Substation cooling

[m2e]

Hi,

I'm doing a substation ventilation design, which is not the kind of building I've dealt with so I'll need some help.

The building is about 23ft x 40ft x 10ft high. The sensible load is about 23MBH. I'm ignoring latent load because normally there's nobody inside. The outside design temperature is 84F and 44%RH. Assuming solar load is small enough in comparison, or make it 25MBH total, would you use ventilation only or refrigeration?

If I choose ventilation only:
Setting the indoor design temperature at 95F, it would require 2100 cfm to cool it. This air flow would be around 14ACH.
What kind of system would you use? Ducted or propeller wall fan?

Thanks so much.

 

[cdxx139]

Caution: IS the 84 the outdoor temp per code? With a substation, I wouldnt just use the code outdoor temp, but use ASHRAE 0.4% Monthly design bulb worst case. For northeast US, that would be 95 F(8 degrees higher than code).

If the room is allowed to get up to 104 degrees, youll get almost the same answer (9 deg delta T vs 11 degree).

I like to go fan when I can, but on the other hand it is only a 2-ton load. Can you do both? First step of cooling is outdoor air, second stage is DX cooling?

If you go with the fan, propeller may be cheaper, but I always like to go inline centrifugal. Give me more leeway, if/when something changes.



knowledge is power

 

[KiwiMace]

What type of equipment is in the substation?

I've used Bard through the wall units with some success on similar buildings with vfd's which needed a lower cap than 10deg over ambient. Also can be maintained without entry, and vandalized too.

Some switchgear have electronic controls. Find out the operating range for the gear you have.

 

[cry22]

Sub-station should be cooled.
You can use a ventilation system for winter operation and it will be a stand-by to your AC system.
And don't be cheap on ACH for such a space, what difference does it make to you to have 5,000 CFM instead of 2100? the cost increase is minimal and you don't know what these guys will throw in there as equipment.