Many years of issues with radiant floor heat.
Comments
-
Sounds like the great room is the great challenge. A room with a high heat load, in all honesty, is tough to heat even with a properly install floor radiant.
The easiest first attempt is crank the boiler up 10°. IF the tube is rated at 150 you are still safe.
Plan B throw in a small hydronic kick space heater somewhere under a cabinet. Adding 10- 12,000 BTU/ hr may solve it If a temperature boost doesn't.d.b
The thing with PE or PEX tube is the tube can run higher temperatures as the pressure is lowered. The testing is done at 73°.
So on this graph you see where the 150 crosses the temperature slope at 73°F.
Some posts back @DCContrarian posted this. I know it is not the correct vintage data. But a sheet like this for the tube you have may be identical? At least in the performance spec.
I suspect they made a change in suppliers along the way.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
Reply to @Jamie Hall
Lots of chatter.
First. Changing the pressure the system operates at will have absolutely no effect on the heat distribution at all. None. Zip. Nada. 20 psig is ample, and it would probably be just fine at 15 psig. I do not think anyone here was suggesting a pressure change, I think it had to do with my tubing's rating and previously having an open system running at 40-50 PSI and now its closed and running around 15 PSI
Fourth. The bad news. The floor arrangement, as installed, simply isn't capable of pumping enough heat into the room to keep it warm. Furthermore, spoiler alert, raising the input temperature enough to do so will damage that flooring as well as giving you a hot foot. A wood floor should not be run over 80 F, so even if you had piping which made the floor temperature reasonably even you couldn't get more than 20 BTUh per square foot out of the floor, regardless of input temperature. So raising your input water temperature isn't going to hellp. I will double-check today, once I find my IR gun, but I think the floor is around 76*F where the tubing is and cooler in the spaces in between the tubing runs. I am nearly certain raising the boiler temp will increase the BTU output of the floor. Once I'm certain the tubing will take it, I will raise the temp and hit the 80*F floor temp.
You have a design which simply won't work. They happen. Yes and in hind sight/23 years later I would "knowing what I do now" gone a different direction with my heating system, but I have a lot invested with time & money and will try to get it to work as well as possible.
The solution, though, isn't rocket science either: as has been suggested, additional emitters in that space. I'd suggest panel radiators. They aren't unattractive, they don't take up much floor space, they work well with the water temperatures you are working with, you can get beneath the floor to install the piping… What's not to like? I could write a book on the what's not to like. LOL. On adding additional emitters, I have 3/4" supply and return lines to the Great Room. Can I use that as my supply feed and parallel into those line to feed additional emitters? My guess is yes, but.
0 -
"I have 3/4" supply and return lines to the Great Room. Can I use that as my supply feed and parallel into those line to feed additional emitters?"
Yes. The 3/4" pipe should be good for at least 4GPM, at a 20F delta that's 40,000 BTU/hr, that's a lot of heat. The "but": you may find that having a parallel path cuts the flow to the floor, which would reduce the output further. But your total output is always going to be greater.
"I think the floor is around 76F where the tubing is and cooler in the spaces in between the tubing runs. I am nearly certain raising the boiler temp will increase the BTU output of the floor. Once I'm certain the tubing will take it, I will raise the temp and hit the 80F floor temp." I agree with this. I also disagree with the sentiment that wood can't take more than 80F, in a house in summer there are lots of places where wood is exposed to much higher temperatures.
Another thought on the pressure/temperature rating: First, I agree that the 150F limit was for when you had an open loop with house water pressure, with just hydronic pressure you can go hotter. Second, even if you do exceed the rated temperature, you're not going to ruin the tubing. Wherever the weakest spot is might leak, but when you dial the temperature back down the tubing will go back to its original strength. Leaks are no fun but raising the temperature isn't a huge risk.
1 -
You have a design which simply won't work. They happen. This. @Jamie Hall
Miss Hall's School service mechanic, greenhouse manager, teacher, dog walker and designated driver
0 -
The warmest point in your system will be where the transfer plate connects to the floor. If you have plywood or one of the waferboard type products as a floor sheathing, 140F- 150 is not and issue.
I have run rubber tube staple up systems up to 160F, trying to improve the output. This seems like a simple 1 minute adjustment? What do you have to lose?
The one issue we had with a super high tube temperature on an old retrofit job was the asphalt impregnated felt paper (aka tar paper) under the old strip hardwood started to off-gas. I remember the RPA seminars cautioning against high sub-floor temperature with certain carped pads also.
All the collected data so far indicates 150 is not an issue for PE. If it is a hydronic tube, 180 may be possible.
If you do want to add supplemental heat, a small fan convector, 1 gpm flow, 19 x 12" will give you a lot of bang for the size and price.
At 140°F you would need a $$ panel radiator about 2' tall 6-1/2' long to get the same amount of btu.
