Using portable A/C for DHW Heater

[xotet]

Some parts start arriving, actually I´m working on the Fan´s due to unable to control the compressor dicharge temp with the condenser Fan. Also investigated the speed regulation of the shaded pole motors wich are mostly used on this kind of fans, I can control the speed using a fase reduction controller (standard).

[Acuario]

How are you getting on xotet? I did a similar thing to you but use it to heat the water in my heating system. You can squeeze a home made heat exchanger into a water heater. I also use solar but on a seperate system for the house hot water.

Does your water tank have a seperate heat exchanger coil for heating as shown on your diagram?

[xotet]

Hi Nigel, nice to take an opportunity to talk with you, I´m also talking from Spain, again I´m apologize for my bad english.

Before start my project I readed and studied your posts, photos....from your project. I have a few questions to you:

1. How can you selected your TXV???

2-Are you having frost on the evaporator?

I think there´s a difference btween your system and what I´m doing, you are heating the water on the tank but always removing heat ( trough rads or trough the pool), this is a big advantage because you have "constant" condensing temp. In my system I will have a 100 or 150L tank, but this is for acumulation only,most of the time there will be no water consumption. This creates a problem because once a large amount of water is heated, it´s impossible to condense the refrigerant because don´t get subcooling, to solve this I think the only way is to put air condenser in series downstream the HX, and control the air condenser fan to get it runing only when the subcooling it´s not reached on the HX.


On another hand, I don´t have the tank at this time but maybe use the same solution as you. or use a solar water heater wich incorporates a HX.


Thanks in advance.

[Acuario]

Hi Xotet,

no problem with the english - much better than many of the Catalans where I live!

Ok, the TXV - no rocket science - when I was working on my first swimming pool project someone suggested I use a Danfoss TX2 with orifice #3 so that's what I did. It seems to work ok so I've stuck with them.

I do get frost sometimes, mainly when it's cold and damp or raining. I was suffering with frosting earlier this year on one of the machines I have but not the other. It turned out it needed a bit more gas adding. Did that and it's now back to working as before.

My system only removes heat when the heating circulation pump is running. Often during the day it purely heats the water in the tank so it acts as an accumulator. The concern I had at the beginning is that as water is a poor conductor of heat I would need to circulate the water. This is why the additional reverse flow pump was installed, along with a non-return valve so I wasn't pumping water around the heating system when the heating pump was off.

You're only ever going to heat the water to between 45 and 55 degrees so why not do what I did - include a thermostat coupled to a relay to switch on/off the compressor and pump as required - effectively the same as would happen with the resistive element.

Nigel

[nexsuperne]

your system sounds very similar to mine. I have the 300 litre thermal store connected to a 12000btu modified air conditioning unit, which has the condenser hx in an 80 litre plastic tank, with 100mm insulation around it. The heat from the woodburner boiler runs into this tank as well. When the tank is below 45C, then the ASHP runs until the temperature reachs 49C. The woodburner pushes this way over 80C, so the ASHP switches off for several hours after the fire goes out. The store runs the domestic hot water and the heating on 2 floors. One is in a room 15 feet by 12 feet, the other is a larger hydronic hx, which heats an area 15 feet by 24 feet. The system holds 21C when it is 0C outside. The solar also contributes to the store, with a 16000btu output on a sunny day. I didn't think it was too bad, when the electrical demand is only 900 watts and to heat those areas should take 4-5KW.

I have a solar differential controller which checks the temperature on the store and the tank. When the tank is 4C hotter than the store, then the circulator pump runs until the difference is only 1C.

[AC_Hacker]

Originally Posted by nexsuperne

your system sounds very similar to mine. I have the 300 litre thermal store connected to a 12000btu modified air conditioning unit, which has the condenser hx in an 80 litre plastic tank, with 100mm insulation around it. The heat from the woodburner boiler runs into this tank as well...

Have you posted photos of your setup?

-AC

[Acuario]

Xotet, a quick question - what is the make/model of the hx you bought, and where did you get it from? I've often thought of using a brazed plate hx but they seem (for a low budget hacker!) expensive, that's why I made my own.

Nigel

[xotet]

Hi Nigel I buyed on ebay store, I´m using a 6000-1000BTU rated, it costs me 154€, there are lower prices but if you work with R410A you need a certified unit at 45Bar.

This is the store:

Tiendas eBay - PWT Split-Klima DTH: Resultados encontrados para DieTerHoeven GmbH.

[xotet]

I´m still working on my setup, a lot of data collected before to connect the HX, in order to get the system with the the correct refrigerant quantity I need to collect as many as data possible before the mod.

Here are the numbers:

HP side = 30bar
Ref Temp (manometer) = 50ºC
Temp Dicharge Pipe = 65ºC
Condenser Out Pipe = 35ºC
Subcooling = 15K
LP side = 7,8Bar
Ref Temp (manometer) = 0ºC
Evap Out pipe = 10ºC
Superheating= 10ºC
Comp Current 2.2A

I confirmed this data on the SOLKANE Software, it´s a very nice soft and it´s free, you can make a llot of calculations and simulations and also can look at the moliers diagrams with your system values. Supports a lot of refrigerants.











According Solkane Soft:

I have a COP of 3,5

And my condenser is generating 2,59Kw


I think this are good numbers.