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Beck's Machine
22-01-2010, 07:37 PM
Hi Folks, a newbie here displaying some of his ignorance! :)

Does anyone have any experience or thoughts on using a reversing valve in a pump down system?

I am experimenting with modifying some Carrier water source heat pumps to work with the cooler water supplied by my ground loops and am debating whether to try and retain the cooling function.

Playing with the reversing valve after removal, it seems to be much too leaky to separate the high/low side pressures for very long. Is this the pilot pressure tap bypassing? Or just an old valve? Or am I asking the wrong questions? ;)

All thoughts appreciated, Dave

sedgy
22-01-2010, 08:12 PM
hi david , I am not sure of your motives, why think you can pump down using a reversing valve? if you want to pump down the best way is a solanoid valve, on the liquid line, all the best -

Beck's Machine
23-01-2010, 02:32 AM
hi david , I am not sure of your motives, why think you can pump down using a reversing valve? if you want to pump down the best way is a solanoid valve, on the liquid line, all the best -

Hi Sedgy,thanks for the response. I think I understand about using a solenoid valve in the liquid line as part of a pump down system. When the solenoid valve closes, isn't the reversing valve across both the low and high sides? Thus if it leaks, it would cause more or less cycling of the compressor to maintain the pump down condition? Thanks, Dave

sedgy
23-01-2010, 11:26 AM
hi david ,yes but you know what the revesing valve is for = it changes the direction of refrigeration in the system, so its not a valve it dose <click <like a solinoid valve but it shutting one side of the valve and opening the other thats why theres a small pipe conecting the 2 sides so what was the high psi side can release its pressure to the lowside to allow the valve seating to move, hope I have explained this correctly but come back on if there is any questions you want to put farward, there are some very good engineers on this foram

taz24
23-01-2010, 03:13 PM
Hi Folks, a newbie here displaying some of his ignorance! :)

Does anyone have any experience or thoughts on using a reversing valve in a pump down system?

I am experimenting with modifying some Carrier water source heat pumps to work with the cooler water supplied by my ground loops and am debating whether to try and retain the cooling function.

Playing with the reversing valve after removal, it seems to be much too leaky to separate the high/low side pressures for very long. Is this the pilot pressure tap bypassing? Or just an old valve? Or am I asking the wrong questions? ;)

All thoughts appreciated, Dave


Hi Dave.

The reversing valve can only work properly when the system is under pressure.

The valve relies on the pressure differance between the high side and the low side.
It is the high side pressure that seals the sliding shuttle on its seat.

The valve will only swap the direction of flow, it will not act as a solenoid valve.

As Sedgy says you need a solenoid valve in the liquid line to pump down.

But why do you need to pump down the system?
Explain a little more what you intend to do!!

Cheers taz.

.

Beck's Machine
25-01-2010, 02:27 AM
Hmm, I can see that I am not doing such a good job describing my question.

Ok, I know this isn't how it ultimately should be done but this set up will illustrate my question. Let say that I install a receiver and solenoid valve downstream from the compressor and reversing valve (heating mode). This puts the solenoid valve between the reversing valve and the evaporator (heating mode).

So when the solenoid valve is closed the compressor will pump down the condenser and evaporator and hopefully shut off when the low side switch reaches it's set point. In this scenario the reversing valve is still connected to both the high and low sides of the system.

So, assuming that the reversing valve is left in it's un-activated heating position, will the reversing valve seal well enough to maintain the pump down condition and keep the compressor off for an extended period, (10-12 hours)?

Hopefully this makes more sense. :) Dave

lowcool
25-01-2010, 04:49 AM
So when the solenoid valve is closed the compressor will pump down the condenser and evaporator and hopefully shut off when the low side switch reaches it's set point. In this scenario the reversing valve is still connected to both the high and low sides of the system.


im missing something here,a pictorial would be a better option.to me its looks impossible without serious design alteration

sedgy
25-01-2010, 03:49 PM
david , if you where to fit the s/ valve just before the r/ v then you would have to fit a new L/P swich on the low psi side to knock off the unit cos if you left it to knock off on the existing L/p swich it would go onto de-frost, how dose that sound?

Beck's Machine
12-02-2010, 02:29 AM
Hi Dave.

The reversing valve can only work properly when the system is under pressure.

The valve relies on the pressure differance between the high side and the low side.
It is the high side pressure that seals the sliding shuttle on its seat.

The valve will only swap the direction of flow, it will not act as a solenoid valve.

As Sedgy says you need a solenoid valve in the liquid line to pump down.

But why do you need to pump down the system?
Explain a little more what you intend to do!!

Cheers taz.

.
An update on progress (?) and maybe some clarification. :)

I understand the "pilot pressure" nature of a reversing valve and how it only works under pressure.

I wanted to try and use a pump down system to avoid problems with refrigerant migrating to the compressor during off cycles and also to avoid inefficiencies associated with cycling, eg, having to re-establish pressure differentials after the equalization that normally occurs during an off cycle.

What I did was to place a solenoid valve and receiver in the liquid line just before what would be the evaporator (heating mode). When I closed the solenoid valve and let the compressor trip off on the high pressure switch, I could hear a very significant leak, and was trying to decide what was leaking.

It is entirely possible that it was the compressor leaking as this is a used unit with an unknown history, but it could also be the reversing valve, thus my original question.

Now I do know that this layout would not work in the cooling mode, it was just convenient to try it this way.

I also understand that this scenario would require "serious design alteration" and in response to sedgy's comment about defrost mode, these are water to air units, so no defrost cycle is involved.

Any thoughts appreciated, Dave

nike123
12-02-2010, 09:04 AM
http://i46.tinypic.com/fviq7k.jpg
...................................

Beck's Machine
12-02-2010, 05:05 PM
Thank you nike123, confirmation of my naive suspicions, even if it isn't the desired outcome.

Dave