We moved into our house a few months ago. The whole wiring and central
heating we think are amateur jobs.

The problem is air getting into the CH system. It's heated by an old
gas boiler downstairs, the pump is upstairs under the floorboards.
Overall, the CH and hot water seem to work OK, except:

Every time the CH is started up after a few hours off, it gurgles like
mad from the pump and three radiators quickly fill with air - two of
them over half full of air (from feeling where they are warm/cold). It
takes a good couple of minutes to bleed them.

Every time, twice a day.

All the other radiators are OK and these three are fine after
bleeding. Until the next cold start.

Now, the dodgy wiring I can fix, I'm an electronics engineer. But
water has me stumped.

Please, any help?

Rick,
Manchester, UK.

Rick wrote:
We moved into our house a few months ago. The whole wiring and central
heating we think are amateur jobs.

The problem is air getting into the CH system. It's heated by an old
gas boiler downstairs, the pump is upstairs under the floorboards.
Overall, the CH and hot water seem to work OK, except:

Every time the CH is started up after a few hours off, it gurgles like
mad from the pump and three radiators quickly fill with air - two of
them over half full of air (from feeling where they are warm/cold). It
takes a good couple of minutes to bleed them.

Every time, twice a day.

All the other radiators are OK and these three are fine after
bleeding. Until the next cold start.

Now, the dodgy wiring I can fix, I'm an electronics engineer. But
water has me stumped.

Water is like electrons, it can neither be created or destroyed.

As is air.
The volume in the system is (more or less (expansion)) constant.
Air can be introduced through leaks in the pipework.

It sounds likely you've got a fairly substantial leak.
You have wandered around the house and environs looking at all the exposed
pipework, and seeing if you can see any damp bits?

On 27 Jan 2005 19:50:28 GMT, Ian Stirling
wrote:

Rick wrote:
We moved into our house a few months ago. The whole wiring and central
heating we think are amateur jobs.

The problem is air getting into the CH system. It's heated by an old
gas boiler downstairs, the pump is upstairs under the floorboards.
Overall, the CH and hot water seem to work OK, except:

Every time the CH is started up after a few hours off, it gurgles like
mad from the pump and three radiators quickly fill with air - two of
them over half full of air (from feeling where they are warm/cold). It
takes a good couple of minutes to bleed them.

Every time, twice a day.

All the other radiators are OK and these three are fine after
bleeding. Until the next cold start.

Now, the dodgy wiring I can fix, I'm an electronics engineer. But
water has me stumped.

Water is like electrons, it can neither be created or destroyed.

As is air.
The volume in the system is (more or less (expansion)) constant.
Air can be introduced through leaks in the pipework.

It sounds likely you've got a fairly substantial leak.
You have wandered around the house and environs looking at all the exposed
pipework, and seeing if you can see any damp bits?

Thanks for the quick response.

Well, my first job in the house (and first foray into plumbing) was to
replace the water mains due to a leak under the building in the old
lead pipe. Great fun! So I've tended to watch for leaks anyway.

I've not seen any, and given the volume involved I think it would be
noticeable. Also, when I first got the system working (after
connecting a vacuum pump to the pilot light to clear whatever was
blocking it) we ran the CH full belt for 48 hours to dry the house
out. Although it needed a little extra bleeding occasionally during
this, it was only a tiny fraction of what we get twice a day from a
cold start.

It's a concrete floor on the ground level and the pipes disappear into
the walls or behind skirting - there are no discernable damp patches
anywhere I can see.

I did have to tighten the compression joint on the inlet to the pump
as it had a very slow drip, but that was a week ago.

I'm still stuck!

Rick.

Rick wrote in
:

I did have to tighten the compression joint on the inlet to the pump
as it had a very slow drip, but that was a week ago.

I'm still stuck!

Rick.

This sounds a bit mad, but is it possible your pump is sucking in air, but
only on startup?

I must admit I can't see why, except that when water is circulating,
pressure differentials would be less than when the pump's trying to get it
going.

Could you turn your pump down a notch, or check the vent on startup to see
if it's sucking.

