Central Heating Question

Radiators not warming downstairs (system is open vent with a y plan valve)

I am having trouble with my heating and its a complete head scratcher.

The system is an open vent with a y plan valve. Water tank and CH tank in loft. Hot water tank in airing cupboard in the bedroom and boiler in the kitchen. There is a thermostat in the hall and 3 out of 6 rads have a tvr fitted (lounge and both beds). The kitchen, hall and bathroom rads don't.

After not needing the heating on for a while we switched on a few weeks ago to find that the rads downstairs did not heat up at all!

I checked the pump and decided to replace it. Once replaced I turned the CH (only) on. Wow! The house got really toasty! Problem solved I thought.

The following morning when the HW and CH turned on, only the hot water got warm. Not as hot as it used to be, but the rads downstairs don't come on now. I did a little online checking and decided to take a look at the motorised valve. This is working as it should with the pipes going to the rads and water tank running hot. The switch is loose and floppy when the power is on. With the power off there is resistance when switching to manual then springs back to auto.

Still with both HW and CH on I get nothing downstairs. A little more trouble shooting online and I thought that because the programmer lost the function to control the HW & CH independently, then maybe that could be faulty. That was changed last night and I am still not getting anything from the rads downstairs when both are on. If I switch just the CH on everything warms up as it should.

I am now out of ideas and would very much appreciate some advice.

Many Thanks

Reply to Evergreen.

Thanks for your comment.

When only the heating is all rads get warm. When both heating and water are on the rads dont warm up much, mainly upstairs ones. The bedrooms and lounge have trvs the rest don't.

I will try your suggestion and let you know. When shutting the rads off, do I leave the trvs on? (they are all set to 5 at present). I have balanced the rads. Most of them have the valves only turned about a quarter to half turn.


3 Answers

Best Answer

Possibly the by-pass valve open too much. This should be tee'd off right after the circulation pump. Close this right down and then open half a turn.

Answered 9th Oct 2015

Aqua Plumbing and Maintenance

Member since 9 Oct 2015

it may just be air in the downstairs drop to the radiators.put heating only on. wait for upstairs rads to get hot, then shut them off at the valves on the end of the rad (only need to do one end, hopefully you have trvs) this will push the heat downstairs and any air up and out the pipe. once they have warmed up, open the upstairs rads again.

hop this helps

Answered 26th Nov 2014

Evergreen Solar and Heating

Member since 3 Mar 2014

On a Y plan system to have heating only the motorized valve relies on hot water off function to get its power either through the time clock or cylinder thermostat. I would check to see if you have 230/240v on the number 2 or the grey wire for the 3 port valve when the hot water is satisfied. It would be fine with just heating on, the 3 port valve will get its power from hot water off on the clock with both selected the heating will only stay on when hot water is satisfied if the cylinder stat switches and sends power to grey wire on 3 port valve.

Hope this makes sense. If not let me know

Good luck and keep me posted.

Answered 18th Nov 2018

Help for Heating Limited

Member since 15 Nov 2018

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