Underperforming system in cold temps
Comments
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"As temp increased at manifold, flow deteriorated. When temp got back to 110 degrees at manifold flow was back to near nothing."
This has me thinking a thermostatic valve somewhere is closing.
"Turning off all loops at the manifold except for one resulted in approx .4GPM through that single loop even with it full open. Opening all loops results in negligible flow at all."
That has me thinking you're getting the same 0.4 GPM either way, but when it's spread over 17 loops it's too small to measure.
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“That has me thinking you're getting the same 0.4 GPM either way, but when it's spread over 17 loops it's too small to measure.”
Yes Sir I agree. Which brings me back to the primary and Taco three way valve. Not enough hot water is getting through.
I’m taking all of those taco valve filters off to rule that out as the primary issue.
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”Filling it shouldn't be a regular event once you have it running.”
That’s true…
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any time you fill, refill, purge the hydronic system, run it through a micron filter water filter. I have one of these with hose connections that I use on my purge cart. Fill the system through this to catch the well debris.
Although you don’t want that grit in your plumbing system either.
I had a 20” Big Blue filter on my well system. Changed the filter yearly.
But don’t irrigate through a filter🤨
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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"With a boiler rated at 137,500 BTU/hr, a back-of-the-envelope load calculation of 135,000 BTU/hr and a temperature at 76% of the delta of the design day, I'd expect the boiler to be running 76% of the time or so. Is that "near constantly"?
Yes sir I’d say that’s accurate…"
Let me make a generous assumption here that you are getting a delta T through the loops of 30 degrees F. Now — our dear old hydronic equation says that to move 137,000 BTUh through a system with a delta T of 30 you need to be moving about 9 gpm of water.
You quote 0.4 gpm.
You also state that the house is at least vaguely comfortable.
0.4 gpm of flow, even with a 30 F delta T, gives me 6,000 BTUh. No way is that keeping the house above freezing, never mind vaguely comfortable. Further, that boiler would only have to run about 3 minutes out of each hour to produce that heat, rather than perhaps 45 minutes out of each hour as your answer to the question implies.
Something does not compute.
I hate to even ask, but is it remotely possible that the flow meters aren't reading correctly?
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
”I hate to even ask, but is it remotely possible that the flow meters aren't reading correctly?”
It’s possible that there was small amount of flow through the lines , but not enough to register on the gauges. I agree there would be no way the house would be comfortable if there was zero flow through the lines at all.
I will say that when I said I closed all the loops except for one, that was just on the two manifolds I was standing in front of - so on that third manifold there were an additional 5 loops open , with those zones also calling for heat. So… some additional flow there most likely.
per @hot_rod recommendation,
I just finished removing the Taco valve filters completely and turned everything back on. Right now the supply water temp is still cool but I’m getting nearly .6gpm through every loop that’s open.
if after the water heats up and I’m getting 110 degrees to the manifold and I’m still getting that flow rate, I’ll be embarrassed - but glad that the problem is solved (contaminated water with an ultra fine filter). I’ve been convinced that this isn’t the only issue because I’ve never gotten design flow rates even immediately after cleaning the filters.I’m anxious to see if these flow rates remain high when this water temp increases.
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"I hate to even ask, but is it remotely possible that the flow meters aren't reading correctly?"
The burner is burning, the rooms aren't cold. It seems likely that the flow is in fact adequate.
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- Elusive problem!
- You have cleaned the Y strainer.
- You have flushed the air/dirt/hydraulic separator, and this flushed well.
- You have cleaned the filters on mixing valves.
- You are getting good flow when mixing valve on full cold.
Just to verify, the actuators are installed on taco mixing valves in correct orientation? (i cannot follow supply return completely behind the vents).
My deductive reasoning suggests an obstruction in your secondary loop, between hydraulic separator and the mixing valves. Is it possible those pipes are full of sand/grit. Can you flush out just the secondary loop using high pressure/flow?
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.6 gpm should be plenty to get the job done, unless you have some very high load areas.
