Pumping Over on HW Only - Modulating Boiler
 

Hi,

Quick question for the Panel.

CH & HW work perfectly from a heating perspective. There are no
hotspots/cold radiators and HW heats up very quickly.

When the boiler runs HW only, pumping over occurs.

I have reduced the level in the expansion tank to a minimum.

There is no way to control the pump speed as the pump is intergrated
into the boiler and modulates depending on the demand for heat.

The Boiler is on the ground floor, the HW cylinder on the 1st floor,
the expansion tank in the loft.

The pumping over on HW is more of a 'trickle' than a gushing, could
extending the loop/overflow thingy by a couple of feet fix the
problem?

Cheers,
--
Steve

Pumping Over on HW Only - Modulating Boiler
 

In an earlier contribution to this discussion,
Ragworm The Abominable wrote:

Hi,

Quick question for the Panel.

CH & HW work perfectly from a heating perspective. There are no
hotspots/cold radiators and HW heats up very quickly.

When the boiler runs HW only, pumping over occurs.

I have reduced the level in the expansion tank to a minimum.

There is no way to control the pump speed as the pump is intergrated
into the boiler and modulates depending on the demand for heat.

The Boiler is on the ground floor, the HW cylinder on the 1st floor,
the expansion tank in the loft.

The pumping over on HW is more of a 'trickle' than a gushing, could
extending the loop/overflow thingy by a couple of feet fix the
problem?

Cheers,

It would appear that there's more resistance to flow when just HW is on,
causing the pump to run at a slightly higher pressure. Is there a gate valve
anywhere in the HW circuit (probably near the cylinder) to balance the HW/CH
flow? If so, you could try opening it a bit - assuming that it's not already
fully open. [If you have independent timing of HW and CH - maybe by having a
programmable room stat for CH - you may be able to set it up so that they're
not usually on at the same time - so balance is less important].

Raising the level of the top of the inverted J of the vent pipe would also
help.

Have a careful look at how the fill and vent pipes are connected into the
flow pipe (or maybe the return pipe?). The normal rule is to put them both
in the flow pipe on the suction side of the pump - but you can't do that if
the pump is integral with the boiler - hence the thought that they should
perhaps be in the return pipe. The important thing is that they shouldn't be
more than a few cm apart in order to ensure that there's no significant
flow-induced pressure differential between the two connection points.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

Pumping Over on HW Only - Modulating Boiler
 

On Thu, 19 Jan 2006 11:39:09 +0000, Ragworm The Abominable wrote:

Hi,

Quick question for the Panel.

CH & HW work perfectly from a heating perspective. There are no
hotspots/cold radiators and HW heats up very quickly.

When the boiler runs HW only, pumping over occurs.

I have reduced the level in the expansion tank to a minimum.

There is no way to control the pump speed as the pump is intergrated
into the boiler and modulates depending on the demand for heat.

The Boiler is on the ground floor, the HW cylinder on the 1st floor,
the expansion tank in the loft.

The pumping over on HW is more of a 'trickle' than a gushing, could
extending the loop/overflow thingy by a couple of feet fix the
problem?


Essentially this is an installation fault.

The vent and feed pipes are too far apart on the circuit and/or there is a
partial blockage between them.

What you do next will depend on many circumstances. Doing nothing is not a
good idea.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

Pumping Over on HW Only - Modulating Boiler
 

I don't plan to do nothing :))

HW has been working fine the past three years - I am not sure what has
caused the problem.

A gas installer replaced the shoe on the 3-way value quite recently
(took him two attempts to fix it). I wonder if he dropped/lost
something down into the pipe / or replaced it with an incompatable
shoe.

The HW does not have a restriction valve on it - but I have opened up
the rad in the bathroom to full to see if this helps. Bathroom rad
comes on with both HW & CH.

I am pretty sure there that gunge is not an issue as I gave the pipes
a good clear out when moving into the house.

I have 4 meters of 22mm pipe in the garage - any estimates on how much
I need? Or just go for broke and use as much as possible? It's more
of a splash of water every second or so rather than a continuious
stream of water.

Many thanks for all received replies, and any future ones :)
--
Steve

Pumping Over on HW Only - Modulating Boiler
 

On Thu, 19 Jan 2006 20:52:02 +0000, Ragworm The Abominable wrote:

I don't plan to do nothing :))

HW has been working fine the past three years - I am not sure what has
caused the problem.

A gas installer replaced the shoe on the 3-way value quite recently
(took him two attempts to fix it). I wonder if he dropped/lost
something down into the pipe / or replaced it with an incompatable
shoe.

The HW does not have a restriction valve on it - but I have opened up
the rad in the bathroom to full to see if this helps. Bathroom rad
comes on with both HW & CH.

