Workaround to pressurise a Combi despite low water pressure
 

Is there a workaround that would enable me to pressurise my Combi to 1bar when the mains water pressure is only 0.75bar ?
The combi is working and when heating the pressure rises to 0.9bar.
I am concerned that the combi should be operating at the recommended pressure.
Some have suggested attaching a 1.5bar shower pump ( with attached water tank). Is there an alternative e.g. water pump that would serve to bring the combi up to 1bar purely for commissioning purposes.
There is adequate DHW water flow.

When the system is cold let the air out of the expansion vessl by opening the schraeder valve (like a car tyre valve). Then open up the filling loop to fill the system up to 0.75 bar. Now shut that, get your bike pump out and pump the air back into the expansion vessel whilst watching the pressure guage, stop at 1.5 bar, hey presto!

Is there a workaround that would enable me to pressurise my Combi to
1bar when the mains water pressure is only 0.75bar ?

Get the water company to increase the pressure. 0.75 bar should be below
their minimum permitted value.

In any case, nothing untoward is likely to come from running 0.75 bar,
unless the boiler is at the bottom of a very tall house. I wouldn't muck
around with pumps for a measely 0.25 bar that will have no discernable
effect on the operation of the boiler (unless it has a very sensitive low
pressure cutout).

Christian.

In article , "Ronald
Fraser" says...

Is there a workaround that would enable me to pressurise my Combi to
1bar when the mains water pressure is only 0.75bar ?
The combi is working and when heating the pressure rises to 0.9bar.
I am concerned that the combi should be operating at the recommended
pressure.
Some have suggested attaching a 1.5bar shower pump ( with attached
water tank). Is there an alternative e.g. water pump that would serve
to bring the combi up to 1bar purely for commissioning purposes.
There is adequate DHW water flow.

You could use a car tyre pump (not an electric one obviously), a
welly and a bowl of water. Just attach a schrader valve to the
filling hose to act as a non-return valve, and fill everything with
water before you start pumping or you'll introduce air into the
system which will need to be bled, losing pressure again.

Ronald Fraser wrote:
Is there a workaround that would enable me to pressurise my Combi to
1bar when the mains water pressure is only 0.75bar ?
The combi is working and when heating the pressure rises to 0.9bar.
I am concerned that the combi should be operating at the recommended
pressure.
Some have suggested attaching a 1.5bar shower pump ( with attached
water tank). Is there an alternative e.g. water pump that would serve
to bring the combi up to 1bar purely for commissioning purposes.
There is adequate DHW water flow.

Garden spray pump adapted to connect to the filling point. You can use
this to introduce inhibitor etc to the system too.

But as Christian says 0.75 is close enough for jazz anyway.

There is no requirement for any water company to provide any amount of pressure. All they are required to provide is water to your tap.

[quote=Ronald Fraser]The workaround QUOTE]
Gentlemen,
Thank you for providing such prompt, elegant and comprehensive solutions and advice. Whereas I shall keep an eye on the thread over the coming period, I am now confident - based on your recommendateions - of a way forward.
My sincere thanks to you all.
Ronald

I would agree with this. In our street we had to start a campaign to get Severn Trent to listen afterwhich they duly sorted something out. We still get a reduction is pressure however if there is heavy summer usage. An electric shower with small capacity pump is near useless.

kafkaian wrote:
Paul Barker Wrote:
There is no requirement for any water company to provide any amount
of
pressure. All they are required to provide is water to your tap.

I would agree with this.

I wouldn't.

Water suppliers must provide an average of a 7 metre static head (~0.7
bar?) at the customer premises in accordance with the 'Water Supply and
Sewerage Services (Customer Service Standards) (Amendment) Regulations
1996' (available at
http://www.legislation.hmso.gov.uk/s...63065_en_1.htm).

Furthermore, many suppliers aim to raise their minimum to greater than
this, and also to provide a minimum average flow rate (10m and 9lpm
respectively for Sutton and East Surrey Water).

Mathew