Heating problems, radiators fluctuating.

[Dave Moore]

Hi,
My step daughter was ripped off by a cowboy builder so I’ve been helping her out and fittted her two radiator. I’ve no idea what is under some of the floors or in the walls but since flushing it all out and starting the combi up she’s been having problems with her heating. She reckons the radiators are going cold and hot and not necessarily the same rads. My heating training was in college when an apprentice and a lots changed in 50 years. I suggested she get an experienced heating engineer to take a look and a guy came and messed with one of the trv’s which I assume was sticking. He’s now suggesting she might have to look under the floors to check the piping. I couldn’t access most of it as the floors were tiled. I’m thinking the cowboy has crossed pipes somewhere as he did this on the hot and cold and the kitchen fitter had to cut holes in the ceiling to swap them back. Any ideas?
Regards,
Dave

 

[Ben-gee]

Sounds like it needs balancing. That is definitely the first port of call.
Crossed pipes shouldn’t cause an issue if you mean flow/return are swapped? What will cause an issue is if a particular rad has two flows or two returns - but then it will only heat extremely slowly if at all.

 

[Dave Moore]

Sounds like it needs balancing. That is definitely the first port of call.
Crossed pipes shouldn’t cause an issue if you mean flow/return are swapped? What will cause an issue is if a particular rad has two flows or two returns - but then it will only heat extremely slowly if at all.

The only thing I thought might make a difference is that none of the pipes were marked up before I got there and a couple of the radiators have the lock shield valves on the feed side. Do you think it might need changing round to get correct balancing?

 

[exedon2]

As above if your trv's are bi directional which side flow comes in don't matter.
Get balancing!

 

[Dave Moore]

As above if your trv's are bi directional which side flow comes in don't matter.
Get balancing!

Yes they are bi directional. I’ll have to ask daughter exactly what the problem is now as I’ve got it secondhand. Thanks

 

[Ben-gee]

You might find it’s just rads shutting themselves off on the trv when the room’s up to temperature- ie it works as it should!

 

[Dave Moore]

Knowing the daughter all the trv’s will be wide open as she likes a warm house. Lol.

 

[Chuck]

As long as the heating is working to some extent you can learn a lot about what's happening underfloor and in-wall with a thermal camera. Pro versions made by FLIR are expensive but can be rented for a few days. I haven't tried them myself, but you can also get much cheaper, somewhat lower performance, sensors that use a mobile phone as a display. Several people here do use them so maybe they can recommend some that they've used successfully to diagnose heating issues.

Keep in mind that modern boilers do cycle-on and off by design, particularly at this time of year when the heating demand from the house is lower than the boiler's minimum output. Reducing the CH flow temperature may help. If you use the 'search' box at the top right of this page you'll find many discussions of the topic.

 

[Dave Moore]

Hi,
I did think using an infrared camera might be the way but I don’t own one so renting may be the way. Some of the pipes are in the walls so I thou I might be able to see them when hot and scan the ceiling for the others. I have set the boiler for 65 degrees but who knows what she has done since I left, probably flat out now. Thanks.

 

[Chuck]

I have set the boiler for 65 degrees but who knows what she has done since I left, probably flat out now.

As you know, but she may not, the higher the flow temperature the bigger the sudden blast of radiant heat from the radiators each time the boiler comes on.

What sort of thermostat does she have? If it's a traditional 'on-off + 2°C hysteresis band' type replacing it with a 'TPI' (time-domain proportional+integral) type is likely give an improved comfort level and save a little fuel in the process.

 

[Dave Moore]

It looks like a bog standard, at the moment it is in the boiler cupboard but she is going to get a new one fitted elsewhere. She tends to just leave the heating on, I think she’s cold blooded.