Inverter Ac converting into air-water heat pump

ferox · 10-21-20, 01:51 PM

My current setup is an 24000btu R22 external unit.
This is heating my 1000L plastic tank once a day, which is insulated with 10cm of extruded polystyrene. Inside the tank I have 10mm copper tube/ 20m for heat transfer.
To have the best efficiency I programmed to start the pump once at 2PM when the outside temperature is the highest.

In the summer 20min of running heating the tank for 24 hours need.
In the winter if the temperature is dropping to 5degC it runing 1, 5 to 2 hours. Under 5 C I need to heat with an electric heater.

Now I want to improve something and extend it to house heating too, not just hot water.

I want to change the external unit with an inverter one.
The idea is simple, not so simple to do it.

I have 2 options:
1. Buy a new heat pump - no fun, spending lot of money
2. Converting an inverter AC unit - lot of chalanges, price is almost 10th of the new one + time spent for fine tuning. I have this idea from long time ago.

I have some knolege about automations, so I can jump in.
My passive house need is 5kW thermal heat, I guess one 18k unit will be fine. This thread can be used for bigger needs.

The chalange:
1. Install the external unit- easy
2. Connect the coil or one heat exchanger to the unit - easy. I prefer heat exchanger.
3. Controller setup
A. Use the indoor PCB and find a way how to cheat to have the needed control of the outside unit
B. Learn how to send specific command to the outdoor unit and build a simple arm based controller
C. Maybe sombody did it an I don't know
D. Buy a ready-made controller with 0-10V input - tried to search but hard to choose

Now I'm writing from the phone, I will put pictures of actual setup later. I will have more updates.

Have a nice day
Ferox

Sadashi · 10-25-20, 04:51 AM

What do you want to achieve when you said that you want to control the outside unit of the inverter ac ? Do you want to control the indoor temperature , keep a fixed flow temperature , or what ? As you see from the pictures , I'm using a 24k btu inverter unit to heat my house of 126 sqm , located in Buzau , Romania . Is your house located in Oradea ? Good luck with your project !

Ps : on my computer the pictures look fine , they don't need to be rotated . I don't know why they've been attached this way and I don't see the option on ecorenovator to rotate them so they look normal .

ferox · 10-25-20, 10:24 AM

Hi Sadashi!
Yo have a nice setup, you did it! Exactly as I want to do it.
My goal is to control the power of the outside unit, than I can keep a fixed flow temperature.
Can you share with us how you control the water temperature? In that case I don't need to reinvent the wheel. I have some ideas but always it is a risk that is not working as intended.
My 140sqm house is located in Oradea, where the weather is not so extreme as in the rest of the country.

Best Regards,
Ferox

ferox · 10-25-20, 10:42 AM

Some pictures from the old inefficient setup.
External unit was modified to be able to have cooling for defrost proposes connected directly to the coil which is in the bottom of the tank. Was installed 7 years ago, working good, controlled with Arduino and Blynk app for remote control and visualizing the temperatures with the nice charts.
The plan is to upgrade with the latest inverter technology for heating the house.

Sadashi · 10-25-20, 01:03 PM

I'm afraid that I will disapoint you with regards to controlling the inverter unit to be able to keep a certain flow temperature . I'm not saying that it's not possible , but for me it wasn't a must , as my system the way it's been setup ( with radiators ) doesn't required a certain temperature , it varies depending on the indoor temperature . The inverter unit modulates the power output to meet the set temperature that I'm asking from it , so the flow temperature varies .

ferox · 10-25-20, 01:51 PM

I understand. You are using the original controller.
Is the easiest way of doing, just instead of internal air heat exchanger is an water HX.
In the same way I can put the temperature sensor of the air to the floor heating, in that case I can go just with temperature lower than 30degC.
Maybe I can find a way to cheat the room thermistor input.
How many sensors has your internal board, did you connected to HX?

