DHW tankless coil in a oil fired steam boiler - cold feed heating up

busdoctor · December 4

I have an oil fired steam boiler with a tankless coil. The plumbing does include a mixing valve.

My problem is the cold water feed becomes very hot up to a good 15' away from the boiler and warm water will come from the cold tap.

I'm going to test that the mixing valve isn't letting hot water into the cold tomorrow. If that isn't the problem any suggestions on how the prevent the cold water from being heated from conduction?

This happens with the boiler running for heat and no domestic being used.

Someone did a repair on the hot and cold near the boiler and the pex softens up like a garden hose in the sun. Replacing that with copper tomorrow.

Thanks

Ron

Larry Weingarten · December 4

Hi, Heat traveling fifteen feet sounds like convection, not just conduction. If so, a spring check valve in the line could do a lot to prevent this.

Yours, Larry

mattmia2 · December 4

https://forum.heatinghelp.com/discussion/comment/1875377#Comment_1875377

but if you add a check valve then you need to account for expansion of the water as it is heated. A loop of pipe forming a heat trap may also solve the problem.

or there is a cross connection between hot and cold at some fixture.

Larry Weingarten · December 5

Hi @mattmia2 , Agreed. A heat trap can work as long as there isn't much of a rise in the piping nearby. @busdoctor , it would be nice to see a photo or two of the setup, if possible. I'm pretty sure we wouldn't need to guess so much about solutions. 😁

Yours, Larry

DHW tankless coil in a oil fired steam boiler - cold feed heating up

Comments

Categories