Hi

After returning from Christmas with the inlaws my neighbour informed
me that one of the loft overflow pipes had been dripping whilst we
were away. I decided to have a root around tonight when I put the
decorations away for another year and was suprised to find the water
in the expansion tank was hot!

We have a Baxi Solo 3 PF with a Honeywell Y Plan control system with
more than the minimum head stated in the installation guide. I then
remembered that the plumbed who last serviced the boiler muttered
something about the pipe layout not being particularly good and
causing turbulence in the flow pipe.

I'm guessing that the dripping overflow is simply condensation from
the hot water, however, why is the tank getting hot?

Regards

Ross

On 5 Jan 2005 14:44:11 -0800, (RossG) wrote:

Hi
... however, why is the tank getting hot?


Could be that your boiler thermostat is kaputt, and the "flow" is
boiling, passing a mix of steam and water up the expansion pipe into
the header tank. A tell-tale sign is "hammering" noises in the
pipework. Chances are that the over-pressure may also have damaged the
impeller of your pump - the sign of this is very hot radiators
upstairs, but cold downstairs.

--
MatSav

... however, why is the tank getting hot?


Perhaps you have the answer in your question.

"....the plumbed who last serviced the boiler muttered
something about the pipe layout not being particularly good"

Probably pumping over, water going down the cold feed and back up the
open vent. Check the layout of the pipes, if there's a lot of pipes and
fittings between the CF and OV connections, or if the CF connects to
the boiler return and the OV to the boiler flow, then this is probably
the cause. The plumber may have noticed and didn't mention it because
he didn't want to get involved in sorting it out. It needs to be
sorted. The oxygen being absorbed by the water will cause internal
rusting of the rads. Had any rads leaking?

In an earlier contribution to this discussion,
RossG wrote:

Hi

After returning from Christmas with the inlaws my neighbour informed
me that one of the loft overflow pipes had been dripping whilst we
were away. I decided to have a root around tonight when I put the
decorations away for another year and was suprised to find the water
in the expansion tank was hot!

We have a Baxi Solo 3 PF with a Honeywell Y Plan control system with
more than the minimum head stated in the installation guide. I then
remembered that the plumbed who last serviced the boiler muttered
something about the pipe layout not being particularly good and
causing turbulence in the flow pipe.

I'm guessing that the dripping overflow is simply condensation from
the hot water, however, why is the tank getting hot?

Regards

Ross

Sounds like it's pumping over. You need to go into the attic when the
heating is running and observe the F&E tank. If there's a constant stream of
water flowing out of the vent pipe back into the tank, this is the problem.
A contributory factor to overflowing could be too high a level in the F&E
tank. When the system is cold, there should only be about 3" of water in the
bottom of the tank - just enough to cover the feed pipe comfortably.

This is thoroughly bad, and will introduce oxygen inti the system - causing
corrosion. If you pump has a speed control and is currently on anything
other than the minimum setting, turn it down a bit. If this cures the
problem whilst still allowing the heating and HW systems to work ok, then
fine. Otherwise you need to sort the pipework out - making sure that the F&E
pipes are both connected into the main flow pipe *before* the pump, and
within a few inches of each other.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

Aidan wrote:
if the CF connects to
the boiler return and the OV to the boiler flow,

Or similarly, CF to pump suction side, OV to pump delivery side.

Watch the OV going into the F&E tank with the 3-port valve in all it's
possible positions (heating on HWS off, HWS on HTG off, HTG & HWS on).

In article ,
RossG wrote:
After returning from Christmas with the inlaws my neighbour informed
me that one of the loft overflow pipes had been dripping whilst we
were away. I decided to have a root around tonight when I put the
decorations away for another year and was suprised to find the water
in the expansion tank was hot!

We have a Baxi Solo 3 PF with a Honeywell Y Plan control system with
more than the minimum head stated in the installation guide. I then
remembered that the plumbed who last serviced the boiler muttered
something about the pipe layout not being particularly good and
causing turbulence in the flow pipe.

I'm guessing that the dripping overflow is simply condensation from
the hot water, however, why is the tank getting hot?

It's pumping over and should be seen to ASAP.

Has the system ever been properly balanced? (see FAQ) Is the pump speed
setting on anything other than low? All the pump is required to do is
circulate the water - speeding it up more than the minium needed to do
this is likely to cause pumping over. If reducing the pump speed to
minimum causes some rads not to work, balancing the system should sort it.
This is a fairly simple but rather time consuming task - but pretty
essential. A plumber could charge quite a bit for this because of the time
involved.

Only if correct balancing results in a rad or rads still not working
should the speed be increased.