Next step would be to bump supply temperature 5 or so degrees
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
”The burner is burning, the rooms aren't cold. It seems likely that the flow is in fact adequate.”
Not adequate enough to satisfy the call for heat for a single zone over the entire night, though.
The design calls for a rough average of .5gpm through the loops. The gauges were barely off the stops.
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”Just to verify, the actuators are installed on taco mixing valves in correct orientation? ”
Yes those are correct, thank you - I verified that and researched dip switch settings multiple times last year - good call to check those.
I think your thought was correct about the water quality and contamination between hydraulic sep and the taco valves
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.6 GPM per zone, I'd agree. But it's 17 zones. My understanding is he's seeing .6 for the whole system.
With a 20F delta, 137 kBTU/hr means 13.7 GPM for the system.
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Does that grundfos (43 watts in photo) also give a gpm estimate? What does it show for gpm when mixing valve is on full hot? And on full cold? Does this supply one of the manifolds in question?
How accurate do you all think the gpm estimate on that circulator is?
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My point exactly. The boiler is running. That means that heat is being input. The boiler is not reaching extreme temperatures. That means that the heat is going somewhere. Where? And how is it getting there? Even if we allow 0.6 gpm for the whole system, that' still only 6000 BTUh out of the 130,000 BTUh the boiler is putting out.
As I said, this just doesn't compute. Sorry.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
Fellas, as of right now it appears that the problem is solved. I’m embarrassed about it - I knew the filters would get partially blocked, but I never suspected it was the main issue based on having the same problem so quickly after cleaning the filters. Maybe the filters themselves are too restrictive…
That being said, since the system was installed I’ve never seen temps over 100 at the manifold with .6gpm being allowed to flow through every loop.
With a partially clogged filter I was getting hot temps at the manifold, but it seems apparent that I wasn’t getting enough volume of hot water through the filters for the pump to push through each loop. This explains why when I manually adjusted the valve to allow more cold return water to the pump, I’d see much improved flow at the manifold.
Hopefully this water isn’t so bad that it will damage the components. I think I’ll hope that it will be okay for awhile until I have time to flush, clean it out with a hydronic cleaner, fill with clean water (not from the well) and add Fernox F1.
If any of you are ever driving through northern Illinois north of Rockford along the Wisconsin border, drinks are on me. Thank you all for your help this forum is a great resource.
-Dan
Sukhoi29SU @ gmail
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”.6 GPM per zone, I'd agree. But it's 17 zones. My understanding is he's seeing .6 for the whole system.”
No, no. Right now after removing the filters I’m seeing .6GPM at each loop. Prior to removing the filters I was barely indicating any flow at each loop.
9 zones total. 27 loops. 10 of those loops for garage, so correct - 17 loops for the house.
17 loops and 7 zones for the house
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Please let us know how the system heats with the flow back to design levels.
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Bburd1 -
“Does that grundfos (43 watts in photo) also give a gpm estimate? What does it show for gpm when mixing valve is on full hot? And on full cold? Does this supply one of the manifolds in question?”
yes sir it does, however that is the pump that pushes water to the two garage floors.The black pump above it is the one for the house - and that does not show GPM. The designer told me to set it at auto adapt however I never did that because I was experiencing flow issues I always have it set to max
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Now you need to figure out where the goop on the filters was coming from!
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England1 -
Since you are now getting flow to the secondary loop, you can turn down your boiler. There is no need for it to make water any hotter than what the floor heat needs. Free fuel savings.
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after a couple hours of sufficient flow through the floors I can finally acknowledge that this system might be worth all the $ I put into it. A few of the zones have already reached the temp set on the thermostat and aren’t calling for heat anymore. I suspect all of them will reach that soon as the temp is 110 at the manifold now, and still holding flow. Cleaning out the system with a proper cleaner and adding proper water with ph treatment will be the next step, followed by hooking up the wood gasification boiler once Switzer delivers it.
next question : do I dare dial back the flow rates at the manifolds on the zones that are spec’d for less? For instance I see the lower great room is only spec’d for a little less than .3GPM and it’s currently getting .6GPM? Or is the higher flow rate generally better and more efficient if I can get it?
