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dark84 11-03-18 01:52 PM

Home made air source heat pump
8 Attachment(s)
Hi for everyone!
I am from Europe. From Serbia.
I'm working on project to heat the house with two 18000btu split ac outdoor unit.
I don't use the indoors. I have a copper tube heat exchanger. The diameter of tube is 8mm and a lenght is 28m. I have two of these for each outdoor unit in a tank of 125 litres.
Metering devices are original cap tubes in outside units.
With my friend we doing this project. He has tools and practice for brazing, and vacuuming, filling refrigerant. We use the original refrigerant for units (R22).
The heating is working. I will add some pictures here.
I have only one service valve on the outside unit. Now i measure here the pressure of liquid line (high side).
I have temperature meters on middle of outside heat exchanger(saturation temp), on suction line of the compressor, on the copper tube before goes in tank (condenser in) and after the tank (condenser out).
In the outside units i have 4 way valves. Now i heating with underfloor heating and 3 fan coil unit. I want to use the system for cooling at summer (with fan coils).

dark84 11-03-18 02:07 PM

I have few questions.
I want to know superheat, but i have only temperature meters.
Now ambient temperature is 14C. When the units are running i measure these temperatures:
Unit1 saturation: 10C
Unit1 suction: 7C
Unit1 53C
Unit1 cond.out: 32C
Unit2 saturation: 13C
Unit2 suction: 9C
Unit2 53C
Unit2 cond.out: 29C
Water from tank: 40C
Water to tank: 30C
With these temperatures i have negative superheat.
We charged system with refrigerant how many on plate.
I measure current of compressors. On the plate i have for heating 8,5A and 2600W (this means about 11A). I measure 7,5A and 9A.
I have pressures on high side 19 bar and 20 bar.
I use DS1820B sensors with arduino for measuring.
I don't know that how accuracy i have.
The system is working good. I want to ask, that i need to modify charge or no? Just use the system with these parameters.
Thanks for the answers and sorry for my bad english.

jeff5may 11-04-18 02:08 AM

For the record, you did what a factory tech would do. Charge by weight, make sure it works, get paid and let it ride. Without accurate pressure and temperature instantaneous measurement, it's pretty much impossible to mess with the refrigerant charge and do any good. After a cold storm moves in, you will quickly find the lower limit of the air source outdoor unit.

pavel 01-16-19 01:17 PM

pressure sensors
If I got it right, you don't have any pressure sensor in your system at all, right? To calculate superheat, I would recommend to install at least one pressure sensor on suction compressor side. I use CAREL sensors for refrigerant and some cheap noname sensors from Aliexpress for water sides.

mrmhf 01-11-20 06:16 PM

How is this project coming along?

MN Renovator 01-12-20 10:52 PM

*shudders at unencapsulated fiberglass* hopefully the unit is inside a space where space heating is desired.

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