CH pump location

Tinkler · 13 Aug 2006

Replacing my current boiler in the kitchen (which has the pump below it within the casing) to one where the pump will have to in the loft. I need to know if there is anything to consider regarding its location and performance.

The most suitable (most practical physically) place puts it next to the vent pipe (immediatly before it on the flow pipe) but a couple of metres past the the 'tap-off' of the bypass (bathroom radiator) on the flow and return pipes - would this situation cause any problems?

Paul Barker · 13 Aug 2006

Traditional order is boiler, vent (preferably via expanded T or AIRJEK) feed/expansion, pump. You would encourage pumping over with your proposal.

DHW cylinder? where is that in your system? Is it with the bathroom rad on a gravity system?

I think you need some major redesign involving full pumped control of heating/hot water, safe vent pipework, autobypass instead of bathroom rad bypass. Make sure return from dhw cylinder is last one before the boiler or some rad's can get warm in the summer by reversae circulation through the returns.

Tinkler · 13 Aug 2006

Paul Barker said:
Traditional order is boiler, vent (preferably via expanded T or AIRJEK) feed/expansion, pump. You would encourage pumping over with your proposal.

DHW cylinder? where is that in your system? Is it with the bathroom rad on a gravity system?

I think you need some major redesign involving full pumped control of heating/hot water, safe vent pipework, autobypass instead of bathroom rad bypass. Make sure return from dhw cylinder is last one before the boiler or some rad's can get warm in the summer by reversae circulation through the returns.

Thanks Paul.

Yes the hot water is on a gravity system; everything bar the boiler and pump is in the loft.

It is an ‘S’ plan system fully pumped open vent system. The flow and return come off the boiler up into the loft where the bathroom rad is tapped off…the flow and return continues on where next the flow is teed of up to be teed again and feed the combi cylinder through a zone valve – incidentally the first tee continues on up to become the vent pipe that overhangs the expansion tank, and the expansion tank’s feed actually tees back into the same vent pipe further down – is that normal? The flow also feeds the CH system through a zone valve and the cylinder return (bottom pipe) tees into the CH return and is the last one on the return circuit bar the bypass (bathroom rad).

I think I understand “pumping over”… means the water could be forced up the vent pipe – yes? I have been told that the pump is normally on the flow pipe, but currently the boiler has it on the return be it within the boiler casing – would it not be possible to put the pump on the return in the loft and does it matter if the pump is before or after the bypass? I would also like to leave the bathroom rad as it is as it ensures a warm bathroom when the hot water only is on.

Paul Barker · 13 Aug 2006

Yes I thought the pump would be on the return in the past, very often that was the way they did it. You would again have to put it after the bathroom rad return and the new system should work as the old did. The combining of cold feed into open vent is employed to stop pumping over. Pumping over is to be avoided as it oxygenates the heating water and causes excessive corrosion.

Your bathroom rad plans are good but not complient with regs so if you came to sell you would pick up a black mark.

Tinkler · 13 Aug 2006

Paul Barker said:
Yes I thought the pump would be on the return in the past, very often that was the way they did it. You would again have to put it after the bathroom rad return and the new system should work as the old did. The combining of cold feed into open vent is employed to stop pumping over. Pumping over is to be avoided as it oxygenates the heating water and causes excessive corrosion.

Your bathroom rad plans are good but not complient with regs so if you came to sell you would pick up a black mark.

Cheers Paul, you have been most helpful.

Agile · 13 Aug 2006

Ifr you are moving the pump then take the opportunity of converting it to a fully pumped system. Thats effectively required when a new boiler is fitted !

Putting any pump with less than 2 m head above is is risking a problem.

I suspect some other aspects here! You casually say the boiler is "being replaced". I do hope this is a NEW condensing boiler ! Being fitted by a CORGI ???

It would be normal to use a system boiler with the pump contained within the boiler casing. That ensures the pump is best placed within the system

Tony

Moz · 13 Aug 2006

King Tony has it right , he IS the DADDY here .......

fully pumped system
after reading
this guys knowledge is 1st Class

Paul Barker · 13 Aug 2006

Quote

"It is an ‘S’ plan system fully pumped open vent system. "

Though I do concur that these days it's worth using a system boiler and capping off the cold feed open vent. I used to use regular boilers but it's so much extra work, system boiler saves loads of time.

However if you are going for an under work bench installation system boilers are on the whole too tall, whereas regular boilers can fit as long as it isn't under a window where the modern flue coming out above the boiler makes it too close to the void in the wall for the window whether openable or not.

