Boiler & Hot Water on at 4am !

[mamonem]

Hi

Our Hot Water has been coming on at around 3-4am in the morning despite the timer being switched off. The Central heating is off.

I know there are 2 x Zone Acuator Valves (Drayton ZA5 2 Port), one for Hot Water and One for Central heating. Digging around in the dark, I can see that the valves are both in the 'A' position, so closed. I presume the Thermostat only calls Central heating so am ignoring that. THe only way of stopping it is to power down the boiler.

In the morning I experimented with the Hot Water Value - call for water switches it on (you can see the motor move from A to B and hold it. If I switch it off, it returns to A. I've sent the videos of how its working internally, and it looks to be working - switching on/off.

SO ....

If the Timer is OFF. If i've discounted the Thermostat because its hot water not central heating. If the Valve in question 'appears' to be working.

What on earth is it?

It had been working fine for a long time. The boiler is relatively new, serviced, all installed by professionals. So dont think a sudden-wiring problem could occur.

Ideas? Or things to try?

 

[oldbutnotdead]

Is the boiler in an outhouse or garage? Does it have frost protection enabled? Or is there a setback temperature on the controller? (Lots of modern ones tend not to actually be off but allow you to set a low room temperature eg 10°). 4am is certainly when it gets coldest up here.
EDIT Quick reread would seem to eliminate the controller. Questions re the boiler still stand.

 

[oldbuffer]

Things to look at:
1. That the clock in the programmer is working properly and is correctly set.
2. Whether the boiler / system has frost protection which is kicking in.

 

[CBW]

Just sounds like the microswitch has started to fail inside the ZA5.

 

[mamonem]

Hi.

Boiler and Tank are in the house. The only control on the boiler is a temperature dial on the front which I think is water temperature - it’s at 3/4.

I’ll check timer clock bur think it’s ok. It has been working.

I wondered about micro switch - the motor turns but is it actually triggering the switch properly and reliably, im not sure. Guess I could multi-meter it but I’d need to take it off etc so might be better to just replace that.

Wasn’t sure if there was anything else before spending the £50 or so

Guessing that hot water is either triggered by the timer - or a failing switch in the flow can open the value and trigger the boiler. Right?

Newbie to this C/H malarkey

 

[CBW]

You don’t need to take it off. Next time it fails, you could test for voltage on orange and earth/neutral, if 240Vac or there about, and it’s faulty.

 

[mamonem]

Great. I shall ready my multi meter and torch then in my Pj’s thanks

 

[stem]

Our Hot Water has been coming on at around 3-4am in the morning despite the timer being switched off.

If it is just a microswitch failure then whilst that would start the boiler running, the hot water wouldn't heat up because the valve would still be shut. For the water to heat up the valve would need to be powered such that its motor it winds it to the open position and keeps it there allowing hot water from the boiler to enter the hot water cylinder.

So, I would be looking to see where the motorised valve is getting the power from that's operating the motor and winding the valve open. This is how it should be connected:

I came across an installation with the same fault. It had a frost thermostat that had been connected to the wrong motorised valve by mistake. Instead of switching the heating on it switched the hot water on; usually in the middle of the night when the temperature had dropped to the lowest point.

However, I see @oldbutnotdead mentioned a frost thermostat and you've not commented on this. So, if you don't have a frost thermostat you can ignore this last bit.

Another possibility is that the hot water channel of the programmer is faulty and permanently 'on', often caused if someone has created a short circuit at some point. Then in the night when the hot water cylinder cools, the cylinder thermostat operates and opens the motorised valve.

 

[mamonem]

Interesting. Last night it didn’t seem to fire.

It’s a Worcester boiler with frost protection that will run water if below 5 degrees.

It seems very hit and miss.

M

 

[stem]

The boilers own internal frost protection system wouldn't operate the hot water motorised valve, it would just fire the boiler, and if your boiler is indoors and the property is heated during the day, there would also be little chance of it dropping to 5C and it kicking in overnight.

The frost protection system I was referring to is an external thermostat located in an area where there was a risk of any components associated with the heating system being exposed to the possibility of freezing, such as an unheated outbuilding or garage. They look something like this:-

Only a relatively small percentage of installations do have them as the majority have their components inside the property.