Gravity feed combi boilers

[Retired Plumber1]

Is it time for manufacturers to make a gravity feed/expansion combi boiler on the primary side. When I was a plumber many years ago I think about 1982 I remember installing an optional gravity feed boiler instead of a presure system. I was never called back to the boiler. Any thoughts

 

[Scott_D]

Intergas allow it I think

 

[fixitflav]

Intergas allow it I think

Is it time for manufacturers to make a gravity feed/expansion combi boiler on the primary side. When I was a plumber many years ago I think about 1982 I remember installing an optional gravity feed boiler instead of a presure system. I was never called back to the boiler. Any thoughts

I can't see why a boiler with expansion vessel (combi or heat-only) couldn't be used with gravity feed. Just connect the open vent and cold fill into the pipework upstream of the pump, remote from the boiler if more convenient. The

expansion vessel is then redundant, but that doesn't matter. The only possible problem is if the boiler low-pressure cutout setting is higher than the pressure from the header tank. If so either lower the setting if possible, if not link out the pressure switch.
Sounds like you prefer open gravity systems, and I agree.​

 

[Last Plumber]

Is it time for manufacturers to make a gravity feed/expansion combi boiler on the primary side. When I was a plumber many years ago I think about 1982 I remember installing an optional gravity feed boiler instead of a presure system. I was never called back to the boiler. Any thoughts

There were a few you could use either way years ago as I remember, sealed system or open vented fully pumped.
One of the main reasons you cannot do it with most modern Boilers is due to the design of the Heat exchanger (coil/Drum type) as they do not naturally vent.
No real reason why you couldn't invent one that works that way though!

Are you trying to think of something to keep you occupied during retirement?

 

[jtsplumbing]

Will keep a look-out on next series of Dragons Den !!

 

[townfanjon]

Open vent verses sealed system , no contest IMO

 

[Last Plumber]

Open vent verses sealed system , no contest IMO

You prefer open vent then?

 

[townfanjon]

You prefer open vent then?

Lol , nah sealed systems everytime .

 

[gmartine]

There are some compelling reasons for pressurizing a system...improved efficiency, lack of oxygen ingress and therefore corrosion not to mention safety.