Green Building Forum - Air to air heat pump

Air to air heat pump

owlman — Sat, 04 Jun 2022 19:14:55 +0100

I'd be interested to hear your experience with Air to Air generally and how well your wall units perform. You could give the cooling facility a try now in Summer? I find that setting the stat at 18/19C for a couple of hours is enough to make an appreciable difference on hot days.

Air to air heat pump

jms452 — Sat, 18 Jun 2022 10:44:25 +0100

Posted By: owlmanYou could give the cooling facility a try now in Summer? I find that setting the stat at 18/19C for a couple of hours is enough to make an appreciable difference on hot days.

Might have tried the cooling yesterday reaches the set point in an hour or two then hold the rooms there on circa 200W.

A door between upstairs and downstairs is invaluable as it meant we could just cool upstairs.
Also works nicely with MVHR as you can just close all the windows fully.

Air to air heat pump

owlman — Sat, 18 Jun 2022 14:44:54 +0100

I'm glad it's working out OK for you, I feel sure you'll not be disappointed with the system. The overall controllability, timer settings, and response are really good with A/A.

I've had my ducted system in one half of the house coming up to 3 years now and it's been excellent. On the odd hot day 25/26C outside I simply move the stat to 19C and coming in from doing outside work, the house feels like a delightful sanctuary.

Air to air heat pump

owlman — Sun, 17 Jul 2022 21:45:48 +0100

@ jms452
John how is your system performing on cooling mode in this hot weather?

Air to air heat pump

jms452 — Thu, 25 Aug 2022 17:07:34 +0100

Posted By: owlman@ jms452
John how is your system performing on cooling mode in this hot weather?

Not used it that much as insulated victorian house never gets too silly (i.e. above 26 upstairs). Maybe 4 or 5 afternoons to take a couple of degrees off the bed rooms.

We also fitted an awning over the south facing patio doors which has been a great help.

Air to air heat pump

jms452 — Thu, 25 Aug 2022 17:16:26 +0100

Starting to think about winter does anyone know a way of monitoring the real world CoP of the system when we start using it for heating?

On paper it should be COP=4.5; SCOP=4.1 but nice to know how well it is actually working.

Air to air heat pump

malakoffee — Sat, 03 Sep 2022 18:36:23 +0100

. . . . monitoring performance of an air2air heatpump . . . . .

This was discussed on Twitter a few days ago . . & although I have lost track of it ( = twitter novice ) . . . I did download this study by CADMUS in Vermont, USA :

* The true performance is very difficult to measure, . .
** with a lot of variability
*** Probaby best to read the Executive summary before I misquote / paraphrase incorrectly

https://www.dropbox.com/s/bw5vfh2qs7fq4ct/Heat%20Pump%20%28ductless%29%20Study%2C%202017%2C%20Vermont.pdf?dl=0

PS. I hope this link works and provides some useful info.

Air to air heat pump

jms452 — Sun, 04 Sep 2022 09:14:24 +0100

Thanks Graham,

Looks like they performed within 10% of rated which is encouraging.

In terms of heat metering they had to create a flow and differential temp sensor (ie.e. the unit didn't monitor it them selves). I might have a go manually and see what I get.

Air to air heat pump

jms452 — Sat, 18 Feb 2023 13:10:03 +0000

There was some interest in how the A2A split was performing (in a small victorian detached house retrofit).

We've now had a winter with no gas space heating and pretty pleased with it.
Attached screen grab is from the 15th Feb (a sunny day).
The max power (of about 1kW) works really nicely with solar in the day.

Also works nicely with Octopus saving sessions as it's easy to schedule the A2A to switch off for an hour and earn a pound or two.

edited: to give date of plot

Air to air heat pump

djh — Sat, 18 Feb 2023 15:43:06 +0000

Interesting, thanks. What are the 5 big spikes?

Air to air heat pump

jms452 — Sat, 18 Feb 2023 17:20:00 +0000

Posted By: djhInteresting, thanks. What are the 5 big spikes?

The two biggest ones in the early hours are the dishwasher and the other three are kettle/oven.
The EV.

On the one below from 14th Feb we put 21kWh in the car (About 85 miles) - Eye opening how much energy it takes to move 1.5 tonnes of metal around!

There was a saving session 17:30 to 18:30 you can just about spot as well

Air to air heat pump

djh — Sat, 18 Feb 2023 20:11:17 +0000

Ah, thanks. I hadn't read your post carefully enough I didn't realize it was overall import.

Here's a rather scrappy equivalent graph from today. The spikes overnight (defined as 0030 to 0730) are the DHW heating and those during the day are most likely the kettle, apart from the blips around 1800 which are cooking dinner and around 1930 there's a blue lump that is the 1 kW fan heater in the shower and a red lump that is the DHW heater again (brief evening top up if required). Last night happened to be the first night this year when we didn't need any space heating.

Air to air heat pump

djh — Sat, 18 Feb 2023 20:23:45 +0000

And here's one from Feb 9. This has nicer solar input - you can see we get some shading in the afternoon from a couple of trees. And pretty much all the solar power is diverted at this time of year. Tou can also see the overnight space heating in red, with the big block of car charging overtopping it in orange (orange is basically sum of red and blue and car charger)

Air to air heat pump

jms452 — Wed, 22 Feb 2023 18:08:18 +0000

Posted By: djh the 1 kW fan heater in the shower

Is this out of the day of the jackal