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Protection of power supply

How to protect power supply against applying reverse voltage?


  • kcopp
    kcopp Member Posts: 3,990
    As in power surge? On the boilers that have circuit boards I install a surge suppressor where it plugs in....
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    It was not practical to install a surge protector where my boiler plugs in because it does not plug in; it is wired in. I had a whole-house surge protector installed in my main distribution panel. Stuff like my computers, stereo, etc., do get supplementary power strips or UPS boxes.
  • Harold
    Harold Member Posts: 249
    I believe the question was protecting against reverse voltage.

    But if you really mean that, you need to provide some additional information of what your wiring looks like and why you would need to prevent "reverse voltage".
  • Leonard
    Leonard Member Posts: 903
    edited January 2019
    Your question needs some clarification.

    Odd question , most power supplies use 120VAC ( that is a sine wave so polarity of hot and neutral switch 60 times a second ( 60 hz)

    Other power supplys run on DC........ Do you want to protect your power supply from wrong DC polarity power going INTO it ( on it's input) .

    OR do you really mean you want to protect a DC LOAD from reverse polarity that a power supply might provide
  • hvacfreak2
    hvacfreak2 Member Posts: 500
    I can't think of better protection than the 400 series ICM ( within common folk price range ).


    Mechanical Enthusiast

    Burnham MST 396 , 60 oz gauge , Tigerloop , Firomatic Check Valve , Mcdonnell Miller 67 lwco , Danfoss RA2k TRV's

    Easyio FG20 Controller

  • mayurilahane
    mayurilahane Member Posts: 2
    Thank you for this guidance
  • PerryHolzman
    PerryHolzman Member Posts: 234
    I consider surge protection a necessary add to any home boiler (and many other things).

    The problem is that the small low cost ones are based on electroic devices that loose life every surge they see... and are often dead in 5-10 years; and they do not tell you that they can no longer protect against any surge (must less a large one).

    Transformer based surge protectors provide basic surge protection that lasts for the life of the transformer (50-100 years). Electronics can be added to make them better... and those electronics are after the transformer and never see most of the surge... and tend to last an estimated 20-30 years (and perhaps longer). Of course, tranformers are not cheap and they take some room.

    I have a hardwired "FF1-20W-120 - #002-00072" from Zero-Surge installed in my power supply wiring to my Vitodens 200 Boiler.


    Some people go for the plug in version:


    I have a variety of both the "2R" 15 W and one 20 W version (for my treadmill) scattered throughout my house.

    For me its peace of mind an knowing that my boiler will never see a surge (and given the cost of the circuit boards....).

    So above is step 1.

    Another possibility is to get a pure sine wave output double conversion uninterruptible power supply. This first converts all incoming voltage to DC, then it converts the DC to a pure sine wave output (no noise) and provides run time if the power goes out.

    In my case I acquired some used pure sine wave double conversion industrial UPS's for my house. I have 4 added battery packs for the 20W version for my boiler - which should provide a range of 2 days to almost a week or added run time in the event of a power outage depending on the condition of the batteries.

    I have found that the batteries need to be changed every 4-5 years. They are due again this year before heating season as the internal monitoring system tells me that the batteries are degrading (I'm not so worried this summer).

    Hope that helps,

  • mattmia2
    mattmia2 Member Posts: 5,540
    Have you tested the run time of the UPS? I found that when powering small loads off a UPS, the inefficiency of the inverter used far more power than the load itself.
  • PerryHolzman
    PerryHolzman Member Posts: 234
    edited August 2020
    Not fully, it only had to run about 1.5 days once. The battery level indicators indicated at least 50% more battery life left at that point.

    The technical literature does indicate how much power its conversion and control unit consumes. Its available storage rating is what is available with fully charged new batteries above internal usage.
  • Zman
    Zman Member Posts: 7,330
    I suspect that this post is an ad for this school https://online.crbtech.in/courses/online-electrical-design-training-course/

    I would think that wiring it correctly would solve the issue...
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein