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Radiant heat flooring problems

Posted by beaglesdoitbetter (My Page) on
Sun, Dec 1, 13 at 9:57

We have a radiant heat system we believe was not installed correctly or according to specifications we were provided.

We were told we would have a system with a 90% condensing boiler for radiant. Instead, we have a gas water heater (Lochinvar Model number LVL 041G0). From what I understand, a gas water heater and a boiler are not the same things?

The second issue is that the tubes run from the water heater to the floor with just insulation below and floor above in the basement. There do not appear to be any type of metal transfer plates to force the heat to be conducted to the floor. This, from what I understand, is incorrect. Is this ever an acceptable way to install radiant heat? We have a large basement and the pipes run a very long way to get to the master bath.

The result of the problems seems to be that our system is extremely inefficient/ non-functional. The radiant system is in the sunroom (right over the tank) and the master bath (opposite end of the house). The water heater runs for around 12 hours a day or more, and costs a fortune to run. Even after running for hours and hours for weeks, the floor in the bathroom is still freezing and the thermostat in the bathroom attached to the radiant heat still reads 57 degrees even when we have it set for 64.

Final issue is that our installer indicated that the thermostat attached to the radiant heat reads the room temperature and not the floor temperature. The thermostat is called Watts Radiant. Is this actually true? We don't understand why this would ever be this way instead of having a thermostat that reads the floor temperature.


Follow-Up Postings:

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RE: Radiant heat flooring problems

A water heater and a boiler are not the same thing, but you can use a water heater instead. That's actually what I have. However, if you paid for a boiler, you should have a boiler. Is it a closed system, meaning that there's a heat exchanger involved? I've never heard of using metal transfer plates for hydronic heat. I'm not sure where you would put them, since the tubes are encased, but I'm certainly no expert on the matter. It's not clear to me if you're heating the basement floor, or how exactly the tubes are running to the master bath (in the basement floor, or in the joist bay of the ceiling). Once they reach the bathroom, however, they will not be visible since they will be encased in the floor.
I don't know about the thermostat you have, but you can get one that reads both room temperature and floor temperature. You need a sensor in the floor for that, however, and it sounds like maybe they didn't put one in.

It sounds like you have major problems with the system, and it isn't because you're using a water heater. I use the same water heater for my domestic hot water and to heat the floors (kitchen, laundry room, mudroom, entry, hallways, 3 bathrooms, some on the 2nd floor, some on the 1st floor). It's set to 115 degrees, and I can feel the heat in the floors within 5 minutes of turning it on. I never run out of hot water, and it certainly doesn't run for half of every day. Are you sure that the tubes are filled? Is the pump turned on?


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RE: Radiant heat flooring problems

beaglesdoitbetter:

You need to hire a consultant with impeccable credentials to assess your system. If he finds problems, you will have metaphorical ammunition. While GW is a lot of fun and informative, it's not much use in court or even in persuading a contractor to make amends.

I'd expect to pay $300-$700.00 for a written report.


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RE: Radiant heat flooring problems

catbuilder the tubes run underneath the floor joists along the basement ceiling to warm the floor above. From the pictures I've seen online of a similar system, there should be metal plates in between the tubes carrying the water and the floor part up above, to transfer the heat through the basement ceiling/floor into the tile above.

Trebruchet, I agree, I think we may need to do that. I'm not sure our geothermal is installed correctly either (we cannot seem to air condition the house down to 69, it stops at 70, and the geothermal installer said it is supposed to do that... seems fishy to me).


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RE: Radiant heat flooring problems

So you did a staple-up system with hydronic heat? I've never heard of doing that. The beauty of hydronic heat in a new build is to encase the tubes and get a very efficient and comfortable method of heating. You are wasting a LOT of heat and energy heating up the subfloor and the room below. Water under the bridge now, though. But I do understand why you're not able to get the system up to temperature. Boilers get much hotter than water heaters, but I don't know how much heat the PEX (did they use PEX?) tubing can safely handle.


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RE: Radiant heat flooring problems

hmm hmm


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RE: Radiant heat flooring problems

The line that runs all the way across the house to your bathroom, was that insulated at all? Or is it hanging out in the open, losing heat all the way until it gets to the bathroom and doesn't have any heat left to transfer? Doing an application like you've done requires the same central location to the two points as a water heater, or you get the same heat loss and lag time as you would by locating a water heater 90' away from the end use.

