CarbonLite and the AECB Water Standards

[Anonymous]

Having read through the CarbonLite Guidance and the AECB Water Standards, we want to ensure that any potential hot water dead legs are designed out or the pipe bore reduced accordingly.

One main stumbling block is that, because it is a barn conversion, the kitchen supply is c.20m long! Rather than have a long length would it be better to opt for an 'instant' hot water tap?

Any advice is appreciated.

[Nick Grant]

you mean instantaneous electric?

Just discussing this today for a new school project. Balancing distribution losses against carbon emissions of gas v electric etc.

Hard to get enough flow for a kitchen sink unless higher power unit. Obviously electric is about 3 x the CO2 of gas heated water (assuming the standing cylinder losses are there anyway for other taps).

20m is a bit long for microbore but might work if you have the pressure and can tolerate say 4-6 l/min flow or so.

Complex solution is to use a re-cirulator pump on a switch but just to get the water to the tap when you need it. Or use the cold water run off for watering plants in summer and flushing loo in winter.

The hot water left in the pipe still goes cold and the energy is wasted.

All depends how often you are using the sink, how your water is heated etc.

Energy in kWh lost per cool off is about = volume of water in pipe in litres x 1.16 x temp drop /1000

Temp drop is from say 60C to 20C room. Obviously in the heating season this will be largely used as space heating. In PHPP we assume 3 cool offs per occupant per day.

The EST water and carbon report looks at all this.

Sorry not to give simple answer but all depends.

Nick

[Anonymous]

Thank you for your reply Nick.

Has a comparison been done between an instantaneous electric tap and a kettle as that could be another factor?

[Nick Grant]

Better check with the client re acceptability before doing sums!

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