Heating overflowing from vent

[John.g]

I don't know why it hasn't always been like this as nothing has changed so am tring to identify a fault that may not be there, what is involved with combined feed and vent?

Look up "Vent Pipe Blanked Off" in Search.

 

[Morrispd]

Thanks for your help so far, I've looked into this a bit now and water pours out of the vent onto the roof when the CH is on. I've turned the pump speed down to 1 and it still does it, I've sketched the layout and I don't think it's anything unusual (but i may be wrong) and I've attached a pic of the feed and vent, both in 22mm. I'm wondering if a blockage could be causing this and how you would begin to clean a vented system (I have flushed sealed systems many times) TIA (again).

 

[John.g]

It's essential correct but the vent should really be installed closer to the cold feed, or visa versa, the closer the better but no further than 150mm apart, but you can't beat the combined cold feed and vent IMO.

 

[Morrispd]

It's essential correct but the vent should really be installed closer to the cold feed, or visa versa, the closer the better but no further than 150mm apart, but you can't beat the combined cold feed and vent IMO.

Sorry for my ignorance, the feed from the CH header tank joins the return to the boiler in the same place (2 adjacent tees) as the vent out the roof joins the return to the boiler. These connections are maybe 2m from the boiler and 1m max from the pump. Where should they be and what pipework would change to make combined feed and vent?

 

[John.g]

Will reply in more detail tomorrow but the vent is on the flow from the boiler? The pump is pumping from the flowside of the boiler through the mot.valves?

 

[Morrispd]

Will reply in more detail tomorrow but the vent is on the flow from the boiler? The pump is pumping from the flowside of the boiler through the mot.valves?

Yes, based on the arrow of flow throught the pump the feed and vent are on the pipework from the boiler, to the pump and then through the motorised valves

 

[John.g]

Yes, based on the arrow of flow throught the pump the feed and vent are on the pipework from the boiler, to the pump and then through the motorised valves

OK, but from the boiler it should be Vent then Cold Feed then the Pump, (VCP), not cold feed ,vent, then pump.

To convert it cut the feed (on the horizontal) close to where it joins main line and cap it, maybe cut in the middle of the short horizontal section and cap it with a compression cap & olive and leave in case you need to reverse the mod, then at the F&E tank, T in the feed to the vent, like mine, below. You will obviously have to tie up the ball cock and partially drain down the system, when finished fill the system very slowly to avoid trapping any air or better again install a isolating gate or lever valve on the mains feed to the F&E tank, you can then use this to refill the system very slowly.

Or T it in like the one in post#11.