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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> 12kw pool heater https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1248088291 Message started by poolboy on Jul 20^th, 2009, 12:11pm

Title: 12kw pool heater
Post by poolboy on Jul 20^th, 2009, 12:11pm

Hi,

Does anyone know if I can run a 12kw pool heater from a single phase domestic circuit. It needs atleast 53amp apparently on an RCD? I have a seperate off peak box which is no longer used. Is it possible to use again - just get it changed for one single rcd, as the max it says on this is 60amp?

Thanks.

Title: Re: 12kw pool heater
Post by Lectrician on Jul 20^th, 2009, 3:36pm

12kw is just under 53amp. You would need to run a 60 or 63 amp circuit.

There is no direct requirement for RCD protection in the eyes of the IEE BS7671 wiring regulations, but the manufacturer may recommend or even stipulate an RCD. It is rare to see them fed via RCD's though.

If you bare in mind that your house supply is likely to be either 60, 80 or possibly 100amp, you can see you do not have much capacity available with your heater running.

In view of this, what else do you have in your house? Electric shower? Electric cooker/hob/oven? What sort of domestic heating and how water do you have?

You would be better to install a new 60amp switch fuse with new tails henleyed to your existing, and doing away with your old off-peak board.

How far is the heater from the mains intake? What sort of cable run is it?

Title: Re: 12kw pool heater
Post by chtechie on Jul 21^st, 2009, 11:53pm

Do you have gas - you'll find it cheaper to heat a pool and you may have enough capacity on your existing boiler (if you've got one)

Title: Re: 12kw pool heater
Post by poolboy on Jul 22^nd, 2009, 3:05pm

Thanks Guys, My Supply is 80AMP total! We will soon have an oil rayburn for water and heating. There's no main gas. I did think of keeping the current exterior oil boiler we have but not sure if I can use this to heat the pool water?

Title: Re: 12kw pool heater
Post by Lectrician on Jul 22^nd, 2009, 3:39pm

You would use a heat exchanger. These have an inlet and outlet for the white filter pipework, and then a standard flow and return for a boiler, typically 28mm pipework.

You simply treat the heat exchanger as a radiator or cylinder. You have a 2 port zone valve, a pump, and of course, the boiler.

It is often specced by plumbers to incorporate an interlock with the filtration pump to ensure the boiler cannot heat the heat exchanger unless the filtration pump is running. Plumbers also often request an overrun timer is installed (such as a multi function din rail timer) to keep the filtration pump running on after the boiler has stopped.

Pools that are used all the time usually have the boiler and filtration running 24/7. Domestic pools usually only have the boiler and filtration running a few hours a day.

I would look to use the oil boiler - It is bound to be cheaper.

Title: Re: 12kw pool heater
Post by CWatters on Jul 23^rd, 2009, 6:18pm

This site has cost comparison figures for different fuels and types of "boiler". It includes heat pumps. Take a look at the middle column which has "Delivered heat cost in pence per KWH after boiler efficiency is taken into account."

Most people are on an electric tarriff that has dual rates (eg once you have used a set number of KWH the price per unit falls to a lower rate). Compare that rate with the pence per kw rate for oil.

http://www.nottenergy.com/energy-costs-comparison3

Edit: In my area British Gas have about the best price on electricity at 9.37p per kWh above 500 kWh p.a. Oil is currently 31p/L or about 3.3p per kWh after boiler eff is considered. That makes electricity nearly three times the price of oil. The problem is what happens to oil when the economy recovers - it's bound to rise but by how much.