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Author Topic: What heat store for UFH  (Read 14004 times)
alfier
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« on: September 28, 2013, 05:46:12 PM »

My son has just put in to his electric only flat
 https://www.tradingdepot.co.uk/DEF/product/!!PLUO303!!/X005004001/Underfloor%20Heating/Polyplumb%20Underfloor%20Heating%20House%20Packs/Polyplumb%20Overlay%20House%20Packs/Polyplumb%20Overlay%20House%20Packs%2030m%3Csup%3E2%3C/sup%3E/Polypipe%20UFH%20Overlay%20House%20Pack%2030m%3Csup%3E2%3C%2fsup%3E,%203%20Circuits%20O303

He now needs to find a boiler/Hot water tank that will supply hot water to the under floor system only using economy 7 topped up with day electric if required. Any ideas?
Alfie
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dhaslam
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« Reply #1 on: September 29, 2013, 01:49:31 AM »

There are two pieces of information needed, the estimated  daily heat requirement and   the space available for a store.    Electric elements can  heat to a high temperature  but  high temperatures can increase losses from the store. The product referred to seems to use  about 3 kW, ie. 3X 15 sq metres at 70 watts/sq metre.    If you take  a temperature  range of 40C  from 70C down to 30C    the tank would need  about 65 litres for every hour at full output.   The calculation is  860  X 3 kW /  40 degrees   =64.5.   
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DHW 250 litre cylinder  60 X 47mm tubes
Heating  180,000 litre straw insulated seasonal store, 90X58mm tubes + 7 sqm flat collectors, 1 kW VAWT, 3 kW heatpump plus Walltherm gasifying stove
chasfromnorfolk
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« Reply #2 on: September 29, 2013, 09:35:54 AM »

Hi Alfie, I can't open the link, but I guess from it, your ref to a boiler/tank plus dhaslam's reply it's a wet underfloor system we're talking about.

Until early this year I ran my 60m2 of underfloor on an Aztec 6Kw boiler

http://www.heatandplumb.com/acatalog/Trianco_Aztec_Classic_Electric_Boiler.html

having no other heat source at the time.
If the mass of the floor the heating's installed in can be seen as a store in this case, your son may find as I did that with E7 over night to warm the place up plus thermostat-controlled use at other occupied times it may work economically without a store. In a flat there may be something to be said for trading the (possible) extra efficiency of a big old store with the tiny wall-hung Aztec bunging the heat straight into the floor where you want it.

Chas
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