistor. A leaking gasket usually causes my overheating. I also keep extra an extra pump on hand and sloenoids for the air inlet as I have have to replace both.
 

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