4 way reversing valve doubts

[nano211991]

Hello friends and experts


I wanted to ask a query

Why 4 way reversing valve is not made for low capacity refrigeration system like domestic refrigerator...

i cannot find a single supplier who is making this for low capacity like 180 Watt cooling capacity..?


Can anybody tell me why? and why hot gas defrosting is not implemented in household refrigerators???

[UmmScott]

Hello friends and experts


I wanted to ask a query

Why 4 way reversing valve is not made for low capacity refrigeration system like domestic refrigerator...

i cannot find a single supplier who is making this for low capacity like 180 Watt cooling capacity..?


Can anybody tell me why? and why hot gas defrosting is not implemented in household refrigerators???
Cost

[nano211991]

i am trying a new project that is trying to defrost evaporator of refrigerator using hot gas bypass method or reverse cycel defrost method instead of using plain heater... any suggestions and answer to my previous query

[nano211991]

excluding cost.capacity is mentioned for every 4 way valve. what if i use a valve of higher specification say a 4 way reversing valve of 1 ton refrigeration . can i use it on my 200WATT domestic refrigerator.

[2sac]

So why not use a solenoid valve?

[Poodle Head Mikey]

Some years ago there were domestic refrigerators which utilized reverse cycle defrost. But manufacturing costs are higher than for resistance heating defrost and so they are no long made so far as I know.

Another issue is the use of capillary tube metering rather than a TXV. To bypass a cap tube requires an entire second liquid line to mount the check valve.

Heat pumps are being made down to 1 HP - that size reversing valve would work if you wanted to build your own system.

Why are you asking these questions?

PHM
-------



Hello friends and experts


I wanted to ask a query

Why 4 way reversing valve is not made for low capacity refrigeration system like domestic refrigerator...

i cannot find a single supplier who is making this for low capacity like 180 Watt cooling capacity..?


Can anybody tell me why? and why hot gas defrosting is not implemented in household refrigerators???

[Poodle Head Mikey]

Yes.

The capacity mentioned is the maximum - not the minimum. So long as the pressure differential exists to shift the valve internally - it will work.

Why do you want to do it?

Are you building an entire system? Or converting an existing unit?

How many BTU's is 200 watts? Would it be about 3200 BTU's at a 40º F. suction temperature?

PHM
-------




excluding cost.capacity is mentioned for every 4 way valve. what if i use a valve of higher specification say a 4 way reversing valve of 1 ton refrigeration . can i use it on my 200WATT domestic refrigerator.

[nano211991]

Yes.

The capacity mentioned is the maximum - not the minimum. So long as the pressure differential exists to shift the valve internally - it will work.

Why do you want to do it?

Are you building an entire system? Or converting an existing unit?

How many BTU's is 200 watts? Would it be about 3200 BTU's at a 40º F. suction temperature?

PHM
-------

Thanks a lot for the assistance...

My project details.

1. Want to implement hot gas defrosting or reverse cycle defrosting in a "domestic refrigerator" of NLPD(no load pull down, evaporator inlet is -18 degree Farenhite after 6hrs) heating load of 180W or 612 BTU/hr and volume 300Liters.

2. The main aim is to reduce energy consumption during defrosting hence overall energy consumption . Electric heater uses 200W or 650btu/hr during defrosting and i have to reduce it which i can do by making the refrigerator work like a heat pump which rejects more heat than the work supplied to it.

3. I am trying to modify existing system using
3.1 hot gas by pass defrost using solenoid valve ( which can cause liquid slugging in the compressor so i have to take some measures to prevent that...)
3.2 reversing valve (by removing the accumulator) in the existing system( why provide separate capillary or TXV ? i didn't understand. during defrosting the evaporator will act as a condeser and capillary is connected to it. and the other end of capillary is connected to condenser which will act as evaporator. tell me if i am wrong somewhere)


Has anybody tried in domestic refrigerator any of the above and how were the results...

[Poodle Head Mikey]

Draw out the system on paper - that's what I just did. <g>

Which is how I realized that you are right - the cap tube is fully reverse-able. <g>

All you need to add is a small RV - say 3/8" connections - and some means to control it. Something like a Ranco V2-408060-270

Can't you leave the accumulator in place and make the new suction connections between the evap and the accumulator?

For automatic control you need a timer and a relay. A termination stat on the evap (this probably exists on the evap now - although it likely open on rise rather than closes) would be a good thing.

Is this a static condenser unit? Or is there a condenser fan?

