Transformer enclosure type for lift station 3

[james64]

Hello,

I am working on a small lift station(pumping storm) that requires a 75 kVA transformer. "Is a Transformer enclosure with a Type 2 driphood enclosure sufficient or should it be a NEMA 4 enclosure?"

 

[waross]

On a range of 1 to 10, 1 being in a below grade manhole and 10 being an elevated pole mount?

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[che12345]

I have the following opinion for your consideration.
1. Google NEMA enclosure rating. There are tones of information, including their protection characteristics. Select one that suits your application, whether indoor or out door ...etc. accordingly.
2. Attention: be aware that 75kVA transformer would generate (about) say 750W of heat when fully loaded. This heat should be ventilated with opening louvers or dissipated by the external cooling surface of the enclosure.
Note: 1. louvers lower the protection.
2. Surface cooling is dependent on the material and the emissivity (cooling surface colour finishing) etc...
Che Kuan Yau (Singapore)

 

[FacEngrPE]

Assuming your transformer is not in a part of the lift station defined as Hazardous by 820. NFPA®. Standard for Fire Protection in Wastewater Treatment and Collection Facilities, environmental protection would be selected same as regular construction.

Indoor protected driptight or perhaps NEMA 2 could be OK, Outdoor I would consider cast coil in a factory NEMA 3R enclosure or encapsulated type. Actual selection depends on more information see waross above.

Putting a 75kVA transformer in a Nema 4 enclosure is asking for overheating trouble.

 

[james64]

Thank Waross,
All equipment, including the control panel, electrical panel, and transformer, must be installed above ground level, not below grade.

Thank che12345,
Do you mean that the transformer will generate heat equivalent to approximately one percent of its capacity? Does 75kVA require a louver for ventilation? This lift station requires a typical ventilation system. I need to check with the mechanical team.

Thank FaceEngrPE,
According to code, NEMA 4x is not required for this location. I understood that NEMA 4x is typically used for outdoor applications such as wastewater and sewage facilities.

 

[FacEngrPE]

NEMA 4x is typically not often used for power transformers in exposed locations, as the effort to provide reliable cooling is too much. Better constructions are Nema 3R, or cast coil.
Some variants of cast coil transformers are suitable for application in harsh environments.

NEMA 4X is really good for panel boards and control enclosures in exposed harsh environments and have low thermal loads or temperature tolerance, but remember the panel drains and condensation heaters.

If your transformer is located inside a control house, the thermal characteristics should be included in the control house HVAC calculations. Likely the calculations will find the transformer heat load will not require more ventilation than is required for other purposes.

 

[che12345]

I have the following opinion for your consideration.
"...#1. Do you mean that the transformer will generate heat equivalent to approximately one percent of its capacity? #2. Does 75kVA require a louver for ventilation? #3. This lift station requires a typical ventilation system. I need to check with the mechanical team...".
#1. One percent is the minimum, could be more !. These losses include iron- core loss and I² R copper losses. Core loss is a constant, where copper loss is depending on the loading. Check the actual losses per the OEM data.
#2. Yes. Inlet louvers place at the front bottom and outlet louvers at the top on both sides + front and back. Natural ventilation cost nothing. Add force cooling fan controlled by thermostat if required. Keep the trafo say 2 K (=2 ^o C) above the ambient would keep it dry. Do NOT allow it to operate above the insulation class limit.
#3. Inform the mechanical team the expected heat generated by the trafo officially in advance, in order to avoid unnecessary additional/alteration ventilation openings.
Che Kuan Yau (Singapore)

 

[jghrist]

What country are you in? What is the utiity voltage? Typically, in the USA, a padmount transformer would be used outdoors which has its own enclosure.

 

[james64]

Thank che12345,
As far as I know, only Type 2 has louvers. Am I right? I will check the shop drawing.

Thank FaceEngrPE,
Will Type 2 be sufficient for a transformer installed indoors not outdoor installation. In addition, both the control panel and the electrical panel with driphood should NEMA 4X.

Thank jghrist,
The transformer will be installed inside the room in Canada. Voltage should be 600V 3 phase.

 

[che12345]

I have the following opinion for your consideration.
"...#1. As far as I know, only Type 2 has louvers. Am I right? I will check the shop drawing....#2. the transformer will be installed inside the room in Canada. Voltage should be 600V 3 phase".
#1. The enclosure to suit all your application requirements would probably not readily available on the market, over the counter. If you are NOT governed by any local regulation/code, you may design it to your need; taking NEMA rating as a guide. There are IEC IP code that are more elaborate on the enclosure design that you may refer to. BTW: Take the IEC IP code as a "reference" , do NOT demand to carry out the costly, one off design to be Type test by the NRL.
#2. For 3ph 600V, observe creepage and clearance > 100mm would be fine. Your enclosure is likely to have air clearance > 200mm all round for good natural ventilation.
Che Kuan Yau (Singapore)

 

[cranky108]

As jghrist said, here the utility would install the transformer for the capacity you need. If the local service is underground it would be a pad mount, or if it is over head, it would be a pole mount.