Netaheat Profile 50e keeps resetting/overheating

[westyrugby]

Hello,

Have a gravity hot water/pumped central heating system with a Potterton Netaheat Profile 50e boiler and a Drayton LP722 programmer.

All has been fine over the snow/cold snap but over the last two weeks or so the pipes started rattling loudly just before the boiler reset button triggers and the boiler goes off. From other posts I have found that this is the overheat button. If I leave it for approximately 15 minutes I can push in the reset button and the boiler/heating returns. Sometimes it can be on 4 or 5 hours before resetting and others a couple of hours. The outlet pipe is too hot to touch usually and the return pipe is nowhere near as hot but still fairly hot.

When it first happened I checked the header tank in the loft which was full and the ball valve was working ok and bled all the radiators and the pump (whilst heating off) We have a towel heater/radiator which expelled a fair bit air before filling up but the heating still did the same thing more or less straight away. I left it for a couple of days and bled everything once more and again air was expelled from the towel radiator but very little.

I am wondering whether there is an air lock somewhere or something but am wondering what is the next logical step to take (probably call a pumber) so has anyone any idea's/pointers please.


Cheers in advance
JW

 

[Netdragon]

its probably in your central heating circit their should be a vent on the highest point on your central heating or your pump.

Pump as either a screw and turning that slowly a few turns will allow air out, if you have a myson pump you will have a nut like plastic cover screw that around with your hand and push at one side to allow air out. Remember to keep a bowl under it.

Once you have done re-operate the controls and feel the pump if it gets read hot no vibration its gone if it gets hot/warm and it vibrates with the impeller going your good to go check for a hidden vent if still noisy.

If not the pump has gone and will need to be replaced.

 

[westyrugby]

Cheers Netdragon, I will give the pump another go tomorrow.
When you say "their should be a vent on the highest point on your central heating" do you mean the vent on the radiator upstairs.

 

[Netdragon]

on your boiler look where the pipes go if they go above it their should be a vent or a pipe that runs up to your tank this should be clear and venting to get the water out.

but anywhere above the boiler and pump if u can vent above them do so.

If not remove the screw slightly on the pump untill ater starts dribling out (as long as its not over the electrics part of the pump place a bowl under it and monitor it and keep it running cyling it on and off to force ater through the air locked parts normaly works and let the system get nice and silent before you close the pump screw and you be good.

With cycling the pump and the vent screw on it loosened it should shove the air lock around boiler clear.

the pump speed could also be adjusted via a knob on its side, worst case is the pumps gone or is very worn out and is barely pumping out the heating and may need replacing.

 

[Agile]

There should only be 11° difference between flow and return.

There is clearly a lack of flow through your boiler.

Suspect failing pump or blockage.

What pump speed setting is it on?

Tell us and increase it if thats possible.

Tony

 

[westyrugby]

Think it is the pump. Have changed speed settings and none sound as though it is turning. Very little if any vibration whatever setting it is on. have bled system each time I changed pump speed setting with no dofference. Having bathroom done anyway soon so plumber has said he will come and look at it tomorrow.

Thanks both for your help.

JW

 

[gas4you]

If this only occurs when the heating switches off, I would check the pump over run stat first (I think this model may have one )

 

[westyrugby]

Have had pump changed (which was on its last legs apparently) but the boiler still keeps resetting so looks like there is a problem with this as well.

Seeing as it is an old boiler I am thinking of changing it at the same time as I have the bathroom redone but am unsure which way to go so wouldn't mind some opinions off people in the trade/or with similar experience.

I know to properly assess you need more info but house is 4 bedrooms with 1 bathroom and small en-suite with shower which is rarely used. Washer is cold feed only and we have 10 radiators of different sizes.

The bolier is currently downstairs with the cistern upstairs and the tanks in the loft. Ideally I would like to get rid/move the cistern as it is in a cupboard between two bedrooms and can be noisy so was considering:

1. System boiler where I could get rid of the tanks in the loft and move the cistern up there (not too sure about practicality)
2. Combi boiler but a bit worried whether it would be powerful enough for everything. The en-suite shower has it's own pump which was put in (not very well) by the previous owner of the house. Also seems like putting eggs in one basket. If we lose pressure we have nothing.

Any advice welcome

Cheers
JW