DIY Doctor UK DIY Forums

Since turning the heating on this winter, the central heating programmer (Drayton UP2) is not working as it should. All other parts of the system seem to be working fine, the boiler boils (Worcester Bosch Greenstar Ri), the pump pumps and the diverter diverts. Both room and hot water tank thermostats are only 18 months old and appear to be working correctly. However, the heating and hot water circuits no longer want to co-operate with each other.
Example 1: A cold day means we want to turn the heating ON mid-afternoon and use the advance feature. The control light turns green, but nothing happens. If we also turn ON the hot water the system fires up and the diverter valve goes to the central position. If the hot water is turned OFF the diverter goes to heating and the system stays on.
Example 2: Early evening when washing up we find we have no hot water. The UP2 is showing both circuits ON as scheduled. If we turn the heating OFF the diverter valve goes across to the hot water and heats up the tank. Turning the heating ON again moves the diverter to the central position.
I have thought of changing the programmer, even upgrading to a Hive, but I am mystified by this and do not want to purchase anything new until I understand the root cause of the problem.
Anyone any suggestions?

I would guess the V3 micro switch inside the motorised valve has failed, you may be able to renew just the head, but until fixed if you latch the bleed lever on the motorised valve it will likely mean heating will work.

Can't leave it like that, as in the summer when there is a call for DHW the CH will also heat up.

But seems very likely problem is the motorised valve, not the programmer.

ericmark wrote:I would guess the V3 micro switch inside the motorised valve has failed, you may be able to renew just the head, but until fixed if you latch the bleed lever on the motorised valve it will likely mean heating will work.

Can't leave it like that, as in the summer when there is a call for DHW the CH will also heat up.

But seems very likely problem is the motorised valve, not the programmer.

Thanks but if it was the motorised valve would it not just be stuck in one position? This has happened before and I am on my third valve in 20 years. At £80 to replace a Draytom MA1, I am well fed up with them. My curent situation is I can get the valve to move to the correct position by jabbing the programmer buttons often enough.

The motorised valve acts as a relay, the valve moving pushes a small micro switch google "V3 micro switch" and you will see what they look like.

They cost less than £5, however as to opening the valve head and fitting new switch, I would not want to do it, I would buy new head, but up to you.

Yes, it was the motorised valve a British Gas engineer fitted a new head today. They were bemused by the way it was behaving and had not seen those symptoms before. However, a new head sorted the problem. The Hot Water and Heating now operate independently of each other, or the valve adopts a mid-position if both calling for heat.