Chris B Wrote in message:
I am assisting with the recovery of an inherited property. The existing
heating scheme was designed and installed by the (now deceased) owner in
the mid 70s or early 80s.

It consists of a floor standing Potterton Diplomat with 2 water outlets
one labelled DHW+Upstairs which is split to supply two separate pumps,
the other labelled downstairs, with its own pump.

Timers/thermostats for upstairs and downstairs but no timer on DHW (Just
a tank thermostat). And a relay box to ensure only two of the three
pumps can run simultaneously. (or maybe its just to ensure upstairs and
DWH don't run together)

No TRVs anywhere, obliviously.

Massive twin panel radiators (no fins) in every room, no obvious signs
of corrosion on any of them (I would assume it has been regularly
inhibited at least until the last 5 years or so)

The current water supply temperature from the boiler is 49C (this is
clearly as designed as each pipe has a clip on thermostat with an arrow
marked on the glass. The water temp is on the arrow.

The system certainly used to function as the house was always warm when
visited - but I have no idea what the gas bills were.

From discussions with the owners brother he believed that large
radiators at low temp was the most efficient way to run the heating.

That might well be true and it might well work if you are in the house
all day but we have recently discovered that it takes 9 hours to bring
the house up from 15C to 21C. (Outside temp 8-12C, the property has DG
and Cavity wall insulation)

All the radiators are barely warm at the top and cold at the bottom.

So something has to be done in the short term but the house may be
undergoing major upgrades in the intermediate future (Showers fitted ,
possibly en suite etc) but the exact detail/layout of all this is still TBD.

The new owners are considering a modern boiler, I think as much for
safety reasons as any other as they don't trust this huge great lump in
the kitchen not to be leaking noxious gasses, (a CO monitor has been
fitted as a temporary measure) and the chances of getting anyone to
service it are pretty close to zero.

So my questions are.
1) I am planning to remove all the radiators take them outside and give
them a good hosing through. Would this leave sludge in the pipes and if
so how can it be removed prior to fitting a new boiler. Would this be
adequate or with radiators of this age should they be replaced along
with the boiler?

2) Would the system described above be suitable for adding a modern
boiler pretty much one for one swap with the existing (having flushed
out all of the radiators and fitted TRVs) or would major changes be
necessary. I have looked at the DIY WIKI and it states that with modern
TRVs oversized radiators are not a problem.

3) If a modern boiler is fitted this winter are they all suitable for
using with a pressurised water cylinder if that is the route taken in a
year or so when other modernisation work is done? The Worcester Bosh
website seems to state that their regular Greenstar boilers are
compatible with gravity HW or their own Greenstore (pressurised) cylinder.

Any helpful advice appreciated.

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Chris B (News)


From experience....
Take off rads and fire mains pressure water through them. Shake
them, turn them upside down and rotate to every angle with water
flowing through to get rid of all crud.
When old boiler has been removed, run mains pressure water through
every segment of pipe work. Put fine gauze on the open-to-drain
end of pipe so you can see the nature and volume of crud removed.
Do this thoroughly and it will clear the system much better than
power flushing.

As others have said, fit a magnetic filter such as MagnaClean or
Fernox to catch metallic crud in future.
If it's a decent size house, consider splitting upstairs and down
to separate zones.

Phil
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