Should combi boiler pressure gauge jump when drawing hot water?

[Ltnman]

Owner of a new Ideal Vogue. Central heating still turned off. I have noticed when drawing hot water that the pressure gauge jumps from 1.1 bar to just over 1.2 bar before slowly descending over a period of time. The boiler was set to 1 bar when fitted 3 weeks ago but has slowly crept up to 1.1bar when no water is being drawn.

Both sides of the top up loop are firmly off. On the fault log it shows "no water flow" on 3 occasions over the last week and low pressure on 19 occasion, not that I have noticed any problems.

What is going on?

 

[CBW]

It sounds like it’s behaving normally and you’re worried about nothing. When you heat water it expands, from 1.1 to 1.2 is negligible.

 

[muggles]

No, it's normal to see a bit of pressure movement when the pump kicks in

 

[Ltnman]

Thank you

 

[Johntheo5]

Up the pressure ti 1.3/1.5 bar when cold.

 

[Ltnman]

I prefer to leave it at 1 bar. Around 12 years ago I had a nightly pressure drop to zero. No leaks could be found so a bottle of leak sealer was allowed to work its magic.
Since then I have always kept the pressure low so not to strain the hidden repair. It might be nonsense but it makes me feel better.

 

[Londoner2]

Perfectly normal.

 

[Razor900]

Some boilers look for the pressure jump and won’t start without it.

Many of the pros on here will know exactly what I’m talking about and what a pain the f code associated with it can be to fix…

 

[Johntheo5]

The EV connection is the point of no pressure change and the EV should ideally be installed just before the pump suction, if the EV filling pressure is 1 bar and the pump head is set at 4M, then the pump discharge is 1.4 bar. If the EV is tied in after the pump discharge then the pump discharge head remains at 1 bar but pump suction falls to
0.6 bar, increased risk of air ingress if system pipework restricted causing high pipe losses.
Probably no big deal if system cold pressure kept to - 1.5 bar.
Boiler schematics show where the EV is connected.