No Hot Water!

[Nevets69]

My boiler has been kettling and the rads not getting very hot, so on Monday I drained the system, filled it/drained it again, then filled and added a bottle of Sentinel X800 cleaner and left it for 24 hours. I had the heating and hot water on for several hours on Monday evening and then left it to do its thing as normal via the timer.

Yesterday I drained it, filled/drained it again and then filled and added a bottle of Sentinel X100 inhibitor. The water came out with an orange tint so I guess the X800 did its job. The rads now get nice and hot and the boiler is running a bit quieter.

However.

The boiler dosn't come on when I switch on the hot water, and if I switch on the hot water when the boiler is running the central heating it shuts down.

I can hear the motor in the 3 way valve whirring, but then the boiler shuts down.

Any ideas chaps?

I'm wondering if some crud has lodged in the 3 way and it's jammed.

The system is a 24 year old Potterton Profile boiler in a conventional open vented system with a small header tank in the attic.

TIA!

 

[stem]

When hot water is required, and where systems have a 3-port valve it's actually the hot water cylinder thermostat that switches the boiler on, and not the motorised valve. So, if the boiler isn't operating that is where I would be looking first to see if any of the connections to the cylinder thermostat have been disturbed.

The whirring will probably be the valve positioning itself in the centre position, for heating and hot water which is the correct position, but the heating will go off because as I said before in this position it is the cylinder thermostat that is responsible for keeping the boiler running.

 

[Nevets69]

I didn't touch the thermostat or any of the wiring to or from the boiler. The only thing I did at the boiler was to turn it off at the mains switch when I drained it.

I've just turn the thermostat up and switched the hot water on, but nothing happened.

 

[Gasguru]

Have a look at a Y plan diagram and check the voltages etc. Be aware that pin no.s on thermostats etc. will refer to the specific labeled controls...yours are likely to be different.

 

[stem]

If you look at the animation here, it shows what should be happening when both heating and hot water are required. If the boiler is working OK with the central heating, but goes off immediately hot water is selected, it means that the switched live to the boiler is missing. In the animation, it's the right hand flashing yellow line shown going from the cylinder thermostat to the boilers switched live connection.

It is possible that the 'HW on' from the programmer that goes to the cylinder thermostat is missing, and would cause the same symptoms, but I would have thought that this would have been less likely to be disturbed by the work you have carried out. It would be fairly easy for someone competent in the use of a multimeter to check the wiring.

 

[Nevets69]

Thing is though when I switch on the hot water, the motor at the 3 way valve whirrs, which suggests that there is power.

I've just had another look and the position switch dosn't move when the 3 way valve motor is whirring.

 

[stem]

If the valve is moving from 'heating' only to 'heating and hot water' you may hear it move. But in your case that is irrelevant it's the cylinder thermostat that will switch on the boiler, not the motorised valve. Once the boiler is working the valve simply directs the water to its destination. Heating / hot water / or both

The lever doesn't always move when it operates electrically, it usually stays in the 'auto' position. The lever is there for manual operation to hold the valve in the centre position during filling to help prevent airlocks.

 

[Nevets69]

OK I hear what you're saying about the thermostat, but I just don't understand how the work that I've done could have affect it or the wiring.

I havn't disturbed any of the wiring and everything was working fine on Monday night....

 

[potterton678]

This is a known issue and easy to fix.

 

[ianmcd]

This is a known issue and easy to fix.

well dont leave it there please enlighten us all

 

[Nevets69]

well dont leave it there please enlighten us all

Yes.

 

[bellairaphon]

Thing is though when I switch on the hot water, the motor at the 3 way valve whirrs, which suggests that there is power.

I've just had another look and the position switch dosn't move when the 3 way valve motor is whirring.

The valve will get power to close the heating port on the valve. As stated the switch live comes from the cylinder stat.

If you can use a multimeter you need to check the voltage to the cylinder stat. This will indicate if the programmer is sending the voltage for hw on and also hw off.

Perhaps a photo of the programmer cylinder stat.