Pull a vacuum against a solenoid valve?

[indy2000]

I get paid by the hour, its up to you.

[frigeguy]

I have some Tyler systems that are in need of filter/dryer changes. The problem is the piping is arranged like this:

king valve>dryer>sight glass>service valve>solinoid valve.


The problem is that once I close both valves to isolate the filter, I have no access to the system. If I use the service valve for access, I will be pulling a vacuum backwards against the solinoid valve. will a solinod valve prevent reverse flow? I wouldn't think so, but maybe I'm wrong.

LLS are dependent upon upstream pressure, Pump system down, close suction sevice valve and proceed. We install aprox 400 conventional systems per year, we make it standard to install schreder on both sides of LLS for proper vaccume.

[stanbyyourword]

if you front seat both valves after pump down, that section wil be isolated with ports on valves to evacuate,im sure this is the reason for th 2nd valve, unless i a missing smeting? stan

[Phase Loss]

I too do not understand the problem, this is common.

Pump it down at the King valve and replace the driers.

Hook up pump and evacuate...you are NOT looking for a micron level vacuum in this situation. Just a good enough one .

If you are looking for micron levels...you will be there all day. The inner walls of the piping have oil with refrigerant mixed in...it will take a looooooooong time to boil the refrigerant out of the oil to obtain micron levels.

This is not a new install nor is it a contamination clean up...its a common practice drier change.

[VTP99]

How about this one turn the service valve 180*

[grimmus]

You could turn the service valve around.

[craig1]

You could turn the service valve around.

Then there would be trouble servicing the liquid line if the situation arose.


anyways I closed the king valve, pumped down the system, closed the service valve, replaced the dryer, brazed a schraeder into the line between the king valve and dryer, evacuated the dryer from that, opened all the valves and started it back up.

[indy2000]

So there is no real problem, with the way you did it?

[surenuff]

I guess the first thing I would consider in trying to decide about a good evacuation or not is why the filter change in the first place. If we were dry and free of contaminates, then why the filter change. I know things take time with a 6 or even 7cfm pump, but if you don't have the time to do it right the first time, where are you going to get the time to do it again? And who pays for the component failures because of a techs failures? Just go ahead and do what you know you should. Leave the solenniod calling(open), close your king valve on the reciever, pump the system down. You may even have to jump that low pressure switch a little to pull it on down. Open your system, make the dryer replacement, then pull a good evacuation. If time is the issue, put that pump on one unit when you get it sealed up, and go start pumping down one or two of those other units you were talking about. You sound like a guy who cares, or you would'nt be asking questions. Do what you have been taught is right and charge for as many hours as it takes to do it right.

[surenuff]

I see what you are sying about back flow, but your suction valve in the compressor will keep you from backflow after the low side is pumped down.

[craig1]

I guess the first thing I would consider in trying to decide about a good evacuation or not is why the filter change in the first place. If we were dry and free of contaminates, then why the filter change.

The filter is being changed because the sight glass indicated moisture. I don't see how isolating the filter and then evacuating just that portion of the system after the change is any different than not isolating the filter and evacuating the whole lineset and evap, except that one method takes a heck of a lot more time. Either way the portion of the system that got opened is evacuated.

[surenuff]

Your the pro!!!!!!!!!! The one thing I have not figured out yet about this site, is why so many people will spend so much time asking questions and waiting for replies to questions that >>>>>by golly they already have all the answers to.

[frigeguy]

Your the pro!!!!!!!!!! The one thing I have not figured out yet about this site, is why so many people will spend so much time asking questions and waiting for replies to questions that >>>>>by golly they already have all the answers to.

Because it always leads to the next question.....If he did this correctly, closed king valve, pumped down, closed suction serive valve, changed dryer and evacuated properly, maintaining power to the LLS, and pulling on both suction and liquid then he might find he's not holding vacume on the low side which would be causeing the sight glass to indicate moisture in the first place???? There is also the possibility that someone ahead of him did not evacuate properly causeing this indication of moisture...geee willicar