New boiler needed

westy23

Morning
A quick question.
Does a open vent boiler (heat only) run at a lower pressure than
a system boiler?
As I suspect some of my pipework will not cope with the extra
Pressure of a pressurised system.
Thanks

gas4you

Usually yes, but only slightly less pressure.

If you are in a house then the downstairs rads/pipes will be around 0.7-1 Bar.

A system boiler will usually run between approx 1 Bar & 2 Bar.

I always change to a system boiler when replacing boilers wherever possible. The increase in pressure shouldn't have any effect on your pipe work.

As I have said in other posts, the chemical cleansing of the system is usually, if ever, the thing that will find any leaks or weak spots.

alleycat`

gas4you wrote: »

Usually yes, but only slightly less pressure.

If you are in a house then the downstairs rads/pipes will be around 0.7-1 Bar.

A system boiler will usually run between approx 1 Bar & 2 Bar.

I always change to a system boiler when replacing boilers wherever possible. The increase in pressure shouldn't have any effect on your pipe work.

As I have said in other posts, the chemical cleansing of the system is usually, if ever, the thing that will find any leaks or weak spots.

Can i ask why you get rid of an open vent system in favour of a pressurised system?

Just curious of the reasoning as i have an open vent system. I'm quite happy with the system so just interested in the perceived benefits of getting rid of the header tank (other than you no longer have an expansion tank of water in the loft?)

southcoastrgi

alleycat` wrote: »

Can i ask why you get rid of an open vent system in favour of a pressurised system?

Just curious of the reasoning as i have an open vent system. I'm quite happy with the system so just interested in the perceived benefits of getting rid of the header tank (other than you no longer have an expansion tank of water in the loft?)

the advantage of a sealed system, is a couple of things, once it's filled then there should be no further oxygen that can get into the system & the ingress of oxygen is one of the reasons for sludge forming as it is your rads rusting from the inside, an open vented boiler can if not properly installed draw air in via the vent pipe, it also gets rid of the header tank & prevents "pumping over", also most sealed systems are easier to fill & less prone to "air locks", the pump is also contained within the boiler & not as normal in the airing cupboard so can make the wiring easier.

gas4you

With an expansion tank in the loft, it is obviously always open to atmosphere.

Whenever the system heats up the water level rise approx 2-3 inches, then as it cools, drops back again.

This contributes to the water getting oxygenated and unless you keep totally up to date with replenishing the system inhibitor you will get corrosion and sludge forming.

A system boiler will eliminate this risk, as once properly cleansed and inhibitor added, the oxygen/air will be expelled and therefore the risk of corrosion and/or sludge has disappeared. Unless you keep refilling the system, there is no way for fresh air/oxygen to get in again.

From what I understand, we are the only country in the world that has ever used the open vent system.

southcoastrgi

ditto what he said, sorry for the hi-jack gas4you lol

gas4you

You just beat me, whilst I was typing