Of course the old flue is bound to have been ncs, they all seem to be, that doesn't mean you can do it (as my corgi inspector sternly told me wagging his finger). Shucks it's no fun being registered, wish I was a fireman moonlighting.

Tinkler · 13 Aug 2006

Agile said:
Ifr you are moving the pump then take the opportunity of converting it to a fully pumped system. Thats effectively required when a new boiler is fitted !

Putting any pump with less than 2 m head above is is risking a problem.

I suspect some other aspects here! You casually say the boiler is "being replaced". I do hope this is a NEW condensing boiler ! Being fitted by a CORGI ???

It would be normal to use a system boiler with the pump contained within the boiler casing. That ensures the pump is best placed within the system

Tony

Yes, it will be a conventional condensing boiler...doesn't come with the pump integral; hence the re-location of present pump which was fitted within the boiler casing originally. Can't grasp what you mean about the "2m head above" - can you explain further. The boiler will be situated in the kitchen with the pump in the loft above...it's a single storey building.

Paul Barker · 13 Aug 2006

I would carry on, put the pump on the return. If there is a problem then consider converting to a sealed system which we'll give instructions for as and when. There is actually a very simple way of doing that wherein you block the open vent retain the cold feed and add a blow off valve, just as long as the boiler has an overheat stat, which if it is a modern boiler surely it has?

However before going to extremes, as long as you can get all legs of the system working and it doesn't pump over you shouldn't need to make any great changes.

Moz · 13 Aug 2006

Paul barker....... do you get you dog biscuits from the main guy

Tinkler · 13 Aug 2006

Paul Barker said:
I would carry on, put the pump on the return. If there is a problem then consider converting to a sealed system which we'll give instructions for as and when. There is actually a very simple way of doing that wherein you block the open vent retain the cold feed and add a blow off valve, just as long as the boiler has an overheat stat, which if it is a modern boiler surely it has?

However before going to extremes, as long as you can get all legs of the system working and it doesn't pump over you shouldn't need to make any great changes.

I was going to change to a combi and put the boiler in the loft as I've mentioned on this forum before, but problems with potential installers (CORGI) all having differing views as to the viability and legality (regs wise) of having it there, and them not actually coming back with a quote p'd me off...yes, you are right about the boiler size being an issue the combi and sytem boilers are bigger and would be unsuitable as direct replacements in its present position as a wall hung boiler - it would mean not being able to have the microwave beneath the boiler as the boiler would have to be lowered to accommodate the horizontal through-wall flue - I've decided to stick with a conventional (but condensing) unit on the present open vent system because it is easier to work with when things go wrong from DIY point of view compared to a sealed system...I've never had a problem over 25+ years other than the pump going twice.

I personally feel the pump re-location won't be a problem as it is like-for-like effectively with the pump placed higher up on the system on the same return pipe.

Just to clarify, "fully pumped" does mean that the pump is utilised by the HW as well as the CH system?

Agile · 14 Aug 2006

Paul, I dont understand your quote that its a fully pumped system because I have lifted the following quote as part of the reply to you:-

"""Thanks Paul.

Yes the hot water is on a gravity system; everything bar the boiler and pump is in the loft.

It is an ‘S’ plan system fully pumped open vent system."""

Now Paul, I do agree that can be interpreted in two ways but I tend to assume the worst until proved wrong!

What I mean is the level in the header tank should be 2 m or more above the pump if you want to minimise problems.

Tony

Paul Barker · 14 Aug 2006

Yes I saw that he gave conflicting ionformation, I was working on the basis of latest information after a rethink is the correct information.

Orfiginal poster, the only likely difference in reliability over your old boiler is that sludge in the system would be more troublesome to wet pocket thermisters and possibly to flow sensing mechanisms, the main heat ex may have smaller passageways which would eventually be a problem. With this in mind I would be more vigilant about system water condition, and as a matter of course fit a MAgnaclean or Boiler Buddy. If you can't powerflush use some Ferroquest for 3 hours, flush it out a few times and put inhibitor of your choice in.

I think you are on the right lines.

Agile · 14 Aug 2006

Paul Barker said:
Yes I saw that he gave conflicting ionformation, I was working on the basis of latest information after a rethink is the correct information.

In this industry I think you would be far safer to always assume the worst case and if it turns out better then that will be cheaper.

Its nice to be able to tell the owner that it will be cheaper.

If I ever had to say it will be more expensive then I would be very embarased as thats an indication of a cowboy to get started and then up the price.

Tony

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CH pump location

Moz

Moz

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