I am pretty sure there that gunge is not an issue as I gave the pipes
a good clear out when moving into the house.

I have 4 meters of 22mm pipe in the garage - any estimates on how much
I need? Or just go for broke and use as much as possible? It's more
of a splash of water every second or so rather than a continuious
stream of water.

Many thanks for all received replies, and any future ones :)


It's possible that the 3 port valve did not go fully to HW only before it
was repaired?

There are several things you can do each with strengths and weaknesses.

The best by far if you can afford it and the boiler supports it is to go
for a sealed system. See FAQ.

You could try putting a higher loop on the vent pipe so that it requires a
bigger pressure difference to start pumping over.

You could route the feed into the vent pipe - this will make refilling the
system harder but definitely fix the problem.

You could try a lower pump speed and provided it still actually heats the
house and HW. It might also cause the boiler to kettle.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

Pumping Over on HW Only - Modulating Boiler
 

Hello Ed, thank you for you reply.

It's possible that the 3 port valve did not go fully to HW only before it
was repaired?

The spring went west, the motor got tired, and the shoe got gummed up,
I believe that the three way at this time is functioning from a
diversion point of view as it should.

The best by far if you can afford it and the boiler supports it is to go
for a sealed system. See FAQ.

I am considering this as a long term fix - it's a Keston Celsius 25
and I really don't think this boiler is happy unless it's sealed.

You could try putting a higher loop on the vent pipe so that it requires a
bigger pressure difference to start pumping over.

Planning to do this at the weekend - the better half got me the raw
materials, all I need to do is ensure I don't set fire to the loft.
Any 'guesstimate's on whether I should make the loop as tall as the
loft roof, or go for something less

You could route the feed into the vent pipe - this will make refilling the
system harder but definitely fix the problem.

I could put a T-Junction join in the loft between the vent and the
overflow tank - or would the join need to be lower down in the airing
cupboard?

You could try a lower pump speed and provided it still actually heats the
house and HW. It might also cause the boiler to kettle.

Unfortunately the pump is modulated directly by the boiler.

Many thanks,
--
Steve

Pumping Over on HW Only - Modulating Boiler
 

On Thu, 19 Jan 2006 22:59:35 +0000, Ragworm The Abominable
wrote:


The best by far if you can afford it and the boiler supports it is to go
for a sealed system. See FAQ.

I am considering this as a long term fix - it's a Keston Celsius 25
and I really don't think this boiler is happy unless it's sealed.

You could try putting a higher loop on the vent pipe so that it requires a
bigger pressure difference to start pumping over.

Planning to do this at the weekend - the better half got me the raw
materials, all I need to do is ensure I don't set fire to the loft.
Any 'guesstimate's on whether I should make the loop as tall as the
loft roof, or go for something less

You could route the feed into the vent pipe - this will make refilling the
system harder but definitely fix the problem.

I could put a T-Junction join in the loft between the vent and the
overflow tank - or would the join need to be lower down in the airing
cupboard?

To be honest, by the time you've mucked around with the other vent
options, you can have disconnected the loft tank and capped off the
pipes with air vent fittings and have fitted a sealed system kit with
filling loop somewhere. It's really not difficult and the kits are
inexpensive.




You could try a lower pump speed and provided it still actually heats the
house and HW. It might also cause the boiler to kettle.

Unfortunately the pump is modulated directly by the boiler.

Many thanks,

--

..andy

Pumping Over on HW Only - Modulating Boiler
 

"Andy Hall" wrote in message
...
On Thu, 19 Jan 2006 22:59:35 +0000, Ragworm The Abominable
wrote:


The best by far if you can afford it and the boiler supports it is to go
for a sealed system. See FAQ.

I am considering this as a long term fix - it's a Keston Celsius 25
and I really don't think this boiler is happy unless it's sealed.

You could try putting a higher loop on the vent pipe so that it requires
a
bigger pressure difference to start pumping over.

Planning to do this at the weekend - the better half got me the raw
materials, all I need to do is ensure I don't set fire to the loft.
Any 'guesstimate's on whether I should make the loop as tall as the
loft roof, or go for something less

You could route the feed into the vent pipe - this will make refilling
the
system harder but definitely fix the problem.

I could put a T-Junction join in the loft between the vent and the
overflow tank - or would the join need to be lower down in the airing
cupboard?


