Radiators farthest from Vaillant combi always cold

[swansea jack]

We have taken over and restored the birthplace of Dylan Thomas.

A Vailant combi boiler was installed about 20 years ago. There is a 22mm flow and return which runs from the boiler in the ground floor outside loo (Ground and first floor plans at 5 Cwmdonkin Drive - Birthplace of Dylan Thomas, Self catering holidays and visitor attraction at Dylan Thomas birthplace of 5 Cwmdonkin Drive, Uplands, Swansea, Wales, UK) up to the first floor landing.

Immediately above the boiler there is a rad tee'd off with 10mm pipes. Then there is a direct copper cylinder used as a rad tee'd off with 15mm pipes (Why? you will ask! Because Dylan talks about leaning against the airing cupboard to keep warm).Shortly after there are a number of manifolds which have 10mm pipes going to five rads on the ground floor and four rads on the first floor.

The rads in the first floor vary from very hot to fairly cool (the two in the front bedroom).

It is the same on the ground floor but in this case the two in the front room are very cool and do little to heat the room.

Domestic hot water is fine
​

I've tried turning all rads off except the cool ones and this makes no difference.

There is no air in the rads

I've turned all the upstairs ones off except the cylinder which appears has no isolating valves and it makes no difference. This would appear to rule out the pump as being the problem (the distance of longest pipe runs is probably about is probably about 22m).

Could the water be cycling through the cylinder and telling the boiler it is hot before the water gets to the farthest rads?

The room the boiler is in is small (1.5 x .9m) and gets very warm from boiler

Or something quite different?

Dylan would love a warm house!

 

[fuzzy]

balancing problem mate, with such a confusing set up of pipes its difficult to say what can be done. my only guess is the pipewrok needs upgrading, the rads that are cool are fed from what size pipe? and how many rads?

 

[tamz]

Interesting property and bit of history. Like the bit about the hot water cylinder. My grannie's back bedroom room was the warmest in the house as that was where the cylinder was. Highly unethical these days but i like it.

As i suspect the system has operated fine in the past the problem is a circulation one. This could be due to sludge build up inside the system. If so it will need flushing out to clean it.
If the rads have thermostatic valves on them it, may be that the pin is sticking. To fix this, remove the valve head and gently pull and push the valve pin to free it. (pull it too hard and it will come right out with a small spray of water. Don't worry, just push it back in).

I gather that you rent this house out so if this advice works for you a complimentary bottle of plonk would be nice if i ever visit

 

[fuzzy]

oh its worked fine before on those pipe sizes? if so yes either sludge, trvs, l/s turned down or pump?

if a new combi its a new pump, is it the same size as before?

 

[swansea jack]

Thanks for the replies

It's the original combi - I'm not at the house at present so don't know the model or size.

The cold rads are fed by 10mm pipes but so are some of the ones that are hot.

The system would have been drained down during renovation as some of rads are in different positions than when we started. I suppose there could be sludge left in some of the pipes.

Can't see it being a balancing problem as they don't get hot even with all the others (apart from cylinder) turned off.

Don't know how well the rads were working before we took the house over

We also do house tours so if you would like a complimentary tour just let me know

 

[fuzzy]

jack, if the rads have moved and only in 10mm the hot water may be struglling to get there, even when others turned off
check trvs and l/s valaves and the pump is on full, my guess is balancing which may be impossible if th pipe is too long and/or not big enough

 

[swansea jack]

Thanks fuzzy

The pump is in the boiler - I couldn't see if there was an adjustment on it to turn it up or down - if you have any ideas I'll give it a try