Any experience with heat pump control board degradation in high humidity environments?

Discussion in 'General Electronics Chat' started by VERYBASIC, May 12, 2016.

  1. VERYBASIC

    Thread Starter New Member

    May 12, 2016
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    Hello,

    Will be installing and starting up various energy infrastructure equipment offgrid in the Peruvian jungle, next week, May 21. It has occurred to me that all three types of equipment utilize printed circuit boards to operate. I am wondering what potential corrosion to expect considering this equipment will not be installed in conditioned space.

    During the rainy season (November through May), the actual relative humidity averages 75-100% RH!!!

    What can we do to avoid the potential train wreck?

    Sincerely,
    verybasic
     
  2. MrSoftware

    Active Member

    Oct 29, 2013
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    Sounds like S. Florida in the summer. ;) Depending on the heat dissipation requirements, you might be able to apply a conformal coating to the boards. Dip them in something to seal them.
     
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  3. VERYBASIC

    Thread Starter New Member

    May 12, 2016
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    Thank you, I will look into this.
     
  4. #12

    Expert

    Nov 30, 2010
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    Here in Florida, I use 5 coats of Krylon Clear, but it only lasts about 4 years. Pretty feeble, but it's better than the, "nothing" provided by the manufacturers. I think you need something better. I think tcmtech recommended a Rustoleum brand of clear spray paint.

    Your first consideration is to evaluate the coating (if any) provided by the manufacturer. Then realize that, after all your connections have been made, you can coat the boards and connections with any of several products. Then you must be equipped to clean off the coating during repairs and renew the coating after finishing the repairs. This stuff called, "conformal coating" seems the right way to do it, but I can't name one. If I had some, I would apply it rather thickly.

    Hoping somebody can name a good product which can be cleaned off for repairs and re-applied after.

    While we're at it, I routinely take all new equipment apart and add pipe insulation which should have been provided by the manufacturer, and oil all motors to avoid losing bearings which were not properly lubricated during manufacture.
     
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  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That is what I use, you can get a solvent if you ever have to repair them.
    You can buy it by the 1/2 Litre can.
    The other is Glyptal available from Electrical suppliers.
    http://www.glyptal.com/Glyptal_Product_Data_Sheets.htm
    Max.
     
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  6. VERYBASIC

    Thread Starter New Member

    May 12, 2016
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    Thank you, #12! Makes sense. Unfortunately, we will have to try applying the Krylon acrylic clear in the field!
    5 coats for Florida probably translates to 10 for the Amazon jungle in Peru!
     
  7. #12

    Expert

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    Well, it dries rather quickly, so it doesn't take all day to put several coats on.
     
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  8. tcmtech

    Well-Known Member

    Nov 4, 2013
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    I use the heavier duty Rustoleum clear coat and so far that stuff has shown it holds up really well. I have a few tings that have been in harsh environments for at least 10 years now and the circuit boards are so grimy you can hardly identify any single component by shape and they still work just fine. :cool:

    As with #12 I put it on heavy though.

    The next step up from that would be a commercial grade two part epoxy clear coat paint/sealer like what is used on vehicle paint jobs.
     
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  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    One thing to look out for if covering them or dipping in coating is if they have PCCT relays and the vents have been opened, you could seal them up again or worse.;)
    Max.
     
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  10. VERYBASIC

    Thread Starter New Member

    May 12, 2016
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    Can the coatings be applied with a brush?
    Because this will have to be applied in the field, I may have to try to seal each CB in clear plastic bags.

    My colleague from Germany thought epoxy would work the best, also.

     
  11. VERYBASIC

    Thread Starter New Member

    May 12, 2016
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    Yes they do have vented relays, so think I am going to try to make thick mil plastic bags work.
    Thank you for alerting me about that.
    Found out way too late in the game, that this application for the control board is below the max temp of 104 F, but the max allowable RH is 78% and the actual annual average is close 100%!!
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Yes possible.
    Max.
     
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  13. Sensacell

    Well-Known Member

    Jun 19, 2012
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    ... and for goodness sake- don't coat the pins of the connectors, you will cause all kinds of havoc.
     
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  14. #12

    Expert

    Nov 30, 2010
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    Could you clarify your idea of, "pins"?
    Heat pumps generally don't have delicate connectors. All the chips are soldered (no sockets) and the connectors to the outside world are usually 0.25" spade connectors or screw clamps. If something like a plastic multi-connector is used, I would hope the TS has enough sense not to paint the inside of a connector.
     
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  15. Sensacell

    Well-Known Member

    Jun 19, 2012
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    Never seen a heat-pump controller.

    Just wanted to point out an obvious peril of coating any kind of PCB with conformal coatings without considering this.
    I could see somebody spray painting a board without considering the IO connections, then having a nightmare of a time getting to work again.
     
  16. #12

    Expert

    Nov 30, 2010
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    That's why I said this in post #4:
     
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  17. Sensacell

    Well-Known Member

    Jun 19, 2012
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    Are you suggesting that the boards should be sprayed / coated while IO connectors are in place?

    I was imagining that one would remove the board, mask the connectors, then coat it.
    Is seems like a ton of work in either case, not much fun.
     
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  18. #12

    Expert

    Nov 30, 2010
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    How can I say this any more clearly?
    After the spade connectors and screw clamps have achieved cold weld by being assembled, you can coat them.
     
  19. VERYBASIC

    Thread Starter New Member

    May 12, 2016
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    Yes, of course. Thank you!
     
  20. VERYBASIC

    Thread Starter New Member

    May 12, 2016
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    We will protect all the removable I/O ribbon connectors from being coated.

    I was aware of the need to protect those connections, but always good in collaborative discussions to touch all the bases. The retired EE who is taking us down to Peru, explained last night in a conference call, that in the past he has used non conductive petroleum jelly as a moisture protective coating.

    It was also verified by a team member who has lived down there (in the jungle side of Peru) for 12 years, that the average relative humidity is 98+%!!!!
     
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