Can you have a 'low pressure' sealed heating system?

[DaveCWK]

Hi All,
I'm thinking about the feasibility of moving our boiler to the loft.

I currently have a typical 40 year old gravity fed hot water & vented heating system, with 2 tanks in the loft, airing cuboard hot water cylinder with immersion (used in summer with excess solar PV generation), shower pump etc - as a setup I have no complaints.

Moving the boiler to the loft will I think mean getting rid of the loft tanks & converting to a pressurised sealed system with accumulator etc.

Does anyone know if it's somehow possible to convert to a sealed central heating system, but continue to run it at low pressure equivalent to a vented system?

The ground floor pipework is all buried in the concrete floor/screed, & where it emerges it looks a bit ropey. I'm a bit worried about pressurising it beyond what it currently is with the vented system (5m head/approx 0.5bar ish?) & getting hard to access leaks everywhere.

[OutInTheShed]

Many boilers will error below a certain pressure.
I suspect you may get issues with the suction from the pump drawing in air via the valve spindles?

A bloke I used to sail with had a townhouse, 4 stories, the rads at the top would let air in if you tried to bleed them with pump running, and he was always needing to bleed the system,

It ought to be fine, but I suspect there may be opportunities for subtle problems.

[119]

Get a pressure test on it for a few days in the summer.

[Huzzah]

Ours works that way, Worcester regular boiler.

The heating is supposed to be pressurised but runs just fine @ 0.