Radiators hot with no demand from room stat

[dolphinesian]

Hi,

I have an issue with my central heating whereby the radiators are always warm. The house gets so warm, even at night when both CH and HW are supposed to be off.

The house is 15 years old, it has:
- Ideal Classic FF240 boiler
- Heatrae Sadia Megaflo CL145 cylinder
- Closed system

There are two motorised valves, one for HW and one for CH
There is a digital Honeywell programmable timer... heating on all the time (but controlled by Nest thermostat), HW on twice a day, hour in the morning, hour in the evening.

There are times when the radiators are warm but hot water timer is off and the Nest is not calling for heat.

By warm i mean the boiler is firing.

Other things I've checked:

There is a stat on the boiler which is set to maximum (6). I turned this down to test and and found that with both the CH and HW switched off, the boiler will still fire up if the boiler stat is turned up (to heat up the primary circuit).

I suspect that the CH motorised valve is either playing up or is not wired correctly.

My reason for thinking this is that when the radiators are getting warm (HW and CH set to off), the pipes either side of the valve are hot. Also, the manual level on the valve is 'stiff' it's not loose. When the boiler stops firing, the lever becomes loose.

Can someone please advise what tests I can perform to verify the wiring/function of this valve?

Thanks.

 

[D_Hailsham]

Turn the power to the system off completely, i.e at the main switch.

Now check the valve opens and closes correctly using the lever.

It should be at the AUTO end and give resistance when the lever is moved to the AUTO end. It should move back to the AUTO end when released.

If the lever is loose in the slot, the valve is stuck in the open position.

If so, remove the actuator (metal box) and check hpow easy it is to turn the valve spindle. It may only turn 10-20deg between stops. If it can't be turned easily by hand, the valve is sticking. A little silicon lubricant may help; otherwise you need a new valve. If it's a Honeywell, you can get a repair kit.

 

[twgas]

Do you have a frost stat? If you do, disconnect it and see if the system works as you would expect it to, if you dont have a frost stat let the system cool right down before trying any mechanical tests.

 

[dolphinesian]

Hi, I do have a frostat, it doesn't appear to do anything. With everything else off I turned the frostat up until it clicked directing the boiler to fire up however it didn't. There's also a pipe stat above the boiler. No idea what it does. Their boiler is in the garage however the temperature in the garage is currently 17 degrees.

Please see below link to valve test.
It's "partly" loose

https://www.icloud.com/photostream/#A2G0ehgLGewsl

 

[twgas]

Disconnecting the frost stat would prove, one way or the other, whether that was the problem, a control clicking is not a reliable test.
After seeing the video, the valve is moving as I would expect, but doesnt eliminate it as the problem.
When the system is cold, with both HW and CH off at the prog. Does the the boiler fire?

 

[dolphinesian]

Hi all,

Thanks for all your help so far.

went to disconnect the frostat, before I do, can I check how it's weird?

See photo at below link.


https://www.icloud.com/photostream/#A2G0ehgLGewsl

 

[twgas]

Looks to be wired correctly, disconnect the blue wire and make it safe.

 

[dolphinesian]

Just did a test:

CH OFF, HWOFF, FS disconnect
turned up nest so it's heating.

The valve opened and the boiler fired on.

 

[dolphinesian]

I'll leave the frostat disconnected for a while and see if I get any different behavior.

I'll need to wait for the system to cool down to verify.

Either way though the boiler shouldn't come on and the valve shouldn't open if the programmer's CH is set to off.

 

[dolphinesian]

Hi all,

Disconnected the frost stat a few hours ago and so far so good, the boiler's been on heating the water at the correct time but the radiators have remained cool. Nest currently reading 23°C.

I'll continue to test for a few days.

Because the 'frost protection system' includes both a frost stat on the wall of the garage and a pip stat just above the boiler in the garage, if it turns out to be the "frost protection" causing the problem, should I replace both stats?

Thanks,

Glyn

 

[twgas]

I would suggest a fault is more likely to be in the "air" stat, but replacing both might be sensible as they are only a few quid each.

 

[dolphinesian]

Frost stat has been disconnected the whole time (pipe stat hasn't been touched).
I think the test has failed I'm afraid.

The house has been warm all evening, above 21°C. The Nest has not requested any heat. However the ensuite radiator has been warm and has gotten warmer and warmer as the evening has gone on.

It currently 'hot' and both the HW and CH are set to off.

I can hear the boiler's pump, although the boiler isn't currently fired up. Just pumping.

I've been checking the valve and it's closed (I.e. It is not loose for the whole length of the lever's travel).

I'm now starting to think that there are some radiators in our house, I.e. Our bedroom and the ensuite, which are plumbed in to the primary circuit on the wrong side of the CH motorised valve. There's probably also a wiring error somewhere too due to the fact that I'm sat in bed right now and can hear the pump going despite there being no demand from HW (timer off) or CH (Nest set to low temp for the night).

Any suggestions?

 

[twgas]

Ensuite may well be "summer operation " unusual though for bedroom.
Can you post a pic of the pipework from pump to valves?
I'm begining to suspect reverse circulation.