HVAC For E-House

[mbk2k3]

For a pre-fabricated e-house that has switchgear/control panels/etc, one of the items is a large 750kVA dry type transformer located inside the e-house that dissipates 7kW of heat when running at full load.

The transformer manufacturer says to provide 12" of clearance on the back of the transformer with ventilation openings in the wall to allow for air to circulate.
But if I have a dedicated HVAC unit for the room as well, wouldn't this result in outside/inside air mixing and causing unwanted moisture/condensation inside the e-house?

For reference, this E-house will be located in Canada that gets warm summers and cold winters. I'm an electrical engineer and am trying to figure out what the HVAC system should look like (e-house vendor isn't giving clear answers).

 

[LittleInch]

Two choices

1) Isolate the TX in its own room and just mechanically vent ambient air through it once the temperature reaches say 25C.

2) Include the 7kW in your cooling load and blow enough cool air to maintain 25C and ignore the outside air issue.

1) will be cheaper, but most TXs are good for outside location.

This becomes a big issue for VFDs and the HVAc load can become very high.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[GT-EGR]

Agree with littleinch

I’d also add that usually it’s a cost savings decision to go with all outside air cooling - but you end up with a hotter room, and with that comes reduced equipment life since most electrical equipment while rated to high temps last longer if you don’t push them to the limit.

Your condensation concern likely doesn’t happen since even when it’s saturated outside, once that air comes into the room it picks up the internal heat which puts it above dewpoint - but i guess it’s theoretically possible if outside air conditions quickly change some of the internal surfaces may linger below dewpoint for a short duration - but I’ve never heard this concern causing an issue in this type of space.

By putting openings to the outside you do end up bringing dirt into the space through the louvers, and potentially wind driven rain too.

All these above reasons are why a sealed room with recirculating HVAC is a much better choice for the room environment, but it comes at the upfront cost premium and also more utility cost to pay for the air conditioning equipment power consumption. Put an economizer on your AC unit and then you can somewhat get the best of both worlds.

 

[lucaspenalva]

Manufacturer requests ventilation openings (with proper filtration!) to provide cooling in case you don't have HVAC unit.

If you have HVAC unit, you'll only need a little bit of ventilation to keep positive pressure and avoid infiltration of untreated air.