Seen this type of thing before, the pump pumping over into the header tank.
This happened many years after a new boiler was fitted. Basically probably
due to the bodged way the water feed and vent pipe were connected to the
pump just via a jumble of soldered 15/22mm T fittings. Anyway a plumber
fitted a thing like www.bes.co.uk item number 11334 (Aerjec water
de-aerator) before the pump (I thing) and generally tidied up the pipe work
and the overflowing stopped. Something to do with the connecting distance of
feed pipe and vent pipe and pipe size, I think

Pumping Over on HW Only - Modulating Boiler
 

On Thu, 19 Jan 2006 22:59:35 +0000, Ragworm The Abominable wrote:

Hello Ed, thank you for you reply.

It's possible that the 3 port valve did not go fully to HW only before it
was repaired?

The spring went west, the motor got tired, and the shoe got gummed up,
I believe that the three way at this time is functioning from a
diversion point of view as it should.

So that's the probable cause.


The best by far if you can afford it and the boiler supports it is to go
for a sealed system. See FAQ.

I am considering this as a long term fix - it's a Keston Celsius 25
and I really don't think this boiler is happy unless it's sealed.

My own KC25 is sealed, but I'v down a couple of vented installs no
problem.


You could try putting a higher loop on the vent pipe so that it requires
a bigger pressure difference to start pumping over.

Planning to do this at the weekend - the better half got me the raw
materials, all I need to do is ensure I don't set fire to the loft. Any
'guesstimate's on whether I should make the loop as tall as the loft
roof, or go for something less





You could route the feed into the vent pipe - this will make refilling
the system harder but definitely fix the problem.

I could put a T-Junction join in the loft between the vent and the
overflow tank - or would the join need to be lower down in the airing
cupboard?

I don't think it will make much difference nearby is simpler and may lead
to less air locks.



You could try a lower pump speed and provided it still actually heats
the house and HW. It might also cause the boiler to kettle.

Unfortunately the pump is modulated directly by the boiler.


Now I know it's a KC25 indeed so. It will always use full powre and pump
when the primary circuit is cold.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

Pumping Over on HW Only - Modulating Boiler
 

All, thank you for the replies to date :)

I have some more information - on opening the bathroom rad all the
way, no more pumping over. This is not ideal as it warm's up the
bathroom a little more than one would really like(!) - but it's a good
temporary solution given my current 'broken list' *grin*

Still, the plan is to extend the existing vent, and if that fails to
put a pipe between the vent and the expansion tank, with a full bore
valve to allow easy emptying/refilling of the system.

My Keston hasn't got a pressure valve - would an expansion kit come
with a seperate valve or would I need to purchase the Keston item?

Cheers!
--
Steve

Pumping Over on HW Only - Modulating Boiler
 

In an earlier contribution to this discussion,
Ragworm The Abominable wrote:


My Keston hasn't got a pressure valve - would an expansion kit come
with a seperate valve or would I need to purchase the Keston item?


I assume you're talking about the possibility of converting it to an
unvented system? In that case, something like
http://www.plumbworld.co.uk/584-705 should provide everything you need.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

Pumping Over on HW Only - Modulating Boiler
 

On Sat, 21 Jan 2006 16:58:41 -0000, "Set Square"
wrote:

In an earlier contribution to this discussion,
Ragworm The Abominable wrote:


My Keston hasn't got a pressure valve - would an expansion kit come
with a seperate valve or would I need to purchase the Keston item?


I assume you're talking about the possibility of converting it to an
unvented system? In that case, something like
http://www.plumbworld.co.uk/584-705 should provide everything you need.


To be more explicit - this is a generic kit for creating a sealed
system. The Keston one is functionally the same but a cosmetic
convenience.


--

..andy

Pumping Over on HW Only - Modulating Boiler
 

On Sat, 21 Jan 2006 16:37:50 +0000, Ragworm The Abominable wrote:

All, thank you for the replies to date :)

I have some more information - on opening the bathroom rad all the
way, no more pumping over. This is not ideal as it warm's up the
bathroom a little more than one would really like(!) - but it's a good
temporary solution given my current 'broken list' *grin*

Still, the plan is to extend the existing vent, and if that fails to
put a pipe between the vent and the expansion tank, with a full bore
valve to allow easy emptying/refilling of the system.

My Keston hasn't got a pressure valve - would an expansion kit come
with a seperate valve or would I need to purchase the Keston item?

Keston do a complete kit with all the bit in a unit which fits under the
boiler.
However my boiler is uite near the floor and was not practical todo this
so I 'rolled my own'.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

Pumping Over on HW Only - Modulating Boiler
 

Popped* a extra 80cm of hight onto the 'inverted J', turned the
bathroom rad off, popped a bit more water into the header tank, and
wound the temp up on the HW cylinder, turned the output on boiler to
max, and waited until boiler modulation went down to zero.

Results so far, no over pumping, but will keep an ear out.

(*my first time soldering so hope I didn't mess up..!)

Many thanks all.
--
Steve