Hot water system stopped working.

[scooby1]

I have a Worcester oil fired boiler system for heating and hot water. The heating system is working fine. The hot water system has just stopped working. The hot water system is controlled by a Honeywell ST9100C programmer and there is power to that because the green light is on and there is data on the screen. When I press the Extra Hour button that shows on the screen as 1, 2, or 3 hours depending on how many times I've pressed it.

But when I do press it nothing happens - the boiler doesn't kick in and it didn't kick in at the normal time this morning. Is this likely to be a programmer issue, something down in the boiler, or something else ? We have of course got a house full of family over Christmas and I bet I'm not going to be able to get our heating service company out tomorrow or Christmas Eve.

Thanks in advance for any help that can be given.

 

[CBW]

Do you have a zone valve? You might be able to kick it in using the manual lever, but try your luck with a heating engineer, you never know. Do you not have an immersion heater?

 

[scooby1]

Thank you for your quick reply. Sorry but I don't know if I have a zone valve. Any pointers to that or is it too difficult to explain ? We have used the same heating/plumbing people for over 20 years and have always had our boilers serviced by them We have a good releionship with them. Yes, we do have an immersion heater and I have switched that on (first time since we built the house 9 years ago ! ) and that seems to be working. We have also got a couple of solar panels ( not PV) that will help if we get a bit of sun. But if it was a case of just replacing the programmer I would pop into Screwfix who have the latest compatible model and fit it.

Thanks again.

 

[CBW]

Very much doubt it’s the programmer, as it’s working. The programmer sends a live to the zone valve (aka motorised valve) and that then powers across hits a microswitch and sends a live out to the boiler. It would be in the airing/cylinder cupboard and looks similar to one of these:

 

[scooby1]

Ah, understand what you mean now. I've got 3 motorised valves in the boiler cupboard. ( none in the loft as far as I can see) We have underfloor heating and I assume that the 2 MVs that are side by side (but on different lines) are for the ground floor and 1st floor manifolds and maybe the lower MV is for the hot water ? Years sibce I dealt with an NV. Can I over-ride it by moving the small lever ?

Thank you very much for your help. It is much appreciated.

 

[CBW]

Yes you can override by moving the lever, but this is only temporary. If you’ve got this good relationship with your heating engineers, contact them and see if they can squeeze you in, if not use the manual lever until the they can. Might be worth moving it to heat the water for a while, then move it back. As I said it’s only temporary, unless you can use the immersion, but don’t forget to turn that off either. Try and trace the pipework to the entry/exit points on your cylinder, then you’ll know which is the hot water valve.

 

[scooby1]

UPDATE I have just moved the levers on all three Honeywell MVs to the Manual Open position and then gave the hot water programmer 1, 2, and 3 hour advances and also put it on continuous mode and it would't fire up.

 

[ianmcd]

UPDATE I have just moved the levers on all three Honeywell MVs to the Manual Open position and then gave the hot water programmer 1, 2, and 3 hour advances and also put it on continuous mode and it would't fire up.

You have to manually open the HW valve and latch it open, then switch a CH one on with the thermostat turned up and it will fire the boiler and pump and hence heat the HW cyl, manually latched valves will not bring the boiler on

 

[scooby1]

But I thought that if I latched all 3 valves open (to make sure that I've got the hot water one open) and played with the programmer I could get the hot water to kick in but just had another thought. I've had the immersion heater switched on since this morning and so maybe the water temperature is so hot that is the reason why I can't get the boiler to kick in ?

EDIT The hot water and heating are programmed to come on at different times. The heating comes on at 6pm I think.

 

[scooby1]

After showers this evening I am going to switch the immersion heater off and then tomorrow morning I will open what I think is the MV for the hot water and see if I can get the boiler to kick in. I have replaced MVs before but a long time ago. Amd I correct in thinking that it's just the guts of the thing that are replaced, not the complete valve which would mean undoing the pipework ? I understand about all that only being a temporary fix but at least ti should show me if the hot water MV is faulty (I think !!)

 

[ianmcd]

you are not getting it, when you latch the valve open, IT WILL NOT BRING THE BOILER ON, if you latch the DHW valve open it will not matter what the temp of the Hot water is, you are just manually opening the valve, you will then need to switch on a heating zone which will fire the boiler, and because the HW valve is manually opened the water will go to the Cylinder

 

[CBW]

Yeah usually just the powerhead (actuator) rather than full valve, although yours look like Honeywell, I can’t see any dimples (an indication if it’s a drain down or not). As per @ianmcd you need to be turning the heating on as well to fire the boiler, which will then send water from the boiler to the cylinder and radiator circuit(s).

 

[scooby1]

Thank you Gentlemen. But I actually don't understand this. Our HW is timed to come on a 4pm. The CH is timed to come on at 6pm. Surely the HW can come on without having to give the CH a kick ? Sorry if I'm being a bit thick. And yes, they are Honeywell MVs. Let me try and clarify. I am supposing that the one MV on it's own, down at the bottom of my image, is the one for the HW. I opened that and then put the HW programmer on to various settings including continuous but the boiler wouldn't fire up. And then I thought maybe that was because I've had the immersion on all day and the water in the tank is so hot that it wouldn't allow the boiler to fire up. Incidentally we are on a pressurised/direct system or whatever it's called. i.e. no header tank, just one tank in the tank room and if the mains goes down then nothing works.

 

[ianmcd]

OK one last try, when a zone valve is working correctly, when a demand is requested power is supplied to the valves motor which opens the valve , once open it moves further and presses in the micro switch , this micro switch then sends power to the boiler to fire it, when you manually open the valve it does not go as far as to make the micro switch it simply opens the valve, so no signal for the boiler to fire, you need to bring one of the working valves on to open properly and that valve will tell the boiler to come on

 

[scooby1]

Ah, now I understand ( I think ! ) Thank you. Have had our showers now and have switched the immersion off. Tomorrow morning I will open the MV for the HW manually and then press Extra hour on both the heating system and on the HW system. That should show me if the MV for the HW is working correctly or not Y/N ?