I'm frankly a bit confused as to why you even chose hydronic for the two applications. It's usually chosen as a whole house heating source, not as supplemental to a couple of rooms. It makes sense to use a boiler for the whole home's heating, where it makes almost no sense to use water and a boiler or water heater of any type just for supplemental floor warming. That type of application is where electric floor warming cables shine for use.


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RE: Radiant heat flooring problems

Not sure what happened here. I wrote a post the other day for you on this. You do need to get someone in there who knows what is going on. Contact Lochinvar's local representative and ask for their BEST local recommendation on a contractor. Visit the local P&H supply house and do the same.

A water heater, your is btw a discontinued model, is about 62% efficient. A Modcon boiler, and Lochinvar, whom I compete against, make good boilers, will be in the 95% range and will have the outdoor reset controls necessary to properly control the system giving you the best economy and comfort. A water heater is 1/4-1/3 the price of a mod con boiler. Staple up systems are common in retrofit applications,and yes, it is best to have some type of reflective surface a couple inches below the tubing. Using an "in-floor" system will allow lower temps to be used by the boiler. Usually a max of 120*. Staple up system will require higher temps to drive the system, usually in the range of 140*.

Catbuilder: Sharing dhw and the same water in the heating loop, especially in radiant with the qty of water being used, can have problems. These are called "open loop" systems. I would suggest you google "Legionella/waterheaters" and sit back an read for a while. I will say this especially at the 115* temps you are running at. I know that 115 is good for dhw, I run my tankless there. I am sure it is good for the heat side as well. It is also on the edge for bacterial growth. In my experience, if this system is doing as well as you say I would suggest that you go out and buy some, pardon me…a, lottery ticket.

Sorry to put it that way, but please look at it as a heads up;)


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RE: Radiant heat flooring problems

Jack,

I'm not sure what you're saying. It sounds like the new "scare of the day", and I'm actually more concerned about the dangers of water that is too hot. I have a closed loop system for the heat. It uses a heat exchanger, with the heat source being from the hot water heater. The water in the two systems don't mix.


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RE: Radiant heat flooring problems

If the other rooms are heating, then it sounds like the flow of the water through the system is not balanced. Another words the hot water takes the path of least resistance and flows through the sunroom (close circuit), but not the far circuit (bath).

The system should have a manifold with balancing valves. First have someone balance the water flow.

Secondly, read your contract, find out what kind of boiler / water heater was supposed to be installed, and get the spec's on how your floor heating system was installed.


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RE: Radiant heat flooring problems

catbuilder we were told the in-floor tubing system wasn't done because it is too hard to repair if something goes wrong w/o tearing up hardwood/tile. Yes, Pex tubing was used.

live_wire_oak, the tubes are insulated in the path along the floor. We did not want electric because we were told operating it would be too inefficient. We (tried to) pay more up front for a more efficient system so that it would cost less to operate over time. The intent was to leave the radiant floors on all of the time.

Jackfre, one possibility we are discussing to resolve this is a more efficient water heater (NOT paid for by us). We went back and forth yesterday for a very long time w/ the builder in which he insists we agreed to a water heater change when we changed to geothermal and we said we did not. Our "change order" adds the geothermal and specifies "closed loop" radiant system but doesn't specify boiler or water heater (our build specifications contract specifies 90 percent condensing boiler, but we were told that was for use before we put in the geothermal system and that when we did the change to geothermal, we "agreed" to a switch to a hot water heater for the supplemental floor heating.) I know we never had any conversation about this though and neither my husband or I have any memory at any time of this ever being discussed.

Geoffrey_B, that is a good idea.

We are having a meeting w/ the installer and our builder here, hopefully early next week. My builder has promised we'll get this fixed and (as of now) I have no reason not to trust him, so....


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RE: Radiant heat flooring problems

Oh, one other question... we were told that one possible reason this is not working is because we keep our house too cold (the house is set at 64, we like it chilly). The floors are set lower than the house temp (61) so it seems like the house temp should not be a problem, right...


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RE: Radiant heat flooring problems

Beagles, this will be a long reply. I'm trying to think if I've ever typed a short one...hmmmm...