@Jamie Hall I wanted to also say that your thoughts were correct - as I was walking through the house checking thermostats I noticed that the kids had turned back in the air heat pump in the lower level. So last night although I might have been getting little and insufficient flow through the pex tubes , the kids were supplementing some heat in the lower level with the heat pump and air. That would explain why the temperatures didn’t drop more in the house overnight. It wasn’t enough to get the temperatures up to kick off the radiant call for heat, but I’m sure it helped in the overall…
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Yes, dial back the flow where it's specified, you can always go back up if needed. The lower the flow, the lower the return temps, which is generally more efficient. Also, you can probably dial down the boiler temp as Kaos suggested, especially if everything warmed up this quickly.
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I dialed back the boiler to just above design temp as there is a long way to travel to some of the manifolds and I will expect some heat loss as it travels to manifolds.
I’ll dial the flow rates back to design specs which is something I was fearing I’d never have to worry about.
Thank all of you guys for the time and advice/input
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i thought the radiant temperature was being modulated by the Taco 3 way valve on ODR?
With adequate flow now, I would dial in those valves to give you near constant circulation and lowest SWT
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
”i thought the radiant temperature was being modulated by the Taco 3 way valve on ODR?”
yes that’s true, dip switch settings allow for a max of 130 degree water. I don’t know what I was thinking with heat loss between boiler and manifold- the max temp leaving those valves is 130 so I can expect a bit less than that at manifold - so I can probably dial the boiler back to that 130 temp.
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I thought bayou had some high temperature zones on the boiler also?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
”I thought bayou had some high temperature zones on the boiler also?”
Not following, sorry.
are you saying that you thought there were zones in the system directly off the boiler that would require a higher temp than 120?
one of those taco three way valves controls the temp to the house zones. The other taco three way controls the temp to the two garage floors.
he has the house design temp set at 120, and the garage floors design temp at 100, however the dip switch settings allow for either 130 or 110. I could probably adjust the garage taco valve dip switch settings to allow for a max of 110 degree water vs 130.0 -
I see, the extra connections are to tie in the wood boiler, not a high temperature zone?
So you do need those 3 way mix valves in the system once the wood boiler supplies 180 temperature.
Correct, the garage slab should not need 130 SWT, ever.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
is this the wood boiler you are getting?
If it is 800 gallons, you will need a substantial expansion tank in the system. I believe that is a closed pressurized boiler?
So a 90 gallon diaphragm type or about a 175 gallon plain steel compression tank
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
“is this the wood boiler you are getting?”
Yes Sir, that is it - only I’m getting a 1750 gal, not listed on his website. It takes up some real estate but I’ve read great things about his boilers.
I’ve considered putting a heat exchanger between the wood boiler and the radiant system - I’m not sure how much efficiency I’ll lose, however.
This boiler does batch burns and I’m hoping I have to fire up the boiler once every couple of days for both DHW and heating. Once every day on cold days.
“So a 90 gallon diaphragm type or about a 175 gallon plain steel compression tank”
I did purchase an extra expansion tank not listed in the plans, however, I don’t think I got anything that big… I’ll have to check what I ended up getting after someone recommended me one awhile back.Picture is of a smaller model off of his website.
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“I see, the extra connections are to tie in the wood boiler, not a high temperature zone?”
Yes, those connections to the top left will run to the wood boiler on the opposite corner of the room.
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Let's see. 1750 gallons. You can probably safely heat it to about 200F and get usable heat down to 110F. So 1750 gallons times 8.3 pounds per gallon times 90F equals 1,307,250 BTU. So about ten hours worth of boiler output.
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for 1750 gallons you need a 305 gallon compression tank, or a bladder tank of 147 gallons, which weighs about 500 lbs empty!
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0
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