Output spec attached for typical products.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
4 -
Just add some radiation or baseboard as @Jamie Hall said. If you look back I posted the same answer back on 1/14.
You have lived with the system long enough. There is no Majic wand that is going to fix this.
1 -
I know the results of all of this discussion is, I need more BTU's in my Great Room, I got that….. But because I'm not going to be able to whip out some additional emitters/btu's in the middle of winter, my current/redefined goal is to tweak what's in place and possibly add few BTU's in the process.
0 -
I went through all of my documents from my initial purchase in 2002 and found the sales sheets stating the tubing is Poly PXC "Parlty crosslinked polyethylene tubing" printed spec says 150*F at 50 PSI
0 -
Well, the bad news is that it may not be oxygen barrier tubing… which isn't the end of the world, but it does mean that you can't use iron fittings or pumps.
Sigh.
I guess given all the above discussion and thoughts your best bet is going to be try running the floor hotter and making sure there is enough flow to keep the delta T down to 10 degrees if you can. That will make a difference. Enough? I have my doubts, but there's no harm to trying it — just don't run it so hot that the floor is uncomfortable to walk in bare feet.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
If it were me, I'd make sure the outdoor reset function is connected on your Laars Mascot, set it to 155° SWT on a 0° day, or whatever is a typical low temperature in your area. Find that data from the local weather station.
So it only runs 150° at the tube on the maybe 3-5% of the winter days that you are at the coldest temperature. And some years it may never run up to 155.
Several wins with this option, you may get the extra output you need, the system will run nice long cycles, and efficiency should be at the peak for that boiler, running condensing temperatures 80- 85% of the heating season.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
3 -
In 2002 we installed the same system in 2 different apartments. Same company. We have 2 pex per bay. Its stapled up with their metal plates. Came down couple of inches and installed some aluminum foil they supplied. Then insulation underneath. Apartment #1 has 5 loops with one circ pump. Did not keep it warm enough. Old house ~130 years old. .Walls had blown in insulation, good double paned windows. This is a first floor apt with occupied apartment above. Flooring 3/4 hardwood, subfloor 3/4 thick. Floors joists not 16 on center. When it got under 20 degrees it was cold in the apt. Installed a piece or 2 of baseboard heat in each room. And 2 stage thermostat set at 2 degrees difference. It solved the issue.
Apt # 2. House built 1935. 2 pex per bay. Exact same set up with total floor height. I think this is 6 loops. Good windows, walls insulated, same basement set up. Cannot get it over 67 on coldest days. Might do the 2 stage thermostat and baseboard. Oddly no tenant ever complained.
Both places are first floor with unfinished old basements underneath.
Both places had to crank the heat up in basement to around 150. In #2 some of the hardwood has dried out creating gaps. Not sure if installation people back in 2002 allowed the wood to acclimate to the room. But in both places when the heat was cranked up the gaps started appearing. Me, I would only do tile or laminant over radiant IF I were to do it again.
Both systems are not getting water directly from boiler. I have flat pack heat exchanger so the radiant water is is isolated from the boiler water. Its set at 10 psi and has a small exp tank.
My guess is you need to do 2 stage and add some baseboard in coldest area. If the runs are long I would consider a reversing valve switching every half hour.
I think that the tubing is 5/8 inch. It was a red / orange color.
Good luck.
1 -
This is what I will do. We typically see a few mornings a winter at or below 0. This week looks like one of them. Thanks @hot_rod for all the help.
As a side note for all following along, over all, three of the four zones have functioned well for 20+ years. 80-90% of the winter, the Great Room zone being discussed here has worked, its when it dips below 20 is when it begins to struggle.
This entire discussion has been valuable and I appreciate ALL of the input from everyone.0 -
If it is that infrequent, get an electric supplemental heater of some sort? Adding a few degrees to a 550 square foot room a few days a year for 8 or so hours should not be a big cost.
You mentioned a lot of glass, in the great room. do you have any sort of insulated shades to lower the heat loss through the glass? The more you retain, the less you have to deliver to the room.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
1 -
@hot_rod , In looking at the photo you posted here for insulating the Rim space. The photo looks like it was just spray foamed or does it also have a piece of DOW board behind it? Currently, my Rim spaces have just rolled insulation cut to fit the spaces. If this is a serious spot to concentrate an effort to seal up the house, I'll make this a project to tackle soon. Can it just be spray-foamed and skip the insulated board cut out?
0 -
Can it just be spray-foamed and skip the insulated board cut out?
yes, if you are talking 2 part sprayfoam. 1.5" of closed cell or 3" of open cell is comparable to 2" XPS.
https://www.lowes.com/pd/HandiFoam-656-oz-Spray-Gun-Indoor-Outdoor-Spray-Foam-Insulation/5015233059
0 -
Spray foam alone works. The reason people do foam board sealed with spray foam is it's cheaper. You need pretty thick foam, check for your climate zone but typically 2-3 inches and spray foam gets pricey. The other advantage of board foam is you can do it as a DIY project, you don't need a big spraying rig.
