Newbie - help with radiant heating system


  #1  
Old 01-22-24, 06:55 PM
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Newbie - help with radiant heating system

I've recently purchased a home, it is heated with a NG furnace but it also has infloor radiant heating in some areas. When looking at some of the systems posted on this site, I'm pretty sure he built it himself. It was installed either in 2020 or 2021, left no documentation.

I was really hoping to turn it on and expand on it but the system was not making any sense to me. So I brought in 2 HVAC companies who professed to be specialists yet both gave me two contradicting reports. The first guys told me that my hot water tank was the wrong kind and that it was mixing with the drinking water and it was dangerous. The other said that it was the wrong kind of PEX, needed a part to bleed out the air and it all needed to be ripped out.

So, based on the pictures below, is it worth trying to get it working (told there was air in the tubes which made the pump very noisy so never turned it on), salvage some parts or should I rip it all out?

Note that one of the zones isn't connected, it's the kitchen (large area 12' x17' + 12' x 8'6. The other zones are much smaller, 2 bathrooms (5' x 10' ) and an entryway 8' x 14' (not sure how much is actually heated).

Be kind, it's my first post ;-p





 
  #2  
Old 01-23-24, 07:46 AM
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Since the underfloor radiant is not your primary heating system, I think it is reasonable to try and get it running. Even though my system is forced hot water through cast iron and fin tube radiation, I have underfloor radiant loops for comfort levels in kitchen, dining, and bathroom.

I will address a few of your questions to get you started.

The tubing and manifold look appropriate. Before reconnecting the disconnected loop you may have to consider that there is a leak in it somewhere. I cannot tell from the pictures whether the correct PEX with oxygen barrier was used.

It looks like the system is using your domestic water heater. Although that type of heater can be used for underfloor heating, it should not be interconnected to supply domestic water to faucets, etc. Can you confirm that the two piping systems are interconnected. If they are then a separate heater or a transfer coil to isolate the two systems is necessary. I think I see two sets of inlet-outlet connections on your tank (top and side) so the proper transfer coil may actually be there. Can you confirm that one set goes to heating and the other to domestic? (BTW I use my domestic water heater at my vacation home to provide heat by gravity flow to a bathroom floor through an interconnected system. The domestic piping is copper and the heating is OB-PEX. Hot water is never used for drinking or cooking.)

You should be able to bleed out any air in the tubing at the manifolds.

It looks like you have zone valves for each tubing loop. Do you know where the thermostats are for each? There could be in-floor sensors instead.

Supplyhouse.com has a lot of good information about installing and operating underfloor radiant systems. Look there for info about heat sources, manifolds, water temperature controls (mixing valve), etc. to learn how your system should work.
 
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Old 01-23-24, 01:44 PM
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I think this explains your setup:


There appears to be a coil in the tank. What is the mfgr. & model no.of tank?

This is not unusual piping and seems to meet all requirements for both HW and heat. Is the gray pressure tank on the heat piping?
Can you confirm the above?
The blue valve near the pump can be used to purge air from the tubing one zone at a time.
Disconnected tubing can be tested for leaks with air pressure to avoid potential water damage.

Water for domestic use is heated in the tank. The underfloor heating coil sits in that water and transfers heat when the pump is running. Water in the two systems are separate. The only potential problem for a cross connect is if the coil in the tank leaks. That would be apparent from the pressure in the heating system. Domestic water is usually 45 to 65 (or more) psi and there is be a pressure relief valve on the tank (with the white downpipe). Heating systems run at 12 to 30 psi with a pressure relief valve at 30#. Can you find one on the heating piping? If the coil leaks then the higher pressure enters the heating system and blows its lower rated safety valve. Since the domestic water pressure is higher, water from the coil cannot enter the tank. Do you have gauges on both systems?

This a straight forward system. The HVAC guys you had look at it either do not know anything about hydronic systems or want to sell you something.
 

Last edited by 2john02458; 01-23-24 at 01:56 PM.
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Old 01-23-24, 02:33 PM
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Welcome to the forums.

This is not a difficult system to understand but it is not simple.
It's actually two systems.... radiant floor heating off a coil in the domestic water heater.
Then there is I'm guessing baseboards off the main boiler.
These two systems should be 100% separate from each other.

I only see one pressure tank.
I know a lot of HVAC techs and maybe only a few that could help you.
You need a plumber specializing in hydronic heating.
 
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Old 01-23-24, 02:50 PM
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PJ, the main system is a hot air furnace. The underfloor is supplemental or for comfort.
 
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Old 01-23-24, 02:52 PM
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Thank you for the quick responses!

