Underfloor heating not working properly/efficiently?

yukimura

Hi Guys,
I have underfloor heating in my house. We moved in coming on two years ago. The heating system was overly complicated and I have simpified things a bit in that time and its all working nicely now aside from the underfloor heating which I am hoping to knock on the head this week.

The pump was gone on it and was replaced last Thursday so that's fine now. However the system does not seem to be heating effectively, there are only small islands of heat with the rest remaining cold. In my own head I suspect an airlock since the house was idle for sometime before we bought it.

I have tested all the roomstats and the live current is getting to each of the thermo-actuators which are opening as expected. However I suspect the water is not flowing as it should.

There are two auto-air eliminators on the manifold, one before the pump on the boiler flow and one after the pump on the boiler return. If I removed the little screw on the boiler return then water comes out. However If I remove it on the boiler flow, nothing comes out except the odd hiss of air, no water though. This seems wrong to me.

The pressure gauge also seems off. The temperature on it is working fine but the pressure does not move at all even when the system is supposed to be on, it just sits at 0.5bar. Again this seems wrong and too low to me.

If I could get some insight into some thoughts on this it would be great since the plumber will be back to me on Saturday and at least I could ask him to check these things for me.

Thanks in advance.

Walter Becket

yukimura wrote: »

Hi Guys,
I have underfloor heating in my house. We moved in coming on two years ago. The heating system was overly complicated and I have simpified things a bit in that time and its all working nicely now aside from the underfloor heating which I am hoping to knock on the head this week.

The pump was gone on it and was replaced last Thursday so that's fine now. However the system does not seem to be heating effectively, there are only small islands of heat with the rest remaining cold. In my own head I suspect an airlock since the house was idle for sometime before we bought it.
Thanks in advance.

Airlocks are uncommon in underfloor heating. I think an airlock would stop the zone it was in working at all. 'small islands of heat' there are often warmer areas in underfloor systems (the cat is usually the one to find them) is the house warm enough, if so perhaps leave well enough alone.

yukimura

Thanks for the quick reply. No to my mind the underfloor is not working. I am unsure if the part that's heating is just the boiler flow as it travels to the manifold or if it is an island of heat. How long should you have to leave it on to be able to ascertain if it is working. Should you feel some heat in it after 2 hours?

The parts that do heat seem very efficient. Once the heat is turned off they are still warm 6 hours later. But no I would not say that its working properly.

I presume as long as I can see the little red plastic cap inside the transparent part of the actuator rise up, it is actually opening. It would not be the case that their not opening would it even though I can see that cap move?

Regarding the pressure gauge, does it sound normal for it to stay at 0.5bar.

Thanks again.

Walter Becket

yukimura wrote: »

Thanks for the quick reply. No to my mind the underfloor is not working. I am unsure if the part that's heating is just the boiler flow as it travels to the manifold or if it is an island of heat. How long should you have to leave it on to be able to ascertain if it is working. Should you feel some heat in it after 2 hours?

The parts that do heat seem very efficient. Once the heat is turned off they are still warm 6 hours later. But no I would not say that its working properly.

I presume as long as I can see the little red plastic cap inside the transparent part of the actuator rise up, it is actually opening. It would not be the case that their not opening would it even though I can see that cap move?

Regarding the pressure gauge, does it sound normal for it to stay at 0.5bar.

Thanks again.

.5 bar is okay.
Can you put up a picture of the manifolds.
Usually the upper manifold has the actuators and the lower one has flow meters that allow you to adjust the flow for balancing but they will tell you if there is circulation. Often they have a cap to protect them. What temperature are the manifolds.

yukimura

Sure thing. Sorry about the poor pic, the phone has no flash and does poorly in unlit areas. You are right the actuators are on top and there is little black flow meters under all of those, I was wondering actually what those were. The adjustor's for the flow as you say are on the bottom, I can see where the allan key goes to alter them. The temperature dial on the manifold is set to 45/50 I believe. I was unsure what to set it at, is that too hot. Either way its not working anyway since the heat is not getting to the floors. The manifold itself and under the stairs is lovely and warm. Thanks for the help on this, I appreciate it.

No water from (1) when opened.

Water flows from (2) and (3) when opened.

(9) flow meters.

(4) wiring box for actuators, boiler demand, roomstats etc. All working fine, I tested all of these.

(8) new pump.

(6) Analog clock which I had fitted to control heating in the house. I prefer this to the automated one which was there and which used a truck load of oil when it malfunctioned. Also it did not have an off button which was a major source of concern for me.

I can't post images because boards tells me that I am a new user but I will PM you the image that the numbers above are from. Thanks.

i65[dot]tinypic[dot]com/55hw8h[dot]jpg

yukimura

Just in case the PM does not arrive I have included the url now, just replace [dot] with an actual dot and it should work fine and bring you to the image. Thanks again for the help.
Barry.

Wearb

Might make it easier for someone to help.

yukimura

Thanks a million for that Wearb.

