Wet central heating system

[baldelectrician]

Just had a call from a customer who got my number through recommendation.

He is wary of gas but wants radiators, he likes the idea of a wet system (ie electric boiler but standard rads)

if anyone had any knowledge of any of these systems can you pop in some details

have had a look on the net and there seem some good off peak systems out there but have only wired up a few of them.

mainly interested in relability performance, and after sales service issues

thanks in advance

the system will probably be a night store system (water vessel charges up on off peak and feeds rads etc through the day)


baldelectrician

 

[ban-all-sheds]

Just had a call from a customer who got my number through recommendation.

Always good.

He is wary of gas

¿que?

the system will probably be a night store system (water vessel charges up on off peak and feeds rads etc through the day)

I know nothing about them either, but reason says this won't work. I could go and look it up, but it would be quicker if one of our resident physicists runs through the calculations to show how much stored hot water you would need to be able to support a CH system delivering x thousand BTUs per hour for 20 hours...

 

[Adam_151]

I get it to be about 18x (assuming a temerature rise of 60 degrees centrigrade)

 

[slippyr4]

very crude calcs, based on the following assumptions:-

Delta T = 50 degrees (eg, water stored at 70, cools to 20 (room temp).
Ignorning heat flow considerations,

If we require our water to give out 1 KW, for 20 hrs each day, we require 20KWh of energy. That is 72 megajoules.

Delta T( K)=50 degrees, specific heat capacity of water =4186J/K/Kg, then one Kg (litre) of water contains 50 * 4186 J = 209300 Joules.

total requirement is 72 Megajoules, so 72,000,000 / 209,300 = 344 litres.

So, we need to store 344 litres of water to provide 20 KWh of energy.

If we assume it's a larger house, and we would otherwise have had say a 24 Kw boiler, then our water storage requirements come to 344 * 24 = 8.2 tonnes of water.

Better get a swimming pool.


PS. I know these calcs are inadequate. they're funny though.

 

[slippyr4]

converted, thats 100 litres per 1000 BTU

 

[baldelectrician]

this was what i found on the web


http://www.acv-uk.com/images/pdfs/etechspages.pdf


looks ok but i wanted to know other opinions


ps customer is afraid of gas

 

[ban-all-sheds]

this was what i found on the web


http://www.acv-uk.com/images/pdfs/etechspages.pdf


looks ok but i wanted to know other opinions

Yup - looks OK. To get one that is the equivalent of an average gas boiler you'll need the 3-phase model.

So that bumps the installation cost up a wee bit.

And there is no way that you'll only need to run it during the night and have it run a CH system all day...

ps customer is afraid of gas

FFS.

How afraid is he of his electricity bill if he's running a 28.8kW appliance for hours on end?

 

[Steve]

explain to him that his electric bills will shoot through the roof, lights will be dim all the time the heating is on, he may need to upgrade his supply (£1000s) to run the appliance etc etc.

suggest oil heating.

 

[ban-all-sheds]

he may need to upgrade his supply (£1000s) to run the appliance etc etc.

There's no "may" about it.

Even if he has a tiny house, and could get away with the 14.4kW model (half the rating of your average gas boiler), that's still an additional 63A to find from somewhere....

 

[Steve]

Why make such an appliance for domestic use??? Even the 3-phase model takes 42 Amps per phase, which is a stupid amount of electricity even for 100 amp 3-phase supplies to sustain over a period of time. You would even still get lights dimming and the other effects with 3-phase.