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wetbar 06-27-2013 10:19 PM

how long can a vacuum pump run
 
he y I have a robinair 5 CFM vacuum pump and I am pulling a vacuum on a new 410 install. The vacuum pump is getting really hot, but I can't seem to get it down to 30, it wants to hang out about 15. I Did a triple evacuation. the line sets were open for about 12 hours and it was very high humidity. How long can I leave this vacuum pump running without frying it? it is getting very hot! I ran it for about an hour change the oil, and ran it again for about 2 hours.
I know there is not a leak because I put nitrogen in it and it held overnight at about 500 psi.

Thanks

hvac instructor 06-27-2013 10:44 PM

how big is the system? the bigger it is the longer it will take. if just a house unit, your pump might be week. I had units that hold 1200 lbs of Freon. I used 2 pumps for 7 days 24 hrs a day with changing oil 2 times a day.

wetbar 06-27-2013 11:14 PM

Wow! 7 days. these are really small units one and a half ton, and my pump is only one year old.

biggles 06-28-2013 02:21 AM

do a vac test on your gauges ..how?add a brass union connect suction discharge hoses on it and pull the vac on the middle yellow hose check your hose gaskets both ends...super hot vac pumps will'nt pull down see it when using a micron guage on commercial sites...had to slide the pump into an air handler to cool it off. are you isolating the vac test from the pump shut off or the gauges..

beenthere 06-28-2013 04:36 AM

Can't get it down to 30, seems to hang out at 15? 30 what? 15 what?

RWolff 06-28-2013 11:32 AM

Quote:

Originally Posted by beenthere (Post 1208299)
Can't get it down to 30, seems to hang out at 15? 30 what? 15 what?

Inches of mercury of course, that's the usual measurement unit for vacuum.
About 30" is the maximum you can get anyway.

At work we have a vaccum pump, it never gets above 15" and when it's in use it runs continuously for hours. Seems like the best thing to do is check with the pump manufacturer about run time, because we have a second smalelr vacuum pump and it specifically stats on the lable "not for continuous use" and it has a maxium run followed by a wait time shown on the label to avoid overheating it.

yuri 06-28-2013 12:15 PM

you must have a leak where it connects to the pump. good that it held pressure overnight but now you added some connections to the pump. The BEST way to do this is have a new set of hoses with quick connect fittings not the basic rubber seat jobs as they tear and you should be using a micron gauge with R410. 30" vacuum is for the OLD days and R22 and not acceptable for 410. I keep a new set of hoses with clean fittings for vacuum jobs and a beater set for everyday use as they get worn and knocked around. Put clean oil in the pump and follow my info and you should be able to get a 500 microns in under 2 hours. use old hoses etc and it will be nothing but headaches.

beenthere 06-28-2013 03:59 PM

Quote:

Originally Posted by RWolff (Post 1208453)
Inches of mercury of course, that's the usual measurement unit for vacuum.
About 30" is the maximum you can get anyway.

At work we have a vaccum pump, it never gets above 15" and when it's in use it runs continuously for hours. Seems like the best thing to do is check with the pump manufacturer about run time, because we have a second smalelr vacuum pump and it specifically stats on the lable "not for continuous use" and it has a maxium run followed by a wait time shown on the label to avoid overheating it.

In A/C and refrigeration, we use microns to determine the level of a vacuum. Inches of Mercury is not accurate enough.

Wetbar, most likely a leak in the system, or your hoses or manifold.

Canucker 06-28-2013 05:45 PM

Quote:

Originally Posted by beenthere (Post 1208551)
In A/C and refrigeration, we use microns to determine the level of a vacuum. Inches of Mercury is not accurate enough.

I use Torr to measure vacuum quality where I work(Not involved in refrigeration)
How does the micron measurements compare? i.e; x number of microns = x number of torr?

beenthere 06-28-2013 05:56 PM

760 torr is atmospheric pressure. 760,000 microns is atmospheric pressure.

yuri 06-28-2013 05:56 PM

Google : torr versus micron lots of info

http://wiki.xtronics.com/index.php/P...nversion_Table

beenthere 06-29-2013 05:58 AM

Quote:

Originally Posted by wetbar (Post 1208229)
he y I have a robinair 5 CFM vacuum pump and I am pulling a vacuum on a new 410 install. The vacuum pump is getting really hot, but I can't seem to get it down to 30, it wants to hang out about 15. I Did a triple evacuation. the line sets were open for about 12 hours and it was very high humidity. How long can I leave this vacuum pump running without frying it? it is getting very hot! I ran it for about an hour change the oil, and ran it again for about 2 hours.
I know there is not a leak because I put nitrogen in it and it held overnight at about 500 psi.

Thanks

Hanging around 15" mercury indicates a leak.

What color is the oil in your vacuum pump. If it is turning white/milky, then that indicates a lot of moisture is in the system. Need to blow it out, and change oil everytime it turns milky. Until you get a good vacuum.

hvac5646 06-29-2013 09:00 AM

Everyone in the know is using a micron gauge these. If you don't understand the value of a micron gauge over a bourdon tube analog I would suggest u Google Jim Bergmann 50 seconds to 200 microns. You will get all the input you need on vacuum technology.

biggles 06-30-2013 03:22 PM

anything below 5000 microns is moisture being pulled and a lot of the newer oils absorb moisture during the pipe up and show as a leak on a humid days job

beenthere 06-30-2013 03:32 PM

Quote:

Originally Posted by biggles (Post 1209483)
anything below 5000 microns is moisture being pulled and a lot of the newer oils absorb moisture during the pipe up and show as a leak on a humid days job


Neither POE nor PVE oil will give up moisture they absorbed by vacuuming. And both can have moisture in them and a micron gauge show 500 microns.

The OP is on a new install. So no POE or PVE oil is in the piping to have absorbed oil.


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