First, the water heater: This is solely for the purpose of heating the water for the two RFH loops? Or does it also heat your DHW (sink faucet, showers, etc) too?

As has been mentioned, if it's just for your RFH, that makes things easy. If it's also for your DHW, the two systems (DHW and RFH) need to be separated. A single water heater can still heat all the water for both, but you'd want a heat exchanger on the water heater.

With a heat exchanger, the water heater will heat water. That heated water will circulate through the heat exchanger, giving up some heat to the water on the "other side" of the heat exchanger (HX), and that water on the other side will be for the RFH system. Heat exchanger:

Example of a heat exchanger set-up:

In the above, you should have two zones. The bathroom and the sunroom.

The RFH system should be a completely closed loop. Once the loop of PEX has been charged and any air bubbles "burped" from the system, for the most part no water will ever leave that loop, and no new water will ever be introduced into that loop. The same water will circulate within that loop for years and years.

For the water to circulate in that loop, you'll need a circulating pump to move the water. I use Taco pumps, they sort of look like this:

These systems can be configured several ways. Since the thermal needs of your two rooms (sunroom versus bathroom) could vary quite a bit, it'd make sense that they are on separate zones. ie, the sunroom needs heat, the sunroom t-stat sends a signal to the circulating pump. the pump turns on and water circulates only to the sunroom. When the water temp in the PEX gets low enough, the water heater kicks on. All the while the bathroom loop is content and quiet.

Or they could have lumped your entire system together into one zone, with several PEX loops within that zone. One or more loops for the bathroom, and one or more loops for the sunroom, but all within the same "zone", meaning they run off the same circulating pump and thermostat for example.

Or the two rooms could have separate thermostats, but share a single circulating pump. But the flow through the loops is controlled by an ON/OFF valve that allows water to flow through the loops to either room as needed.

There are several issues that come into play:

1) The water heater needs to heat the water. What is the temp of the water in the heater?

2) The water need to be circulated through the PEX. You should have at least one, and maybe even two circulating pumps. They might look like the TACO pump I posted. When your rooms are demanding heat, is the pump running? You can sometimes feel it vibrating a bit. If you grab the PEX with your hand, The PEX should feel warm on the water heater side of the pump as well as on the room side of the pump. If the PEX gets colder the further you move away from the pump, the pump might not be circulating.

3) The PEX: Do you know the diameter of the tubing? Most likely 1/2". It should be stamped on the tubing every few feet.

3.5) Runs per joist. Typically there should be two runs of PEX er joist bay.

4) More PEX: Do you know the length of the tubing that makes up the run to your bathroom? Tubing usually has "length" marks printed on the tubing. The tubing loop that heats the bathroom will start at a certain point; could be the water heater, it might be the heat exchanger, it might be a manifold...but it'll have a starting point. It will then run the length of your house to the bathroom. It'll then zip back and forth through the joist bays under the bathroom. It'll then run back to the starting point. If you can find a "foot" marking on the tube at the starting point, as well as at the ending point, and take the difference between those two numbers, that should be the length of the tubing for the bathroom loop. As long as there are no splices.

The longer the loop, the more resistance to flow. For 1/2" tubing, roughly 225' is a maximum length of tubing for a single "to/from" loop.

If you feel the PEX at the start/supply end of the loop, is it warm? How about at the end/return end of the loop?

5) Insulation: What type and thickness of insulation, or total R-value if you know that, is under the tubing in the bathroom joist bays?

6) Flooring: What's on top of the tubing? Example; 3/4" ply subfloor? Plus 1/2" ply underlayment? Plus cement board, tile, etc?

I mentioned circulating valves. If you have a single valve but the sunroom and bathroom have separate controls, then one fo the rooms might also have an on/off valve. If so, make sure the valve is actuating (opening) when needed.

7) Balancing the flow: If your two rooms are simply plumbed as one large connected system, realize that water takes the path of least resistance. It might be easier for the water to flow through the shorter sunroom loop compared to the longer length of the bathroom loop. So the sunroom could be getting 90% of the flow and the bathroom loop could be near stagnant. A balancing valve could be added to adjust the flows as needed.

So there's some basic thought.

