Odd central heating issue

[stevedwyer]

Hi All

Hope you might help at all. In short we have no heating upstairs, all rads are stone cold from the feed and return pipes of each rad up to the top of the rads - not even tepid.

We have two heating circuits. one which is underfloor heating to the entire downstairs of the house. The other circuit is for upstairs, however there are two rads downstairs linked to the upstairs circuit. This has all be totally fine in the 7 years all the work was done. The odd thing is the two rads downstairs linked to the upstairs circuit are both nice and hot as well as the underfloor heating circuit.

Ive checked the following:

• CH pump. Its only 6months old (Digital Wilo) and operates fine. It has a air purge function which ive run a couple of times
• Bled all rads - all full, no air
• checked all TRVs and pins are free
• All motorised valves actuating when the Nest thermostats call for heat
• checked tank in the loft and the float is free and tank is full
• Boiler firing up and heating the two rads and underfloor circuit
• Hot water all fine.

Is there anything else to check? or is this going to need a power flush of some kind?

Many thanks
Steve

 

[sxturbo]

Do you have any flexible hoses in the system leading to upstairs rads?

I ask because I had a similar issue a few years ago and it transpired that the hoses had deteriorated over the summer months and caused a severe restriction on both the flow and return.

Had numerous heating experts round who couldn't figure it out. After a few weeks went through all the pipework and found them, the flow pipe was hot one side of the Flexi hose and cold the other, so removed them, when we looked through them it was obvious. Replaced for clean bits of copper and the system was fine and dandy again.

You never know what the installers do to just get the job done asap so they can get paid and move on to the next one.

 

[stevedwyer]

Ive checked the flow of pipes from the garage to the airing cupboard and all solid copper pipes as these go straight up into the airing cupboard

 

[sxturbo]

Follow the temps round with a heat gun, see if you can find a point where they suddenly go cold.

Do you have any switching valves in the heating system?

 

[stevedwyer]

Do you mean zone valves? if so yes one on the upstairs circuit the other downstairs.

 

[sxturbo]

Zone valves yes.

Are you certain these are working?

 

[stevedwyer]

Yes. The downstairs circuit is hot and the two rads connected to the upstairs are hot. So the valves are actuating, otherwise I wouldn't have the two rads downstairs working. If they didn't then I would have thought it was a zone valve. Ive even switched the zone valve that does the hot water over temporarily and it did the same.

 

[sxturbo]

Then you need to trace the pipes and see where they are not getting hot. Where the flow pipe suddenly goes cold will be where the blockage is. But I doubt that would be the case of the heating system is only 7 years old, one would have thought it would have been flushed at the time.

Has anyone tampered with the valves at all meaning the system needs to be re-balanced?

 

[terryplumb]

Are you sure the rads downstairs are on the same circuit as the upstairs rads ? Where is the thermostat that controls the upstairs zone ?

 

[sxturbo]

Are you sure the rads downstairs are on the same circuit as the upstairs rads ? Where is the thermostat that controls the upstairs zone ?

That was why I asked about the zone valves, but the op is adamant the rads are all on the same circuit

 

[oilhead]

Is your pump set for manual or automatic circulation?

 

[mcmoby69]

Air lock or some crap has got into the system.

 

[stevedwyer]

Thanks both for your reply. As far as i’m aware the downstairs two are connected to upstairs. This historically evident as when the upstairs is on the downstairs two come on.

I’m having difficulty tracking a cold spot as the pipes leading from the downstairs rad that then goes up to the airing cupboard are hot.

However an interesting discovery is i used my phone stuck down the floorboard in the airing cupboard and i can see another zone valve sitting somewhere in the hallway. It’s a honeywell metal valve where all the ones in the airing cupboard are newer plastic ones.

So i wonder if the installers piggybacked the two zone valves together and the honeywell one has packed up and needs a new motor. The only way to be sure is to rip up the carpet and take the floor boards up and manually switch it across and see if it when gives heat?

 

[Madrab]

The only way to be sure is to rip up the carpet and take the floor boards up and manually switch it across and see if it when gives heat?

Yup, if there's a hidden zone valve connected to the system then it needs tested.

 

[stevedwyer]

Ok so it seems as if the installers just piggy backed the hidden valve and the new valve together. The hidden valve didn't move when called for heat. So I went out and got a replacement motor and swapped it over. I can see the motor and springs now turning, however the switch bar (auto - manual) isn't moving, so I wonder if the valve itself is screwed. However if I flick the switch to Manual I now get heat upstairs, so that would assume the valve is fine? I suppose the next option is to completely replace the head.