2john02458 I think that there are 2 kinds of tubing: WIRSBO ePEX tm plus 5/16 SDR9 PEX-a and WIRSBO - PEX-A UB21001020 08730 (see pics) only because the labelings seems different and diameter.

The hot water tank is a Bradford White combi designed to do both domestic and space heating (see pic).

The thermostat are in each zone with a programmable Flextherm FLP35 in the kitchen.

I doubt that my domestic water pressure is at 45-60 psi. It barely has enough to get to the shower on the 2nd floor :-( That is for another thread ie improving water pressure. A plumber is coming by for a quote on a hot water recirculating loop and adding bathroom plumbing in basement. I'll ask that he do a pressure test and hoping that there is a way to raise it.

I believe that the first device on the left side of the "cold water to heating system make up" is the pressure valve set to 15 psi, then the backflow preventer, then the shutoff valve.

There are no pressure gauges at all.

I agree with your evaluation of the HVAC guys.

PJMAX - yes there is only 1 pressure tank (little gray one on the wall). The main heating is forced air.




 
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Old 01-23-24, 03:20 PM
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Additional background, the house is open concept, with 18' vaulted ceilings in the living room, kitchen and main bedroom with no door to the finished semi-basement. It is about 1700 sqft on main and basement with a 800 sqft mezzanine that is open to the living room below. If I can get the current system going, I would like to add radiant heating to the basement and the bedroom over the garage on the mezzanine. In the end, it would be great to have radiant flooring throughout but that is a long term project. I would love to convert the hot water tank to heatpump but it's still too cold in winter to completely get rid of gaz. Maybe when it's time to replace the current tank in 10 years or so.
 
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Old 01-23-24, 03:49 PM
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I didn't see an air elimination device on the radiant system, maybe hidden.
5/16" radiant tube? if that is correct it may not heat very well, <3/8".
 
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Old 01-23-24, 06:33 PM
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Rbeck19, yeah there isn't an air elimination device, but at least it's simple to install. If the kitchen loop is intact, I'll purge the system, add the air elimination device, pressure gage(s) while I'm at it and anything else that is deemed required.

5/16" is pretty small, but they are both for bathrooms around 5'x10' . What I'm more puzzled about is why such a large tube for the 2nd floor bathroom, it's also 5'x10'? At first I thought it was for the bedroom as it's above the garage and it's 12'x12' but no, the thermostat is in the bathroom.

I've read that loops have to be the same size otherwise the water will flow through the easier path (short loop). 3 of the zones are barely above 50 sqft each while the kitchen is over 300 sqft. How is that going to work? Is that why they went with such a small diameter? But then why so large for the 2nd floor?
 
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Old 01-24-24, 08:37 AM
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open concept, with 18' vaulted ceilings
​​​​​​​
An ideal situation for radiant underfloor heat as a supplement to hot air that rises.

WIRSBO PEX is the appropriate type for radiant underfloor heat. Sizes may vary. I have used the 5/16" version in 1/2" thick Quiktrak panels on subfloor below tile and below engineered wood flooring. I have also used that size in metal panels screwed to the bottom of subfloor below 3/4 inch hardwood flooring. Perhaps your larger size is buried in concrete or a mud tile base.

If there are flow issues because of the various loop lengths, that can be adjusted at the manifolds. (That is why they exist.) My loops are not on manifolds and they work fine for me as a comfort addition to my main hydronic heating system. (I call them parasitic additions. I run my main system at 150 degrees.)

Wall mounted thermostats do not control radiant heat very well because it is not intended to heat space. I have a wall mounted programmable thermostat for radiant floor heat in an en-suite bathroom that works in tandem with the bedroom thermostat. The bathroom thermostat works more like a time clock to heat the bathroom floor when the bedroom temperature is lower. That being said, I can tell you that the bathroom thermostat reads a higher temperature than the bedroom when the bedroom heat is not on.
 
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Old 01-24-24, 04:03 PM
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All zones appear to be set in some sort of thin concrete (saw it advertised but forget the name) with tiles on top. Some of the ceiling is exposed in the basement and there are no loops on the bottom of flooring above. Silly question, is it possible to remove the tile without damaging the radiant floor? We hate some of the tile choices of the previous owner.

Thermostats, each bathroom zone has it own mechanical thermostat (not programable) and the kitchen has a digital unit which allows to set a schedule. The digital unit can measure either the ambient air or floor temp but not both at the same time. If anything the bathrooms should have a schedule (ie warm up in the morning for the shower, then daytime temp and night time temp. Some will be replaced sooner rather than later. Mysa (smart device, Canadian to boot ;-)

The previous owner’s logic escapes me. Why the kitchen? It isn’t as cool as the living room. Why the bathrooms and not the bedrooms. It would have brought a lot more value for the similar investment and be more functional.
 

