Oil combi pressure rising quickly.

[simond]

My understanding was that gases have a higher rate of expansion than liquids, in the 0-99C region.

If this true (I can't remember where I got this from) then it is possible you could have an airpocket trapped in the boiler heat exchanger, causing a rapid pressure rise.

Others more technical may prove me wrong.

 

[oilman]

Possible, but it wouldn't explain why the pressure rises quickly when filling.

 

[Dick Puller]

have come across a couple if instances of the pressure in a combi rising quickly when the boiler is warming up. One happened today. I had fitted a new vessel. I had checked water was able to pass through the hose to the expansion vessel. I checked that releasing all the air in the expansion vessel significantly reduced the water pressure. These test seem to confirm the integrity of the expansion vessel and connecting hose.

The system is small, only 4 rads for heating.

What causes this?

Have you established the system volume?? Have you checked the air pressure on the expansion vessel when the system is empty - this has a direct relation to the volume of the expansion vessel. Remember many of these oil combis have large water content with boiler, heatbank etc.

Have you checked all valves on the appliance, NRVs, pump gate valves & ballvalves?? Does it go over 3 Bar & blow off?? Any 'kettling' when the boiler is reaching it's boiler stat higher settings??

 

[Dick Puller]

Sorry, I forgot to add; is your pressure gauge calibrated correctly??

 

[bengasman]

A calibrated pressure gauge?
What do you think this is dicky? a fga?

Have you found your list of qualifications yet? I think you just slipped up mate, you have no current corgi card, and if you ever had one, it was more than 20 years ago.

 

[Dick Puller]

A calibrated pressure gauge?
What do you think this is dicky? a fga?

Have you found your list of qualifications yet? I think you just slipped up mate, you have no current corgi card, and if you ever had one, it was more than 20 years ago.

Sorry, I mean is the pressure gauge reading correctly.

Hope you had a lovely Easter Ben, sorry I did not get back to you with my details here you go;
Gas; full ACS Domestic & Commercial.
Oil; all Oftec qualifications for pressure jet burners.
Time-Served in Domestic/Commercial Plumbing & Central Heating.
Full range of C&Gs.
Technical Grade Plumber at the age of 21.
Steel pipe fitting & welding qualifications.
Part time Lectured in Roof Lead Work.
Have been a Master Plumber for 30 years.

 

[bengasman]

Now that is really very impressive.
Not only good theoretical knowledge as a boy, and decades of experience, gone back to school after that to keep up to date.
You are indeed miles ahead of myself, so far that I did not even know of a single lecturer in leadwork existed in the entire country.
I hope you will soon join us in the cc, we could really do with somebody with that much knowledge.

 

[Dick Puller]

Sorry Ben, I only pass on my fountain of knowledge to real Plumbers via any apprenticeship schemes....................As has been done for 100s of years.

 

[bengasman]

Sorry Ben, I only pass on my fountain of knowledge to real Plumbers via any apprenticeship schemes......

I must be having a blond day.
I thought you were giving advice on this here, and the screwfux forum.

 

[Agile]

Its alright Ben!

Dick momentarily thought he was still back at Screwfix!

Different protocols here!

Tony

 

[bengasman]

Thanks Tony, I was getting a bit worried.

Still, why somebody would do a nvq, a c&g, and acs, all leading to the same corgi registration eludes me, should ask him next time.

Mind you, if he works on pipes so big they have to welded in stead of screwed, he must be working on some pretty big stuff, you can't be too well educated when you handle that kind of gear I suppose.

 

[bengasman]

Thanks Tony, I was getting a bit worried.

Still, why somebody would do a nvq, a c&g, and acs, all leading to the same corgi registration eludes me, should ask him next time.

Mind you, if he works on pipes so big they have to welded in stead of screwed, he must be working on some pretty big stuff, you can't be too well educated when you handle that kind of gear I suppose.
That must be a really big burner.