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  1. #1
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    Correct Method For PUMPING DOWN.



    Can anyone please advise on a CORRECT method for pumping down a small AC unit.

    Please keep it as simple as possible.

    Thank-you.



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    Re: Correct Method For PUMPING DOWN.

    Extract Advice.
    The HVAC technician closes the liquid line valve and turns the air conditioning on. The compressor pumps all the refrigerant into the condenser coils. The HVAC technician watches his gages carefully and when the pressure gets to zero on the gages he quickly closes the suction line valve to trap the refrigerant in the condenser and then turns the compressor off.
    Ok, but are both lines connected (Liquid - Suction) ?. Or just the Suction...is this done whilst running or stopped.
    Do you have to turn the unit off then on.
    Advice welcome

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    Re: Correct Method For PUMPING DOWN.

    its already being spoken of on the forum.
    look harder,you will find it.

    Ice

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    Re: Correct Method For PUMPING DOWN.

    Thank-you,but where ?
    It is early.
    Mike

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    Re: Correct Method For PUMPING DOWN.

    Ice Cube - I found the thread.

    So it's 1. Connect Lowside or Suction gage line. 2. Close Liquid Line whilst compressors running 3. Watch suction pressure lower, get to 0bar, 4. Close suction line valve and switch off unit.

    Am I there ?

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    Re: Correct Method For PUMPING DOWN.

    yes that's correct, if you try and visualize it, it will become clear, you are closing the liquid line which is essentially refrigerant leaving the condenser, thus none can leave, your suction line is still open so the compressor sucks all the remaining refrigerant back and it gets stored in condenser/accumulator.

    it should be noted that if there is a long pipe run on a small "unit" the condenser may not be sufficient to hold all the refrigerant, in this case you will also need to reclaim any remaining refrigerant.

    hope this helps

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    Re: Correct Method For PUMPING DOWN.

    be aware if you are pumping down,the unit is in cooling mode.

    Ice

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    Re: Correct Method For PUMPING DOWN.

    Quote Originally Posted by icecube51 View Post
    be aware if you are pumping down,the unit is in cooling mode.

    Ice
    So to re-cap, is this right please.
    1. Connect LOW pressure gauge to SUCTION valve, Open SUCTION valve.
    2. Purge Line.
    3. Run system.
    4. Slowly close LIQUID line.
    5. Observe SUCTION pressure.
    6. When down to zero (6A)
    6a. Close SUCTION line.
    7. Swith off unit by isolator.
    8. Remove Gauges.

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    Re: Correct Method For PUMPING DOWN.

    1 connect gauge LP line
    2 purge unit
    3 close HP line
    4 run sytem by remote control or relais.
    5 observe suction pressure
    6 when down to zero and going to -0,5
    close the LP line valve
    7 stop the unit a.s.a.p by isolator,relais or main current.
    8 remove gauges.

    suc6 M8,

    Ice

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    Re: Correct Method For PUMPING DOWN.

    Thank-you very much indeed.

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    Re: Correct Method For PUMPING DOWN.

    Guys.
    Can I please point out a flaw in the above discussion.
    Whilst what is being said is quite normal practice!

    Special conditions apply when dealing with a scroll compressor install!

    Please read the paragraphs below which I pinched froa manuel somewhere?
    Grizzly

    1. Can the scroll compressor be tested similar to a reciprocating compressor by allowing it to pump into a vacuum?

    No. The compressor should never be pumped down into a vacuum--neither by "manually" pumping down the system nor by attempting to test the efficiency of the compressor by closing off the suction ball valve on the system.

    Because of its very high volumetric efficiency, the scroll compressor in a chiller can pull a very low vacuum level. Since this scroll compressor uses a low-side shell, the oil and the motor connections are in the same environment--oil and refrigerant vapor are present. At deep vacuum levels, the dielectric strength of the refrigerant vapor is greatly reduced. This greatly increases the potential arcing across motor windings (if there is a small crack in the varnish) or fusite connections into the compressor. Therefore, if the compressor is allowed to pump into a vacuum, the potential for arcing inside the compressor is high. This arcing will result in a damaged or failed compressor. In addition to the internal arcing, the operation of the compressor at very low vacuum conditions may cause tripping of circuit breakers, blowing of fuses, or merely tripping the internal motor safety (a bimetallic single pole, single throw) thermostat.

    The last few lines may answer some other questions related to scrolls and electrical trips etc.
    Last edited by Grizzly; 13-10-2008 at 07:08 AM.

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    Re: Correct Method For PUMPING DOWN.

