Heating/hot water issue - unable to find anything similar

[Matt_Gordon]

Hello,

Apologies if this is a very simple fix and I haven't yet found the solution.

I have a Y-Plan, open vented system with a Worcester Greenstar Ri
generally everything functions as expected except for one particular situation and that is:

If the hot water is on and I switch the heating on (manual override at timer controls), everything works as normal, but if I then attempt to switch the heating off it continues to heat the house and will not stop unless I also turn off/cycle the hot water (set to manual 'on' 24/7). I can then switch the hot water back on and it not affect the heating at all.

Its as if the hot water being on, blocks the heating from turning off.

Any thoughts and pointer would be appreciated.

FYI. I am happy to look at wiring at the consumer parts (thermostat, remote controls, etc..) but will not be going anywhere near the boiler apart from the two consumer available/allowed dials on the front of the unit.

 

[doitmyself]

If the hot water is on and I switch the heating on (manual override at timer controls), everything works as normal, but if I then attempt to switch the heating off it continues to heat the house and will not stop unless I also turn off/cycle the hot water (set to manual 'on' 24/7). I can then switch the hot water back on and it not affect the heating at all.

Is this a new problem, i.e it worked correctly previously?

 

[Matt_Gordon]

Unfortunately I can't be 100% sure as the previous controls failed and were replaced with a digital set. To try and test the controls I swapped out the timer for a simple '2 relay' type and can replicate the issue as described by manually setting them on/off. My gut feeling is wiring or boiler but I was hoping this might be a "oh yeah we see this all the time" type of issue.

 

[doitmyself]

If you employed someone to install the new digital set, I would get him back to sort the problem out. It sound like a wiring problem, which could be difficult to resolve remotely.

 

[Matt_Gordon]

No, as it was just the controls I bought a honeywell off the shelf timer which just slotted onto the existing plate on the wall. I checked the wiring and there are no loops or anything at that end, and it also matched the wiring as shown in the diagrams on the instructions. I guess I will need to get someone in.

 

[doitmyself]

Which model timer did you buy?
Did you check that it was set to (P)umped and not (G)ravity? (not all timers have this feature)?
A pic of the backplate would help - to check wiring - as would a pic of the junction box (with lid off - careful 240V present) where everything is connected.