Water heater energy efficiency query

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muskrat

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Where I work, we have wall mounted water heaters for dispensing hot
water for tea / coffee. There is a debate raging between the
'greenies' who think they should be switched off at night, and the
'techies' who think it would use more energy to heat it up from
scratch every morning than to keep a 'trickle-charge' going to keep it hot 24/7.

I am firmly in the 'leave it on' camp. (entirely due to me being the
first one in in the mornings, and needing my cup of coffee immediately. [:)])

I contacted the supplier who said they 'don't have figures' for energy
efficiency, but it was designed to be left on, and they believe most
customers do leave them on. (They also tried to sell me a timer! LOL!)

Any budding physicists out there?
 

Benji

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You need to know the volume of water.
The temperature the water is when you leave, i.e. switch it off.
The temperature of water when you arrive, i.e. switch it on.
 

muskrat

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For the sake of argument:

2.5 litre capacity
100 deg. C (as near boiling as makes no odds)
Room temp. or thereabouts.
 

Enigma

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For what it's worth water that is kept as near to boiling as practical does in fact lose it's oxygene level which is why tea always tastes better from fresh brewed water. I would also say switching it off is good fire prevention advise and the heating element is likely to last longer and also reduce the amount of lime scale build up.

However also sometimes being the first in there is nothing worse than waiting for the brew.

Muskie - all I would say is that if the office is debating this you can't be doing much work.......
 

muskrat

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I usually get in around 07:00, switch the heater on, then whip
out the emergency kettle and make a brew! [:D]

I don't know any more details of the heater, except that it's
a Heatrae Sadia - Supreme 140 model.

(I do work sometimes [;)])
 

Dave

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That particular model is only 2.5lt so to keep it running overnight will use more power than to heat from new in the morning assuming it will be unused for at least 10-12 hours

Specification

Product Number(s):
95:200:140 - Supreme 140
95:200:141 - Supreme 155
95:200:142 - Supreme 170

Approvals:
BEAB approved. Manufactured in the UK in a BS EN ISO 9001:2000 registered factory.

Capacities:
Supreme 140 2.5l max 140 cups/hr
Supreme 155 5.0l max 155 cups/hr
Supreme 170 7.5l max 170 cups/hr

Outer Casing:
White High-impact thermoplastic

Rating:
Supreme:2.5kW @240V
Supreme:2.3kW @230V

Safety Features:
All models are low-pressure vented.
Dry start protection by self resetting bi-metal disc type thermal cut-out.
Boil dry protection by manually resettable disc-type bimetal cut-out.

Thermal Insulation:
CFC/HCFC Free (ODP Zero) Pre-moulded polystyrene and thermoplastic blend.

Thermostat Spec:
Electronic to control water temperature up to boiling point.

Water Container:
Moulded Polyphenylene Sulphide.
Removable steam condensation chamber for maintenance access


You could however put the mains circuit on a timer so that it starts to heat up half an hour before you need it - problem solved [:D]
 

Enigma

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Sounds like Dave also has too much time on his hands......Does it also come in a varity of colours????LOL
 
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