Potterton Suprima 40

[bster]

My mates fully pumped (3port mid pos) open vented with combined feed and vent system, is playing up!

when there is a call for DHW the sytem works fine but when there is a call for CH the boiler fires then locks out after 10seconds odd?

We have replaced the programmer and the 3-port valve and have recently drained the system for rad work, the house is being done up and the owner doesnot know if the system has ever worked properly as the programmer was broke and the 3 port valve actuator was not attached when he bought the house, he also removed the programmer himself and may have messed the wiring up (Horstmann C21, i think) but i'm sure it is correct.

I am confident its nothing to do with the boiler as it doesnt lock out when there is demand for DHW, but wanted to double check that this is correct?

I am going to check\replace the room stat (currently a Potterton with the demand and satisified LED's) then if that fails rewire the wiring centre.

Can some confirm that the boiler cannot be the problem if the DHW works fine, saves me downloading the manual.

 

[croydoncorgi]

Roomstat cannot be causing the lockout problem - if the boiler fires at all for CH then the stat has operated (or is stuck shut).

If you're SURE the 3-port, pump etc. are correctly connected, then they can't be causing the problem either! If the boiler works fine for HW, then it (and the pump) should be OK. But if it locks-out immediately in CH mode, I reckon there must be a serious plumbing problem: one or both of the output ports on a 3-port mid-pos valve are ALWAYS open, so if it's correctly plumbed there SHOULD always be an open path back to the boiler -so no overheat lockout. Look for isolating valves left shut, airlocks in the CH pipework, blockages. Is the pump correctly wired? (it should be connected to the correct tags ON THE BOILER.

 

[Agile]

I think we can discount the pump as thats works ok on HW.

It seems to me as if there is no CH flow. Probably either a pipe is blocked or all the rads are turned off at at least one valve.

Maybe all the TRVs have their pins stuck down or just off because the weather is hot!

Tony

 

[bster]

I doubt there is a pipework prob as the system is 12years old and original, the guy gas had rads off and on so i'll double check that they are all open and bled properly there is a gated 15mm bypass though the MI says 22mm bypass.

The pump is wired correctly to the boiler for it to overrun.

I'm going there to do some taps tonight so i'll post back later with an update on the blocked pipe unopened rads thing.

cheers people.

 

[Agile]

Pipes can block in two weeks if its pumping over!

If rads have been off then they are probably still turned off!

Tony

 

[bster]

i've just put a new rad and pipework in, all the rads turned on, refill and the same problem again????

The programmer is correct, so now i'm going to rewire the wiring center from scratch (the 4 wire cyl stat needs replacing anyway).

update soon.

BTW the 3 port CH on (white cable) is correct from the roomy

 

[bster]

Right then.. Switched the 3port to manual and fired boiler (CH) same thing happened, so this means that there is no blockage as the flow would circulate around the coil (because DHW works fine) if the CH pipes were blocked\airlocked, yes?


Defo the wiring i thinks.

 

[Vic Spanner]

so now i'm going to rewire the wiring center from scratch (the 4 wire cyl stat needs replacing anyway).

4 wire cyl stat is it out of the ark royal
Deffo time for a rewire.Buy a control pack for £70 and then wire up by numbers

 

[bster]

I've put a new Honeywell 3port in but the Potterton cylstat works fine.
so its not necessary to replace it, the home owner is doing the place up to sell so is not really wishing to spend money on things that ar'nt broken.

 

[bster]

All fixed!

Rewired the wiring centre (all over the shop) and have had to replace the broken room stat and cyl stat (apologies and thanks to Poxi!).

 

[Vic Spanner]

(apologies and thanks to Poxi!).

Thats my boy