Dumb idea of the week

The weather has suddenly turned hot so we have turned the central heating off.
All fine and dandy - however we spend the winter with these large panel radiators heated by a boiler chucking out heat to keep the place warm.
Why don't we have a chiller alongside the boiler so that in the summer we can pump ice cold water around the system and cool the whole place down?
Could it be the temperature differential?
Water at 50C to raise the temperature from 1C to 20C?
Water at 1C to lower the temperature from 30C to 20C?
We don't blow hot air round for heating (well, some do) so why do we blow cold air round for cooling?
With anti-freeze in the system the temperature of the radiators could go below 0C (just don't lick them).
Presumably there isn't a good design for a water based chiller which compares with air con systems.
AS I said, dumb idea.
But why?
Cheers
Dave R
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Radiator at 1oC in a room at 20oC... o Problem #1 - condensed water running off the radiator onto the floor o Problem #2 - rather limited ability to cool the room
If a room is too hot... o Good - Blinds with curtains are good, particularly if blackout/foil lined o Best - Stick an old dust sheet over the window outside
Obviously CWI & Loft I will help keep a house cooler.
Takes a 1-ton HVAC compressor a long time to cool a semi, and at considerable cost with current/future electricity prices. So treating the cause rather than the effect is a lot cheaper. -- Dorothy Bradbury
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David WE Roberts submitted this idea :

I was thinking about this last year, the year before that and last night as a matter of fact.
One thing which might cause problems is the condensate. Chill the radiators below the room temperature and condensation will form on pipes and the radiators.
--
Regards,
Harry (M1BYT) (L)
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It has been done, there are heat pump boilers about that do just that. Its a good way to top up ground heat sources too. Its not done more because of cost and complexity, the average "engineer" struggles with the combi systems.
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On 9 May,

Condensation! You'd need a drain below each 'radiator'.
--
B Thumbs
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'kin expensive and inefficient
--
geoff

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Several reasons, that being one of them. You'd get some cooling from the rads but the temperature differential means it would be insignificant.
You'd need a huge radiator/heat exchanger radiator to get some useful cooling. It has been done with UFH (big heat exchanger area) but you need to ensure the water temperature remains above the room dew point or you get condensation forming on, or within, the floor. I think the dew point is about 11 degC at average indoor conditions of about 21degC & 50% Rh.
The heat exchanger area is also why you usually blow air around; the area necessary is achieved in a small package volume by using a coil of finned tubes, similar to a car radiator; or more like 4 car radiators in a row. Heating coils are usually 1 row with water at 70/50 flow/return. Cooling coils are typically 3 or 4 row with chilled water at 6/12.
If you were to just cool the room, without causing any condensation, this has the effect of increasing the Rh, i.e., same moisture content in gms water per kg of air, but lower temperature. In a UK summer, this makes it horribly humid & clammy, more uncomfortable than being just hot. Your personal evaporative cooling system, sweating, is less effective. It's also why those nasty swamp evaporative coolers are pants. It will work in a dry environment.
Condensation is another reason; You'd not only get puddles under radiators, but you'd get moisture migrating into the building from outside, adding greatly to the cooling load. Condensation tips out of air handling units' drains in summer like there's a tap running inside it. It an absolute bitch if the chilled water pipework and fittings are inadequately insulated and the vapour barrier is ineffective. I know of plantrooms that will be 2" deep in water in summer.
The common strategy now is to supply the fresh air required for ventilation from central air handling plant; that is, air cooled to condense out the excess moisture and then reheated to the supply temperature. The cooling loads are dealt with locally by circulating chilled water, above the dew point temperature, to chilled beams. Any high heat loads (typically computer rooms) are handled with a fan coil unit (mini air handling unit).
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wrote:

A very sensible and accurate analysis if I may say so, there is your answer David.
Regards Don
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The temperature differential wouldn't be great enough. When heating, the rads run at something like 3 to 4 times the room temp.
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*A plateau is a high form of flattery*

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

They would be fine, if it was designed to work in the first place. I can't imagine someone just replacing a boiler with a heat pump unit without a redesign to use the cooling effect.
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It could be made to 'work' if you used a fluid that allowed rather less than 0C - but there are lots of other problems as have been stated.
--
*Does fuzzy logic tickle? *

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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David WE Roberts wrote:

Possibly because aircon is (afaik) an American invention? In most parts of the country they tend to heat with air rather than water, so natural to do the same with cooling?
Pete
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... Nothing like what I thought he was going to write
The thread appeared immediately below the "Grand Designs Live" thread, and I thought it was going to be another one along the same lines :-)
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This link will take you to a website which actually makes something similar, these panels can be used for cooling too, just make sure you read it properly. http://www.spcoils.co.uk/Products/RadiantHeating/CeilingPanelsMain.html
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