Pumping over introduces air to the system resulting in much accelerated
corrosion. If you can't stop it after this, make sure the water level in
the header tank is only a couple of inches above the bottom, and consider
extending the vent pipe as high as physically possible - although of
course the opening must still be above the tank. Doesn't matter if it has
to go off at an angle to clear the roof joists.

--
*Real men don't waste their hormones growing hair

Dave Plowman London SW
To e-mail, change noise into sound.

After returning from Christmas with the inlaws my neighbour informed
me that one of the loft overflow pipes had been dripping whilst we
were away. I decided to have a root around tonight when I put the
decorations away for another year and was suprised to find the water
in the expansion tank was hot!

By the time you've diagnosed a pumping over/venting/feed issue in an F&E
system and attempted fixing the thing for the xth time, you might as well
have just chucked the lot out at the start and replace the tank with a
sealed system kit that just doesn't have these issues. The conversion kits
cost around 40 quid and are a simple fit with only basic plumbing required.

http://www.plumbworld.co.uk/584-0000

Not all boilers support this course of action, though, so you need to check
the actual make and model. Baxi still make a Solo 3 PFL model, which is
compatible with sealed operation. I don't know if your model is also
compatible, but strongly suspect so.

Christian.

In article ,
Christian McArdle wrote:
By the time you've diagnosed a pumping over/venting/feed issue in an F&E
system and attempted fixing the thing for the xth time, you might as
well have just chucked the lot out at the start and replace the tank
with a sealed system kit that just doesn't have these issues. The
conversion kits cost around 40 quid and are a simple fit with only basic
plumbing required.

Hmm. Have you counted the number of recent threads where people are having
problems with pressurised systems? Of course if the OP's system is so
badly installed it has fundamental problems then it might be the answer.
But I'd make a start at balancing it and turning down the pump before
spending any money.

--
*Toilet stolen from police station. Cops have nothing to go on.

Dave Plowman London SW
To e-mail, change noise into sound.

Aidan wrote:
Probably pumping over, water going down the cold feed and back up the
open vent. Check the layout of the pipes, if there's a lot of pipes and
fittings between the CF and OV connections,

Depends on what constitutes a lot of pipe(s), the layout is roughly like
this

OV.
|___________
CF |
_____|_____|
| |
| ---------
| | |
| | |
| |Boiler |
|
|
|
Pump

The flow comes out of the top of the boiler enters a T-joint, continues
straight up for 50mm before turning horizontally. The pipe then runs
600mm horizontally before turning upward again. This is the overflow
pipe and it goes through the ceiling to the cistern. This vertical run
must be over the 1m min height specified in the installation manual.

The other leg of the T-joint proceeds about 300mm before another T
which is the 15mm cold feed. This run is obviously longer than the
150mm max specified in the manual. It sounds like this is the problem?

or if the CF connects to
the boiler return and the OV to the boiler flow, then this is probably
the cause. The plumber may have noticed and didn't mention it because
he didn't want to get involved in sorting it out. It needs to be
sorted. The oxygen being absorbed by the water will cause internal
rusting of the rads. Had any rads leaking?

Not yet, and most of them are pretty long in the tooth.

Thanks for the info

Kind regards

Ross

Set Square wrote:

Sounds like it's pumping over. You need to go into the attic when the
heating is running and observe the F&E tank.

Will do

If there's a constant stream of
water flowing out of the vent pipe back into the tank, this is the problem.
A contributory factor to overflowing could be too high a level in the F&E
tank. When the system is cold, there should only be about 3" of water in the
bottom of the tank - just enough to cover the feed pipe comfortably.

Blimey, not at all, OK the tank is small, roughly a foot in height but
the water level is very high, probably about an inch or two at most
below the top. I mean the ballcock is nearly horizontal

This is thoroughly bad, and will introduce oxygen inti the system - causing
corrosion. If you pump has a speed control and is currently on anything
other than the minimum setting, turn it down a bit.

Will do

If this cures the
problem whilst still allowing the heating and HW systems to work ok, then
fine. Otherwise you need to sort the pipework out - making sure that the F&E
pipes are both connected into the main flow pipe *before* the pump,

Yes they are

and within a few inches of each other.

Ah no they are at least a foot apart :-(

Thanks for replying

Kind regards

Ross

Dave Plowman (News) wrote:

Has the system ever been properly balanced?

Hard to tell, we have only been here for a year and a half, probably not
though.

(see FAQ) Is the pump speed setting on anything other than low?

Medium at the moment, but I shall reduce it ASAP!

Pumping over introduces air to the system resulting in much accelerated
corrosion. If you can't stop it after this, make sure the water level in
the header tank is only a couple of inches above the bottom,

Right, well, someone else mentioned the water level and it is indeed
relatively high so they looks like another reason.

