I have just moved into my first house and have a Potterton Myson Fanfare Apollo
Gas Wall Mounted Boiler.
For the first few days there was heating upstairs but not downstairs, then I
turned off the upstairs radiators and we had
hot radiators downstairs for just ONE day and then the whole system stopped
Now the boiler ignites and runs for a few seconds, then makes loud bangs and
clanging noises and cuts out.
I have checked the diverting valve this is free to move although it moves very
I can hear the pump and it sounds like it is operating.
No hot water is being fed through the system but we have had hot water up until
I'd suspect the pump for the initial problem and maybe some air in the
system for the second problem.
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Is it a sealed pressurised primary system or a vented system?
My guess is that it is a vented system with a small header tank (not the
large one for domestic hot water) in the attic. My guess, further is that
the water level in this header tank is too low - probably as the result of a
sticking ball valve - and that lots of air has been drawn into the system.
However, it *could* be the pump - even though it sounds as if it is working.
There should be a large cover with a screwdriver slot - covering the end of
the shaft. Remove this and check that the shaft is actually rotating when it
should be. If it isn't, you may be able to free it by rotating the shaft
with a screwdriver - otherwise, a new pump is needed.
Assuming that the pump is ok, check the header tank - making sure that there
are several inches of water in the bottom, and that water comes in when the
ball valve is pushed down. Then, you'll need to bleed the system
throroughly. Bleed all the radiators until water rather than air (or a
spluttering mixture thereof) comes out of the bleed screws. You will
probably also have one or more bleed screws on the primary circuit in the
vicinity of the airing cupboard. Bleed these until water comes out. You may
need to do this several times - checking that the header tank is maintaining
its level all the time. That should fix the problem.
IF, on the other hand, it's a sealed pressurised system, don't do any of the
above (apart from checking the pump) but come back here - because you will
need a different solution.
Thanks for your response. It is a vented system - I have checked the header
tank and there is plenty of water and the ball cock is
working. I have taken the cover off the pump as suggested and the shaft is
spinning when the pump is on and I can feel water moving
along the outlet pipe from the pump. The problem seems to be that the boiler
does not stay on long enough to heat the water - any
On Sun, 30 Nov 2003 00:18:45 -0000, "Roger Mills"
header tank and there is plenty of water and the ball cock is
is spinning when the pump is on and I can feel water moving
boiler does not stay on long enough to heat the water - any
Well, it would seem that - for whatever reason - water is failing to
circulate in your system, so the boiler is getting hot very quickly and
switching off. From what you are now saying, the possible causes - starting
with the most likely - are:
1. Knackered pump [It's possible that its impellor is shot despite the fact
that the shaft is rotating]
2. Air in the system
3. A blockage somewhere - or failed zone/diverter valve
In your position, I think I would:
1. Thoroughly bleed the system (because it's easy and doesn't require
spending any money
2. If that doesn't work, replace the pump (not very expensive, and easy
enough to do provided the isolator valves work ok)
I have now bled the radiators and the boiler seems to crank up for approximately
40 secs then cut off. This is longer than before.
Infact the upstairs radiators are now warm (from the brief time it comes on) but
downstairs still ice cold. im stumped, could this
still be the pump?
On Mon, 1 Dec 2003 00:33:01 -0000, "Roger Mills"
approximately 40 secs then cut off. This is longer than before.
on) but downstairs still ice cold. im stumped, could this
It's quite likely that it's the pump. When the boiler stops, does it cool
down and then come again for another 40 secs all by itself - or does its
overheat thermostat trip such that you have to reset it manually?
When did it last work *properly* and have you or anyone else done anything
to the system since then?
It cools down and then comes back on again for around 40 seconds.
I have done nothing else to the system other than trying the boiler thermostat
from low to high (as the downstairs radiators weren't
getting hot) then nothing worked. We have since changed this back and now have
On Mon, 1 Dec 2003 14:59:02 -0000, "Roger Mills"
thermostat from low to high (as the downstairs radiators weren't
have heat upstairs.
I think the next thing is to have a look at the pump. Turn the whole heating
off at the main isolating switch. Does the pump have gate valves either
side? If so, turn these both off and undo the big nuts which hold the valves
onto the pump. The pump can then the withdrawn. Be prepared to catch a small
amount of water - or a large amount if the gate valves don't turn off
When you have the pump out, you will be able to see whether its impellor is
intact or not. Connect it to the mains to make sure that it spins - for only
for a second or two - they are not designed to run dry! If you find either
that the pump doesn't rotate or that its impellor is knackered, you'll need
to replace it. When you put it back, use new fibre washers between the pump
body and gate-valve flanges.
Thanks for your continuing help
Last night I changed the pump and still have a problem.
The radiators upstairs are all boiling hot but the radiators downstairs remain
The house is a VERY small two bed terraced house built around 1985.
It has radiators in the lounge, hallway, bathroom and bedrooms
Upstairs the plumbing is 15mm downstairs its 8mm (don't know why)
I would appreciate any more suggestions that you have.
On Mon, 1 Dec 2003 19:20:14 -0000, "Roger Mills"
On Tue, 02 Dec 2003 06:08:12 +0000, email@example.com wrote:
It could be that the system is way out of balance. The smaller bore
pipes downstairs will carry less water than the upstairs ones.
Try turning off all of the upstairs radiators using their normal wheel
valve or TRV controls and see if the downstairs radiators become warm.
If they are still sluggish in getting warm, then check the lockshield
valves of the downstairs radiators and open them fully.
Ultimately, you could even turn off all radiators bar one, putting the
full pump output through it.
If you are still not getting the radiators to warm reasonably quickly
then it's possible that there is sludging in the downstairs radiators
and pipes. You can check this by feeling the centre bottom area of
the radiators. If it feels cool after the middle and tops have
warmed in the shape of a pyramid then there is a fair chance that
there is sludge. If this is the case then you really need to drain
down the system and clean out the radiators and flush the pipes to
each radiator position. (Care because sludge is an indellible dye).
If you search back in Google Groups I have posted a method of how to
do a thorough cleaning, radiator by radiator.
You should be able to arrive at the downstairs radiators heating up by
this point. You can then balance the system as described in the
FAQ. In general, the upstairs radiator lockshield valves will be
closed down more than the downstairs ones.
To email, substitute .nospam with .gl
Sounds like you are making *some* progress! Does the boiler now run for a
longer period rather than cutting out after 40 seconds?
Where does the piping run to your downstairs radiators? My guess is that the
downstairs floors are solid - and that the heating pipes run between the
floors and drop down to each downstairs rad. Is this correct? With such a
system it is easy to get air locks in the feed to the downstairs rads - and
quite difficult to get rid of them. The usual trick is to deal with each
downstairs rad in turn - by turning off all other rads so that the water has
nowhere else to go. You may have to repeat this more than once - but
generally, once each rad gets the idea, it keeps going!
That's because there's still not enough circulation to take the water to
where the boiler's output can be dissipated - so the boiler simply cycles on
and off on its own stat.
Have you tried the trick of forcing all the water through each radiator in
turn, by turning all the others off?
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