rookie4now
Senior Member
Why do transformers have a marking that says "Keep all wires below this line?" The only thing I can think of is heat, but if you came in high and routed the wires properly it doesn't seem like that should matter.
Routing wires on transformer
- Thread starter rookie4now
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I can't recall that warning being included on any transformers that I have sold over the years.
- Location
- Massachusetts
You must not have sold any dry type transformers between 30 and 300 kva because the vast majority have that label.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I have seen those labels many times. I'm guessing that it depends on the manufacturer. Some transformers are designed so that the conductor must terminate at the top so it's anyone's guess as to why some have those stickers.
- Location
- Massachusetts
I don't know, and I have wired some that required top entry of the conductors.
I recall wayyyy back reading some manufacturer instructions that referenced heat with the instructions to keep the cables below a certain point, but, as noted, some are top wired.
I have not checked but I wonder if "Temp. Rise" values between transformers makes a difference
I have not checked but I wonder if "Temp. Rise" values between transformers makes a difference
rookie4now
Senior Member
Hmmm, looks like I'll be calling FP today. I'll post their response.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
The location of the lugs on the coils is probably not that much of an issue.
But, distrupting/affecting air flow above and around the coils may be a big deal.
But, distrupting/affecting air flow above and around the coils may be a big deal.
rookie4now
Senior Member
I called FP today. They said that the reason the make that "recomendation" is that by entering down low there is less liklihood that the wires will be routed such that they will come in contact with the coils. Since she used the word recomendation, I asked if it was a recomendation or a requirement and didn't get a clear yes or no. It seems to me that as long as that sticker says "keep all wires bleow this arrow" that an inspector could and maybe should fail the installation if your wires are above the arrows.
Interesting. I worked for Westinghouse as well as another dry type transformer manufacturer that manufactured transformers from the ventilated baby ones of 30kva up to 10mva and during my tenure with either manufacturer there was no signage such as the one described and to be an issue. I have transformers on the island of Guam, Saudi Arabia, Trinidad, Australia, and in many of the US states so I've sold a transformer or two, 2ph-3ph, 3ph-2ph, 3ph-1ph, in all sorts of enclosures. I even have a couple of transformers on an oil rig on the east coast of Africa and had one customer who wanted a 1500kva core and coil only designed such that it could be installed in a nitrogen filled TENV enclosure that they would be fabricating themselves which I had shipped to Australia.
Yes, I've have my share of transformers and No, since entering this industry in 1982 I have never recall such signage on a transformer and it has never been brought up as being an issue. There have have been some markings that directed the installer to enter and exit the enclosure in certain areas however for structural reasons such as obstructions.
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I see It all the time on 30 - 150kva delta/wye transformers. It's no wonder I learn something new every day. I take it for granted they will have such a label inside them.
- Location
- Illinois
- Occupation
- retired electrician
I just installed a 30kva where the conductor entry had to be near the bottom (per the instructions) but the terminations were all near the top. I guess the heat only causes a problem where the conductors are close together as they would be at the point of entry.
- Location
- Massachusetts
No disrespect intended but how many of these have you had your eyeballs inside of?
We install tons of transformers of different brands and the overwellming majority will have stickers inside that say things like 'No field entry above this point' or 'Conductors must remain below'. Etc.
Same here. I will admit that I have seen some without a line but that is the exception not the norm.
Roger
Good point. Thanks.
The OP as well as others referred to the assumption that heat was the problem which it has never been to my knowledge. Any signage that I have seen has always been for mechanical reasons that the manufacturer directed the installer to make their entry into the enclosure in certain areas and regarded the signage as something that I hadn't given a second thought to. I may have misunderstood the direction of this series of posts as to be regarding heat.
It was extremely important for me to nail down the way that the installer planned to enter an exit a transformer enclosure so that I could assure that there would be as few installation difficulties as possible. I have always tried to foresee installation issues for the installer if at all possible.
It would be interesting to find out if there were installation instances where the installer found it would be more convenient or necessary to make their cable entry and exit above or below those designated points. Or is it an assurance that it really doesn't matter to installer where to make their entry and exit but to keep them out of trouble be directing them to the areas above or below the areas as designated by the signage.
I guess that I never really thought it to be an issue for the installer other than their curiosity. What is strange is that I have never entertained a question regarding such signage in over 20 years in the industry with 3 of those years working directly in sales and applications in a manufaturing plant where I saw transformers assembled every day and just took it for granted.
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