AC (indoor) to water heater: remove fan/motor from outside unit

Phil_E · 06-15-22, 04:11 AM

Hi there, first post so please be gentle!

I’ve been inspired reading some of the threads on here and done a bit of searching to see if anyone has achieved what I’m thinking of setting out to do.

I’d like to install AC in my house, 4 internal wall units. I’d like to have them all run from a single outdoor unit. I think this is called multi split. It’s not especially hot in the European summer, so I don’t think I need loads of power. It’s been 26 degrees C with the windows open / curtains closed to try and keep the heat out and the building has a high thermal mass.

I’d like to mount the outdoor unit inside! Having removed the fan, condenser and replaced those with a heat exchanger and circulation pump.
I have a 1000l thermal store to dump heat into, from the other side of the new heat exchanger.

On the modern systems, I’d imagine they’d get pretty upset if you simply removed the electronics (sensors in the fan motor, condenser etc). Id like the user experience to be seamless (ie each remote works normally for the wall unit).

I’m not looking to have any heating functions, only cooling.

So is this something that can be achieved?

What brands should I consider? Inverter unit may be quieter if inside, would that make the electronics harder?

Thanks all

Robl · 06-15-22, 03:52 PM

Hi Phil
I’m sure it’s something you could do, there’s lots of different kit out there though - if you’re buying new is there anything you can use directly?

There are several small capacity (700W elec) air:watertank heatpumps, where the cold airflow can be routed internally or externally - you could use this, and duct the cold air internally (Vaillant aroSTOR):
https://www.theheatpumpwarehouse.co....gaAgVOEALw_wcB

Some multihead minisplits can have one outside unit, multiple indoor, and heat some indoor while cooling others. Is that helpful?

If you do change the heatexchanger, you’ll need to vacuum it down, braze, refill. You can do that with r290 and other non F gasses, all those gasses are a bit nasty (explosive or toxic or high pressure). I’ve made my own gshp from 2nd hand compressors with r290 by the way, and I’m very cautious with the gas itself.

NiHaoMike · 06-17-22, 10:00 PM

Quote:

Originally Posted by Phil_E

It’s not especially hot in the European summer, so I don’t think I need loads of power. It’s been 26 degrees C with the windows open / curtains closed to try and keep the heat out and the building has a high thermal mass.

Sounds like the most economical option would be to open two windows at night and set a fan in one to take advantage of nighttime cooling. Even in a much hotter climate like Texas, it's enough to delay A/C use by at least an hour or two every day so the energy used leaving the fan on all night is more than made up for.

Phil_E · 06-18-22, 03:08 AM

Thanks both for the posts.
Robl, I read your pdf for your gshp build, very impressive! The nearest commercial product is called a hotspot and is an additional heat exchanger to put tin the refrigerant loop to pump heat to a cylinder. I guess that retains the ability to dump heat to atmosphere once the cylinder is charged.
Nihaomike, I like your thinking, engineers always jump straight to engineering..! I’d also read that solar panels reduce the extent to which the building warms up, so I’ll stick to that part of the plan too!
Thanks again

Robl · 06-19-22, 05:40 AM

We have on roof PV, which keeps out a lot of heat. We also have mvhr, which automatically heat excahnges or bypasses- it doesn’t handle huge amounts of air though. We keep windows closed on hot days (house upstairs 25, outside 33C recently), then open windows at night when it gets cooler. I’m wondering about getting a ‘brise soleil’ to cut out more heat from 3 south facing windows. External blinds work well, although difficult to retrofit.

06-15-22, 04:11 AM	#1
Phil_E Lurking Renovator Join Date: Jun 2022 Location: Chamonix, France Posts: 2 Thanks: 3 Thanked 0 Times in 0 Posts	AC (indoor) to water heater: remove fan/motor from outside unit Hi there, first post so please be gentle! I’ve been inspired reading some of the threads on here and done a bit of searching to see if anyone has achieved what I’m thinking of setting out to do. I’d like to install AC in my house, 4 internal wall units. I’d like to have them all run from a single outdoor unit. I think this is called multi split. It’s not especially hot in the European summer, so I don’t think I need loads of power. It’s been 26 degrees C with the windows open / curtains closed to try and keep the heat out and the building has a high thermal mass. I’d like to mount the outdoor unit inside! Having removed the fan, condenser and replaced those with a heat exchanger and circulation pump. I have a 1000l thermal store to dump heat into, from the other side of the new heat exchanger. On the modern systems, I’d imagine they’d get pretty upset if you simply removed the electronics (sensors in the fan motor, condenser etc). Id like the user experience to be seamless (ie each remote works normally for the wall unit). I’m not looking to have any heating functions, only cooling. So is this something that can be achieved? What brands should I consider? Inverter unit may be quieter if inside, would that make the electronics harder? Thanks all Last edited by Phil_E; 06-15-22 at 04:48 AM.. Reason: More info

06-15-22, 03:52 PM	#2
Robl Helper EcoRenovator Join Date: Oct 2020 Location: Cambridge, UK Posts: 31 Thanks: 3 Thanked 27 Times in 14 Posts	Hi Phil I’m sure it’s something you could do, there’s lots of different kit out there though - if you’re buying new is there anything you can use directly? There are several small capacity (700W elec) air:watertank heatpumps, where the cold airflow can be routed internally or externally - you could use this, and duct the cold air internally (Vaillant aroSTOR): https://www.theheatpumpwarehouse.co....gaAgVOEALw_wcB Some multihead minisplits can have one outside unit, multiple indoor, and heat some indoor while cooling others. Is that helpful? If you do change the heatexchanger, you’ll need to vacuum it down, braze, refill. You can do that with r290 and other non F gasses, all those gasses are a bit nasty (explosive or toxic or high pressure). I’ve made my own gshp from 2nd hand compressors with r290 by the way, and I’m very cautious with the gas itself.

06-18-22, 03:08 AM	#4
Phil_E Lurking Renovator Join Date: Jun 2022 Location: Chamonix, France Posts: 2 Thanks: 3 Thanked 0 Times in 0 Posts	Thanks both for the posts. Robl, I read your pdf for your gshp build, very impressive! The nearest commercial product is called a hotspot and is an additional heat exchanger to put tin the refrigerant loop to pump heat to a cylinder. I guess that retains the ability to dump heat to atmosphere once the cylinder is charged. Nihaomike, I like your thinking, engineers always jump straight to engineering..! I’d also read that solar panels reduce the extent to which the building warms up, so I’ll stick to that part of the plan too! Thanks again

06-19-22, 05:40 AM	#5
Robl Helper EcoRenovator Join Date: Oct 2020 Location: Cambridge, UK Posts: 31 Thanks: 3 Thanked 27 Times in 14 Posts	We have on roof PV, which keeps out a lot of heat. We also have mvhr, which automatically heat excahnges or bypasses- it doesn’t handle huge amounts of air though. We keep windows closed on hot days (house upstairs 25, outside 33C recently), then open windows at night when it gets cooler. I’m wondering about getting a ‘brise soleil’ to cut out more heat from 3 south facing windows. External blinds work well, although difficult to retrofit.