Murdock · 10-31-20, 02:52 PM

Sadashi,
As I understand, you use the original controller of the inverter airco. You have placed the temperature sensor from the indoor coil on yhe brazed plate heat exchanger, and the air temp sensor on the water return.
But what did you do with the fan of the indoor unit? Did the original controller not complaint when you run the ac without an indoor fan connected?
Love to hear more details on this setup,
Murdock

Sadashi · 10-31-20, 03:57 PM

Hi Murdock and welcome to the discussion . There are two sensors with this C&H ( Gree made ) unit that I'm using , one was attached to the copper heat exchanger ( evaporator ) and the other one is the air sensor . The one that was attached to the evaporator I've placed it on the refrigerant liquid line right after is coming out of the brazzed plate heat exchanger and the air temperature sensor I've extended the wire and I've placed it somewhere inside the house on a wall along with the small led display that's got the ir receiver as well incorporated . You have to keep all the electronics of the indoor unit and also the fan motor to be able to control the outdoor unit . You detach the fan motor from the fan and place it somewhere in a box and secure it somehow so it won't move when it starts spinning . I haven't tried to trick the pcb and not keep the motor because I believe the motor got a sensor on the inside that communicates with the pcb and if it detects that the motor does less than 450 rpm it will shut down the unit .

Acuario · 11-01-20, 03:24 AM

Quote:

Originally Posted by Sadashi

I haven't tried to trick the pcb and not keep the motor because I believe the motor got a sensor on the inside that communicates with the pcb and if it detects that the motor does less than 450 rpm it will shut down the unit .

If you investigate the motor a bit more you'll probably find one of the wires is providing a square wave pulse output that varies depending on the speed of the motor.

It should be fairly simple to build a circuit (i.e. 555 timer) to simulate this output and allowing you to dispense with your 'motor in a box'.

Murdock · 11-02-20, 03:40 AM

Agree with Acuario. It can be relative easily hacked. On the orher hand, I guesse the motor spinning without any load, will probably comsume ony a few watts. All in all, Sadashi, it looks quite easy to modify the airco to an air-water heat pump. Have you got an idea about your COP? Since you haven't altered anything of the outdoor unit, I would assume you 'll have a COP close to factory spec.

10-21-20, 01:51 PM	#1
ferox Lurking Renovator Join Date: Mar 2013 Location: Oradea Posts: 21 Thanks: 6 Thanked 5 Times in 3 Posts	Inverter Ac converting into air-water heat pump My current setup is an 24000btu R22 external unit. This is heating my 1000L plastic tank once a day, which is insulated with 10cm of extruded polystyrene. Inside the tank I have 10mm copper tube/ 20m for heat transfer. To have the best efficiency I programmed to start the pump once at 2PM when the outside temperature is the highest. In the summer 20min of running heating the tank for 24 hours need. In the winter if the temperature is dropping to 5degC it runing 1, 5 to 2 hours. Under 5 C I need to heat with an electric heater. Now I want to improve something and extend it to house heating too, not just hot water. I want to change the external unit with an inverter one. The idea is simple, not so simple to do it. I have 2 options: 1. Buy a new heat pump - no fun, spending lot of money 2. Converting an inverter AC unit - lot of chalanges, price is almost 10th of the new one + time spent for fine tuning. I have this idea from long time ago. I have some knolege about automations, so I can jump in. My passive house need is 5kW thermal heat, I guess one 18k unit will be fine. This thread can be used for bigger needs. The chalange: 1. Install the external unit- easy 2. Connect the coil or one heat exchanger to the unit - easy. I prefer heat exchanger. 3. Controller setup A. Use the indoor PCB and find a way how to cheat to have the needed control of the outside unit B. Learn how to send specific command to the outdoor unit and build a simple arm based controller C. Maybe sombody did it an I don't know D. Buy a ready-made controller with 0-10V input - tried to search but hard to choose Now I'm writing from the phone, I will put pictures of actual setup later. I will have more updates. Have a nice day Ferox

10-25-20, 04:51 AM	#2
Sadashi Lurking Renovator Join Date: Jan 2020 Location: Romania Posts: 13 Thanks: 0 Thanked 0 Times in 0 Posts	What do you want to achieve when you said that you want to control the outside unit of the inverter ac ? Do you want to control the indoor temperature , keep a fixed flow temperature , or what ? As you see from the pictures , I'm using a 24k btu inverter unit to heat my house of 126 sqm , located in Buzau , Romania . Is your house located in Oradea ? Good luck with your project ! Ps : on my computer the pictures look fine , they don't need to be rotated . I don't know why they've been attached this way and I don't see the option on ecorenovator to rotate them so they look normal . Attached Thumbnails Last edited by Daox; 10-25-20 at 06:48 PM..

