Need Advice

Ed Lentz_2

I think Weezbo might have something here. There does seem to be more humidity when this is happening. The outside walls are not the best when it comes to insulation. Brick outside with a 25 year old blown in insulation into the cavity, lath and plaster inside. Most of the outside walls are either cool or cold to the touch. I doubt that I have ice inside them, but for sure the insulation isn't the best.

Ed Lentz_2

Need Advice

I have a self installed staple up system. I have a Stadler-Viega basic controller. I am using a Stadler manifold with an injector station. I have 4 zones of stapleup pex with plates. The flooring is 60 yr old oak. I installed it 3 years ago. The boiler is a Crown . I live in Michigan. My design temp is at 0, max water temp is set at 145. I have no automatic valves on the injection station. There is an outdoor temp for reset. If I check the control I can see the water temp fluctuate. For the most part the system works just fine. Where I am perplexed is when the outside temp is about 25 - 40 degrees the house is cool. So, here's the question. Why is it that between those temperature the house is or percieves to be cooler? Just the nature of the beast where the differences in the outside and inside are perceptually different than at 0 degrees outside? Inquiring minds want to know. Thanks for a most informative board.

Mark Eatherton

Generally speaking...

When I have a home that is uncomfortably cool at a less than design condition, I suspect mega infiltration issues. But in your case, it cold be something else...

ME

fatty

a novice here: just want to take a shot at it before a pro rolls around.
to me it sounds like an issue with the outdoor reset functioning with a low-mass radiant heat system. if it is below 20, i could see the reset poking the temp up near max, and depending on the house, running the tubing hot for long stretches. but during the milder periods, you may see cooler, shorter runs. - with wood as your main thermal mass... the heat wont stick around. maybe some day by day tuning of your reset to bump up the design temp.
now ignore what i said!

Ed Lentz_2

The house is fairly tight, new windows last spring, new doors. I think fatty has something there tho, never thought about that. I can see the water temp hovering around 75 - 90 degrees at the troublesome temps. Higher when the outside temp is lower

Thanks

hot_rod

If you supply 145F at 0 design

how is your heating curve set? What temperature do you supply at 25 or 40 outside.

It may just need a little shift in the reset curve. Not much output from a staple up under that floor build up below 120F supply. The ends of the loops may be below 100F.

hot rod

Ed Lentz_2

I am only guessing here that I probably supply somewhere around 70 when the temp is around 40. The curve is in the basic control unit. I am assuming that a shift in the 0 degree setting will change everything.

CC.Rob_3

If...

you are saying that the house is cool in the 25-40F outdoor range, but fine in the <25F range, then you need to shift the curve up.

My guess as to why is as follows.

If the control is really a re-badged tekmar 256 or control of that series, it has a (limited) processor that appears to suffer a quantization error such that it does not follow a smooth curve. It functions fine in the band from ~44-20F, accummulates errors from ~20-15F that increase the supply temps at a rate double that specified by the curve, then settles down again at a new, upper curve at temps <~15F. See the attached, which is data from my 260.

So my guess is that if you are comfortable at <20-25F, then you are sitting on the upper "overshoot" part of the curve, and you need to move the core part of the curve upwards. This may impact your comfort and/or system performance at lower outdoor temps as the supply in that range is now several F higher than it used to be. You can mitigate this to some extent by setting the BOIL MAX lower. In my case, the overshoot kills the constant circulation because the house starts bouncing off the thermostats instead of heat input matching heat loss.

The processor also has that problem at temps >44F. In my case solar gain masks any deficiency here; this happens primarily in the shoulder seasons when we have more insolation, and the house coasts through most or all of the night anyway.

Weezbo

ventilation is what it sounds like.

not knowing the construction processes off hand in your area, what seems significant is that, this is somewhere in the range of where water freezes...

some places have various humidity hassles, that and opposition to quality control on the insulation and vapour barrier can create some startling revelations when one opens up a wall. i have seen some buildings where the only insulation is the ice buildup within the walls, these homes always seemed to have some proclivity to a mean cold streak at certain temps until.... the ice actually closed all the leaks and provided some real insulation.... in the way of ice in the walls ... i just thought i would put that thought out there to see if it might help ...

i might take to looking at plate interfaces etc. along rim joist, sloe plates and around electrical boxes..any ice build up in these areas would somewhat support what i am saying...