No control over hot water from central heating.

[barrata]

Hi guys

I hope someone can help.

I have an Ariston boiler, hot water cylinder and honeywell controls.

I've only just noticed that I am unable to turn on the hot water at the programmer(honeywell st6300a) yet the water heats up when the heating comes on. I can control the heating from the programmer but not hot water.

The mid position valve is a honeywell v4073A which gets very hot when the heating is on and it's obviously letting the ch water heat up the water in the cylinder even though the light indicating hot water is on does not light up on the programmer.

There's a standard honeywell thermostat on the cylinder, I've tried turning this fully down and up but it still doesn't allow the programmer to turn on the hot water or make the boiler kick in for water only.

I guess one of these 3 items is faulty but not sure where to start. I've checked the wiring and nothing seems lose in any of the connections.

Any suggestions as to which to change / look at first would be greatly appreciated.

Thanks

andy

 

[D_Hailsham]

Possible faulty mid-position valve. Here is how you check it.

1. Turn off CH and HW at the programmer and turn CH and HW stats down low
2. Turn HW on at programmer and turn the HW stat up to max. The boiler should light and the pump work.
3. If it works go to next step. If it does not work, either the programmer or the HW stat is faulty.
4. Turn the CH on at programmer, leaving CH stat low. The boiler should continue to run for HW
5. Turn CH stat up. The motorized valve motor should run and the valve move top mid position, so CH and HW are both on.
6. Turn HW stat down. The motor should run to open CH only and the boiler continue running for CH only.
7. Turn HW off at programmer. The CH should still run
8. Turn CH stat down. The boiler/pump should stop

The motorized valve only works if CH only or CH and HW are being heated. If HW only is being heated the valve is not operational

 

[barrata]

Possible faulty mid-position valve. Here is how you check it.

1. Turn off CH and HW at the programmer and turn CH and HW stats down low
2. Turn HW on at programmer and turn the HW stat up to max. The boiler should light and the pump work.
3. If it works go to next step. If it does not work, either the programmer or the HW stat is faulty.

The motorized valve only works if CH only or CH and HW are being heated. If HW only is being heated the valve is not operational

Thanks D. Well My problem is at no.1. I can't turn on the HW at the controller and the therfore the boiler won't fire. I guess it's the programmer or the HW stat then.

Thanks for the help. I'll get a new stat first and see what happens.

Andy

 

[D_Hailsham]

My problem is at no.1. I can't turn on the HW at the controller and the therfore the boiler won't fire. I guess it's the programmer or the HW stat then.

Do you mean that you cannot physically turn the HW ON at the controller (faulty controller) or that, when the controller shows HW ON, the HW Thermostat does not have any effect.

If you have a multimeter, check that there is 230V AC on one terminal of the thermostat when the programmer is turned on. the other terminal should show 230V AC when the thermostat clicks on.

 

[barrata]

Well it was the programmer that was faulty.

I disconnected it and there was a lot of dust in and around the casing so gave a good blow and then got the vaucuum cleaner on it carefully and cleared it all out. Works fine now.

Thanks v. much for the help.

andy