    Pumping down for relocation purpose or service should never go below atmospheric pressure! It is advisable to leave 0,1-0,2 bar of pressure in system before opening.
    That way impurities and moisture doesn't enter in pipes!
    Refrigerant in them is heavier than air, and if pipes closed soon enough you have no need to long evacuation after recommission.

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    Re: Correct Method For PUMPING DOWN.

    Quote Originally Posted by icecube51 View Post
    1 connect gauge LP line
    2 purge unit
    3 close HP line
    4 run sytem by remote control or relais.
    5 observe suction pressure
    6 when down to zero and going to -0,5
    close the LP line valve
    7 stop the unit a.s.a.p by isolator,relais or main current.
    8 remove gauges.

    suc6 M8,

    Ice
    Purge unit Icie? Ilabatjes :-)
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

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    Re: Correct Method For PUMPING DOWN.

    so many different units,so many different ways to do this. yes peter , by purging i mean units whit longer tubes then prescribe.a normal unit has a tank for approx 4mtr of tube length. Grizzly,your right to,for scroll comps,and Nike123,never reuse the refrig blend for a other unit,please.or you have the right tools to make a nice clean refrig.

    Ice

    Ice

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    Re: Correct Method For PUMPING DOWN.

    Quote Originally Posted by icecube51 View Post
    and Nike123,never reuse the refrig blend for a other unit,please.or you have the right tools to make a nice clean refrig.

    Ice

    Ice
    I don't following you here. Please, clarify!

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    Re: Correct Method For PUMPING DOWN.

    I just meant that this is forbidden now, you may no longer purge but must vacuum your lines... anyhow...in theory.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

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    Re: Correct Method For PUMPING DOWN.

    Quote Originally Posted by Peter_1 View Post
    I just meant that this is forbidden now, you may no longer purge but must vacuum your lines... anyhow...in theory.
    Hello Peter,

    if the attachment to the system is a shrider valve, purging will still be required, if you don't have ball valves on the ends of your lines.

    Kind Regards Andy
    If you can't fix it leave it that no one else will:rolleyes:

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    Re: Correct Method For PUMPING DOWN.

    The Belgium F-gas regulation states "Never purging..."
    Isn't it then up to you to buy access valve for your lines or new lines?
    It's not because you don(t have the proper tools you don't have to follow the law...at least that's how we see it in Belgium.
    You have to invest so that you can work according the regulation.
    Is it also the same in the UK as in Belgium that you as a technician must be certified but that there's also another compulsory certification for the company, even it's a one-man company?

    I always use a 'Kwik-Coupler' for Schraeder valves
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

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    Re: Correct Method For PUMPING DOWN.

    Quote Originally Posted by Peter_1 View Post
    The Belgium F-gas regulation states "Never purging..."
    Isn't it then up to you to buy access valve for your lines or new lines?
    It's not because you don(t have the proper tools you don't have to follow the law...at least that's how we see it in Belgium.
    You have to invest so that you can work according the regulation.
    Al that you say is OK, but realty is that all produced refrigerant is going to end up in our atmosphere sooner or later.
    Purging refrigerant lines will not make more damage to environment than introduction of non-condensables in system and their purging along with refrigerant already in system (and then refilling that system with new refrigerant).
    As we all know, legislations are not always in same track with reality. In fact legislation doesn't always reflect real life problems.

    That doesn't excuse us for not buying quick couplers, but I am sure that you know what I want to say!

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    Re: Correct Method For PUMPING DOWN.

    If you vacuum them, then you don't introduce non-condensables in it.
    I agree with you about he sense of regulation but if you agree or not, you have to follow those or the consequences are yours.
    It's all about common sense, making you aware that can't blow or clean a condenser with a hose connected to the HP of the running compressor.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

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    Re: Correct Method For PUMPING DOWN.

    Quote Originally Posted by Peter_1 View Post
    It's all about common sense, making you aware that can't blow or clean a condenser with a hose connected to the HP of the running compressor.
    Where in this discussion is said that someone need to blow or clean condenser? As I understood this thread, here is question about purging gauges and hoses before pump down in order to not allow that non-condensables are introduced to system. If I got something wrong, please point me to right direction.

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    Re: Correct Method For PUMPING DOWN.

    Is this better Nike: The new F-gas regulation tries to make peoples aware that you no longer can't blow or clean a condenser with a hose connected to the HP of the running compressor.

    I didn't said someone has told this in this thread, you made that assumption.

    I call it common sense when handling gas, even if you purge the lines. I just exaggerated it to clarify, apparently it was misunderstood by you.

    Better now?
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

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    Re: Correct Method For PUMPING DOWN.

    But purging is not allowed in Belgium, simple as that and that was what I said to this Belgium poster whom I resepct for his knowledge and contribution to this forum BTW.

