Potterton Suprima 70 L with Danfoss thermostat- new PCB & flow sensor - Fixed one issue now always on?

Joined
22 Aug 2022
Messages
5
Reaction score
0
Country
United Kingdom
So I moved into a house with a Potterton Suprima 70 L about 7 years ago, never really fiddled with the heating much as it just seemed to work on auto when required and be "off" in summer, hot water was always hot, great times. Those ended earlier this summer when the hot water ran out, boiler wouldn't fire after running the blower for about 7 seconds, turned immersion on and started troubleshooting.

Having never looked at a boiler before I was a bit out of my depth and spoke to a local plumber & gas engineer who had done work on a number of houses built at the same time with the same boilers, he popped round and did some bits, checked the air pressure sensor and it seemed ok (listened for the click I assume as didn't have a multimeter) and suggested swapping the PCB, I'd seen the new ones were nearly £300 do picked up a refurb for £70, this didn't solve it, no gas, no spark.

I kept on trying bits and after probing around with the multimeter for a while I discovered the mod to add the water flow sensor in series with the airflow sensor, this appeared to be the issue, discovered there's a pump behind the laundry rack the previous owners had installed which had seized, popped that off and disassembled and graunched as much iron grit out of it as I could and it now runs a treat, boiler instantly fired up which was exciting with half the covers off!

Fast forward a couple of hot summer days and I'm in the kitchen and realise the boiler is happily cracking on despite the hot water demand being off from the danfoss thermostat?! There's another danfoss box up in the hot water tank cupboard - is that likely to be it's power switch with fuse above the immersion switch? Anyway what do I need to do to fix the demand side? both Potterton PCB's seem to work fine, unless they've both failed in this exact same way? I'm more suspicious that after being turned off for a couple of weeks something has happened with the danfoss?
 
Sponsored Links

CBW

Joined
26 Sep 2019
Messages
14,172
Reaction score
4,338
Location
North
Country
United Kingdom
Sounds like a failed motorised valve. Either the head or complete valve would want replacing if this is the case.
 
Joined
30 Jan 2021
Messages
270
Reaction score
55
Country
United Kingdom
Photos are always good.
e.g. Danfoss box? Could be all sorts of things.
 
Joined
22 Aug 2022
Messages
5
Reaction score
0
Country
United Kingdom
Pictures below,
I'm not sure but I don't think it's a valve, more likely something reset in the danfoss manager bit because it was switched off for a couple of weeks

20220823_181330.jpg

20220823_183208.jpg
 
Sponsored Links
Joined
15 Aug 2010
Messages
26,278
Reaction score
12,782
Location
Livingston
Country
United Kingdom
As per @CBW most likely a motorised valve fault, first place to look for it is next to your HW cylinder, not always but a good place to start
 
  • Thanks
Reactions: CBW
Joined
22 Aug 2022
Messages
5
Reaction score
0
Country
United Kingdom
The motorised valves are the white blocks on the pipes right? Why would they effect the fact the boiler lights even when the little management unit has both hot water and central heating turned off? I know CBW said it but I don't understand how the two can possibly be related?
 
Joined
2 Oct 2021
Messages
508
Reaction score
219
Location
North Notts/South Yorkshire
Country
United Kingdom
Permanent live on motorised valve switched to feed boiler/pump when valve opens. If valve or micoswitch gets stuck live all time to boiler/pump.
If they are danfoss valves check valve is not latched on manual .
Lever should move easily.
 
Joined
22 Aug 2022
Messages
5
Reaction score
0
Country
United Kingdom
That fixed it, Thanks! The HW valve was jammed open, put a spanner on it and gently worked it back and forth till it was easy to move without the spanner, now all is working well,

I see how it works now, that seems really strange to me but I guess it's a kind of "pull" demand, if the thermostat says it's too cold, open the valve, once the valve is open then light the boiler to heat water?

Because it's the bit you interact with/what stops working I assumed the boiler would be the main control
 
Joined
4 Oct 2012
Messages
10,069
Reaction score
3,221
Location
East Renfrewshire
Country
United Kingdom
Thermostat calls for heat and powers up relative valve, valve opens and internal microswitch throughputs the switched live to the boiler, that fires the boiler up.
 
  • Like
Reactions: CBW

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Top