Heat seeping up thru return lines

[larryjbjr]

Ok, first of all thanks to all for all the help I've received on this site already!

Now, I've a new problem.

House is a two story farm house, over 100 years old, on a full basement.

I have a Johnson Little John OWB outside, and an LP boiler inside feeding several cast iron rads and a couple baseboard heaters, and a kickspace heater as well. I just got my OWB hooked up the other day. What I did was run lines from the OWB to the basement and thru a 40 plate heat exchanger. Then I took the main return line going back to the LP boiler and ran it thru the other side of the 40 plate heat exchanger. I then turned the aquastat for the LP furnace down as far as it would go, 140 deg, so that the LP burner would only kick on if the water from the OWB gets below that.

So far everything is working well, though the inside furnace hasn't had to run at all other than starting it up just to test everything. That's because the radiator upstairs and one of the rads on the ground floor are staying warm all the time. Best I can tell is that the heat is seeping up thru the return lines and heating the rads, because both supply lines are cold while both return lines are warm. Also, the rad upstairs is staying much warmer than the one on the ground floor.

Now, that will be nice in the winter but right now not so nice. It's keeping my upstairs nearly 80 degs!

So, how to I stop this from happening?

 

[TCaldwell]

How many heating zones do you have, are both rads on the same zone, you might need a flow check on the return line

 

[larryjbjr]

Two zones. Zoned by pumps.

Rads are on separate zones.

Flow check?

 

[peakbagger]

You are getting thermo syphoning, warm water rises up to your baseboards through the pipes, the water in the radiators cools down and and sinks to the basement.No need for a pump. A flow check is a check valve in the line that has a weighted plug, its stays closed unless the circclator pump is running. Its usually near the boiler and has a screw in it so that it can be forced open or closed. They sometimes stick open.

The same thing can happen with hot water heaters where the hot water heater in a basement is heating a kitchen sink of a bathroom at a higher level of the house .In this case there can be thermal traps installed on the outlet lines or there can be loops installed on the piping to prevent the heat from naturally rising.

 

[leon]

You have circulators not pumps. With the baseboard you can put old blankets or old towels under the baseboard to keep the heat from being allowed to escape. With radiators you can simply shut the valves off or partially close them.

So you can do this or install flow checks if the circulators do not have them. Are your circulator's outside or in the basement of the home? It is better to have them in the basement to prevent them from freezing and breaking from expansion.

 

[larryjbjr]

The circulators are all located in the basement.

For now I’ve shut the valve for the upstairs rad. The one on the ground floor isn’t getting near as warm so I’ll leave it for now.

 

[Bad LP]

I had the same thing going on many years ago from my oil fired boiler. It was a nightmare of a system the way it was done. The original installer installed the circs on the returns so we added zone valves to the supplies to prevent any possible flow.

3 or so years ago we removed both manifolds and repiped pumping the supply side using Grundfos pumps with check valves for each zone and removing the zone valves.

 

[salecker]

I have cast iron rads through out my house.
I have one Grundfos Alpha circulator on my manifold in the basement, and TRV's on each zone of Rads.Most have 2 smaller rads and i have two big rads with their own TRV.I have one unit heater in the basement,i like to have the air moving around because we don't spend much time down there anymore.we lived in the basement for 14 yrs while i built a business then the rest of our house.
I have had zero issues with this system,i even added the 2 big rads last year without any issues.
Thomas

 

[NateB]

A check valve is the hands free answer to your problem, but just closing the valve a little in the warmer months should correct the issue. They do sell circulators with check valves build in.