Help with Great Room heating strategy and the wrong thermostat

SuperJ

ok that probably rules out system pressure as a problem.

schreib

The design load of the Great Room is NOT likely correct because it failed to take into account the heat sinks from the 3 other walls being weight bearing walls and NO insulation under footings. However, I believe I DID place insulation on the pipes that penetrated these "wall areas" so they did not loose BTU's in the transit.

SuperJ

How confident are you in the 30% glycol mix? Too much glycol will make it tough to pump and I suspect make the manifold flow meters not accurate since the fluid is much more viscous.

schreib

It is 50% mix, pretty sure. May be a problem then? Is best way to drain out a bit and measure specific gravity to verify mix ratio?

SuperJ

Look up glycol pumping power multipliers, it definitely would be a factor.

SuperJ

Glycol is a double wammy, it has a lower specific heat factor and is much harder to pump. I think 50% glycol only has about 80% of the heat capacity of pure water, so to move the same amount of heat at the same temp delta you have flow 16% more volume. It takes more horsepower than water to flow the same volume.

Definitely a factor. 50% glycol is a lot of freeze protection.

schreib

It seems like a no brainer to drain out my fluid and dilute to 30%, at least. That may be enough to solve entire great room problem since it is only marginally off from meeting demand at low ODT's. assuming I am correct about it being at 50%. . . another odd setup condition from my not so great plumber.

Gordy

Why use any glycol unless this is a vacation home, or you are gone for weeks at a time, or you have frequent, and lengthy power outages?

schreib

I cannot answer that. Good question. It seems this is just "what is DONE" in Minnesota as a normal install. That was the general idea I got from my plumber. Then again, you certainly have gotten the picture about "my plumber" by now! ha! I can't believe he knows much. Still, my brother designed the system planning on 30%, I believe, and he is in Denver. Denver is MUCH milder than Minnesota. Why would Denver not use 100% H20? maybe there are redeeming factors such as reduced corrosion. By the way, I was recommended to buy Fernox(European product) to prevent corrosion by the Aquaheat Tech. Ever heard of that? Necessary to use this? (My water used to mix with the glycol was ultra filtered and went through a softener before mixing.) It appears you agree with at least diluting down to 30%. Can I use specific gravity as a means to test for actual ratio when I dilute down? Not a good way to know how many gallons are in the tubes so as to make a calculation.

Gordy

If you read the boiler manual there is specs on water quality to prolong its life, and other system components. Ph, hardness, TDS etc. Fernox is a great product to achieve this. Water quality should be monitored, and maintained periodically.

With concrete slab radiant there is a lot of mass to cool down in the event of a power outage, deep set backs are not recommended any way for obvious reasons unless extensive vacancy is on the horizon.

I think the glycol is a lot of the issue in your case as @SuperJ pointed out. However you deffinetly have a low flow condition, or a high heat loss area in some of those higher delta loops.

schreib

Thanks Gordy.
I will read over the manual more fully on water treatment.
I also now plan to thin down the concentration, for now, goal is 20 to 30% and have whoever does this adjust fluid for Ph, etc and add Fernox. (Thanks for the added comment on that.)
Decreasing the viscosity and increasing flow a bit with the lower concentration will both work to increase heat transfer in all areas. I will only consider adding a pump as last resort anyway as the Great Rm zone is just "marginal" for keeping the room in comfort control. There may be one more tweak available in the stat also: I believe I can offset the stat for what it "reads" as true temp. Between these I may be able to move the zone into being OK.

NOTE: with only the Great room in demand system was pumping 2.4 GPM into the 2 loops per flowmeters. Room is about 380 sq ft.

neilc

schreib said:

No have not used the FLIR to asses the great room windows etc.
However, I have top of the line Marvin windows and the house blows 1.0 on the blower door test. VERY tight house even with the big fireplace.

wait, we're chasing a cold room? a cold great room, with a big fire place?
When the blower door blew the 1.0, I assume they sealed the fireplace ?
and it's operational now?
with some sort of damper system? which might get closed when not in use?
Where is make up air coming from ?
I'll assume HRV, but with fire place firing, you're pulling in more than your tempering(?)
or is fire place sealed combustion?
I hear fire place and think big chimney sucking heat up.
Do you feel a draft at door, or entry point, or if cracked a window?, or at face of fire place?
I would wonder what the blower door would do with the fire place open.

schreib

This thread is related to my attempts to FINE tune the boiler, not some major problem.
Your points are way off base:
-- I designed and built the house.
-- Fireplace is an Accucraft, dual side glass doors, tight seals
-- sealed combustion air feeds: foamed insulation around two 4" ducts; at entry to home each has hard closing blast gate preventing ANY air flow in, in addition to having standard inlet dampers for each on fireplace itself, chimney damper on 10" dia. sealed, double walled, SS chimney 22 ft tall.
-- this is a closed system, period
-- NO drafts. The house blows 1.0 on blower door with all installed.
-- T'stat sensors slab temp, not room temp.

The room has all walls weight bearing and having thickened slab under 3, found. wall under window wall. No foam under walls, 3" foam under rest.
In addition to the 80,000 Btu/hr(possible) fireplace there is a 12,000 Btu/hr Mini-split head in this room. Not necessary for heating(but available) there primarily for summer cooling.

Gordy

I’m quite sure the heat loss is conductive to the slab from outside.

Is the thickened slab insulated from the outside?


I say that because in my neck of the woods for slab construction using frost walls the inside perimeter of the frost walls only need insulated by code. The slab is poured against the frost wall with no insulation break. These are non radiant slab homes I speak of. I can tell you the slab sucks the cold in like a sponge.

neilc

my bad,

schreib

no prob, Neilc!
Gordy: construction is this:
-- 56" found wall, with footing below on ext. wall
-- 2" x 24" wide styrofoam on outside of block, 1/8" thick PVC for foam-cover
-- planned for a 2nd 1.5" foam on interior of slab radiator but concrete contractor failed to install and I did not "catch" the error. I should have forced him to saw cut a 1.5" slot to make up for it. (First house build, I didn't. A mistake similar to choosing some not so great contractors.)
I figure you meant conducting heat FROM the slab TO the found wall. You are correct sergeant-major.
-- review of photos from construction shows 5 to 6" spacing of tubes near found wall, average out to 11" spacing, then up to about 14" in middle of Great room.
CONFESSION: Yesterday it got HOT out-- 50°F. I checked the Great room as it was still pumping it up with my 90°F slab set pt on t'stat. ROOM air temp: 78°F. So, uh, maybe 90°F is a bit high and I have more headroom here than I thought. My guess is that on the real cold days, especially night time TV time, the -zero temps make it still "feel" pretty cold as the window wall then becomes a black body heat sink, like effect in outer space. I will still thin out the PG though. I think this thread is probably done with. . . I got a lot of help from some great folks, learned a lot, and tweaked a lot to fine tune things. THANKS AGAIN GUYS!

Gordy

Well you're certainly right about the windows. Insulated window treatments will solve that.