Thanks for the information I shall return to the loft

Kind regards

Ross

MatSav wrote:

Could be that your boiler thermostat is kaputt, and the "flow" is
boiling, passing a mix of steam and water up the expansion pipe into
the header tank. A tell-tale sign is "hammering" noises in the
pipework. Chances are that the over-pressure may also have damaged the
impeller of your pump - the sign of this is very hot radiators
upstairs, but cold downstairs.

Hmm there are no hammering noises although the upstairs rads could be
a hotter than those downstairs but they are not stone cold. Couldn't
it just mean the system needs balancing?

Thanks for replying

Kind regards

Ross

Hmm. Have you counted the number of recent threads where people are having
problems with pressurised systems?

The problems with the pressurised systems have been nothing to do with being
pressurised, though. They are mainly leaks. The reason you don't see quite
so many issues with non-pressurised systems is that the water just dribbles
away for years (causing timber rot) and gets replenished without anyone
noticing.

Christian.

Gents,

After taking all the useful advice on board I turned the pump
to it's lowest setting and bailed out the expansion tank,
to the tune of 26 pints in fact. I left the tank with
approximately 5" of water in, which was the point at which the
ballcock kicked in.

I've been popping back up, on and off, over the last couple of
days and the water has been consistently cold. However, the
water level has crept back up, in fact it has risen by 3 or
4 inches! I then noticed that the rust coloured high water
mark was ABOVE the level of the open vent exit. I bailed the
tank out again, then help a cup of water over the end of the
OV. I could then see Brownian motion at the entrance to the
cold feed pipe with my torch, and after poking my index finger
in the cold feed I could feel hot water emerging. I took the
cup away and the flow quickly stopped.

My gut reaction is that the ballcock is gently leaking, the
tank is filling up, submerging the OV, and the system is
then seesawing. I suspect a new ball cock and some inhibitor
are called for, what do you think?

Regards

Ross

In an earlier contribution to this discussion,
Ross Galvin wrote:

Gents,

After taking all the useful advice on board I turned the pump
to it's lowest setting and bailed out the expansion tank,
to the tune of 26 pints in fact. I left the tank with
approximately 5" of water in, which was the point at which the
ballcock kicked in.

I've been popping back up, on and off, over the last couple of
days and the water has been consistently cold. However, the
water level has crept back up, in fact it has risen by 3 or
4 inches! I then noticed that the rust coloured high water
mark was ABOVE the level of the open vent exit. I bailed the
tank out again, then help a cup of water over the end of the
OV. I could then see Brownian motion at the entrance to the
cold feed pipe with my torch, and after poking my index finger
in the cold feed I could feel hot water emerging. I took the
cup away and the flow quickly stopped.

My gut reaction is that the ballcock is gently leaking, the
tank is filling up, submerging the OV, and the system is
then seesawing. I suspect a new ball cock and some inhibitor
are called for, what do you think?

Regards

Ross

The ballvalve *could* be faulty - but there's another, perhaps more likely -
and expensive(!) - explanation.

Do you have a tap on the supply side of the F&E tank? If so, turn it off so
that no water can enter through the ballvalve, and see whether the level
still rises. If not, just put a piece of wood across the top of the tank,
and tie the arm of the ballvalve to it.

If the level still rises (other than just by expansion when the system gets
hot) you could have a leak in the indirect coil inside your hot water
cylinder, which is allowing domestic hot water to enter your primary heating
circuit.

Do you have a large header tank for the DHW in the attic? Is the water level
in this *higher* than that in the F&E tank? If so, and if there *is* a leak
in the coil, the higher static pressure in the DHW system will cause water
to flow into the primary circuit.

If this *is* the problem, you'll need a new hot water cylinder. If you *do*
need to replace the HW cylinder, make sure you get a fast recover one (with
a large heat exchanger inside). Unless the existing cylinder is fairly new,
the new one will almost certainly be better insulated - so you'll end up
getting faster hot water, and wasting less heat.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

The ballvalve *could* be faulty - but there's another, perhaps more likely -
and expensive(!) - explanation.

Eek

Do you have a tap on the supply side of the F&E tank?

No

If so, turn it off so
that no water can enter through the ballvalve, and see whether the level
still rises. If not, just put a piece of wood across the top of the tank,
and tie the arm of the ballvalve to it.


Do you have a large header tank for the DHW in the attic?

Yes

Is the water level in this *higher* than that in the F&E tank?

Ah, no, in fact the top of the tank is lower than the bottom of the cold
feed tank

If so, and if there *is* a leak
in the coil, the higher static pressure in the DHW system will cause water
to flow into the primary circuit.

So it looks like the ball valve is the culprit then?

Kind regards

Ross