Oil combi pressure rising quickly.

[oilman]

I 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?

 

[bengasman]

Is this on a particular model or various makes?

 

[wilhelm]

pump on way out?

 

[oilman]

Yesterday's one was a Grant outdoor.

The pump seemed ok. It was able to to pump water round the central heating, though not with spectacular effect as the auto bypass was more bypass than not.

 

[Dick Puller]

Have you checked the system capacity in relation to the expansion vessel size??

 

[bengasman]

Have you checked the system capacity in relation to the expansion vessel size??

Thought crossed my mind as well, but if the pressure goes significantly down when releasing air from ev, the size should be ok.

 

[Agile]

What pressure did you put the air with the system open?

What pressure did you set the system water to?

Tony

 

[Dick Puller]

Thought crossed my mind as well, but if the pressure goes significantly down when releasing air from ev, the size should be ok.

Eh??!! Have a wee think about what you are saying there fella!!

 

[bengasman]

Thought crossed my mind as well, but if the pressure goes significantly down when releasing air from ev, the size should be ok.

Eh??!! Have a wee think about what you are saying there fella!!

ch volume x, needs expansion volume y.
if letting air out of y results in pressure going down noticeably, the available space in ev is proven sufficient. leaves finding the most effective precharge.
that's how it works down south anyway.

 

[Dick Puller]

Ben son, do you understand the concept of sealed systems??

 

[kevplumb]

Ben son, do you understand the concept of sealed systems??

dick bonny lad do you understand the concept of being a patronising g i t

 

[Dick Puller]

Kev son, next time you got something to say, put your hand up & cover your mouth!!

 

[bengasman]

Ben son, do you understand the concept of sealed systems??

Judging by your comments, I know as much about them as gordon knows about economy.
Come on sire, enlighten me; that is what we are here for.

I have always believed that generally, what comes out, must have first have gone in. Be so kind to explain to me (in simple English) how this is not true in this case.

 

[Dick Puller]

Here's your first wee 'clue' EXPANSION vessel!!

 

[Agile]

Judging by your comments, I know as much about them as gordon knows about economy.

I have always believed that generally, what comes out, must have first have gone in.

Not much came out of the Icelandic banks!

That would imply that not much went in!

But a terrific amount DID go in!