Transformer oil - top up with regular mineral oil?
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  1. #1
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    Default Transformer oil - top up with regular mineral oil?

    Well, the UK foul weather got to my RPC's transformer, the cover blew away in a gale and I just cleared 3 gallons or so of revolting once-rain-water from the bottom of its tank. That of course displaced the same amount of Diala-B transformer oil (fun clearing that up...), I have a fair few gallons of ISO VG32, 68 and 100 straight mineral oil and as Diala-B is "uninhibited mineral oil" according to Shell's www, is there any good reason NOT to use straight mineral oil to bring it up to the right level? (It only covers about half of the transformer windings). Transformer is low voltage (240 and 415) 9 KVA, when tested before reconnecting the earth resistance was above 5 MegOhms so it appears that sitting the trans in water was tripping the RCD...

    Thanks,
    Dave H. (the other one)

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    If water has gotten into the xfmr you may have to bake it. Contact a repair shop before doing anything like putting power to it.

    Tom

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    Quote Originally Posted by TDegenhart View Post
    If water has gotten into the xfmr you may have to bake it. Contact a repair shop before doing anything like putting power to it.

    Tom
    Already done, thanks (some of us have the equipment!) - the insulation resistance went from about 3 KOhms before, 10 KOhms during clean-up (pulled from tank and dripping) to over 5 Meg back in the tank with too little oil, a combination of heat and high vacuum on both coil bobbins has pulled the moisture from it. It's now not tripping the RCD (residual current device, <30 mA imbalance between live and neutral will trip it) - RPC now runs fine, clamp meter with several turns through the yoke doesn't see any earth current but concerned that I don't want to run it without adequate cooling (only ran to about 2 kw load, 3 kVA input to be safe).

    Dave H. (the other one)

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    Fix it to not repeat...

    Sent from my SAMSUNG-SM-G930A using Tapatalk

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    I'll be building a nice little doghouse for it

    Dave H. (the other one)

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    Bump - nobody's screamed DON'T DO IT! IT'LL KILL YOU! so I'll go ahead with straight mineral oil to get it deep enough to cool the windings.

    UNLESS there's a reason not to?

    Dave H. (the other one)


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