Kingfisher potterton thermostat playing up?

[masona]

I have a 25 yrs old potterton kingfisher f/s boiler (I don't have the rest of the details model as I'm at work) Is there a way of testing the boiler thermostat to see if it's faulty?

 

[ChrisR]

Should click and switch boiler on/off . Cold end around 60 , hot 82. You can put the phial in water. Hysteresis is pretty wide, sometimes wider when they're older.

 

[masona]

Thank ChrisR, I shall test it when I get home. I can't make up my mind if I have sludge or thermostat problem.

I have a indirect cylinder and when hot water is called, within the first 10 minutes I can hear bubbling in the expansion tank but okay when settled, so I'm guessing the water is overheating therefore escaping to the tank. Doesn't do it when it called for heating maybe because of a longer run pipework?

I also have 2 motorised valve, 1 for hot water & 1 for heating

 

[ChrisR]

Check for pumping-over into the header. Old systems like yours and mine develop blockages which lead to such problems. It would do that cold, if it's going to, with the boiler off.

 

[weareleeds]

If i were you i'd call in a pro as there is a safety alert with pott kingfisher (conventional flue) there is a potential for excessive c.o. levels

 

[Soggy_weetabix]

if its a stat problem, they can be adjusted.

Look hard for the adj screw in the middle right of the stat.

You need clock menders screwdrivers to get in there

Dave

 

[masona]

if its a stat problem, they can be adjusted.

Look hard for the adj screw in the middle right of the stat.

You need clock menders screwdrivers to get in there

Dave

Yes I've found that, do I adjust it to the minus side?

Thanks.

 

[masona]

Just for info or if you have a similar problem, I have changed the boiler themostat (£14) on my 25 yrs old potterton kingfisher Rs60 and no water is now bubbling back to the F&E tank . I think what was happening is that the water was overheating therefore expanding back to the F&E vent the first few minutes as it has nowhere to go and being it was when calling for hot water being the shortest circulation. Didn't happen on the heating side as it was a bigger circulation to get away with the overheating problem.

 

[masona]

Oh dear

It's pumping over to the F&E again in the first 10 minutes on the hot water side, I have check the indirect cylinder coil on the flow & return and both is hot as I'm thinking a possible blockage unless the sludge/blockage is somewhere else bearing in mind it doesn't pump over when the heating is on Any pointer

So far in the last 12 months 2 new motorized valve (1 for hot water & 1 for the heating) new pump and the boiler thermostat, new O rings in the boiler cast iron casing (has a small leak) and a new programmer SM805

 

[masona]

The latest news, it's now pumping over with just the heating on whereas it was the hot water side that was causing the problem before, it seems the problem is now bigger than ever. I have now shut it all down as it's now leaking everywhere from the F&E tank

I've done quite a few search on here & cannot find the answer. I'm guessing I may have a cold feed blocked from the expansion tank and I understand you can check the blockage with a magnet to see if there's a attraction, right the next question is, if I find the blockage, what's the best way to unblock it or is it best to cut a section of pipe out?

 

[croydoncorgi]

Given the likely age of the pipework, probably best to cut out the area where the vent, cold feed and Return come together and replace it, unless it's easy to disconnect compression fittings so as to be able to actually 'rod out' the blockage. Trying to dissolve it out is usually a waste of time.

 

[masona]

Thanks, good point and quicker to do it that way I reckon.

 

[masona]

probably best to cut out the area where the vent, cold feed and Return come together and replace it,

Sorry, forgot to ask, do you know if that is the most common area for the blockage?

 

[ChrisR]

On systems which go boiler, vent, feed, pump, motorised valves, the commonest area is where the feed joins the circuit. Can be a tiny protruberance, or several feet of pipe blocked!
The reason is apparently that that's where the fresh water, with nasty oxygen and calcium in it, comes in. Iron particles get involved too because the deposits are magnetic. Never seen the chemistry explained properly though.
SOmetimes you can push things up/down the pipes to clear bits out, such as the thin drain clearing springs. (Down the feed pipe or back from the pump). If access is good, just excise it though.

 

[masona]

If access is good, just excise it though.

Thanks, ChrisR.

I'm dreading this because the access isn't good , 16 yrs ago I has to moved all the plumbing to one side because of the loft conversion.

I'm begining to wonder if the power flushing might be the answer as the access isn't good.