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tbh these days seal the system unless its ropy like the one im doing

and some boilers have flow switches in dont fire unless theres flow
 
Why not seal without pressurising. Use the header as top up, with gate and non return fitted. Sealed system controls as required with heat only or system boiler ( Worcester Cdi used to not need minimum pressure to operate, but check with them).
 
Why not seal without pressurising. Use the header as top up, with gate and non return fitted. Sealed system controls as required with heat only or system boiler ( Worcester Cdi used to not need minimum pressure to operate, but check with them).

thats not a bad shout would the non return open tho also would need a prv
 
Non return is to stop the water backing up into the header. Therefore system controls required, i.e PRV and expansion vessel required either external or internal to boiler (system). Doesn’t need filling loop as header acts as top up vessel. Works a treat without stressing existing pipe work. As the system is sealed and there is no open vent non return will stay shut as for air to get in water would need to get out.
 
Non return is to stop the water backing up into the header. Therefore system controls required, i.e PRV and expansion vessel required either external or internal to boiler (system). Doesn’t need filling loop as header acts as top up vessel. Works a treat without stressing existing pipe work.

yea but would it open under gravity and not stick
 
Have got two systems like this operational now in their sixth year and no problems.

head of the tanks vs the position of check?
 
Top of system for header. Followed by gate or lever in downfeed, so you can turn system of and for easy replacement of check valve. I positioned them in airing cupboard. Check valve can be anywhere between isolation valve and where it tees into the system.
 
Top of system for header. Followed by gate or lever in downfeed, so you can turn system of and for easy replacement of check valve. I positioned them in airing cupboard. Check valve can be anywhere between isolation valve and where it tees into the system.

Trying to work out how much head you have
 
Use the header as top up, with gate and non return fitted.
Does the gate valve stay open in normal operation?

I can't see how this differs from just having an expansion vessel, but with pre-charge pressure somewhat lower than normal.
Still need to put the expansion vessel connection in the right place, to avoid having negative pressure somewhere.
 
I am actually having the same problem trying to decide how I convert a gravity hot water/pumped rads to all pumped on a very old system, without pump over or corrosion.
I converted mine about 20 years back. Old cast iron floorstanding boiler, gravity HW, pump next to boiler, pumping downwards. No controls. Cold feed to boiler return.
Scrapped the boiler and installed wall-mounted condensing. Moved the pump to the airing cupboard, added diverter valve (system W), open vent, cold feed and DV in the airing cupboard. Added cylinder and room stats. Re-used the gravity 28mm pipes as pump suction and cylinder return.
Still working OK.
 
Does the gate valve stay open in normal operation?

I can't see how this differs from just having an expansion vessel, but with pre-charge pressure somewhat lower than normal.
Still need to put the expansion vessel connection in the right place, to avoid having negative pressure somewhere.
Gate valve stays open. Ans yes you can just seal, add vessel and PRV and have virtually no pressure. Its just convenient using the existing header instead of a filling loop if its already there.
 
I converted mine about 20 years back. Old cast iron floorstanding boiler, gravity HW, pump next to boiler, pumping downwards. No controls. Cold feed to boiler return.
Scrapped the boiler and installed wall-mounted condensing. Moved the pump to the airing cupboard, added diverter valve (system W), open vent, cold feed and DV in the airing cupboard. Added cylinder and room stats. Re-used the gravity 28mm pipes as pump suction and cylinder return.
Still working OK.

That is exactly what system I have to work on! :)
Cast iron oil boiler with 28mm gravities to cylinder and 28mm pumped (pump is also on return pipe) to rads. No controls.
The feed pipe joins in at tee at return at cylinder.
Your new pipe up arrangement would be nearly what I would ideally do, but difficult on this house. I might risk trying to seal the system - but at a low charge.
As to Vee’s point about sealing the system using gravity feed from f&e tank and non return valve, - I have came across systems done that way, some of which are fed from the cwt cold supply.
Personally I don’t like it because risk of contaminating cwt, also disadvantage that the sealed system will keep being topped up in an event of a bad leak, like nail through a pipe. Although constant top up has also advantages.
 
That is exactly what system I have to work on! :)
Cast iron oil boiler with 28mm gravities to cylinder and 28mm pumped (pump is also on return pipe) to rads. No controls.
The feed pipe joins in at tee at return at cylinder.
Your new pipe up arrangement would be nearly what I would ideally do, but difficult on this house. I might risk trying to seal the system - but at a low charge.
As to Vee’s point about sealing the system using gravity feed from f&e tank and non return valve, - I have came across systems done that way, some of which are fed from the cwt cold supply.
Personally I don’t like it because risk of contaminating cwt, also disadvantage that the sealed system will keep being topped up in an event of a bad leak, like nail through a pipe. Although constant top up has also advantages.
In my case the F/E tank is almost directly above the airing cupboard, so open vent and cold fill no problem. I chased the wall in the hall for the roomstat, and it was fiddly getting the lead through to the airing cupboard. Eberle roomstat, because it was cheap, but no complaints, has anticipator heater and gives excellent control. I guess you'll use a radio-controlled roomstat so won't have the cabling problem.
There is a common heating flow pipe not far from the airing cupboard so I ran a pipe under the floorboards and tee'd into that with CH flow from the DV.
 
My very scientific experiment :D

34" of head
1" single check valve
22mm feed
1 Williams f and e tank :D

Result

It works brilliant

IMG_3675.JPG


IMG_3676.JPG
 
Didn't think there was going to be enough head to open the check valve
With the suggested scheme the valve needs to close to prevent upward flow, if I understand correctly. Does it have a spring-loaded flap? Unlikely it will close otherwise. Or maybe use 2 90° bends so the valve is in a horizontal section, if it's the right type of valve. Or maybe 2 return bends so it's vertically down, but that gets a bit messy.
 
That's looks like low-head check valve. Am I right?

dont have a clue, bought the check valve on the designed i liked the most :D
 
With the suggested scheme the valve needs to close to prevent upward flow, if I understand correctly. Does it have a spring-loaded flap? Unlikely it will close otherwise. Or maybe use 2 90° bends so the valve is in a horizontal section, if it's the right type of valve. Or maybe 2 return bends so it's vertically down, but that gets a bit messy.

yes its spring loaded in the closed position
 
Job done I think it looked ok

Took 5 hours to fill tho (due to no head f and e tank about 2" above the rads)

IMG_3681.JPG


IMG_3682.JPG


IMG_3685.JPG
 
I'd like to think pushfit can with Stand 1bar!! Although I dispise the stuff.
3bar @ 82deg C otherwise it should not be used.
No one seems to pressure test anything anymore, testing systems using A or B testing method should identify any poorly made joints because the both involve reducing the pressure below working.
 
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