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  1. #1
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
    Posts
    1,462

    REVIEW: Testo 550 Digital Gauges

    Review: Testo 550 Digital Gauges

    This is my third installment in my DRSA reviews. I've been a fan and supporter of Testo products for a long time. I purchased my first set of digital gauges about 6-7 years back, the 2nd generation Testo 523. I had some issue with those but I enjoyed the setup and accuracy. So, when Testo introduced the 550 series - I was very excited. I purchased the 550 about 2 years ago. Being that I've had these for 2 years, I have a little more experience with this DRSA than with some of the others that I've reviewed.

    When I opened up the box inside was a hard carrying case, the gauge/manifold apparatus, two pipe scissor clamps, and a instruction manual.

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    In removing them from the protective case, I first noticed the small compact size of the gauge/manifold. It is small compact and completely rubber encased. The small compact size allows the gauges to be hung or placed in numerous places when checking and servicing a refrigerant issue.

    I really like the hard plastic carry case. The case is built strong and sturdy. I know, if some of you guys are like me - I won't leave them in the case. I will hang them up in the back of the van for easy access. But it sure is nice to have the option of putting them in the heavy duty case.

    Turning on the unit, it has a smaller display than some of the other DRSA. But not smaller than a set of analogs. It comes equipped with a bright white backlight. On the top line, it displays pressures. On the second smaller line, it displays pipe temp, sat temp, or SH/SC. You will have to toggle the up and down arrows to scroll through the second line displays. The controls are very intuitive but some features require a little reading in the manual.

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    It has hose parks that swivel. So you can park your hoses in the front or in the back. Also, it comes equipped with a hanging hook. This is different than the usual manifold hook. It is thicker and can swivel up and down along with 360 degrees around. This hook has been an issue with the 550's. They break right at ball point. I'm currently on the my third hook. After the second one, I ordered 2 extra hooks and I will swap them out myself if they fail again. Testo did offer to upgrade the hook to the thicker hook like is found on the 557 and 570 but I would have to send them in and be without for a couple weeks.

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    Testo uses sealed proprietary thermistors for their pipe temp sensors. This provides much more accuracy than "K" type sensors which are subject to stray induced/EMI voltages. The two sensors plug into each corresponding side of the unit. This is one of my dislikes. They simply push in and do wiggle loose easily. Plus, you need to have the sensors hooked up prior to powering up the unit. If powered up without the sensors attached, it won't display any temps even if the sensors get plugged in after a power up. You have to cycle the power and then they will show up.

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    The pipe clamps jaw opening isn't very large. It looks like it will fit 1 1/8" pipe max. They do offer an additional Velcro strap that fit a pipe as large as 75mm (which equals almost 3"). One concern that I have is the way the wire is routed in the clamp. It kinda just hangs out there and looks like it has a high potential to get caught on something. I've also noticed that after some use, the metal sensor in the boot of the clamp likes to try to slide out of the grove. Not a big deal, just have to adjust the metal sensor every so often. Reaction time for the clamps is fast. It adjusts to any temperature changes quite nicely.

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    The 550's are equipped with a 580 psia low pressure transducer and a 780 psia high side transducer. Accuracy is +/- .75. This makes them fairly accurate but not the best on the market. Testo also recommends clearing hoses of refrigerant and zeroing out the gauge before each use. Sounds like a little bit of overkill but that's their suggestions.

    The 550's have several modes. The snowflake mode which should be used for cooling and will calculate SH/SC conventionally. The flame is for heat pump and eliminates the need to swap hoses and probes and will calculate SH/SC reversed. The auto mode is when the snowflake and flame appear at the top of the display. In this mode, the 550 will automatically calculate superheat for the side with the lowest pressure and calculate subcooling for the side with the highest pressure. Speaking with the Testo rep, he suggested keeping it in the auto mode.

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    The gauges also come with a pressure drop test mode. When entering this mode, a delta P is displayed on the screen. It can performed two ways. Using the gauge only or using the gauge and OD temp probe (extra accessory). This is meant to be a longer timed test (from 1 hr to 24hr). During this test, the 550 measures intial pressure and temp and compensates for changes in pressure due to temperature. This feature can be very useful for leak checking newly installed systems.

