On 21/05/2017 10:54, Terry Casey wrote:
In article ,
says...

Some background things to check. Is your mains flow rate adequate for a
combi? (you need a minimum of 15 lpm really, and more is better).

We are away at the moment but I will check it when we return in early June

Yup, time filling a bucket of known volume from your fastest tap.

Is the pressure adequate. 3 bar or better is good.

I have no way of checking this unless there is some simple method I could use

You can get a pressure testing kit from a plumbers merchant. Normally
about 10 to 15 quid. Includes a gauge and selection of adaptors to
attach it to different types of tap.

Is the water supply reliable? (if not, some stored water may be handy).
Have you though about backup water heating if the boiler were in need of
repair?

No supply problems in the year we've been there - although not all the time!

The electric shower heater should suffice for washing and the dishwasher and
washing machine would take care of most other essentials. The kettle will,
hopefully, cater for any more demand.

Yup, that's a resonable backup plan.

If looking at stored water systems, have your installers been thinking
about using a conventional gravity fed cylinder, or an unvented one?
(the latter tend to give better overall system performance if there is
adequate mains flow rate availble)

As the quote we are most interested in offers the option of a like for like
replacement instead of the combi, I was assuming that the cylinder would
remain gravity fed but will check.

You can also use a combi to heat a cylinder, but then pipe its DHW feed
to somewhere where it will be of advantage. Say feeding a shower (high
pressure without a pump), or a kitchen hot tap - e.g. save time by
filling a saucepan with pre-heated water prior to boiler etc.


--
Cheers,

John.

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