Just popped my Air ...
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Just popped my Air Source Heat Pump cherry...

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Active Member Member
41 kWhs
Joined: 4 months ago
Posts: 2
Topic starter  

Hi, Newbie here.


Recently did a self designed ASHP install to replace a gas boiler.

(Mains gas was condemned, and is too costly to reinstate, so weve gone ASHP).


I'm an ex Aerospace and Automotive engineer, and have specified and fitted a few heating systems, so felt confident that I could do this.

The big suprise was the lack of knowledge out there and the poor flow of "28mm" pipe fittings. 

TBH, its a bit of an emergency/ trial tostop us freezing and to see if the external noise is acceptable - It's a massive old place converted to flats,  and the HP is on the roof and is overlooked by other residents.

So - new DHW tank from Vaillant, ASHP from Grant.

We put the HP on the roof, with an additional circulation pump in the return to HP to make sure the HP pump could cope. The circulation pumps can push a head, but are very poor at drawing a suction.

Install works well, although struggles in these low temps - I knew this was going to be the case - the HP was so incredibly cheap, it was worth the punt just to prove the concept.

Pump is a Grant Airona 6kw - and ideally we needed a 10kw, but when it was so cheap, it was worth trying.

The house has 22m pipes in the CH system, with 15mm at the radiators. Flow is excellent - in fact, It's currently running on the lowest pump setting in the HP, and the auxiliary pump is off.

Delta T is 2 degrees at the highest pump setting, and up to about 4 to 5 degrees with the pumps turned down, but the loop is a little cool at 30c, as the HP is underpowered.

Heat calcs on the rads indicate we need 40c water in the loop, but the HP cant get up there at these cold temps -2c due to reduced efficiency and defrost cycles - works fine at 5c. We have upgraded one radiator in a bedroom due to its small size, and the rads are just about OK we think.

Install has shown a few issues with noise - one issue is vibration - we fixed this with anti vibration feet, and the fan noise was audible down a light well. Overall the feeling is very positive - and it's allowed a better conversation to happen about where to put the pump on the roof that will mitigate this (further from the light well. We will either fit a second HP, or a bigger one - I am looking for a candidate now. Weight and size are an issue, as there is a tight and restrictive staircase to navigate to the roof, which limits what we can get up there , so I may fit a second Grant 6kw unit if I can get a good deal on one, and run them in parallell.

Cheers for now.

Mars and Derek M reacted
Active Member Member
41 kWhs
Joined: 4 months ago
Posts: 2
Topic starter  

Ive had some interest in this - and been asked to do a write up (I cant respond to messages yet - I dont have enough posts....).

I'll gladly run through the process and install - it'll take a little time as I'm working abroad right now, so let me work it out.

Most suprising was the poor local knowledge from installers - and the poor array of normal plumbing kit is.

Mars reacted
Noble Member Contributor
2920 kWhs
Joined: 2 years ago
Posts: 416

@captainbeaky Well done, Im a self installer myself and its nice when things comes together. There are quieter heat pumps out there than the Grant, my Samsung is very quiet, you might also want look at Daikin and a new kid on the block Acond which you might be able to get cheap

House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60

Mars reacted


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