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    Overall, a good solid accurate instrument. I've been a fan of Testo products and will continue to do so. They create accurate and useful instruments. I agree that some Testo tools may not be very durable but if you treat this instrument with just a little bit of care - I believe it will last a long time. Like I stated above, I've had these for two years and the only mishap was the hanging hook, which Testo's customer service took care of in a timely manner.

    I created a list of good and bad features below.

    Good.
    1. Pipe clamp accuracy
    2. Hard carrying case
    3. Pressure drop test
    4. Bright backlight
    5. Compact size

    Bad.
    1. Small display
    2. Pipe clamp construction
    3. Hanging hook


    Once again, the good outweighs the bad. These are great accurate set of digital gauges. The 550's are more of an entry level option where as the 570 are more advanced. These gauges offer features that no DRSA can provide. I hope this helps someone in the market for a digital refrigerant system analyzer (DRSA) aka Digital gauges. Keep a look out next week for the review of the Testo 570 then many more tools in the weeks to come.

    Thanks,

    Brent A. Ridley

    [Sorry for pictures being sideways. If someone knows how to flip them, let me know]

  2. #2
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Wow, someone who's first experience with Testo DRSA's was a 2nd gen 523, and you were actually willing to give them another shot?
    I think that if the fist generation 523 hadn't shown me that Testo was capable of making a really good, reliable, DRSA, I'd have never given the 550 a 2nd look after the experience I, and many others, had with the unreliability of the 2nd gen 523.

    I'm not sure I'll ever really trust the temperature clamps though, as they have told me things that were not true way to many times...

    I do appreciate how compact the 550 is, especially after a few uses of the SMAN3 I won 2 weeks ago, that thing is ginormous relative to the 550!
    The ones I got back under warranty, after the display died from a fall off the top of a refrigerant cylinder, seem to be holding up well, but I do treat them a little more gingerly than I do either of my Digi-Cool manifolds.
    I have the original problematic hanging hook on mine, but it hasn't broken yet. I don't hang them in my truck by it, or put much stress on it when I hang them on a unit.

    FYI, the temperature compensated pressure test mode works just fine using one of the clamp probes, no special air probe required.
    If more government is the answer, then it's a really stupid question.

  3. #3
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    6,848
    Thanks for the review, you do a great job describing each instrument with no bias. I enjoy reading the reviews, keep it up.

  4. #4
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
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    Mark,

    For the pressure test mode, I was going by what was stated in the manual. But thanks for the additional info, I will try that!

  5. #5
    Why do you feel the display is small?

  6. #6
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
    Posts
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    Compared to the SMAN's and DC's, the display is smaller.

  7. #7
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Quote Originally Posted by Brent Ridley View Post
    Mark,

    For the pressure test mode, I was going by what was stated in the manual. But thanks for the additional info, I will try that!
    Well, they are in the business of selling instruments, and the probes for them.

    Looking at Testo's probe prices for various instruments, I sometimes wonder if in some cases the instrument itself isn't a loss leader to get you to buy probes, where they make their real money....
    435 anyone?
    If more government is the answer, then it's a really stupid question.

  8. #8
    Join Date
    Apr 2009
    Posts
    70
    Thanks Brent for another fantastic review. They are very detailed and in depth. I'm curious off all the digital gauges which one you like the best?

  9. #9
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,073
    Thanks Brent.

    My 550 is now a paper weight, first it stopped reading temp on the high side, then it stopped reading pressure on the hi side. Also has a broken hook. Due to the multiple issues with these, I just cut my losses and now use a different set.

  10. #10
    Join Date
    Aug 2009
    Location
    Maine
    Posts
    3,252
    Great review. I am looking forward to the one on the 570.
    BTW Although the hard case is a great idea, it doesn't play nice with the black hoses.

  11. #11
    Quote Originally Posted by lytning View Post
    Great review. I am looking forward to the one on the 570.
    BTW Although the hard case is a great idea, it doesn't play nice with the black hoses.
    If you have the the 570 case the hoses fit with no difficulty.

    Testo provided mine to me gratis when I had a small problem with my 557.

    (They over-nighted it and my 557 to me no charge. Great customer service.)

    Just have to wind the hoses round the provided space for them.

  12. #12
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
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    Standard hoses will fit into the 550 hard case also. You just curl them up around the outside edge.

  13. #13
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
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    Mark,

    Yes, I came back to Testo after the 523's. I didn't have near the problems that others had with this model. I had to send them in once for an issue w/the high side knob but I still have the 523's and they're fully functional.

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