HGD is a little tough to do on a single evaporator system as you very quickly 'run out of heat' as the system cannot gain additional heat once defrost begins. Using reverse cycle gives you pretty much an endless source of heat for accomplishing defrost.

When I used to build reverse cycle refrigeration systems I found that lots of small defrosts are better overall. The defrost on-cycle is a matter of 1-2 minutes usually.

PHM
--------





Thanks a lot for the assistance...

My project details.

1. Want to implement hot gas defrosting or reverse cycle defrosting in a "domestic refrigerator" of NLPD(no load pull down, evaporator inlet is -18 degree Farenhite after 6hrs) heating load of 180W or 612 BTU/hr and volume 300Liters.

2. The main aim is to reduce energy consumption during defrosting hence overall energy consumption . Electric heater uses 200W or 650btu/hr during defrosting and i have to reduce it which i can do by making the refrigerator work like a heat pump which rejects more heat than the work supplied to it.

3. I am trying to modify existing system using
3.1 hot gas by pass defrost using solenoid valve ( which can cause liquid slugging in the compressor so i have to take some measures to prevent that...)
3.2 reversing valve (by removing the accumulator) in the existing system( why provide separate capillary or TXV ? i didn't understand. during defrosting the evaporator will act as a condeser and capillary is connected to it. and the other end of capillary is connected to condenser which will act as evaporator. tell me if i am wrong somewhere)


Has anybody tried in domestic refrigerator any of the above and how were the results...

[nano211991]

Draw out the system on paper - that's what I just did. <g>

Which is how I realized that you are right - the cap tube is fully reverse-able. <g>

All you need to add is a small RV - say 3/8" connections - and some means to control it. Something like a Ranco V2-408060-270

Can't you leave the accumulator in place and make the new suction connections between the evap and the accumulator?

For automatic control you need a timer and a relay. A termination stat on the evap (this probably exists on the evap now - although it likely open on rise rather than closes) would be a good thing.

Is this a static condenser unit? Or is there a condenser fan?

HGD is a little tough to do on a single evaporator system as you very quickly 'run out of heat' as the system cannot gain additional heat once defrost begins. Using reverse cycle gives you pretty much an endless source of heat for accomplishing defrost.

When I used to build reverse cycle refrigeration systems I found that lots of small defrosts are better overall. The defrost on-cycle is a matter of 1-2 minutes usually.

PHM
--------

Thanks a lot for your enthusiastic involvement in my problem. Better change your name to Enthusiastic poodle head mikey.

Mikey it is actually small domestic refrigerator . having hot wall condenser. no fan.

The ref is having R600a and the temperature goes as low as -27DegC or -18degF . at the same time the discharge from the compressor is going to be at 80-90 DegC. so this temperature difference will have any effect on reversing valve.?

2. the mass flow rate of my system is very less during normal refrigeration operation. i.e 0.6 grams/sec. so this very less mass flow rate will it have any problem actuating the reverse valve? althoug pressure limits of my cycle is from 7bar i.e 100psi(condenser pressure) to 0.7bar 1psi(evaporator pressure)...


3. about HGD system . you are absolutely right . i am expecting to lose heat very fast since it doesn't have any heat reservoir from where it will pump the heat so i was thinking of making a heat reservoir which will gain heat during normal operation of refrigeration i.e act as a condenser( water coooledi.e water acts as a heat reservoir) and during defrosting if i make a secondary refrigeration system using another capillary and one more bypass valve at the evaporator end practically making a secondary refrigeration system it might workout but reliability and cost is going to shoot up....

[nano211991]

https://www.johnstonesupply.com/storefront/product-view.ep?pID=B14-873

i checked the valve Ranco V2-408060-270 . it is saying maximum capacity with r22 as 1.6 and min capacity 0.7. so it will not work with lower capacity refrigeration system.

what i am not understanding is conceptually why the valve will not work with lower capacity ? i mean my low capacity system also has a big pressure difference between condenser and evaporator pressure. i.e 100psi and 10 psi or 0.7bar . this pressure difference along with the electrical actuation should be enough to actuate the valve . so criteria deciding the valve actuation should be the pressure difference ? how capacity is deciding?.

[captaincompressor]

hot gas defrost is without doubt the best way to defrost. a 1 ton valve should work fine with a check valve to bypass the cap tube. you could go one step ahead and install a txv on the evap. Your superheated would be maintained accurately. I have an old holiday upright freezer that has to be defrosted with a heat gun. I have always thought about a reversing valve and defrost controls. I may go ahead and do it.