It's critically important that the rim area be sealed to air. If not, warm humid air can get in there during the winter, which will lead to condensation and eventually the house rotting from the inside out. Air sealing that strip will make the whole house more comfortable.
Batt insulation like fiberglass or rock wool is not an effective air seal and should not be used as such. However, if there is a couple of inches of foam providing air sealing batt insulation can be put over it for extra insulation.
1 -
Here is how I did mine. Measured the bays, cut the blocks, left a small gap to squirt the foam around it.
Use the minimum expansion version spray cans, the "big gap" cans tend to push the foam blocks out, and the cans don't last as long.
A hand saw cuts the foam easily, or a hot knife. It can be done on a table saw or with a circular saw, but it makes a mess. And the blades can grab if you are not careful.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Any recollection on how many bays got done with one can?
0 -
If it is that critical, I am adding it to my to-do list. Thanks
0 -
It depends on the gap.If you cut the blocks accuratly, leave a 1/4" gap along way.
If you are super accurate cut the blocks exactly the dimension and push them in.Then you don't need the spray foam at all.
The spray foam will seal crack you might not even see! It's worth the effort. Wear old clothes and gloves, or a disposal painters suit. It can be a messy job workingt with spray foam.
I buy some clear vinyl tube to make a longer nozzle for the cans, to reach into the bays easier.
If you have a lot to do, an insulation supply house, or online you can get larger dispenser kits. They have a better dispenser gun also, easier to control.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
I think its a given after this entire thread discussion, that my great room is BTU deficient. So I need more BTU’s. What about vented gas wall heaters? look like a possible answer during the coldest winter days. Thoughts?
0 -
My preference would be for some sort of radiator tied into the existing system, if possible. What's below the room? Do you have a basement to work in?
0 -
It is a finished basement with a drop ceiling. I saw in previous replys the mention of a panel radiator? Will they work with my current 140*F or do they need 180*?
0 -
I just looked one up and found this:
Technical Specifications:
- Dimensions (H x L x D): 24" x 36" x 2-3/4"
- BTU Output @120°F: 1,389
- BTU Output @140°F: 2,237
- BTU Output @160°F: 3,145
- BTU Output @180°F: 4,104
- Water Content (Gal): 0.76
- Max Operating Pressure: 145 psi
- Max Operating Temperature: 200°F
0 -
yes, at reduced BTU/ft from 180F but still very nice heat at 140F. My house runs low temp through radiators with max of 120F SWT and is very comfortable.
0 -
can’t do panel radiator with non barrier tube in system, you will regret it. Panel rads are pretty much all ferrous steel. Rust out.
2 -
Hi, Another idea is to use the finned copper tube used in solar thermal collectors. I used it and just put 1/2" sheetrock over the fins, and mudded over the tube. It keeps my place at 70F using 80 F water.
Yours, Larry3 -
Slantfin baseboard is just copper tubing with aluminum fins, it can handle oxygenated water.
0 -
AET solar in Florida still sells plain copper absorbers, tube/ plate pretty much any length you want.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
You mentioned there is floor heat in the basement. The simplest is to turn on the zone under the great room and use that as supplement heat. Doesn't require any extra equipment and would be the same operating cost as adding more emitter.
0 -
Not and expert, but educated and experienced. To increase heat delivered to the "great room", it is doubtful that single run of pex tube under floor will ever be adequate, even if you raise temperature of water, and insulate under. You are trying to deliver heat through more than an inch of wood, which is not a great conductor of heat. You will increase risks if you increase water temperature. Greater thermal expansion of the plastic could cause stress, and a lower yield strength of the plastic (gradual explosion from thermal cycles). Greater Thermal expansion of the water could require a larger expansion tank. Many risks. In my opinion, you want to add a water-to-air heat exchanger to your system heating that room: Either a finned copper pipe (baseboard radiators) or a plenum and fan including a dense heat exchanger, cut through the floor. Great rooms are hard to heat regardless. Better to use wood fire heat and perhaps a thermal mass heater.
0
Categories
- All Categories
- 86.7K THE MAIN WALL
- 3.1K A-C, Heat Pumps & Refrigeration
- 56 Biomass
- 423 Carbon Monoxide Awareness
- 104 Chimneys & Flues
- 2K Domestic Hot Water
- 5.6K Gas Heating
- 103 Geothermal
- 159 Indoor-Air Quality
- 3.6K Oil Heating
- 69 Pipe Deterioration
- 941 Plumbing
- 6.2K Radiant Heating
- 385 Solar
- 15.3K Strictly Steam
- 3.4K Thermostats and Controls
- 54 Water Quality
- 43 Industry Classes
- 47 Job Opportunities
- 18 Recall Announcements