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Thread: Testo 557

  1. #1
    Join Date
    May 2012
    Location
    Mayfield, KY
    Posts
    39

    Smile Testo 557

    I got my new Testo 557's today. Kind of excited to hook them up to a unit.
    Anyone have any do's or don'ts?

  2. #2
    Join Date
    Mar 2009
    Location
    Triad - North Carolina
    Posts
    328
    Good luck with getting responses. There does not seem to be a lot of talk about them and I wonder why.

  3. #3
    Join Date
    May 2010
    Location
    Canada
    Posts
    799
    I have a 550 but I'm sure they are pretty similar in the programming.

    Make sure you plug in the temp sensors, before you turn the unit on (wont read them)
    You should also turn the unit on and zero it before you add any pressure (I have gotten weird readings for add pressure then turning the unit off after)
    When you are in heat pump mode (fire and ice symbols at the same time) you will haves issues if you are trying to set a TXV with just one sensor and hose hooked up ( the unit wants to switch the high and low sides because the low side is at a higher pressure. I was unable to get the unit to give me superheat because it thought it was reading the high side) This can be avoided by switching modes (to snowflake) or hooking up both hoses (in heatpump mode).

  4. #4
    Join Date
    Sep 2012
    Location
    London, England
    Posts
    24
    I have had my set of the 557 for about 2 weeks now, personally i really like them and so does others at work. Few of my work mates have the 550's but i like the added vacuum port on the 557 .

    Don't worry it shouldnt take you too long to get used to them.

  5. #5
    Join Date
    Sep 2012
    Location
    London, England
    Posts
    24
    one thing im not happy with though. The rubber probe caps on the side of the gauges. They are held on by a thin piece of rubber and one has already snapped off and ive only used the gauges a few times.

  6. #6
    Join Date
    May 2011
    Location
    Western, KY
    Posts
    2,900
    Quote Originally Posted by hvacguy99 View Post
    I got my new Testo 557's today. Kind of excited to hook them up to a unit.
    Anyone have any do's or don'ts?
    Use them on your personal unit first so you fully understand all the features before you get in the field and get confused with a customer hawking over your shoulder.

  7. #7
    Join Date
    Sep 2012
    Location
    London, England
    Posts
    24
    anyone had problem with these testo gauges leaking? done couple pressure tests over last 2 days and found pressure drops very slowly. Not sure as yet if its the gauges but im kind of suspecting them.

  8. #8
    Join Date
    May 2011
    Location
    Western, KY
    Posts
    2,900
    Quote Originally Posted by kadafi View Post
    anyone had problem with these testo gauges leaking? done couple pressure tests over last 2 days and found pressure drops very slowly. Not sure as yet if its the gauges but im kind of suspecting them.
    Digital gauges show leaks much faster and shows smaller leaks due to resolution. First pressure test and soap your gauges and hoses at home to make sure they are tight. Then in the field if your joints are good check any other schrader cores or screwed together fittings. I've found 3 leaking schraders in the last week because my gauges could show .25psi per 4 minutes leak rate. On analogs that would have been 1/2 a psi in 10 minutes and you would not have seen it and called it good.

  9. #9
    Join Date
    May 2011
    Location
    Western, KY
    Posts
    2,900
    Oh and another thing, make sure your braze joints have completely cooled, hot pipes will show a pressure drop as they cool, similarly if you start a pressure test on a cloudy morning and the sun and heat pick up it can cause a pressure increase as the copper warns.

  10. #10
    Join Date
    Sep 2012
    Location
    London, England
    Posts
    24
    Cheers. I pressure tested a trimco serve over fridge, left 350 psi in it for nearly 3 hours and it had dropped 4 psi. It continued to drop 0.1psi very slowly. Obviously at this rate i could not hear anything and nothing showed on a bubble leak test. I guess there must be a leak on it somewhere but ive not been able to find anything.

  11. #11
    Join Date
    May 2011
    Location
    Western, KY
    Posts
    2,900
    350psi sounds like a really high pressure test, what does it do at 150psi, might be a small enough leak rate to ignore.

    Do the service valves back seat or do they have schraders? Might be worth changing schraders and retightening any flare fittings with either oil on the threads and mating surfaces or nylog, just don't overtighten and crack the copper. With leaks that slow I usually look somewhere other than welds.

  12. #12
    Join Date
    Sep 2012
    Location
    London, England
    Posts
    24
    I could not really notice a drop at 150 so i put it up to 250. It dropped about 0.5psi so i put it up to 350 to help find the leak but with no joy. The system has no flared joints and i very much doubt it will be on a braze with a drop that slow. Im guessing if the system is losing refrigerant its more than likely on the high side?

    Yes I could try changing the schrader.

  13. #13
    Join Date
    May 2011
    Location
    Western, KY
    Posts
    2,900
    Quote Originally Posted by kadafi View Post
    I could not really notice a drop at 150 so i put it up to 250. It dropped about 0.5psi so i put it up to 350 to help find the leak but with no joy. The system has no flared joints and i very much doubt it will be on a braze with a drop that slow. Im guessing if the system is losing refrigerant its more than likely on the high side?

    Yes I could try changing the schrader.
    That sounds tight to me but I don't typically work with critically charged systems. If I hold 150 without any drop at all for 15 minutes I call it good, I then double check by using a micron gauge on the vacuum and isolating the micron gauge on the system and checking for rise.

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