Boiler thermistor broken?

[Robert Irons]

So why are you on here then? or do you just want help from Diyers and not Professionals?

Andy

Fair point - but when I wrote that I was feeling very disappointed with the advice of my most recent professional.
I like to have some understanding of the problems with my system so I can have an informed discussion with a pro when I do involve one.

 

[ianmcd]

A 28 KW system boiler ? do you live in a mansion ?

 

[DP]

DP you don't seem to hold DIY'ers in very high regard, but the way I see it whatever you say Ive saved myself at least £400,

In my first post I suggested that you seek professional help because there are folk here, at least one DIYer, who dish out advice that lacks substance. This advice is very much like programmes on TV that do a house renovation in 60 minutes

My advice fell on deaf ears at which point I said crack on.

Going through your initial post it was clear where the failure was. I as a pro of 30 years still make mistakes but these mistakes do not cost the end user, glad to say these slips are few and far in between.

It is my practice to invite the end user to watch the repair, service or breakdown task to learn from what I do ( I care not if they will subsequently attemp repairs themselves- have plenty work to worry about that).

A failure like you had, first slip was draining the system.
Second was putting chemicals in- I take it you have carried out multiple fills and drains in order to remove from the system the debris that chemicals have suspended in system water. If you used Ferroquest/ Sentinel X800 and system has not been adequately flushed, expect the chemicals to play games with your new pump

Another point is vent and expansion pipes. These pipes cause so much confusion among regular plumbers and so called self claimed top engineers, no surprise you had modified pipes in order to resolve suspected problems. You can read another post about pump over in this section if you doubt what I say.

An easy approach on your boiler malfunction would have been to take temperature reading at various points to realise issue was lack of or poor circulation. Listening to the pump rather than suspecting pump was defective and changing it.

Have to say you are right in leaving the system open vented as sealing an old system ( unless valves are new and pipe fittings are secure) is asking for trouble.

I am all for a householder who is an able DIYer to have a go. Nothing wrong in that.

Come here to see what is going on and if I can, to help out. If I fail to understand the issue I will not offer advice that has no substance. As a gas engineer mainly doing repairs, see all aspects of breakdowns and as such have a good idea what is what but will never say I can fix every fault every time- far from it.

 

[DiyNutJob]

If the boiler is not producing high temperature water on the boiler exit then you need to get the flame bumped-up. You would assume the boiler man had the flame set correctly, he may not have. The other thing you can try is reduce pump speed to slow the water passing through the boiler. You can slow it until the boiler start kettling and then speed up the pump a notch. Kettling will indicate an overheat, and the water will be at maximum temperature. If you are unable to force an overheat, then maybe there's something wrong with the boiler thermostat, or knob. Still, since you said the flame is continuous, this suggests flame too weak or boiler too weak for your property. The next thing you can try is turn off all radiators except one. If the boiler exit water is still not hot, then maybe your boiler is heated by a candle.

You can tell from my nick name I am a DIY'er.

 

[Agile]

The immediately obvious problem would appear to be an internal temperature control problem. Although those are rare on that model if it was correctly set up initially.

But another potential problem could be a restricted gas supply to the boiler. Unless a valve is half closed that would need a gas registered engineer to check.

 

[DP]

If the boiler is not producing high temperature water on the boiler exit then you need to get the flame bumped-up.

Doubt it. If the flame was subsize, boiler would not be cycling.

The other thing you can try is reduce pump speed to slow the water passing through the boiler.

Take note boiler flame is shutting down. Reduce pump speed will make things worst

Still, since you said the flame is continuous, this suggests flame too weak or boiler too weak for your property.

A 28kw boiler undersize for a property. What ever you are smoking, I would like some of that

 

[DiyNutJob]

Doubt it. If the flame was subsize, boiler would not be cycling.

Your terminology is incorrect. You should say if the gas-rate is low ...

I briefly scanned through the OP's posts. He said the boiler burn is continuous. So I assume, there's no cycling.

A 28kw boiler undersize for a property. What ever you are smoking, I would like some of that

It's not clear what property the OP has. I don't automatically assume he hasn't a castle. If he has, I would recommend a jigga watt boiler.

 

[DP]

Your terminology is incorrect

Sorry headmaster, I did not know I was in a classroom

If you were not a nutjob ( your signature not being rude there ), you would be able to add 2 plus two and get the correct answer. That is how I came to the conclusion about boiler size