Heating controls faulty after power cut

[Alicia Leonard]

Hello,

We have a robust, relatively new hot water & central heating system including a hot water tank and a system boiler.
We live in a fairly rural location and unfortunately experience power cuts quite regularly. In January this year, we had a power cut which resulted in a failure in our heating system (the hot water was working perfectly!). A British Gas friend determined that the heating valve was not responding when the heating was switched on. However, when forcing open the valve, the heating would work but ONLY when the hot water was firing up the boiler. Eventually a plumber came and fit a new heating valve which seemed to fix the problem. Only a couple of months later, the same thing happened again. A power cut resulted in our heating not working. We have lived with it for a while now but as the weather is getting colder, it’s just not heating the house up (as the hot water tank obviously heats up fairly quickly, therefore by the time the radiators are warm, the heating stops when the hot water stops firing the boiler.)

Id love to know if anybody can elaborate on why this is happening? Is there any way to prevent it in cases of future power cuts? Would it help to get an isolator switch with a fuse for the heating system? Any help would be much appreciated.
Thank you!

 

[ianmcd]

What motorised valves do you have, if not sure post pics, some are cheap rubbish, power outages shouldnt reall affect them though, they are disigned to power on and off

 

[flameport]

The fault is more likely to be a programmer/timer/thermostat not working as intended after the power is lost.
You need someone who can actually identify the problem - just wwapping components randomly is a very expensive way to eventually locate the fault.

 

[stem]

As you have had the valve fixed at the time, your query relates as to why it failed.

First of all, the symptoms you describe do fit the pattern of a failed motor in the motorised valve.

A British Gas friend determined that the heating valve was not responding when the heating was switched on.

The valve sits when 'unpowered' in the hot water only position, when the heating calls for heat, the valve's motor (when it works properly) winds it across to open the heating outlet.

when forcing open the valve, the heating would work but ONLY when the hot water was firing up the boiler.

When the valve is opened manually, it goes to the centre position (heating & hot water) which is generally not far enough to operate the switch at the far end of its travel which it needs to do to start the boiler. However, when the hot water is turned on, the hot water cylinder thermostat starts the boiler instead, and hey presto, as the valve is in the central position, both the hot water and central heating come on.

The valve is operated by a synchronous motor.....

.....so when the motor fails it won't move the valve away from the hot water only position. These motors are not particularly robust pieces of equipment and do fail. In use, once the motor has wound the valve away from its rest position, it remains powered but in a 'stalled' state to hold it there whilst ever the heating is running and so using energy and cooking its windings. 3-Port valves can also stay "stalled" in their last used position, even overnight when the heating has gone off, shortening their life even more.

If this happened only once, I would put it down to coincidence, twice, not so sure... (assuming it is the motor again). If it happened every time there is a power cut then it maybe that there is a surge when the power is restored, but if that was the case, I would expect other devices to suffer also. Especially in the sequence of operation, it would mean that the programmer and thermostat (if mains powered) would both be energised before the motorised valve was.

When the motor fails, it can be replaced very quickly and cheaply. The whole valve head doesn't need replacing, and there's no need to drain the system down. So my suggestion would be to keep a spare motor to hand. That's what I do.

You can buy one online here for £10

I wonder if anyone else in your area that has suffered the same power cuts has had any similar problems?

 

[Gasguru]

Don't waste your time with that motor...or anything from Banico. Some of the worst knock off heating products around.
Always get a genuine motor...easily available as the bagged Drayton replacement from Screwfix etc. It will say Synchon Made in USA on the lid.
All other motors are hopeless...I've had them barely last a year.

 

[Alicia Leonard]

What motorised valves do you have, if not sure post pics, some are cheap rubbish, power outages shouldnt reall affect them though, they are disigned to power on and off

The valve we used to have, which was replaced, was the Honeywell 2 port valve. The newer valve is a Drayton valve.

The fault is more likely to be a programmer/timer/thermostat not working as intended after the power is lost.
You need someone who can actually identify the problem - just wwapping components randomly is a very expensive way to eventually locate the fault.

Should I be getting an electrician to check these? Or could the plumber/gas engineer check the other components?

As you have had the valve fixed at the time, your query relates as to why it failed.

First of all, the symptoms you describe do fit the pattern of a failed motor in the motorised valve.

The valve sits when 'unpowered' in the hot water only position, when the heating calls for heat, the valve's motor (when it works properly) winds it across to open the heating outlet.

When the valve is opened manually, it goes to the centre position (heating & hot water) which is generally not far enough to operate the switch at the far end of its travel which it needs to do to start the boiler. However, when the hot water is turned on, the hot water cylinder thermostat starts the boiler instead, and hey presto, as the valve is in the central position, both the hot water and central heating come on.

The valve is operated by a synchronous motor.....

View attachment 251822


.....so when the motor fails it won't move the valve away from the hot water only position. These motors are not particularly robust pieces of equipment and do fail. In use, once the motor has wound the valve away from its rest position, it remains powered but in a 'stalled' state to hold it there whilst ever the heating is running and so using energy and cooking its windings. 3-Port valves can also stay "stalled" in their last used position, even overnight when the heating has gone off, shortening their life even more.

If this happened only once, I would put it down to coincidence, twice, not so sure... (assuming it is the motor again). If it happened every time there is a power cut then it maybe that there is a surge when the power is restored, but if that was the case, I would expect other devices to suffer also. Especially in the sequence of operation, it would mean that the programmer and thermostat (if mains powered) would both be energised before the motorised valve was.

When the motor fails, it can be replaced very quickly and cheaply. The whole valve head doesn't need replacing, and there's no need to drain the system down. So my suggestion would be to keep a spare motor to hand. That's what I do.

You can buy one online here for £10

I wonder if anyone else in your area that has suffered the same power cuts has had any similar problems?

Thank you for your detailed response. The photo posted above shows my entire heating system - there are two separate valves, so one for heating and one for hot water. Its very odd - the first time it happened we couldn’t say 100% that the power outage did it. But the second time, the heating worked the previous day and once the power outage happened, the heating wouldn’t work. the thermostat clicks when we turn it so we think it’s still functional. The controls on the wall seem to work for the hot water etc but just not for the heating valve.

 

[stem]

OK, having seen the photos, you don't have a 3-Port valve, but have 2 x 2-Port valves instead. However, the description of the fault still applies to the valve, the heating valve when opened manually won't trigger the boiler switch, but the hot water valve that does work will when the valve opens electrically, so the symptoms are the same.

If you, or someone you know has a multimer and knows how to use it, it's easy to measure the voltage across the L & N supply to the motorised valve. If there's 230V there when the heating should be 'on' and the valve isn't opening, then the programmer / thermostat have operated OK, but the valve has failed. (again!)

 

[ianmcd]

If it is the valve that has failed, the power outage is just a coincidence, more likely to be a faulty programmer if the power outage was a factor