Interesting cold radiator query

[madge1]

Hi

Just moved into a house with an interesting issue.

It’s a chalet style conversion, with a loft. The combi boiler is pre conversion and was discontinued in 2001. Every radiator has TRVs, and until we moved in there wasn’t a room stat (we’ve installed a wireless Honeywell).

The boiler seems to work fine – [most] radiators get hot, and there’s hot water on demand. It seems to cycle a lot, but I think that’s due to the demands of so many TRVs.

Only issue is the room radiators on the ground floor don’t get that hot, even with the TRVs on full, and even with all the other radiators turned off. They get warm, but never scorching like the others. Apparently the pressure flow in them is fine, and the valves do work. There’s no leak, as when you bleed them water comes out straight away. On the face of it, everything seems fine, except they don’t get as hot as I think they should.

Any ideas?

Ta

 

[JohnD]

radiators on the ground floor don’t get that hot, even with the TRVs on full, and even with all the other radiators turned off.

So if the pump is working and circulating the water, and all the hot radiators are turned off, where is the hot water going?

Either you have a bypass, or it is taking some other path.

 

[madge1]

I know - this is what's confusing; it's not escaping as the pressure in the system doesn't decrease.

Could I just ask one halfwittish question though - what's a bypass? A spur off another, which if it remains on 2 (say, rather than 4) is then limiting what goes through to the other rads?

 

[JohnD]

On a system with no room stat and all TRVs, once the house is hot, all the rads will close but the pump will keep running. There is therefore a pipe linking the flow and return pipes to allows the pressure to circulate. It may have a pressure valve on it.

Now that you have a room stat, if you can bring yourself to remove the TRV on at least one radiator, and leave it permanently on (for example the bathroom and hall) then you will no longer need a bypass.

It might be internal to the boiler, if not, feel the flow and the return pipes and you will probably find they are hot, follow the hot pipes until you find where they join.

 

[madge1]

So if we do have a bypass in the boiler, do we have to replumb it to avoid this? And if it's under the floor, it could be a real pain to do!

thanks for all the replies

 

[barrymanifold]

How many down stairs rads only get warm ?

 

[madge1]

two get warm, one gets warmer, and then there's 4 that get the usual scorching when on max.

 

[barrymanifold]

If it was only happening on 2 rads you could have 2 returns going to one rad and 2 flows going to the other .Instead of a flow and return going to each .Thats the reason i asked.

 

[madge1]

well don't get me wrong, two are a definite cause for concern. So basically you think the furthest room uses the next room (closer to the boiler)'s pipes, so we're feeding two rads off one set of pipes, which could mean we can't do a lot about it?

Would that be right?

ta

 

[barrymanifold]

Each rad has a in and out to and from the boiler one of your rads may have 2 ins and the other 2 outs so you dont get circulation .you will have to get someone to trace the pipework back to the heating mains.This said iam assuming your system is a 2 pipe system.Is it micro bore ?

 

[madge1]

That I'm afraid I don't know. The heating engineer is coming back on Friday, so I'll mention all this; at the moment he seems somewhat stumped, but he's mentioned a pressure clean etc.

Thanks

 

[picasso]

Anybody checked that the pins aren't stuck on the trvs?

 

[madge1]

he's taken them off, and apparently they're okay; was the first thing I thought of to be honest. I'll get him to possibly switch one with a rad that I know gets scorching.

 

[madge1]

on a followup, we're definitely not microbore, as the pipes are normal inch size (or 22mm anyway).

And last night I turned the boiler up to max, put the room stat in a cold room and turned all the other radiators down. And the two errant rads did get hot - it took time, but they were scorching.

Does this just mean a pressure flush will solve all problems? And how much do they cost - roughly, obviously.

thanks

 

[rebelbuttmunch]

I had a house where all the downstairs rads were hot, except the last one in the loop. A new pump fixed it.