Other things you asked about:

Boiler versus water heater: In many cases, for RFH, a water heater is better than a boiler. To be efficient, a boiler will typically heat water to 160-180 degrees. To circulate that water through a RFH loop, the water temp then needs to be dropped down to around 120 degrees or so. That usually entails adding a mixing valve that mixes cooler water with the 180-degree water. Sort of counter-intuitive.

With a water heater you can simply set the water temp to the temp you want the water to circulate at; 120-degrees.

So not having a boiler isn't necessarily a bad thing. But the fact that you ordered a boiler and got a water heater? That's a huge disconnect.

Staple-up plates: Whether you need them or not depends on the heating needs of the room. Plates do help transfer heat. But if you have adequate insulation beneath the tubing, plates may not be needed.

Room versus floor thermostat: A wall thermostat isn't "wrong". Confort-wise, it can actually be a better installation than a floor thermostat.

FWIW, when I built my house many moons ago, I DIY'd my house's RFH system. Staple up. No plates. Boiler with mixing valve. It is indeed a closed system, so circulation-wise it's independent of my house's domestic hot water supply.

I wrote a lot of clutter. I think if I wrote any more without feedback from you I'd confuse more than help due to going off on tangents, as there are myriad ways to plumb a RFH system.

If your sunroom gets heat but your bathroom doesn't, I'd try to "follow the flow" and see if they are lumped together into one zone, or if they are separated into two zones.

Circulating pumps? Any flow control valves?

I'd also be concerned with the overall length of the run of PEX that runs to the bathroom, through the floor joists, and from the bathroom. Too long and you'll lose flow.


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RE: Radiant heat flooring problems

Wow, thanks mongoct for the incredibly detailed reply. I've printed it out to read over more closely. And not for the first time, I wish you were located near us and that you had done all our installs!


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RE: Radiant heat flooring problems

I think we are missing the circulator pump, and also our tubing runs are too long. I will see if we can find out if we have flow control valves.

Our system is a closed loop, the water heater only runs the radiant. There are separate thermostats in the bathroom and in the sunroom.


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RE: Radiant heat flooring problems

Make sure if your builder decides to upgrade the water heater that he doesn't throw a tankless on-demand type at it. At least make sure, if they do this, that they select a manuf who specifically allows this use of their product. I am most familiar with Rinnai and they specifically exclude closed loop heating in their warranty. I would suggest a Lochinvar Cadet or a Rinnai E50C. Those are both small boilers that have the outdoor reset package to give you best performance, and again they are boilers.


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RE: Radiant heat flooring problems

With two separate thermostats and two different rooms, I'd prefer to see a setup like the one below. It's certainly not the only way to do it. But it's fairly simple:

Hopefully you can sort of reconcile what you have with the bits and pieces in the schematic. Again, you might not have all of them, or you might have more. And the bits and pieces don't have to be in the order or in the locations I have them.

I'll start by writing about the shutoff valves. There are several in the schematic. They bracket some of the bits and pieces to allow maintenance on your system. Example, if you have to replace a pump, you can isolate the pump by turning off the shutoff valves on either side of the pump. If you have no shutoff valves, when you pulled the pump out of the loop, you'd lose all the water in your system.

I prefer full port valves for shutoff. The photos are just for reference:

So you have the water heater. Hot water comes out of the water heater and flows through a check valve. That valve prevents backflow or reverse flow through the water heater.

Typical backflow valve:

The pressure gauge allows you to monitor the pressure of the water in the system. I usually run closed systems at about 12psi of water pressure.

After the pressure gauge is a "fill" hose bib. Just like a garden faucet hose bib, though you can certainly use something better. There's normally a hose connection down low on the water heater. You connect a garden hose to the water heater bib, open the "fill" hose bib, and fill the system with water. Or a water/glycol solution if you need freeze protection.

After the fill bib is the expansion tank and the air eliminator. Since it's a closed system and water expands when hot and contracts when cool, the expansion tank allows the system to absorb those changes in water volume while allowing the system pressure to remain constant as 12psi.

Expansion tank:

Air eliminators have a couple of different looks:

or this:

To the right of the expansion tank is another "fill" valve that has a cold water supply plumbed into it. That's a pressure compensating valve set at, you guessed it, 12psi. If the system pressure drops below 12psi, that valve automatically opens and recharges the system to 12psi. The little lever on top allows you to add water manually. The valves are usually pressure-adjustable. I just happen to use 12psi as my setting.

