shop is warmer than thermostat setting without the pump running. and yes it's cold outside

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.

sdviking

New Member
Oct 11, 2019
10
South Dakota
Its 30 degrees outside, I have a central boiler classic edge that has run without problems the past three years. We just fired up the boiler and th shop thermostat is set at 52 yet the shop is currently warmed to 68 degrees. The Pump inside the shop is on but isn't running so the thermostat must be working. Could the thermostatic valve be allowing hot water to run straight through the mixing valve and through the pump heating the floor? SD Viking
 
Would need more details on how it's piped. Are there two pumps? Primary/ secondary?
 
On the wood burner boiler unit I have two pumps one that runs to the house and one that goes to the shop. So two different insulated lines that go to two different buildings. Once the pipes come into the shop they go to a thermostatic valve then off to a hot water temperature control valves then to the building pump then to the manifold and off to the shop floor.
1570898346095.png
 
On the wood burner boiler unit I have two pumps one that runs to the house and one that goes to the shop. So two different insulated lines that go to two different buildings. Once the pipes come into the shop they go to a thermostatic valve then off to a hot water temperature control valves then to the building pump then to the manifold and off to the shop floor. View attachment 249090
1570898420631.png
 
system has worked with now issues over the past two years. This year I did have to replace the pump at the boiler that supplies heated water to the shop due to it seizing up.
 
Woke up this morning and now the wood burner is steaming out the vent cap. Fire in the wood box is not burning hot in fact there are just a few ambers yet the temp gauge says 206. The fuse operated air intake is shut and there is nothing keeping it from closing fully, fuse is ok but still have too hot of water in the tank. All Pumps appear to be working. outside air temp is 30 and ground is not frozen even though its covered in snow. Thermostat on wood burner unit is set at 185 like the owners manual says. We do have strong winds so maybe there was a down draft that kept the fire burning longer than normal. First time I have had it steam through the boiler vent cap. Oh and here is the picture of the plumbing at the wood burner boiler.
1570900401749.png
 
Last edited:
Woke up this morning and now the wood burner is steaming out the vent cap. Fire in the wood box is not burning hot in fact there are just a few ambers yet the temp gauge says 206. The fuse operated air intake is shut and there is nothing keeping it from closing fully, fuse is ok but still have too hot of water in the tank. All Pumps appear to be working. outside air temp is 30 and ground is not frozen even though its covered in snow. Thermostat on wood burner unit is set at 185 like the owners manual says. We do have strong winds so maybe there was a down draft that kept the fire burning longer than normal. First time I have had it steam through the boiler vent cap. Oh and here is the picture of the plumbing at the wood burner boiler.View attachment 249092
Ok bleed the lines in the shop and now it seems like things are working normal. Lowered thermostat at the wood burner boiler to 175 and it hasn't over heated in the first reheating of the boiler. SO I am guessing I had air issues in the shop lines which was causing my issues.
 
Ok bleed the lines in the shop and now it seems like things are working normal. Lowered thermostat at the wood burner boiler to 175 and it hasn't over heated in the first reheating of the boiler. SO I am guessing I had air issues in the shop lines which was causing my issues.

Still having issues. Shop is running a temp of 66 yet thermostat is set at 55. Seems like the pump at the boiler is pushing the hot water completely through the system without any resistance. The other issue is that the wood burner boiler is still over heating the water. I now have the boiler thermostat set at 170 and it still heats water up into the 190s. The rope seal looks in good shape and the air intake flapper appears to be closing completely without obstruction. I think one of those two is still leaking air..
 
There has to be an air leak in the stove somewhere to keep heating up.
By the pictures it appears like the pump on the furnace is running continuously, with the one in the shop starting and stopping? If the supply manifold going in the floor stays hot you've got some kind of ghost flow going on (stove pump pushing into the floor).
 
I don't see a heat exchanger either. I'm thinking the main pump on the outdoor furnace is pushing through the mixing valve and putting flow into the floor? Why did it work before? I've got to be missing something.
 
I don't see a heat exchanger either. I'm thinking the main pump on the outdoor furnace is pushing through the mixing valve and putting flow into the floor? Why did it work before? I've got to be missing something.

What's the red thing?
 
What's the red thing?
The system has worked without issues for two years. This is the beginning of the third year and the first time I have had any issues. I have never had to bleed the air from the system during start up before. I have monitored the systems PH level like the factory says. Unless there is a little rust in the system now that it has aged. But this shouldn't happen if PH has been maintained.

I do plan on purchasing a new rope seal for the front door and replace it. Just in case air is leaking in which would allow the boiler to go past shut off temp. Hope to replace seal in the next two days.
 
I would get the boiler temp issue under control first then see if you still have the overheating shop issue. Sounds like the system is seeing hotter water than it is used to which is throwing something off in the way the system usually works.
 
That's where my mind was going. It appears to me that the way it's plumbed there is a possibility that the pump on the outdoor boiler could out pressure on the mixing valve and not have equal pressure at the hot and cold inlets on it. This could keep it from maintaining a set temp going into the floor.
?