10-25-20, 10:42 AM	#4
ferox Lurking Renovator Join Date: Mar 2013 Location: Oradea Posts: 21 Thanks: 6 Thanked 5 Times in 3 Posts	Some pictures from the old inefficient setup. External unit was modified to be able to have cooling for defrost proposes connected directly to the coil which is in the bottom of the tank. Was installed 7 years ago, working good, controlled with Arduino and Blynk app for remote control and visualizing the temperatures with the nice charts. The plan is to upgrade with the latest inverter technology for heating the house. Attached Thumbnails Last edited by Daox; 10-25-20 at 06:49 PM..

10-25-20, 01:03 PM	#5
Sadashi Lurking Renovator Join Date: Jan 2020 Location: Romania Posts: 13 Thanks: 0 Thanked 0 Times in 0 Posts	Inverter control I'm afraid that I will disapoint you with regards to controlling the inverter unit to be able to keep a certain flow temperature . I'm not saying that it's not possible , but for me it wasn't a must , as my system the way it's been setup ( with radiators ) doesn't required a certain temperature , it varies depending on the indoor temperature . The inverter unit modulates the power output to meet the set temperature that I'm asking from it , so the flow temperature varies .

10-31-20, 03:57 PM	#8
Sadashi Lurking Renovator Join Date: Jan 2020 Location: Romania Posts: 13 Thanks: 0 Thanked 0 Times in 0 Posts	Sensor position Hi Murdock and welcome to the discussion . There are two sensors with this C&H ( Gree made ) unit that I'm using , one was attached to the copper heat exchanger ( evaporator ) and the other one is the air sensor . The one that was attached to the evaporator I've placed it on the refrigerant liquid line right after is coming out of the brazzed plate heat exchanger and the air temperature sensor I've extended the wire and I've placed it somewhere inside the house on a wall along with the small led display that's got the ir receiver as well incorporated . You have to keep all the electronics of the indoor unit and also the fan motor to be able to control the outdoor unit . You detach the fan motor from the fan and place it somewhere in a box and secure it somehow so it won't move when it starts spinning . I haven't tried to trick the pcb and not keep the motor because I believe the motor got a sensor on the inside that communicates with the pcb and if it detects that the motor does less than 450 rpm it will shut down the unit .

10-25-20, 10:24 AM	#3
ferox Lurking Renovator Join Date: Mar 2013 Location: Oradea Posts: 21 Thanks: 6 Thanked 5 Times in 3 Posts	Hi Sadashi! Yo have a nice setup, you did it! Exactly as I want to do it. My goal is to control the power of the outside unit, than I can keep a fixed flow temperature. Can you share with us how you control the water temperature? In that case I don't need to reinvent the wheel. I have some ideas but always it is a risk that is not working as intended. My 140sqm house is located in Oradea, where the weather is not so extreme as in the rest of the country. Best Regards, Ferox

10-25-20, 01:51 PM	#6
ferox Lurking Renovator Join Date: Mar 2013 Location: Oradea Posts: 21 Thanks: 6 Thanked 5 Times in 3 Posts	I understand. You are using the original controller. Is the easiest way of doing, just instead of internal air heat exchanger is an water HX. In the same way I can put the temperature sensor of the air to the floor heating, in that case I can go just with temperature lower than 30degC. Maybe I can find a way to cheat the room thermistor input. How many sensors has your internal board, did you connected to HX?

10-31-20, 02:52 PM	#7
Murdock Lurking Renovator Join Date: Aug 2017 Location: Essen (Belgium) Posts: 4 Thanks: 1 Thanked 0 Times in 0 Posts	Sadashi, As I understand, you use the original controller of the inverter airco. You have placed the temperature sensor from the indoor coil on yhe brazed plate heat exchanger, and the air temp sensor on the water return. But what did you do with the fan of the indoor unit? Did the original controller not complaint when you run the ac without an indoor fan connected? Love to hear more details on this setup, Murdock

11-02-20, 03:40 AM	#10
Murdock Lurking Renovator Join Date: Aug 2017 Location: Essen (Belgium) Posts: 4 Thanks: 1 Thanked 0 Times in 0 Posts	Agree with Acuario. It can be relative easily hacked. On the orher hand, I guesse the motor spinning without any load, will probably comsume ony a few watts. All in all, Sadashi, it looks quite easy to modify the airco to an air-water heat pump. Have you got an idea about your COP? Since you haven't altered anything of the outdoor unit, I would assume you 'll have a COP close to factory spec.