Walter Becket

yukimura wrote: »

Thanks a million for that Wearb.

Attached to the top manifold on the left is a mixing valve it's purpose is to mix water coming back from the floor with hot water from the boiler to get water at the right temperature for underfloor heating about 45°C . What's it set to?

yukimura

Currently at 45 degrees Celcius.

Walter Becket

yukimura wrote: »

Currently at 45 degrees Celcius.

Ok do you think the top manifold is 45° and what does the bottom feel like?

yukimura

They both feel nice and hot to me. There is one thing which I don't know is normal or not, if I open the little plastic nut on the air eliminator(1) at the top of the manifold no water comes out there even though it does come out the bleed nut at (2). Sometimes I hear a hiss out of (1) when I open it.

If I open the plastic nut at (3) water runs freely there.

Walter Becket

yukimura wrote: »

They both feel nice and hot to me. There is one thing which I don't know is normal or not, if I open the little plastic nut on the air eliminator(1) at the top of the manifold no water comes out there even though it does come out the bleed nut at (2). Sometimes I hear a hiss out of (1) when I open it.

If I open the plastic nut at (3) water runs freely there.

I can't see the picture well enough to say much about that but water should not run freely from an automatic air eliminator only air and perhaps small spits of water with the air I can't see if they are manual air vents or automatic.

yukimura

OK great well that seems right then that I only hear the odd hiss of air out of it. I guess then my best bet would be to drain it and re-pressurise/fill it with the plumber from the mains on Saturday to eliminate any airlocks in the system if they have found their way in for some reason. The system was left unused for a number of years prior to us buying the house so perhaps that was the issue. Thanks again for all your input, I am much clearer on things now.

Walter Becket

yukimura wrote: »

OK great well that seems right then that I only hear the odd hiss of air out of it. I guess then my best bet would be to drain it and re-pressurise/fill it with the plumber from the mains on Saturday to eliminate any airlocks in the system if they have found their way in for some reason. The system was left unused for a number of years prior to us buying the house so perhaps that was the issue. Thanks again for all your input, I am much clearer on things now.

Ah no don't drain it the air should come out without draining. Can you hear the pump running. If you can then there may be air in it stopping it pumping. Take off the big silver screw with a straight screwdriver water will come out and air be careful not to loose the screw!!

yukimura

Ah that's great, yeah I can hear the pump running, every so often I can hear whooshing sound like air and water flying through the pump and the it returns to normal again. To bleed it in this way do I remove the screw while the pump is operating? Thanks.

Walter Becket

yukimura wrote: »

Ah that's great, yeah I can hear the pump running, every so often I can hear whooshing sound like air and water flying through the pump and the it returns to normal again. To bleed it in this way do I remove the screw while the pump is operating? Thanks.

You can do both. Set the pump to its highest speed if it has a selector for this.

yukimura

Last question for the night if thats ok. The thermostatic actuators, if I take off the actuator head how do I tell if they are working and are actually opening the heads? Thanks.

Walter Becket

yukimura wrote: »

Last question for the night if thats ok. The thermostatic actuators, if I take off the actuator head how do I tell if they are working and are actually opening the heads? Thanks.

If they are like one I have worked on they open & close very slow. A part at the top comes up when they are open. If you take one off you'll see what it does the valve is operated by pushing down a pin in the manifold a spring pushes it back up. The valve is open when up, so the head normaly pushes it down and when operating allows it to come up. The pins can stick in the down position, the heads can fail. They usually fail in the closed position.

yukimura

Sorry about the late reply. I checked out the pump bleed and also the actuators and all looks fine. The last thing that I need to check is the flow meters. My flow meters(9) are part of the pipes from the manifold. I can see the numbers 1 to 4 on them but cannot see any line or anything which indicates the current flow rate through the system. I do notice that the inside the flow meters is a bit dirty alright. Through the dirt on two I can make out a red bit of plastic but cannot see it effectively. I was looking at the manual and it seems that I should be able to feel an effective heat after 2 hours of being on, but this is not the case. How would I tell that the system is actually flowing?

wilser

Are you sure that the thermostats are connected to the correct valve? Mark and disconnect the 9 valve heads and then see does it make any difference, have seen it before where the hall stat was turning off half of the sitting room.

Walter Becket

yukimura wrote: »

Sorry about the late reply. I checked out the pump bleed and also the actuators and all looks fine. The last thing that I need to check is the flow meters. My flow meters(9) are part of the pipes from the manifold. I can see the numbers 1 to 4 on them but cannot see any line or anything which indicates the current flow rate through the system. I do notice that the inside the flow meters is a bit dirty alright. Through the dirt on two I can make out a red bit of plastic but cannot see it effectively. I was looking at the manual and it seems that I should be able to feel an effective heat after 2 hours of being on, but this is not the case. How would I tell that the system is actually flowing?

