The Saga continues....Please Help!!

[dave12]

first a bit of back ground to the problem. I have a Potterton performa 28i which has just had the Diverter valve changed. Since changing this, only half the heating appears to work (upstairs).

The downstairs radiators have hot water getting to them, but is cold at the return side. I have cracked one of the return pipes and surprise surprise the radiator starts to get hot.

I was thinking that there as a blockage in the downstairs manifold or something. So I tried putting a hose down the return of one of the bad radiators and draining through the drain pipe. So the mains water flushed back through the manifold and out through the drain. No issues!

I then started paying more attention to the Boiler again. The first thing is the boiler is certainly a lot quieter than it used to be! the next thing, when heating from cold, the temp lights go from 20 to 80deg in around 30 - 45 seconds. So I was thinking. Could the pump be on the blink? I opened the big vent screw while the pump was running and the water only trickles out. I was expecting it to p*ss out?

I'm getting desperate now and need help! My next 2 thoughts are, strip the pump, then try pouring sentinel 800x into the radiator!

Any suggestions?

 

[easyflow]

Its a circulation problem and 3 things to check are pump/blockage or air lock .
Is the return pipe getting heat back to the boiler.

 

[Blagard]

first a bit of back ground to the problem. I have a Potterton performa 28i which has just had the Diverter valve changed. Since changing this, only half the heating appears to work (upstairs).

Does this not suggest to you that this is where the problem now lies! How about getting the person back who did it.

 

[gigz]

The downstairs radiators have hot water getting to them, but is cold at the return side. I have cracked one of the return pipes and surprise surprise the radiator starts to get hot.

Have you tried opening all the returns ? Sounds like a balancing issue possibly.

 

[gigz]

P.S. Only been on this site 8 yrs, i will get the hang of quoting eventually

 

[dave12]

Thanks for the responses,

Gigz, all returns are open......

Blagard, this is the second Diverter valve they have installed! It was Scottish Power who done it. I insisted the change it for another after the first due to this problem. So they came, fitted another one, and no change. But your right, I never had this problem before the valve was changed.

easyflow, the return comes from a T. One leg goes upstairs (This leg is warm) The other leg (downstairs) is cool. although the return pipe to the boiler is only luke warm!

I'm not convinced the upstairs is working as it should as it does seem to take longer to heat the rooms!

 

[easyflow]

I would be lookin for a blockage in a T or Elbow on the heating circuit.
Has the system been converted fron open vented to combi sealed system.?

 

[Ihavenojob]

These boilers usually have a filter in the return isolating valve,you could try cleaning this.

 

[dave12]

I checked the return, and right enough, there is a strainer mesh at the valve. Unfortunately, its spotless!

The system was changed from open vented ie storage tank etc to combi about 9 years ago. The pipe work is 20mm (I THINK.) For both feed and return. I assume these go to manifolds somewhere under the floor. All rads are fed by microbore.......

Do you think it worthwhile to strip the pump?

 

[gigz]

What happens to the downstairs rads when upstairs are closed ? Can you get every rad hot by itself ?

 

[dave12]

When I do this, the rads begin to warm up slightly more. Warmth travels up over the top of the rad then back down to the return side (I have flushed these rads with a hose in the garden). But the boiler cuts out too quickly for it to ever get up to temperature.

I haven't tried just one radiator on yet. But will give it a go.

 

[gas112]

As temp is rising within boiler swiftly .
Right hand connection(return ) there is a filter in the front of it clean it out .

 

[dave12]

Gas112 is this the round strainer in the return pipe T piece? If so, I have checked this and there is nothing in it, not even a bit of black gunk.

I now have sentenil x800 in the system an am running the boiler with only 2 bad rads open. They get hot but it takes an age!

 

[dave12]

Just thought id post an update on the problem that hasn't gone away. The x800 is in the system circulating 4 radiators (out of 10). All radiators do get hot eventually, but the rooms can never get above 16deg because the boiler keeps cutting out (flame).

I also timed how long the heat from the boiler takes to travel along a pipe. From burner ignition it takes 15sec for heat to travel around 800mm from the boiler to the T piece. It takes another 20 seconds for this pipe to become to hot to touch.

Does this tell me anything?

I keep thinking that the problem is in the boiler. The only thing that has changed is the Diverter valve and the pcb. I remember seeing scale build up in the diverter valve, and cant help think that there will be more either in the heat exchanger, or pump.

Are there any tests I can do to prove this? All your posts are greatly appreciated!