I have an eichler with the heat in the floor. When the furnace was
replaced, I had 2 zones plumbed, one for the main house, and one for a
part of the house that didn't have heat installed.
I plumbed the second zone, using Slant/Fin, hooked it up, turned it
on, and poof! the heat works just fine. Until the first zone comes
on, then the second zone gets nothing. I'm not sure, but I think the
first zone even pulls cold water backwards through the second one,
because the second zone pipe turns cold quite quickly.
When the furnace was installed, both zones were run individually by
separate pumps of the same size. No zone valves were used. But that
pump wasn't strong enough to pump through the eichler floor, so the
heating guys put in a bigger pump. The second zone has a smaller pump
that works quite well when the first zone's not on.
I tried balancing the heat by adjusting the flow valves for the first
zone. This works, the second zone gets heat, but I can tell the
furnace is not working very hard, and the house doesn't come up to
I thought about hooking the zones up so only one can run at a time,
but this won't work because the second zone is so small that it only
drops the water temp by 10 or so degrees, and the furnace doesn't run
until the water temp drops by 15 degrees, so the house is cold, and
the furnace is not running.
Any ideas? I'm having the heating contractor come back and look at it
next week but would appreciate any feedback.