If this is a load of cobblers, please don't singe me bum

mike

On Thu, 27 Jan 2005 19:28:21 +0000, Rick wrote:

Every time the CH is started up after a few hours off, it gurgles like
mad from the pump and three radiators quickly fill with air - two of
them over half full of air (from feeling where they are warm/cold). It
takes a good couple of minutes to bleed them.

Sounds like the pump speed is too high. You are probably sucking air
in down the vent when the pump is switched on. Try turning the pump
speed down.

M.

Rick wrote:
On 27 Jan 2005 19:50:28 GMT, Ian Stirling
wrote:

Rick wrote:
We moved into our house a few months ago. The whole wiring and central
heating we think are amateur jobs.

snip
Every time the CH is started up after a few hours off, it gurgles like
mad from the pump and three radiators quickly fill with air - two of
them over half full of air (from feeling where they are warm/cold). It
takes a good couple of minutes to bleed them.
snip
It sounds likely you've got a fairly substantial leak.
You have wandered around the house and environs looking at all the exposed
pipework, and seeing if you can see any damp bits?

Thanks for the quick response.

Well, my first job in the house (and first foray into plumbing) was to
replace the water mains due to a leak under the building in the old
lead pipe. Great fun! So I've tended to watch for leaks anyway.

I've not seen any, and given the volume involved I think it would be
noticeable. Also, when I first got the system working (after
connecting a vacuum pump to the pilot light to clear whatever was
blocking it) we ran the CH full belt for 48 hours to dry the house
out. Although it needed a little extra bleeding occasionally during
this, it was only a tiny fraction of what we get twice a day from a
cold start.

It's a concrete floor on the ground level and the pipes disappear into
the walls or behind skirting - there are no discernable damp patches
anywhere I can see.

I did have to tighten the compression joint on the inlet to the pump
as it had a very slow drip, but that was a week ago.

I'm still stuck!

Ok, do you know where the header tank is?

Probably the easiest way to see if it's leaking a lot, is to turn off the
system, for a couple of hours, then turn off the feed valve to the header
tank, and see how fast the level drops.

The other possibility is if the header tank is overflowing, to somewhere
you haven't seen, and you've got oxygenated water being constantly pumped
in, as the system heats and cools, with the water 'leaking' out of the
overflow (I don't think this is likely).

On 27 Jan 2005 20:41:32 GMT, Ian Stirling
wrote:


Ok, do you know where the header tank is?

Probably the easiest way to see if it's leaking a lot, is to turn off the
system, for a couple of hours, then turn off the feed valve to the header
tank, and see how fast the level drops.

The other possibility is if the header tank is overflowing, to somewhere
you haven't seen, and you've got oxygenated water being constantly pumped
in, as the system heats and cools, with the water 'leaking' out of the
overflow (I don't think this is likely).


Hey hey, thanks to Google I now know what a header tank is. I wondered
about what happened when all that water expanded...

I've just turned down the pump as suggested by Mike and Markus
(thanks) - it was on full. I'll see if there is any difference
tomorrow morning. I do recall a neighbour (who seems to know a little
more than me) telling me that the pump was too small for the job -
don't know if this is true or makes a difference. The pump seems to be
a "Bosch UPS 15-60" if that means anything to you.

If not, I'll go and investigate the header tank and try your
suggestion to see if the level drops. I don't recall seeing a cutoff
valve up there (I had a nosey around the tank because I didn't know
what it was for), but I can tie the ballcock up.

I know where the overflow for the header tank is and have not noticed
any overflow, but I'll check.

I did notice a lot of corrosion around the tap on the inlet to the
pump, around the joint, where the cap that the tap's shaft goes
through joins the body of the tap. No sign of any water though - dry
as a bone since I tightened that compression joint.

I'll get up in the loft and have a good play with it this weekend and
report back.

Many thanks,
Rick.

hi

you could have any one or more of a few faults. installation fault:
the pump if turned up to too high speed will pull large gulps of air
down the expansion pipe from the header tank in your loft.blocked cold
feed pipe from header tank will cause same symptoms. very unlikely to
be air leaks as mensioned above from joints. another favourite is a
failing washer on the suction side of the ch pump (may not leak water
but can suck air in).

my advice: call an expert heating engineer.

mike ring wrote:


This sounds a bit mad, but is it possible your pump is sucking in air, but
only on startup?

