Some radiators going only lukewarm after time

CalamariFritti

As the title says.

I have a new oil boiler and EPH controls in its first winter. EPH has 3 zones downstairs, upstairs, hot water. Each zone has a little radio unit/thermometer. And downstairs is giving me trouble.

Downstairs master control is set to ON from 8 to 10pm basically all day. Downstairs radio unit is in the coldest room (the hall) and target temp is set to 21 degrees. Each of the 5 radiators has a regular thermostat, too. The thermostats are set to something just above 3 which should match the 21 or thereabouts. Dont mind the hall being a little cooler.

System comes on in the morning all rads going piping hot. Gets nice and warm to 20 or 21 in all rooms lovely. But then the system wont hold it there in all rooms. After a while some of the rads go lukewarm and the rooms get cooler. Well below 20. And those rads never warm up again they stay at whatever they are now which is just too cold to hold the 21.

When I open the thermostats up in those rooms just a little notch I hear flow again and the rads go warm and the rooms warm up again. And then after a while they go cool again never coming back up never holding the temp. Then I have to open up the thermostats another notch and it gets warm again. And after a while they go cool again. I play that game all the way up to 5 (max) in little notches and thats it then for the rest of the day.

I've tried to set the target temp to 25 or even higher to make sure the zone is firing but not firing doesnt seem to be the problem the water in the circuit is hot. The pipe coming out of the floor just under the thermostat is hot just the rad isn't.

When you google you read balancing and flow and whatnot but I'm no plumber and wouldnt know.

Am I doing something wrong? Does the system need looking at? Any ideas? Thx

Dubstar07

The rad in the hall, does it have a TRV on it (one with dialled numbers)? If so, that could be the issue, the control space shouldn’t have a TRV on the rad, just a regular rad valve. Have you contacted your installer to explain the issues? Also, the TRVs are designed to stop the flow to rad once the space has reached its set temperature. So, they shouldn’t be on all day in theory.

Mr321

Have you a master thermostat beside your circulating pump? If so what's it set at?

CalamariFritti

https://www.boards.ie/discussion/comment/118293313#Comment_118293313

Thx. All rads have TRVs including the hall. I contacted my installer and he changed a setting on the pump but that didnt do it and I will have to contact him again.

Am I right saying that between the master temp and the TVRs I should be able to smoothly hold target temp all day in all rooms if its all set/balanced right?

CalamariFritti

https://www.boards.ie/discussion/comment/118293360#Comment_118293360

Not sure would have to ask installer. Do you mean the boiler thermostat? The boiler is a Grant outdoors and I think the pump is in the back of it.

Mr321

Find out where the overall thermo is. It might need to be adjusted / either that or there may be air in the system.

Dubstar07

https://www.boards.ie/discussion/comment/118293368#Comment_118293368

If the system is balanced right, it should be able to deliver hot water where required. However, in your hall, the wall stat and the TRV are fighting each other to try maintain the required conditions on that zone, which is impacting other spaces. Also, is the wall stat positioned away from the rad on opposite wall or other end of the hall? So, the rad isn’t influencing the stat more than it should.

CalamariFritti

https://www.boards.ie/discussion/comment/118293722#Comment_118293722

Thanks for the info.

The master thermostat in the hall isa bit away from the rad. I can easily move it around too, its wireless.

As for the TVR being in that room. Do I need to have it removed? Or if I just opened up that TRV to the max wouldnt that be the same as not having one at all?

Also should the master thermostat even be in the hall (coldest room in the zone)?

Michael Collins

Sounds like the issue is with the TRVs. They're shutting off the rad when it gets hot. The odd part is that they should let the rad come on again once the room cools down.

There's always some dead zone i.e. where the room temp drops and the rad stays off for a while until the TRV responds, but if the room gets significantly colder for a long period of time, something is not right. Could be dodgy TRVs?

You say the problem only happens with some rads downstairs? You could try swapping the plastic part of the TRV of a malfunctioning rad for a good one, just to see if the TRV may be at fault.

Or, as you say, open one fully...or, even better, take off the plastic part. That'll leave the rad fully open. Should stay hot then as long as the master thermo is reading less than your set point.

Yes, the coldest room probably makes sense for the master thermo, assuming you want to guarantee your setpoint is reached in every room (and don't mind going over that temp in some).

Although, as others have said, having the thermo and the TRVs trying to achieve the same thing probably doesn't make a lot of sense, as they will end up interfering with each other a little.

Might be an idea to consider going the whole hog and getting automated wireless TRVs e.g. the Drayton Wiser system. Just a thought!

10-10-20

Like others have said, this could be a TRV problem.

It sounds like what's called a "hysteresis" failure, where the TRV valve is setting into a closed position when hot, but not returning to the same open position when cooled back down to the target temperature.

What's I'd advise is simple: screw off one of the affected TRV's and bring it into a plumbing supply shop and ask them for a replacement. The replacement will possibly be a different vendor, but the screw thread and operation should be the same. Install it on the same rad and see if that makes a difference.

If it's still the same after that, start looking for an environmental problem such as localised overheating or a radiator cover affecting the TRV, etc.

CalamariFritti

Thanks, yes, it looks like its got to do with the trvs. Took them all off running the zone with the main thermostat only and its now working. All rads have flow and all rads come back on when the zone fires up again. Means the system is working, pump is fine etc. Great.

So either some trvs are dodgy or some weird effect where the trvs and the main thermostat counteract each other or something.

Which is great news overall cos the house is warm now. Id be happy to run the zone without the trvs if it works. Thats perfectly ok isn't it?

10-10-20

I'd test out a new TRV and then install new TRV's all round, otherwise you have no room control and can't back-off the heat. But at a minimum you should fit TRV's to the less used rooms.