Danfoss FP975 - Light on, but boiler not switching on

[IanM18]

Hello Experts!

I have a Danfoss FP975, controlling Hot Water, and Central Heating.

Was working fine until yesterday, and this morning woke up to no hot water.

So, after some messing around, this is what i have unearthed.

The Hot Water buttons dont power up the boiler, the programmer unit clicks and the red light comes on, but the valve by the boiler doesn't whirr, and the boiler doesn't switch on.

If i use the manual switch on the Valve by the boiler, boiler comes on, and we get hot water.

Central Heating Control on the programmer, works fine red light on, valve whirrs and boiler comes on.

So, by the process of elimination, assuming its either 1) The HW Valve is faulty, 2)The signal isn't getting to the valve, or 3) the programmer is bust.

Any thoughts on what it could be?

 

[ianmcd]

Most likely the HW valve is faulty but could also be a faulty Cylinder thermostat (if you have one ) you need to get a multimeter and see if you are getting 240v AC at the Brown and blue wires feeding the HW Zone valve, if you are you will have to either fit a new Synchron motor or the actuator head if removable and if not the whole valve, synchron motor is the cheapest option if you are confident with electrics, if not get someone in

 

[IanM18]

Cheers, thank you.

I think it is the actuator thingy. Might have to get someone out, I could replace the head easy, as it’s one of the danfoss HPA2 and they are fairly cheap and easy, the problem might be, that the three we have, have been installed in such a way, as I don’t think there is room to lift the head unit off...I’ll try to post a piccy later

 

[ianmcd]

The HPA2 is a very easy one to change

 

[IanM18]

Lol, just had a look - might be easier than I think! There is a good two inch clearance at the top!

Guessing as it’s just a 2 port, it’s the two wire version I would need?

 

[ianmcd]

No it will have 5 wires

 

[IanM18]

This one?

https://store.danfoss.com/gb/en_GB/...uators-2-Way/Type:-HPA/p/087N6580?language=tr

Thanks for the help by the way, really appreciate it!

 

[ianmcd]

your link is not working, if you want to change the HPA2 and are uncertain about going in to the wiring center get one of these and power off and match like for like, makes it a lot easier although slightly more expensive

https://www.ebay.co.uk/p/REGE105-Re...ith-Strain-Relief/1405254704?iid=172837191838

 

[IanM18]

Sorry its taken so long to reply, had some other domestic stuff that had to take priority, and flicking the manual switch wasnt too much of a problem, but now is the time to fix! Have removed the old one, and it says HPA2 on the cover, haven't removed the wires yet so dont know if its 4 or 5 - does that mean its the HPA2 or the HPA2C? The only 5 wire one i can find is the C.

Before i mess this up, and give up and call the plumber - whats the difference between the 2 and the 2C? Would it be easier for me just to call the professionals? If its like changing a plug or removing one and replacing with another (with that connector), i can do that - but if there is some kind of 4 vs 5 wire wiring magic - then might leave it for the experts

 

[ianmcd]

check and see if the existing has 4 or 5 wires if HPA2 will only be 4 if HPAC will be five