I have seen this where the vent pipe that returns to over the expansion
tank was about six inches from the suction side of the pump. Every time
the pump fired up it sucked a gob of air into the system.

If this is the case, see if running the pump on a slower speed (if it
has one) helps. Or move the position of the vent pipe.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

We once suffered from these symptoms - the cause was as simple as the
ballcock valve in the header tank was sticking due to corrosion. I
bled radiators to my heart's content, but of course the air just moved
around and eventually stopped due to lack of pressure.

"The pump seems to be a "Bosch UPS 15-60".

Grundfos UPS 15-60

" I now know what a header tank is. I wondered
about what happened when all that water expanded..."

"I do recall a neighbour (who seems to know a little
more than me) telling me that the pump was too small for the job -"

An important point. The heater tank is a feed and expansion tank. When
the system is cold there should be just a couple of inches of water
covering the outlet and about 3 gallons worth of air space to
accomodate the expansion- I thinks that's in the FAQ. When the system's
hot, the tank will contain more water, but ensure it doesn't reach the
overflow. This may be relevant 'cos your knowledgeable neighbour
suggests the system capacity is large.

When the system is hot and operating with the pump running, make sure
there's no circulation of water through the F&E tank, no pumping over.

You've got corrosion problems, so reckon on power flushing in warmer
weather. Probably a new boiler when the problem(s) is/are sorted.

Peter Ramm wrote:
On 27 Jan 2005 19:50:28 GMT, Ian Stirling
wrote:

snip
Water is like electrons, it can neither be created or destroyed.

what do you get if you burn hydrogen?

Helium.

Thanks to everyone for the help - I really appreciate it.

Turning the pump down seems to have cured the problem - no more air.

I'll put some anti-corrosion stuff in tomorrow and keep the suggestion
of flushing in the back of my mind for the Summer hols.

This whole house really is a botch-job. I noticed when we first moved
in that using the microwave and electric oven together caused the
lights to *really* dim. Checking it out, I found the whole kitchen
(including electric oven, sockets and lights) is run from a single
piece of 2.5mm standard ring cable straight from the fuse box. Arrgh!

Thanks again,
Rick.

wrote in message
oups.com...
We once suffered from these symptoms - the cause was as simple as the
ballcock valve in the header tank was sticking due to corrosion. I
bled radiators to my heart's content, but of course the air just moved
around and eventually stopped due to lack of pressure.

Another reason might be that the pipe that feeds water down from the
header tank might be blocked by sediment. This happens to me about
every five years. I am in an exceptionally hard water area and there seems
to be no way to stop the sedimentation.

Peter Scott

This whole house really is a botch-job. I noticed when we first moved
in that using the microwave and electric oven together caused the
lights to *really* dim. Checking it out, I found the whole kitchen
(including electric oven, sockets and lights) is run from a single
piece of 2.5mm standard ring cable straight from the fuse box. Arrgh!

And of course now it would be legal for you to leave this as it is, but not
to fix it without getting the installation tested! Politicians are plonkers
!

Peter Scott

On Thu, 27 Jan 2005 20:35:58 +0000, mike ring wrote:

Rick wrote in
:

I did have to tighten the compression joint on the inlet to the pump as
it had a very slow drip, but that was a week ago.

I'm still stuck!

Rick.

This sounds a bit mad, but is it possible your pump is sucking in air, but
only on startup?
FWIW I had this sort of problem a couple of years ago!
Just in case it has not been covered, I had a problem when the pump
stopped. It syphoned over into the header tank. Improved it by
balancing system which enabled me to reduce pump speed significantly. It
still pushed a little over into the header so I had to raise the vent pipe
(top bend) another 10cms which did the trick.
Apparently it is due to system design (on my system), and was caused by
the inertia due the mass of water being stopped abruptly when the pump
stops. When this problem occurs the header gets VERY "sludged" up and
can also cause a blockage (which makes the situation worse).
Sorry if terms are not technically correct!
I hope this may be useful as it took quite some time to find my problem!


I must admit I can't see why, except that when water is circulating,
pressure differentials would be less than when the pump's trying to get it
going.

Could you turn your pump down a notch, or check the vent on startup to see
if it's sucking.

If this is a load of cobblers, please don't singe me bum

mike