ASHP - can they be too big and what to look for on eBay

[Roz]

Hello

 

So, can an ASHP be too big? What happens if you get one too big? Most of the ones on eBay are bigger than I need.

 

What do you look for on eBay? e.g. I saw this... https://www.ebay.co.uk/itm/Panasonic-Aquarea-air-source-heat-pump-mono-block/123766732587?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D5e846c3469db42d38f0d758ffe82c585%26pid%3D100675%26rk%3D1%26rkt%3D15%26sd%3D123766732587%26itm%3D123766732587&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3Acd726edc-7aec-11e9-b063-74dbd180aaac|parentrq%3Ad4db63b016a0a9ca38858292ffe978be|iid%3A1

 

What sort of things do you need to ask about them? There's not much detail.

[ragg987]

ASHP seem to run more efficiently if not at max, however a scroll / inverter generally means it cannot run below 30% of max. So a 10kW HP (nominal output) would run at 3kW (nominal) lowest. In a low energy house this is quite a lot and HP will be cycling when demand in below 3kW, which you can reduce by using a buffer tank.

[SteamyTea]

I think one problem is short cycling, this could lead to premature wear and tear.  There is also the start up current needed, but I think most good quality ones soft start to stop this.

 

Shortened URL to that Panasonic model.

https://www.ebay.co.uk/itm/Panasonic-Aquarea-air-source-heat-pump-mono-block/123766732587

Edited May 20, 2019 by SteamyTea

[ProDave]

Make sure it is a reputable make (LG, Mitusbishi, Panasonic, Carrier etc)  

Make sure it is inverter driven.

 

This one ticks all those boxes.  The questions to ask in this case a WHY has it been removed?   It appears to be 4 years old

Also make sure it IS in working order (i.e not removed because it stopped working) and make sure it comes with the manuals and ALL controllers that came with it (they can be hard to find or expensive if missing)

 

Here is the service manual for this unit http://www.icglimited.co.uk/library/web/2. Panasonic/7. Air To Water Heat Pump/4. Service/MDF 06_09 E 3E5 Service Manual (PAPAMY1209176CE).pdf

 

This is a 9KW ASHP  Is that the size you need?

 

It comes with a "easy to use remote control"  Make SURE that is included.  EDIT There is a picture of it in the advert so make sure if you win it that you get that with it.

[Roz]

1 hour ago, ProDave said:

This is a 9KW ASHP  Is that the size you need?

No I am pretty certain I don't need one this big, this was one of the things I was confused about. All the ebay ones tend to be bigger than I need.

 

I have just asked those questions, even if I don't get this one it's good to start somewhere!

[SteamyTea]

Do you know what size you need.

If your maximum heat load was 5 kW, then a 9 kW one would not be too bad.

Also you can possibly run DHW and space heating at the same time (maybe).

[ProDave]

1 minute ago, SteamyTea said:

Do you know what size you need.

If your maximum heat load was 5 kW, then a 9 kW one would not be too bad.

Also you can possibly run DHW and space heating at the same time (maybe).

Not normally. Most of them run at a higher temperature when doing DHW and a lower temperature for space heating (so they run at a better COP) so you would not normally do both together. 

[SteamyTea]

True, but that does depend what sort of space heating is fitted.  If it is radiators, then they could possibly be run together.

Though I shall repeat my mantra that DHW and space heating to different things, at different times and at different temperatures.

[Simplysimon]

also looking at his feedback, he's sold a lot of cameras. you don't tend to own that many so where is he getting his stock?

[Roz]

13 hours ago, Simplysimon said:

also looking at his feedback, he's sold a lot of cameras. you don't tend to own that many so where is he getting his stock?

I didn't go for it in the end, felt a bit too quick off the mark but was good to get the ball rolling and thinking about it. He said he was a mitsubishi engineer and that they had removed it in order to put in air to air.