On Fri, 30 Jun 2006 08:28:17 +0100, TheScullster wrote
(in article ):


"Martyn Pollard" wrote


Is there any reason why you aren't having a sealed system? It would make
life a lot easier for yourself and simplify the heating system. Also, low
water content boilers tend to operate better (quieter) on a sealed system
anyway.

Thanks Martyn

I am hoping that someone with serious experience of vented systems will
comment here!
If I can stabilise the system and prevent the pump over, modifying the
existing layout will be the most "comfortable" route.

Yes I have considered/am considering a sealed system, but I am concerned
about the age and state of the piping and its ability to cope with increased
pressure. The ground floor is solid concrete with buried pipes and some
plastic has been introduced upstairs (not sure if it's barrier quality).
The original install is 1970s and this is probably the worst period in UK
history for build and service quality IMHO.

Phil




I've installed and worked on both and migrated from a vented to a sealed
system.

- If you want to retain an open vented system, then the solution to pumping
over is to make sure that the vent and feed/expansion pipes join the circuit
close together (within 150mm); or more conveniently use an air separator like
a Myson Aerjec to do the hookup. The important things to avoid are
certainly having them connect on opposite sides of the pump and almost
certainly on opposite sides of the boiler. Putting both on one side of the
boiler avoids the pressure differential that can otherwise arise.

- Making a system sealed does not mean that you are taking it up to mains
water pressure or anywhere close. You are going to take it from around 1bar
to 1.5 to 2bar. If the pipes are going to have a problem with this (which
I think is very unlikely), then it won't be long before they do with a vented
system.

- If there is going to be an issue, it is more likely to be radiator valves
leaking and seeping around the stems. As part of a system refurbishment, it
would make sense to proactively swap these out anyway. The system is going
to need a thorough cleaning, and the summer is the perfect time to take the
radiators outside for a thorough pressure wash. The whole process of doing
that and swapping valves can easily be done in a day.

- This cleaning should be done regardless of whether the system remains open
vented or goes sealed. What I did last time was to take the old boiler out
of service (switch off but leave installed), swapped in the sealed system
components. Then I had mains pressure available to flush the pipes as the
radiators were removed. Considering you have buried pipes downstairs, this
would be a good way to get the crud out of them.