Leave the system on if the manifolds are warm and the room stats are calling for heat then if the house isn't warming up there is no flow. I don't think 2 hours is enough 8 hours would be better. How long it takes will depend on things out of the person who writes the manuals control such as the floor slab thickness, pipe spacing in the slab, floor covering and the type of pipe used. Uisualy I can tell if the floor is getting heat from cold because the boiler will run continously it takes a huge amount of heat to warm up the slab from cold. Leave it on.

hatchman

yukimura wrote: »

I do notice that the inside the flow meters is a bit dirty alright. Through the dirt on two I can make out a red bit of plastic but cannot see it effectively. I was looking at the manual and it seems that I should be able to feel an effective heat after 2 hours of being on, but this is not the case. How would I tell that the system is actually flowing?

Get a good torch and put it to side of flow meters and you should be able to see the red bit of plastic clearer and where this lines up with on the graduations on flow meter tells you the flow of that particular circuit. (if any)

yukimura

OK I will try leaving it on. The floor covering is screed 65mm of it I believe with tiles in all areas except the hall and sitting room which are wooden. I have the schematic for the UFH by Begetube at home. The thing is some small parts of the floor heat up nicely but they are marooned by colder areas all around them. These areas typically stay hot for hours then afterwards so it seems efficient if only it would work.

At this stage I have tested absolutely everything so the only thing that can be wrong is the flow I reckon. Coincidentally I did the torch thing last night. On one of the flow meters the little plastic thing comes to life once the actuator opens. On one of the others it does too but then it disappears again even though the actuator is still open. I cannot see the red little plastic piece floating in any of the other pipes. The pump is working fine and is not air locked and the water is flowing through the manifold and mixer I can both hear it and feel it. The heat is not getting to the floors though I think since the return manifold is every bit as hot as the flow. Also the flow meters and pipes going to the underfloor do not get any way warm at all to the touch.

Also I had forgotten to mention that I also tested that all the actuators were pointing to the right room-stat with the phase tester in the wiring centre the other day too so that should be OK I think.

What would you think of that conclusion, does it sound reasonable?

Can I just leave the bleed nut open while its working as before for a few minutes. Would the system re-top itself up to compensate for the lost water or is it sealed and not fed from any mains if it drops below a certain point?

Thanks again.

Walter Becket

Yes you can leave the nut open for a while the system may not top itself up depends on the installation.
Sounds to me like the mixer valve may not be working correctly.
Can you upload a better picture of the manifolds

yukimura

I'll take a few high quality pictures of the manifolds and various parts this evening when I get home first thing.

On the mixer valve now that you mention it, when the system is on, I can hear water rushing or air & water sounds through it, sort of what you hear when you close a tap a bit and the water is spitting/gurggling through it. It may be nothing but just in case I thought I had better mention it. Basically if I am standing outside of the stairs I can hear the water passing through the mixer valve.

Thanks,
Barry.

yukimura

As promised here are the high res pictures of the manifold. Thanks.

Walter Becket

I think the water is short circuiting through the pipe on the left that goes from the bottom manifold to the mixer valve. The head of the mixing valve has a wire at the end of which is a temperature sensing bulb where is this located? Does the pump pump up or down. I think you could try adjusting the mixing valve to see if you can stop the water going through it so much but remember the water going to the floor shouldn't be hotter than 55.

yukimura

Yeah that would make sense, that would explain why there would be no flow at the top and yet the manifold on the bottom is hot. The temperature sensor is attached into the pipe just below and behind the temp/pressure gauge. If you look at the first picture you can see the wire going into the pipe in the bottom right of the picture. That could have been clearer sorry. I have tried changing the temperature on the mixing valve but it does not seem to make much of a difference. Would reducing the temperature make any difference?

Walter Becket

You should be able to adjust it so the gauge reads 45 if you can't then the mixing valve probably needs replacing. One thing I can't figure out is what the pipe on the left going between the manifolds is for. If the flow through this pipe could be restricted it would be worth doing for troubleshooting .

rolion

I had similar issue.

Stopped system,removed and cleaned the mixing valve,ut was blocked by some thick solid black dirt.
Flushed the water too,until from a dark scarry black to a clean clear colour.
Installed one of those magnetic dual filters.

No troubles since then.

hatchman

rolion wrote:

Stopped system,removed and cleaned the mixing valve,ut was blocked by some thick solid black dirt. Flushed the water too,until from a dark scarry black to a clean clear colour. Installed one of those magnetic dual filters.

Did u flush the entire system and did u do it yourself I am thinking of flushing mine and am fearful I will have air locks when done. Is there an easy method for flushing under floor heating ?

rolion

hatchman wrote: »

Did u flush the entire system and did u do it yourself I am thinking of flushing mine and am fearful I will have air locks when done. Is there an easy method for flushing under floor heating ?

No,I had a plumber with me.
Connected the system to the pressure pump,got 3bars in and let water flow trough the rads and ufh for minutes,until water came clean.

I have an automatic aif flow for dealing with the air and i had to vent the rads later myself.

Nothing serious,max one hour.
I recommend doing it every summer,flush full system.