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Author Topic: Which is the best way to set up a air source heating system  (Read 1751 times)
mpooley
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« on: September 21, 2017, 12:06:45 PM »

Hi all. Not been on here for years as I did all the sums and realised that an air source system was not viable for me.
Unfortunately being a bit senile now I have forgotten most of what I learned back then.

My nephew has just bought a house which has a air source system which I don't think is suitable for the house. No underfloor and the rads are too small ! and even a mixture of one electric underfloor system in the kitchen!

They will be home a lot of the time and are used to a very warm home (by my standards onpatrol)

Do you think they should set it up to be on all the time? Just controlled by room thermostats?
They have two daughters who love the heat BTW

any advice gratefully received.

Mike
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It's not easy having a good time. Even smiling makes my face ache.

“Science is the belief in the ignorance of experts.” Richard Feynman
dhaslam
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« Reply #1 on: September 21, 2017, 12:31:53 PM »

One of the problems is to decide between cheaper electricity at night or higher higher input temperatures during the day.    Generally it is better to use lower rate electricity and perhaps then use the warmer periods of the day as necessary.   Selecting running periods also depends on having some spare capacity as well as the ability to store heat in the house.   Running at night in cold weather can also mean more wear and tear on the equipment as well as needing some thawing out of the collector.    I tried  some reheating of the input air which did help a little and I think that that is part of the answer to the problem of inefficiency in cold weather.   The problem is that underground air feed systems need large diameter pipes.
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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
brackwell
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« Reply #2 on: September 21, 2017, 01:31:41 PM »

In general a system designed to provide 50% of what is calculated to be necessary will in fact cater for 80% of the times.

I believe that most people brought up on boilers have been trained in a certain way that is inappropriate for HP.  Basically heat pumps need to be run at the lowest temp possible for very long periods even permanently in cold weather.  Only after running like that can one say it is/is not suitable.

Whats the alternative anyway?

It may be appropriate to change a few of the rads to bigger ones but unless it as already been done a good dose of insulation everywhere will produce a better overhaul result.
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mpooley
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« Reply #3 on: September 21, 2017, 02:27:35 PM »

Thanks
At the moment we don't know how well  the house is insulated, so I might just suggest they leave it on permanently and see how that works out.
How do you know if the immersion heater backups kick in?

as I remember 35c was the optimum water temp to aim for. this is a Diakin Altherma BTW.
perhaps they could try that for now and increase the water temp as it gets colder.
It has a weather setting though so maybe they don't need to do that?

Mike
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It's not easy having a good time. Even smiling makes my face ache.

“Science is the belief in the ignorance of experts.” Richard Feynman
brackwell
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« Reply #4 on: September 21, 2017, 06:00:08 PM »

The immersion heater back up will kick in when the demanded temp of the hot water is greater than the supplied temp from the HP.  The temptation from boiler days is to turn up the HP supplied temp but this destroys the efficiency of the HP so better to heat to a higher temp in the storage tank as against the HP although in both cases the temp needs to be kept as low as poss.

I like the idea of 35C but if poss do not increase the temp but increase the run time.

The weather setting depends how well its been programmed to match the house.
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mpooley
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« Reply #5 on: September 22, 2017, 11:07:46 AM »

I think this is going to be a suck it and see experience  snow
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It's not easy having a good time. Even smiling makes my face ache.

“Science is the belief in the ignorance of experts.” Richard Feynman
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