Heating on when only ho****er selected

[Unregistered]

When heating only is selected, no problem - heating goes on/off controlled by the room thermostat.

When hot water only is selected and hot water is below temp, 3 way valve moved to 50/50 position and both hot water tank and radiators get hot. When hot water reaches temp, 3 way value moves to 100% heating, boiler carries on and central heating keeps getting hotter. Room thermostat is set to min/off and ignored.

Originally thought it was the programmer, so changed the elderly Drayton LP241 for a new LP522. No change in behaviour.

Boiler: Glow Worm Ultimate 30
New Programmer: Drayton LP522
Old Programmer: Drayton LP241
Thermostat: Drayton CombiStat (9 months old)
3 way motorised value: Danfoss

 

[SimonG]

First thing is to register on the forum.

 

[zilly88]

now registered

 

[finchy01]

3 way valve sounds like it's stuck. Remove the head and see if the spindle moves by turning it with your fingers. If not it will need replacing.

 

[zilly88]

3 way valve sounds like it's stuck. Remove the head and see if the spindle moves by turning it with your fingers. If not it will need replacing.

Thanks for your reply. I removed the head from the value, and the spindle turns freely an easily, so it isn't stuck. If power to the system is turned off, by turning off at the isolation breaker, the valve motor powers down and the valve resets to the water only setting because of the internal spring. The value motor is being powered to move to the heating setting which is why I originally suspected the programmer unit, but replacing it hasn't fixed the issue.

The installation is many years old, but it has only started doing this in the last 3 days, so something has changed/failed. Another possible candidate is faulty frost detection by the boiler, but I would have thought this would cause the heating to fire up regardless of the programmer's setting, not just when the water is on.

 

[Gasmk1]

possibly the wiring is different for the programmers it may not have been like for like.

 

[zilly88]

possibly the wiring is different for the programmers it may not have been like for like.

Drayton claim compatibility and I can't see any difference in the pinouts from the manuals.

Also checked the manual for the boiler, a Glowworm Ultimate 60FF, not the Ultimate 30 stated above (I misread the model label). It doesn't have built in frost detection, so that rules that out.

 

[mejmag]

Sounds like your 3 port is faulty. Which model is it? Drayton, Danfoss, Honeywell etc...?

 

[zilly88]

Sounds like your 3 port is faulty. Which model is it? Drayton, Danfoss, Honeywell etc...?

It's a Danfoss

 

[zilly88]

It's a Danfoss

Actuator model is HSA3. One of the internal micro switches may have jammed. I'll replace the head unit at the weekend to see if that makes a difference.

 

[mejmag]

That's what I'd do. Head just unclips and its 5 wires. Changed a lot of HSA3's.

 

[SimonG]

Heads on two flat head screws.

Hard to know what to replace with.

Hsa's are cack.
Honeywell not what they used to be.
Drayton, dont change many but dont find many installed.

 

[mejmag]

That's right. Two screws to take the head off. I was mistakenly thinking about a Drayton MA1. I do agree with simonG, damfoss hsa3 are unreliable. Drayton MA1 is just as unreliable. Honeywell seems to be most robust, as I rarely change many of these. That's just my experience.

 

[zilly88]

Thanks everyone! I replaced the actuator and everything is OK now. Used another Danfoss HSA3 as that's what the local spares shop had.

I'd missed that when the motor was in the mid position, it was clicking. Apparently this is a sign that the actuator is faulty. I'll take the unit apart later to see what the fault was.

 

[zilly88]

Took the actuator apart. One of the two micro switches in the actuator had jammed in the 'on' position.