Unvented heating system pressure

[Matthew Score]

I have an issue with a Ideal logic 35kw boiler and system pressure.

Boiler was over pressuring and the prv kicked into action and released the excess pressure as it should.

My issue is I have changed the expansion vessel and prv.

Filled the system to 1.5 and set the heating running and at full temperature it went up to 3.

The system is quiet large, dormer bungalow with 12 x 600 x 1000 K2 rads.

Does the system need a second expansion vessel? Is the water volume to large for the one 10l internal vessel?

I have never had this issue before, just scratching my head a little bit.

Thank you for any advise given

 

[king of pipes]

Left a valve shut ? Maybe

 

[Matthew Score]

Left a valve shut ? Maybe

All valves open, pressure slowly builds as the temperature rises and slowly returns as it drops.

Prv has started to drip again at 2 bar, well ypu cant even really call it a drip but its wet. which I can only put down to muck getting stuck under the seating

 

[king of pipes]

Yes that often happens need to change that is a bit on the low side for expansion but you say it worked before , drop the system pressure to 1 bar see what happens ? Kop

 

[townfanjon]

Start off with pressure at 1 , not 1.5 .
Are you gas safe pal ?

 

[Matthew Score]

Start off with pressure at 1 , not 1.5 .
Are you gas safe pal ?

Yes Gas safe,

I don't get my hands dirty to often though as I am manager but this is for my wife's friends, it's always the just can ya jobs

I haven't seen such a rise in pressure on a system like this before so a little unsure what's going off.

 

[townfanjon]

I will summon our supermod lol
@ShaunCorbs

 

[ShaunCorbs]

You rang ?

 

[ShaunCorbs]

You check the hose isn't blocked to the expansion vessel

Rule of thumb 1l per rad

 

[townfanjon]

You rang ?

Whats the crack for Matthew here

 

[ShaunCorbs]

Whats the crack for Matthew here

Mathew send us your gas safe number I will process the request while he's building his post count past 10

Help away will sort the thread out after

 

[Matthew Score]

You check the hose isn't blocked to the expansion vessel

Rule of thumb 1l per rad

I changed the pipe, it was a bastard to get it to re-seal as it's down the side of the pump and wouldn't engage properly and weeped.

 

[ShaunCorbs]

I changed the pipe, it was a bastard to get it to re-seal as it's down the side of the pump and wouldn't engage properly and weeped.

In the block wasn't crudded up / blocked ?

Eg got water at expansion vessel

 

[SimonG]

Vessels too small.

 

[Matthew Score]

Vessels too small.

It's the standard

In the block wasn't crudded up / blocked ?

Eg got water at expansion vessel

Water freely running out the connection pipe to the vessel.

 

[ShaunCorbs]

Would say vessel too small then defo

 

[SimonG]

Doesn't matter wether it's standard or not its too bleeding small.
I do a lot of oil boilerwork and one of the biggest issues is undersized expansion vessels.

 

[Matthew Score]

Thank you or the advise I will let you know how I get on.

 

[king of pipes]

Did you measure the pressure in the new vessel often over charged ? I would say fit a extra 8 litre vessel . Kop

 

[Stigster]

+1 for the vessel being too small. Basically, the internal vessel is there to protect the boiler itself and will also do a few rads on a small system. Good advice given in this thread.

 

[Ben-gee]

I think they keep the vessel size down to allow a nice neat boiler to go in your fancy kitchen , sod the installer who then has to explain you’ll need a big ugly red thing elsewhere....

 

[Scott_D]

It’s an 8 l vessel in a logic