No switched live to boiler when hot water tank thermostat demands heat + CH staying on.

[zipster]

Hi folks. I have a couple of issues, any help advice much appreciated.
1. When my hot water tank thermostat demands hot water (wired into Honeywell wiring centre), I do not get a switched live to the boiler. I get 69 volts ac for both on and off wires from the tank stat. I have fitted a new tank stat, same results.
2. When my heating comes on, it stays on. ie the spring on the Y plan motorised mid position valve stays open. I have to turn the power off and then back on in order for the spring to recede and stay there (once CH temperature is satisfied).

 

[SJB060685]

1. Have you checked the voltages from programmer to wiring centre and cylinder stat? You should have 230volts on grey wire when HW is off or cylinder stat satisfied and 230 volts to cylinder stat common when in HW mode.
2. What you're describing is how the mid position valves work, it holds the last port of call

 

[John.g]

Hi folks. I have a couple of issues, any help advice much appreciated.
1. When my hot water tank thermostat demands hot water (wired into Honeywell wiring centre), I do not get a switched live to the boiler. I get 69 volts ac for both on and off wires from the tank stat. I have fitted a new tank stat, same results.
2. When my heating comes on, it stays on. ie the spring on the Y plan motorised mid position valve stays open. I have to turn the power off and then back on in order for the spring to recede and stay there (once CH temperature is satisfied).

These may be of assistance.

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[Ziggie]

The 69 volts is normal . It’s a back voltage from the 3 port when both HW and Heating are on



my guess is you have a wiring problem.
Heating off HW on
trace voltages from programmer, in to stat, out of stat, and common (3 wires needed)
Connection 1 (demand)from stat should give 240 on orange.
Test schedule
hW on heating off
240 orange from cyl stat(demand)
Turn cyl stat off
240 Volts Grey wire from stat (no demand)
Turn programmer heating off cyl on same result
Heating on HW off
240 V grey 240V white
Both on
3 port mid
240 v orange 240 V 69v Grey


Hope this helps

 

[zipster]

The 69 volts is normal . It’s a back voltage from the 3 port when both HW and Heating are on



my guess is you have a wiring problem.
Heating off HW on
trace voltages from programmer, in to stat, out of stat, and common (3 wires needed)
Connection 1 (demand)from stat should give 240 on orange.
Test schedule
hW on heating off
240 orange from cyl stat(demand)
Turn cyl stat off
240 Volts Grey wire from stat (no demand)
Turn programmer heating off cyl on same result
Heating on HW off
240 V grey 240V white
Both on
3 port mid
240 v orange 240 V 69v Grey


Hope this helps

Thanks Ziggie. It was the Honeywell wiring panel. It was one with a circuit board and some cut links. I binned it and replaced with a length of screw in electrical connectors. It’s worked perfectly ever since.