No hot water (CH works)

[Malakym]

Suddenly lost hot water (Boiler + Hot water tank) - a few days ago it wasn't as hot as we expected so I thought the thermostatic valve in the however this time check a normal tap and nothing.

Turning CH on, boiler runs, pump runs, valve to CH opens, can feel the pipes get hot.

Turning HW on, boiler doesn't start, pump doesn't run, valve to HW doesn't open.

Manually opening HW valve doesn't help since pump isn't running (pump is connected to the boiler, not the honeywell controller).

Next step check the thermostat on the hot water tank - I can hear it click round the 10c mark to show its trying to activate. Check the contacts and I can get continuity (and not) if I turn the dial above and below the current temp - I think this is working okay.

Check the continuity to the Honeywell terminal junction box (to the tank's thermostat) and this is okay.

It's a run of the mill Honeywell ST9400C. The relay for CH and HW both click as I would expect.

I'm guessing the issue is with the timer still?

 

[terryplumb]

Is the motorised valve for hot water receiving voltage from the cylinder stat ?

 

[CBW]

Sounds like a faulty motorised valve, not making the microswitch inside. If the head is detachable, then detach, move spindle to manual, or even lock the hot water valve into manual position and fire up the CH, this should give you some hot water unto you can fix it.

 

[Malakym]

Yes it seems to be the valve - It is receiving 240.

I had thought the pump would have still started (so I could lock it open) so didn't check the valve sooner.

If the valve needs to provide continuity - can it be bypassed and locked on? (We're no longer using CH)

The head has a lock on it, thanks for the suggestion, I had thought of that but wanted to avoid it for the moment.

 

[CBW]

The head has a lock on it, thanks for the suggestion, I had thought of that but wanted to avoid it for the moment.

Pump would only start once microswitch made, unless it’s a 3 port valve.

 

[Malakym]

Pump would only start once microswitch made, unless it’s a 3 port valve.

The (external) pump is connected directly to the boiler, it seems the timer is switching the power to the boiler entirely.

It's a 2 port valve with microswitch (40003916-001). Okay to bridge this switch manually?

 

[terryplumb]

Manually latching the valve open will not fire up the boiler.
The valve has 240v permanently to its microswitch. Is it getting 240v from the cylinder stat ? If it is replace the actuator head.

 

[Malakym]

The motor was getting 240 but not moving so assume the motor is at fault.

Will get a motor on order, easy swap.

Microswitch itself is working.