Fan Cooled Transformer's

[steve66]

Good pictures Roger!! (And some people say we're not nice enough )

Bob & Larry:

I guess its a good thing the engineer didn't specify 3 parallel sets of cable as the primary feeder. It would be a real PITA to try and split that third wire in half!!

I240.8 allows parallel circuit breakers where they are factory assembled in parallel and listed as a unit. 310 doesn't say parallel sets have to land on the same device, but it does say they have to be electrically connected at both ends. I am starting to think these are two separate feeders, but then the OCP at the source would be too large??

Steve

 

[sandsnow]

Good pictures Roger!! (And some people say we're not nice enough )

Bob & Larry:

I guess its a good thing the engineer didn't specify 3 parallel sets of cable as the primary feeder. It would be a real PITA to try and split that third wire in half!!

I240.8 allows parallel circuit breakers where they are factory assembled in parallel and listed as a unit. 310 doesn't say parallel sets have to land on the same device, but it does say they have to be electrically connected at both ends. I am starting to think these are two separate feeders, but then the OCP at the source would be too large??

Steve

The plans very well could call for 3 sets of conductors. I'd like to know GE and UL answer to that. I assume this is a listed XFMR.

these are not C/B's but molded case switches. So 240.8 would not apply. Isn't this section for installs such as UPS bypass set ups??

310.4 - has the words ...electrically joined at both ends to form a single conductor. I don't see how this is accomplished using two molded case switches.

 

[bonding jumper]

I found out a while ago that GE is producing and maybe replacing some of its transformers with fan cooled transformers. Has anyone installed these on a project? And what is everyone's comfort level on using these?

Your replies are greatly appreciated.

Meh, its hard to get sexy with a transformer but if you are into that kind of stuff, the fans are a way to go. When you get to larger transformers, the fans will allow you to purchase a 2500kVA and have it fully rated at 3000kVA by just installing fans

 

[don_resqcapt19]

When you get to larger transformers, the fans will allow you to purchase a 2500kVA and have it fully rated at 3000kVA by just installing fans

But remember that the transformer heat is costing you money. You are paying for the kwh required to make that heat. If you are going to be operating in the "fan rated" area of the transformer, you may be better off installing a more efficient transformer that doesn't need the fans and has a lower rated temperature rise.
Don

 

[kc8dxx]

I can understand why OEM's put fans inside these transformer cases. Rising costs of copper have driven large KVA/MVA transformer prices thru the roof. I have seen them rise over 2x what they were within 2 years. It can be difficult in a competitive situation, unless the customer puts a no-fan stipulation in the bid package, to win with the fully rated transformer. Sign of the times. :-(

 

[bonding jumper]

But with any type of a redundant system, where you require nameplate data that is greater than 50% of your loads, the fan option is great because you don't typically operate within that fan over rated area. This is evident in say, double ended switchgear with main tie main configurations and a transformer on each end.

 

[necnotevenclose]

But remember that the transformer heat is costing you money. You are paying for the kwh required to make that heat. If you are going to be operating in the "fan rated" area of the transformer, you may be better off installing a more efficient transformer that doesn't need the fans and has a lower rated temperature rise.
Don

That is very interesting so not only are you paying for the additional kwh but you also need to cool the room based on what the transformer would be rated at without the fans. Larger HVAC unit = more $$$$.

 

[RayS]

I'm guessing this "gift" of cooling fans is really a way (cheesy, IMHO) to reduce the copper (or aluminum) required to build. There are now higher I2R losses, more heat load to the building, and gotta be less life.

 

[iwire]

Update

Update

More info and pictures can be found here

 

[necnotevenclose]

More info and pictures can be found here

Great pics iwire and thanks for the update! Also just a few questions:

1. Was this installed in a existing facility?
2. I noticed gutters on the sides of the transformers. Is that typical installation for transfromers?
3. Since you have had experiance installing this type of transformer is it fessiable to feed this transformer from the bottom? (I have to ask)
4. What are your thoughts using/specifying this type of transformer?


Again thank you!

 

[iwire]

1. Was this installed in a existing facility?

Yes they are increasing their available optional standby power.

2. I noticed gutters on the sides of the transformers. Is that typical installation for transfromers?

No I would not say so, I was forced to do this for the secondary side as I could not fit four 4" raceways into the side.

It was just as easy to do the same thing on the primary side.

3. Since you have had experiance installing this type of transformer is it fessiable to feed this transformer from the bottom? (I have to ask)

Yes and it could worked very well if I had good cut sheets on the transformer. There is an area along the front edge that I could have fit all my conduits.

4. What are your thoughts using/specifying this type of transformer?

If I was writing the specs I would add a 'no fans' clause.

Of course I do not know what the costs of that specification would be.

 

[petersonra]

People make decisions based on many different factors. Ease of installation is not always a primary factor nor is service life.

We have a customer who usually tells us how big the equipment can be and we are expected to shoehorn it into the available space. Most of the time the available space is not really conducive to an easy to maintain arrangement, but they do not care about that, because foot print is so critical to them.

In this case, I would not be surprised if the fans were on some kind of thermostat so they only run when needed. It is entirely possible the fan will run only a few days a year. They may well last indefinitely. most transformers are only fully loaded for short periods of time. It seems to me that a fan cooled transformer makes a lot sense in that type of case. Why pay a lot for the extra capacity you only use a few days a year?

 

[iwire]

Bob there is a lot of truth to what you said.

However GE did not tell us and we did not ask for a smaller foot print.

Most definitely there are some installations that do not have space for full size equipment and having an option for a smaller foot print would be handy.

I can tell you the customers electrical engineer was not impressed with the fan cooling, I believe he is adding a no fan clause in his future specs.

The fans are thermostatically controlled and it so happens that this transformer will be 'live' only 1/2 hour per week plus any time the utility is down.

The transformer is connected to the output of a standby generator.

So in this particular case the fans should last a long, long time.

Still not impressed, they sell these from 75 to 1000 KVA, the last place I would want to see one is on a 75 KVA.