Boiler Pressure Reading High after Service

BeefSteakTomato · 24 Nov 2015

We've had a boiler serviced and the readings from the pressure gauge don't seem right.

The boiler after it's been on for a while goes up to 3.5 bar (64DegCel central heating setting). Before the service it would hardly fluctuate and would stay around 2 bar (from 1.5 bar cold).

Called the plumber and he thinks it's the pressure vessel.

Seems a bit strange it's okay one day, and after the boiler is serviced then the pressure is very high. What are your opinions?

Cheers!

ScottishGasMan · 24 Nov 2015

99.9% of pressure vessel issues can easily be solved by recharging them, or replacing the tryre valve on them then recharging.

Did he bleed any radiators? if so, air in the systme could have quite easily masked the issue with the vessel.

BeefSteakTomato · 25 Nov 2015

Not sure if he bled any of the radiators - I wasn't there - I will ask.

A little more info. When I ran a bath this morning (didn't have the central heating on) the pressure didn't increase (remained at 1.5 bar). It looks like the pressure ramps up for central heating only.

Agile · 25 Nov 2015

You may have learnt at school that things expand when they get hot.

That includes water which expands quite a lot and in a sealed system increases the pressure.

A good engineer will check and repressurise the expansion vessel if required.

Sounds as if yours bled some radiators but never checked the expansion vessel.

He may also expect to charge you to fit a new one when all that is needed is 10 minutes to increase the air pressure.

Not very impressed by your plumber!

I saw an invoice from Pimlico Plumbers where they had removed the expansion vessel and taken it to a service station to repressurise it taking 1/2 hour. They charged £55 plus VAT then per 1/2 hour.

Myself, I have a small air pump that I use to pressurise them in the boiler and take about 10 minutes! Maybe Pimlico should get one?

Tony

Dean744PiN5 · 25 Nov 2015

another thing i often come across after someone has "serviced" the boiler is that they check the expansion vessel by depressing the schrader valve to see if air hisses out (this is completely wrong), this can lead to one of two things, either it lets out the last bit of pressure in the vessel and it now has no charge or the schrader valve starts letting by, again releasing any charge that may have been in the vessel.

Agile · 25 Nov 2015

A friend with BG cover has a fairly new Worcester boiler. My experience is that on that make they often lose air every few months or so.

BG just repressurise the water and so there is less and less air in it.

She then pays me £84 every year or so to properly repressurise with the system at zero pressure.

I try to tell her that she pays for the cover so should use it. But she replies that I always sort it out for her and she has little confidence in BG and does not have to wait all am or pm for them to come at some unspecified time!

BeefSteakTomato · 26 Nov 2015

Once again I thank you all for your terrific answers

The plumber came over last night. What he did was take the cover off the boiler, didn't see how but he said "he released some of the pressure", and told me he "probably set the pressure too high after he bled the radiator in the loft". He said to "watch my overflow" and if water keeps escaping then the pressure vessel has probably had it.

He released the pressure, but of course when the boiler got cold after it turned off I got the low pressure errors and I had to add pressure by using the top up valve ! I'm thinking he's not pressurising the expansion vessel, but just adding pressure with the top-up valve. What are your thoughts?

nortonj · 26 Nov 2015

BeefSteakTomato said:
Once again I thank you all for your terrific answers

The plumber came over last night. What he did was take the cover off the boiler, didn't see how but he said "he released some of the pressure", and told me he "probably set the pressure too high after he bled the radiator in the loft". He said to "watch my overflow" and if water keeps escaping then the pressure vessel has probably had it.

He released the pressure, but of course when the boiler got cold after it turned off I got the low pressure errors and I had to add pressure by using the top up valve ! I'm thinking he's not pressurising the expansion vessel, but just adding pressure with the top-up valve. What are your thoughts?

sounds like hes released the pressure using the pressure relief valve.
not sure why he didnt just check the expansion vessel while he was there?

nortonj · 26 Nov 2015

Sounds like the expansion vessel needs re charging though

Phill Peck · 26 Nov 2015

Sounds like your plumber is a moron

Agile · 26 Nov 2015

Makes me wonder how these morons ever get any work.

Where did you find him?

BeefSteakTomato · 28 Nov 2015

He came recommended. I can understand why though - he comes across as a really nice chap and I guess unless you question a supposed experts practices you wouldn't know otherwise.

oph · 28 Nov 2015

Using the PRV is release water out the boiler is fine...........just as long as your going to bung another PRV in

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Boiler Pressure Reading High after Service

Dean744PiN5

Phill Peck

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