tegwin
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| posted on 21/4/15 at 11:07 AM |
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Central heating upgrades... its an odd one
Have a bit of a quandry regarding installing a gas boiler in series with an air souce heatpump.
Ideally I would install a thermal store to manage input from various sources but the cost of doing that would be far to high.
Currently there is an 8kw air source heatpump installed along with a 6KW electric heater in series.
That's fine in the summer but when its bitterly cold and the heatpump efficiency drops there simply isnt enough heat in the house...
So I am looking at installing a gas boiler (non combi) in series with the heatpump.
Cool water returning from the rads/HW tank would be fed into the heatpump to be warmed before being passed into the gas boiler to be fully
heated...
My concern is that the temperatures of both machines would have to be controlled closeley to ensure that they work in the correct order... when air
temp is good then the gas boiler should not have to do much work atall. When it starts to get a bit cooler... gas boiler does more...
Anyone have experience of doing such things?
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Would the last person who leaves the country please switch off the lights and close the door!
www.verticalhorizonsmedia.tv
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big-vee-twin
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| posted on 21/4/15 at 07:37 PM |
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Are you sure the heat pump is at fault, are your radiators correctly sized
Radiators sized for heat pumps are 1.5 times larger than Rads used on boiler systems because of the mean temperature difference.
You will need to ensure the return water temp when boiler is in circiut still allows HP to work
And water temp out of HP allows boiler to work
if you run boiler at lower temps then still need to check rads.
The best way to do it is use a thermal store but rads could still be undersized.
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
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tegwin
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| posted on 21/4/15 at 09:39 PM |
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The house was specced and built with radiators designed for HP... So lots of radiators. Designed to run at 50 degrees C water temp.
I calculate the house heatloss to be around 17-20Kw. This means that from the initial build (in 1988) the heating has been inadequate in the winter
when the hp is kicking out more like 4kw. (plus the 6Kw inline electric).
The house is a sieve so any heat pumped in doesnt hang around for long.... At some point the place will need serious modernisation.
My 80+ year old grandmother lives in the house and can't cope with the cold...expecially as lighting the coal fires is getting difficult for
her.
I believe the HP cuts off when the return temp is 45 degrees.
So in an ideal world the loss through the radiators should be enough to drop the temp of the gas boiler flow to below 45 degrees to enable the HP to
raise the temp before passing it to the boiler... Not sure what the max input temp is for most modern boilers....
I do totally agree that a thermal store would be the best option... and adding solar hot water at the same time.... but the cost of a suitable thermal
store runs into the many thousands.
Could maybe split the system a differnt way... Use the HP for heating only the hot water tank.... as that can be done at the warmest time of the
day... And then use the gas boiler for all radiator heating duties as that will mostly be in the winter/night time when its cold outside
anyway...
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Would the last person who leaves the country please switch off the lights and close the door!
www.verticalhorizonsmedia.tv
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big-vee-twin
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| posted on 22/4/15 at 07:27 AM |
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I recently set up a system to use manual change over valves to disconnect HP and put boiler in circuit. Perhaps could do same with solenoid valves and
a intelligent heating controller using a weather compensating external sensor?
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
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