Last edited by Ididthis; 01-24-24 at 06:40 PM. Reason: Clarity
  #12  
Old 01-25-24, 11:18 AM
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is it possible to remove the tile without damaging the radiant floor?
If it is in thinset you could probably pry up the tiles and and break them off/out without going too deep and damaging the tubing. If the tubing is in Quiktrac panels only the top of it is exposed. If it is embedded in the concrete or mortar it will be more susceptible to damage when removing the tile.

If you use an IR camera or even just an IR scan thermometer to locate the tubing you could avoid doing any heavy work in those areas and do most of your prying between the tubes.

Why the kitchen? It isnít as cool as the living room. Why the bathrooms and not the bedrooms.
People probably spend more time on their feet in those areas. I added underfloor in the kitchen when my wife complained because the main work counter-sink-stove are along a north wall and without much radiation nearby and that is where she spends most of her time on her feet in the kitchen.

Unheated tile floor in a bathroom definitely feels colder than a wood floor at the same temperature in a bedroom. And again more likely to be standing on it--and in bare feet!

​​​​​​​What I'm more puzzled about is why such a large tube for the 2nd floor bathroom, it's also 5'x10'? At first I thought it was for the bedroom as it's above the garage and it's 12'x12' but no, the thermostat is in the bathroom.
Are you sure that the larger tubing is not heating both the bedroom and the bathroom? (Measure the floor temps with IR thermometer.) Is the garage heated? Is the floor insulated above the garage? Larger tubing could've been used there to offset heat loss to the garage below. Although not ideal a single thermostat in the bathroom for a bathroom/bedroom zone would prioritize the area where the heat is more likely to be noticed.
 
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Old 01-25-24, 03:19 PM
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Good question, we never thought of testing the bedroom because the thermostat was in the bathroom. It is carpeted so I'll lift up a corner to see if there is thinset or just OSB. I would be really awesome if it was heated. I get what you are saying about cold tile. Wife wants the bathroom floors heated (why I'm trying to get what is there working ;-)

The garage isn't heated, I'll have to bleed the lines before I can try turning the heat on to test.
 

Last edited by Ididthis; 01-25-24 at 03:21 PM. Reason: Brevity
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Old 01-26-24, 07:38 AM
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Damn!!!!!!! I the page just reloaded and I lost about 15 minutes of typing.
Follow-up to earlier posts.
Short answers:
No pressure relief valve needed on heating system. Transfer coil isolates it from the source of heat and PRV sets pressure in loops at 15psi.

Zone valves for each loop offsets the possible need to precisely balance loops of different lengths. Balancing for flow (at the manifold) is mainly an issue when multiple loops are all running simultaneously. May not be an issue unless all zones constantly call for heat at the same time.
 
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Old 01-26-24, 06:26 PM
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Argh!!! I know how you feel, it happened to me as well.

So for now, all I really need to do to turn it on is to install the air separator / airscoop and purge the air in the tubes? Should I be concerned of the colouring of some of the tubes? Some have this redish colouring. Is it rust?

If understand correctly I should install the air separator/airscoop here?


 

Last edited by Ididthis; 01-26-24 at 06:41 PM.
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Old 01-27-24, 07:12 AM
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Air scoop/separator would not hurt but may not be necessary. I would purge each zone loop separately first. (Having a gauge would be handy. You could get one that screws onto the hose fitting of the coil drain valve at the tank for now.)

Close all the zone valves.
Open the supply valve to the coil. Leave the return valve to the coil closed.
Open the water supply valve (red handle). Lift the lever on the PRV to add pressure (to about 20-25 psi.)
Open one zone valve. (There may be a manual lever on the valve or raise the thermostat. If you use the thermostat you will have to shut off or disconnect electrical to the pump. The pump should not be running while purging.)
Open the drain (purge) valve on the return manifold and let water run until air bubbles stop. Connecting a hose and running into a bucket of water helps to see the bubbles.
Keep the PRV lever open while purging the zone. You want as much water to flow as fast as possible through the loop to move the air bubbles along.
When (most) bubbles stop, close the purge valve. Close the zone valve. Go to the next zone and repeat.
When finished purging all zones, close the water supply valve (red handle). Open the coil return valve. Reduce the pressure to 15 psi and purge any air in the pipe between the coil and the manifold by opening the purge drain. Run the system.

If air continues to be a problem then add the air scoop.

I would not be concerned about the color of the water.
 

Last edited by 2john02458; 01-27-24 at 07:24 AM.
Ididthis voted this post useful.
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Old 01-27-24, 08:39 AM
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Thank you so much for all your valuable information. It is greatly appreciated. It has most likely saved me a lot of money that I can now put into more of the basement flooring to be done with radiant heat.
 
 

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