Gas pipe capacity

Have look: Farnell supply flow switches Farnell number: 1006771 with 22mm compression joints.

Flow Switch, makers site: The FS06

What I am saying is that the Rinnai can do the CH when the CH boiler needs replacing.

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OK - thanks - found it. I'll have good look at the data sheet before I buy.

Cic.

CPC version:

It may need a NC contact switch or a throw-over.

Cic.

What model of Rinnai have you chosen?

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I haven't chosen a model yet (it's a job for the Summer) but I'm seriously considering an exterior model. This or a higher capacity version:

Rinnai Infinity 16e External Multipoint Water Heater 35kW | Natural Gas

Provided that this has total weather proofing it will be easier to fit into the (approximate) space vacated by the present Worcester model which is under the kitchen sink drainer.

Cic.

Externals are neat. No flues needed. They save a lot of space in small homes. There are no external gas boilers, unless you make your own casing. One is available in Italy. They also have a balcony model that is designed to sit on balcony with minimal flue problems.

The external Rinnai can still do the house CH, using a flow switch, plate heat each and bronze pump. They take up little space in a house. You can have a DHW secondary circulation loop and the plate after the last tap. Then instant DHW at the taps as well.

The new condensing model I linked to is excellent and cheaper to run. However they do not import the external version yet. It took them long enough to import the condensing multi-point.