Why would you need to add water to a closed system? The air eliminator "burps" air from the system. Air in the system can cause turbulence noise when the water flows, a large bubble could cause flow problems or pump problems. So the air eliminator eliminates air. But sometimes water can dribble out too. So if/when you have water loss, the 12psi valve will recharge the loops with water.

The "Temp in" gauge shows the water temp as it enters the loops. Usually about 120 degrees. Maybe more or less.

Then the system branches off into two zones, one for the bathroom, one for the sunroom. Each zone has its own circulating pump. When the room's thermostat calls for heat, the circulating pump kicks on and circulates hot water through the zone and to the loops in the zone.

Typical Taco pump:

You can add a Grundfos Alpha pump. Very energy efficient:


With two pumps, the rooms can be heated individually or concurrently.

When the water returns from the zone(s), it goes through another temperature gauge. You can compare the Delta T or the change in temp of the water to see if the heat is being given up to the rooms. "Temp In" minus "Temp Out" equals Delta T.

And there you go.

Again, each zone can simply be a single loop of PEX. Small rooms can sometimes be served by a single loop that is on it's own zone. If the room is large and you need more PEX, then you can install a manifold for that zone and you can have several loops on that manifold. Again, each loop should only have about 225' maximum of tubing in the loop. If a room needed 350' of tubing, I'd split it into two loops of 175' each instead of a 225' loop and a 125' loop.

Example of a four loop manifold, this manifold has the "temp in" and "temp out" gauges built in:

That's a basic system with no real automation.


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RE: Radiant heat flooring problems

Wow! Thanks. It looks like we have some of those parts but are missing others (the pump and temperature gages are missing).

Thanks so much for taking the time to type all of that detail out! It is SO helpful!


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RE: Radiant heat flooring problems

Your welcome.

Obviously, the pumps are key. It's not going to work without a pump. And I'd prefer two pumps, a pump for each room, so they can run independently of one another.

If you're in an area with high electrical costs, take a peek at the Grundfos Alpha pumps. They're more expensive ($150) than the typical circulating pumps ($50-$75) but they can pay off that differential within a couple of years, and from then on out you're saving money.

Good luck with the repairs!


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RE: Radiant heat flooring problems

Thanks! I'd rather pay more up front for lower utility bills down the line, for sure so we'll look at the Grundfos Alpha pumps.


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RE: Radiant heat flooring problems

I would suggest going to pexsupply.com and have them design a system for you for 25 dollars. You will then see all the parts they recommend. They will even give you a heat loss report and tell you want temperature to run your loops. The main difference between a tankless water heater and a boiler is that the boiler does not normally have a minimum operating flow rate. I am using a takagi tankless in my radiant system so I had to have a system pump to keep the flow rate up at all times. I have just one other pump that runs two zones. That pump goes to a manifold with actuators on them. The actuators and pumps are wired into relays which go to the thermostats in the individual zones.


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RE: Radiant heat flooring problems

Two of my return lines are nearly cool instead of being mildly hot like the rest of them. thinking of an "air lock" I cracked open the lines individually, I've closed off, (then re-opened) all the others, increased the flow rate for a few minutes, yet where my home has been in the mid 70's for temps outside of 28 degrees, I now have just gotten up to 65. How far should I have the zone valves open 0-23 notches ? I now have them at 10 In the past week it has been as much as 9 below zero and still 70 inside but not above 65 now when it's +28


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RE: Radiant heat flooring problems

Do you have glycol in your system?

If not, there's a chance that the cold might have caused the two cold loops to freeze up.

In cold snaps sometimes it's a loop that flows through a cantilevered bump out where the bottom of the bump out is not part of the basement, but instead it's open to cold air. Or a bump out on a second floor, for example.

Or when the PEX was installed, the the loop in the joist bay could be too close to the rim joist with too little insulation between the PEX and the rim.

The zone valves should have been set when the system was first balanced. After that you shouldn't have to touch them at all. But for sure, if you've choked them down and now the house is cold, you can open them up.

Once you get the zones rebalanced, just leave them alone and use the thermostat to control the inside temp.


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