Do we have any folks on here knowledgeable about underfloor heating?
Came home from a short break tonight to find it not working. All other heating fine. I can see the actuators are working but worried it looks like there's no pressure in the system.
Pic of how it looks:
Can feel the pipes to the valve are warm. But everything on the manifold side is cold
If the UFH has no pressure what about the rest of the system? The blue and red handled valves appear to be open (which I’d imagine they must be - flow and return) so the pressure loss could easily be caused by a problem elsewhere.
Just had a second diverted valve replaced on a 9yr old Vaillant boiler; the first was when it was only 2 years old. So it may be something like that; the only visible symptom was loss of pressure in the system but being a combi that meant no heating or hot water.
If the rest of your heating is fine it’s unlikely to be a pressure related thing. Also there’s not usually a pressure gauge attached to these things, only a couple of temperature dials as shown in your picture, so pressure would be checked at your boiler- provided it is a pressurised system.
As the actuators are working, and the circulation pump is working, as shown by the lights on it, I’d say my initial guess would be the zone valve to the system sticking, or possibly the thermostatic mixing valve on the inlet to the system
Zone valve can be checked by feeling the manual actuating lever. If there’s resistance to sliding it over then it’s shut, if it moves easily then it’s open. Just make sure everything is turned on an and calling for heat a good 5 minutes minimum before you check as ufh is very slow to wake up and request heat
Ah, on my computer screen I can see the °C on the dials now - I assumed they were pressure gauges from Merv's post
@jamcg - I hope you don't get too annoyed at my enthusiastic amateur posts on heating stuff. I know I'm not an expert but I understand thermodynamics, fluid dynamics and so on, and when you get into it it seems pretty logical. What I don't know as an amateur is how things are generally done. I'm sure I bore my boiler/heating man who is a lovely guy because he understands the stuff properly and allows me to talk to him about it to understand it better.
I probably ought to go and do a City & Guilds course or whatever they're called now to learn the practice of it, since I do tend to get stuck in at home.
jamcg wrote: ↑Thu Feb 15, 2024 6:34 am
If the rest of your heating is fine it’s unlikely to be a pressure related thing. Also there’s not usually a pressure gauge attached to these things, only a couple of temperature dials as shown in your picture, so pressure would be checked at your boiler- provided it is a pressurised system.
As the actuators are working, and the circulation pump is working, as shown by the lights on it, I’d say my initial guess would be the zone valve to the system sticking, or possibly the thermostatic mixing valve on the inlet to the system
Zone valve can be checked by feeling the manual actuating lever. If there’s resistance to sliding it over then it’s shut, if it moves easily then it’s open. Just make sure everything is turned on an and calling for heat a good 5 minutes minimum before you check as ufh is very slow to wake up and request heat
Cheers @jamcg
I noticed again last night that one of the flow guages had actually moved off min but there was still no temp differential.
Anyway, I also looked at the zone valve and it appears to be stuck in the manually open position? I can't budge the fecker at all. I'm going to take another look in a mo but haven't found much online yet about them being stuck in the manual open position
mik wrote: ↑Thu Feb 15, 2024 11:52 am
Looks like a job for a persuader.
I have already tried the Manchester hammer @mik . No budge.
If I weren't supposed to be working I'd be disconnecting the valve motor and having a look inside and also checking that the valve itself isn't stuck. Will try and find a local CH bod - the one we use for boiler servicing doesn't do UFH sadly (although I did explain i thought it was the zone valve which is standard stuff)
Turn off your controls or even just knock off the power. Push it down, out of the little notch and it should spring return to the closed position. If it doesn’t then it be fucked
Just a little important note that’s good for anyone who has zoned systems to know- your heating controls don’t communicate with your boiler. It goes controls to zone valve to boiler. It’s actually the valve opening that fires the boiler, so if your controls are on and nothings doing, it’s probably the valve
Turn off your controls or even just knock off the power. Push it down, out of the little notch and it should spring return to the closed position. If it doesn’t then it be fucked
Just a little important note that’s good for anyone who has zoned systems to know- your heating controls don’t communicate with your boiler. It goes controls to zone valve to boiler. It’s actually the valve opening that fires the boiler, so if your controls are on and nothings doing, it’s probably the valve
Had to replace the head on our valves twice. The second time the heating was sticking on. Waking up in the middle of the night to a boiling hot house!
Good advice there - took me a while to realise the mechanical zone valve had a microswitch in it which fired the boiler. Clever because it means the boiler is effectively locked out if the zone valve fails, meaning it doesn't heat water which isn't circulating. But it also means the boiler is locked out if the microswitch fails. Keep a spare in stock.
I did go through a run of replacing them but have realised that our valve in the pipe is sticky and the zone valves just didn't quite push it all the way, therefore not triggering the microswitch. So it's worth removing the head and working the valve a few times too.
I've had a tinker earlier and I'm fairly sure that the lever on the valve has been mullered by someone in the past. Can't think who though as it shouldn't have been touched since installation, but maybe it was when installed.
Anyway, I took the lid off it and gave it some thorough poking, including trying to turn the valve internally to see if it was free (although limited movement because of the stuck lever). It now seems to have freed something off though because the system is flowing and there's temperature in it as well.
Got someone coming first thing though to take a look. I think it still needs a new valve actuator.
@jamcg - how long do these valves typically last? Our install isn't yet 3yo.
Further update. Now the rooms with UFH aren't calling for heat, the pump for the UFH has stopped etc. But the valve's lever is still stuck in the open position. So not sure how that works with calling the boiler as at present the controls aren't calling the the valve, but the valve appears to still be stuck in the manual open position.
Depending on the water quality in the system they can last anything between 1 and 100 years. Hope that helps
The switch will have been fucked by someone tightening the valve nuts. I always remove the heads when fitting one
As a general rule replacing a head is throwing good money after bad. It’s usually the valve body getting sticky that puts too much stress on the motor. So best advice is to just replace the lot. If you can diy it’s not too expensive a job but it’s having the confidence and knowledge to do it. Top tip is don’t fuck around in the wiring centre if you don’t need to, just cut the wire off the old head and join it to the new
Will see what this guy says in the morning tomorrow. Would the valve still function as it should if the lever is in the locked open position? That's the bit I'm struggling to get my head around to be honest - the fact that my tinkering seems to have allowed it to pump and then stop even though the lever is stuck.
When you put it into that manual position it just opens the valve, it doesn’t move it enough to click the micro switch to fire the boiler, so the controls will push it that little bit further to click it on
Jobbo wrote: ↑Thu Feb 15, 2024 8:51 am
I probably ought to go and do a City & Guilds course or whatever they're called now to learn the practice of it, since I do tend to get stuck in at home.
You’re welcome to these if you want to look into the more technical side of stuff. They’ve not been opened for 13 years
