After 2 hours of playing around and swapping pumps, I figured this out
last night. My plumber had put a mixing valve in between the low loss
header and the radiant controls. I guess this isn't usually a problem,
but for some strange reason my mixing valve isn't working right...
when I shut it off, I now get full flow at all my 6 manifolds. With it
on, I get almost no flow. Weirdest thing - plumber and my radiant
designers can't figure it out, but the valve is coming out ASAP.
Tom - not sure about your system, my radiant designers did all the heat
loss calculations for my house and tell me I'm supossed to be able to
run this system at 90-95 degrees. Obviously, if I'm not getting enough
flow to the manifolds, the water isn't moving fast enough thru the
system, and the system doesn't heat up as quickly (if at all)...
especially where I'm doing a cold start when it's 20 degrees outside.
It was losing most/all of it heat just running between the boiler and
the manifolds. Thus, my boiler was working overtime heating up water
to 90 degrees plus and we weren't getting this heat into my system - so
it was "wasted". To compensate, I had to crank the boiler up to
140-150 degrees, just so we could get some heat into the system. They
also tell me that under stable conditions, the drop from your supply
temp and return temp should be 15-20 degrees.... I was getting
something like 70 degrees drop and still not getting the house warm.
Now with proper flow, I should be able to run it at 95 degrees and
still heat my whole house (saving a lot of energy vs heating to 140).
Plus these boilers are [supposedly] designed to run these systems - it
has different settings depending on what kind of heating system you're
using - radiant, baseboard, etc.
I just cranked the boiler back down, but they tell me I should be able
to run the boiler at around 100 degrees, my supply lines should be
around 90 degrees and the return lines should be around 70-75 degrees.
We'll see. This is my first time with radiant, I've spent a lot of
money on it, i'm just hoping it works...
Anyone else have problems with these mixing valves?