    That was all and it was a reply on his post which was correct.

    It's even one of the 250 exam questions here in Belgium to get your qualification.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

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    Re: Correct Method For PUMPING DOWN.

    Quote Originally Posted by Peter_1 View Post
    Better now?
    Yes! .....

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    Re: Correct Method For PUMPING DOWN.

    Slightly but I think the use of the word purge is taken differently around the world.

    We, in Europe for example, may take purging to mean 'venting something to atmosphere'.

    Whereas, in the Far East to "air purge" means to empty the refrigerant pipelines of air using a vacuum pump before charging.

    OK, I've finished now.....
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    Re: Correct Method For PUMPING DOWN.

    Quote Originally Posted by nike123 View Post
    I don't following you here. Please, clarify!
    Ice, I catch you now. You probably taught that I said that evacuation is not needed after relocation and recommission if pipes are leaved with refrigerant in them.
    I didn't mean like that. I mean that time for pipes evacuation could be significantly shorter if you leave slight overpressure in them when disconnecting them from system and instantly close them with some tap.
    Later when reconnected, time for evacuation is significantly shorter, because air and moisture is not much introduced in pipes.
    If pipes are 1/4" and 1/2" diameter and 10m long and you leave 0,1 bar of R407C in them, you release in atmosphere 19 g of ("environmentally friendly") gas! Ad to that evaporator of max 10g of gas, and total gas released is 29g. I could sleep without problem with that sin on my soul.

    That was my point in this discussion.
    Last edited by nike123; 15-10-2008 at 07:21 AM.

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    Re: Correct Method For PUMPING DOWN.

    thats why this forum was made,to proper discus al possible terms and uses of engines and refrigeration.so at the end whe come to understand eacht other.

    Ice

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    Re: Correct Method For PUMPING DOWN.

    but a small question Peter_1, on the new connections you mention, do we have to change the old connections in the future each time we encounter one, or is there a delay on existing plants???

    Ice

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    Re: Correct Method For PUMPING DOWN.

    Quote Originally Posted by Peter_1 View Post
    The Belgium F-gas regulation states "Never purging..."
    Isn't it then up to you to buy access valve for your lines or new lines?
    It's not because you don(t have the proper tools you don't have to follow the law...at least that's how we see it in Belgium.
    You have to invest so that you can work according the regulation.
    Is it also the same in the UK as in Belgium that you as a technician must be certified but that there's also another compulsory certification for the company, even it's a one-man company?

    I always use a 'Kwik-Coupler' for Schraeder valves
    Hi Peter

    I had two of these very connections in the past, but they kept wearing out.
    I'm thinking of buying a nice new set of digital Mastercool gauges, with the lines that include shut off valves.

    I suppose I could ask what you do with the gas left in the line after disconnecting the H.P line, but you would only say pump the system down and let it go back to the suction

    Suppose I should look for a small handy to carry vac pump for purging my gauges.

    Kind Regards Andy D
    If you can't fix it leave it that no one else will:rolleyes:

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    Re: Correct Method For PUMPING DOWN.

    Quote Originally Posted by icecube51 View Post
    but a small question Peter_1, on the new connections you mention, do we have to change the old connections in the future each time we encounter one, or is there a delay on existing plants???

    Ice
    Perhaps a little confusion here Ice....

    The connector on the hose and the connector on the pipe are both threaded and detachable. The hose unit stays put and the pipe Schraeder adaptor is moved from unit to unit.

    Clear as mud now ?
    Brian - Newton Abbot, Devon, UK
    Retired March 2015

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    Re: Correct Method For PUMPING DOWN.

    thnx Brian_UK,as i understand it is just an addition to the existing gauges connection and unit shreaders.

    Ice

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    Re: Correct Method For PUMPING DOWN.

    Ice, just joining again, too busy yesterday. You can buy those in Gent at ECR or Heynen. There are 4 types available: angle and straight and normal 1/4 SAE connection and R410a connections (5/16 SAE)
    They're really helpful when releasing a hose from a schraeder.

    Heb je je aanvraag bij Vincotte of Veritas al ingediend voor je certificering. Wacht hier niet te lang meer mee.
    Examen certificering al gedaan?
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

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    Re: Correct Method For PUMPING DOWN.

    just use antiblow back fitings, a duble acting check valve, when threaded onto a schrader they open alloing bydirectional flow, when removed the checkvalve disallows any gas leaving the guages!

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    Re: Correct Method For PUMPING DOWN.

    Thanks GUYS !!!
    Duc, sequere, aut de via decede - Lead, follow, or get out of the way !

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