What size wire for a humidifier feeder?

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steve66

steve66

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I need to provide power for 2 Dry-steem VLC humidifiers. One is 11.1 amps 1 phase, and the other is 14.4 amps 3 phase. The total is 25.5 amps. 125% of this is 32 amps.

I think I need 35A fuses and #10 wire, since article 424.22(D) requires the overcurrent protection and branch circuit conductors to be sized for 125% of the load. (Does this even apply to a humidifier?).

But 240.4(D) requires #8 wire for the 35A fuse. Or does 424.22 overide this?

Steve
 
Re: What size wire for a humidifier feeder?

I would think that humidifiers would fall under the category of air conditioning equipment, however, you could probably wire them in accordance to Article 422 for appliances.
 
Re: What size wire for a humidifier feeder?

S66 -

Just curosity - With one single phase feed, and one 3 phase feed required, and two separate pieces of equipment, how come you aren't using two circuits?

carl
 
Re: What size wire for a humidifier feeder?

I admit I'm not real familiar with how industrial humidifiers work, but I wouldn't think it would be considered an AC unit. I think it basically heats the water to make it evaporate. No motor or compressor.

One circuit because I think it would be cheaper to install a fusible single bus plug, and one conduit run. The two humidifiers are realitivly close together compared to the run to the bus duct. I would have them run 3 phases to the first humidifier (with its own fuses), and then just run a single phase to the next one.

I'm still not sure: can I put the #10 wire on the 35A fuses per 424.22?

Steve
 
Re: What size wire for a humidifier feeder?

Originally posted by steve66:
I need to provide power for 2 Dry-steem VLC humidifiers. One is 11.1 amps 1 phase, and the other is 14.4 amps 3 phase. The total is 25.5 amps. 125% of this is 32 amps.

I think I need 35A fuses and #10 wire, since article 424.22(D) requires the overcurrent protection and branch circuit conductors to be sized for 125% of the load. (Does this even apply to a humidifier?).

But 240.4(D) requires #8 wire for the 35A fuse. Or does 424.22 overide this?

Steve
Click to expand...
Steve will you be providing individual OCP for each unit?

I doubt a 35 amp fuse protecting the 11 amp unit would be compliant.
 
Re: What size wire for a humidifier feeder?

Posted by Iwire:

Steve will you be providing individual OCP for each unit?
Click to expand...
Yes, each humidifier has its own control panel with its own fuses.

benaround:

#8 really sounds excessive!! 50A wire for a load that will only draw 26 amps. I know 240.4(D) says #8 is required for the 35A fuse, but I still think article 424 might override that.

Steve
 
Re: What size wire for a humidifier feeder?

Originally posted by steve66:
Posted by Iwire:

Steve will you be providing individual OCP for each unit?
Click to expand...
Yes, each humidifier has its own control panel with its own fuses.
Click to expand...
Still not sure if that makes it OK.

Are these units tagged with Minimum circuit ampacity and Maximum OCP?

You have to feed it in the same way it was tested by UL.

I would use individual branch circuits.
 
Re: What size wire for a humidifier feeder?

Steve something to compare this to is HVAC equipment. Most are labeled with maximum OCP even though most times the first thing the feeder hits (on large units) is a main breaker.

Regardless of that main breaker I can not exceed the maximum OCP rating.

I looked up Dri-Steem but I can not read most of the web page as it is foreign.

Dri-Steem Humidifiers

I feel that these units would be subject to 422.11(E)

422.11(E) Single Nonmotor-Operated Appliance. If the branch circuit supplies a single non?motor-operated appliance, the rating of overcurrent protection shall

(1)Not exceed that marked on the appliance;

(2)If the overcurrent protection rating is not marked and the appliance is rated 13.3 amperes or less, not exceed 20 amperes; or

(3)If the overcurrent protection rating is not marked and the appliance is rated over 13.3 amperes, not exceed 150 percent of the appliance rated current. Where 150 percent of the appliance rating does not correspond to a standard overcurrent device ampere rating, the next higher standard rating shall be permitted.
Click to expand...
That being the case the branch circuit suppling 11 amp unit can not exceed 20 amps.

The branch circuit supplying the 14.4 amp unit can not exceed 25 amps.

Bob

[ December 01, 2004, 10:47 AM: Message edited by: iwire ]
 
Re: What size wire for a humidifier feeder?

Originally posted by steve66:
I admit I'm not real familiar with how industrial humidifiers work, but I wouldn't think it would be considered an AC unit. I think it basically heats the water to make it evaporate. No motor or compressor.Steve
Click to expand...
I'm not sure what they are either, but UL seems to consider them A/C equipment. Look here: AHIV.GuideInfo
 
Re: What size wire for a humidifier feeder?

Posted by Iwire:

Still not sure if that makes it OK.

Are these units tagged with Minimum circuit ampacity and Maximum OCP?

You have to feed it in the same way it was tested by UL
Click to expand...
I always assumed if there was overcurrent protection on the unit, that would satisfy the MOCP requirement. I just found out the single phase unit doesn't even have fuses, so I guess I will add fused disconnects at the units.

STeve
 
Re: What size wire for a humidifier feeder?

I don't understand why you would do the installation this way. I would run two seperate circuits in the same conduit. Are you concerned with derating the wire because of the 5 current carrying conductors? #12 THHN is rated for 25 AMPS and is already derated at 20 amps. You would need two disconnects either way. With my way you could use non-fused disconnects and size the breakers correctly, saving some dollars.
 
Re: What size wire for a humidifier feeder?

I second the motion! Hear Hear!

I do this all the time, it's a bad habit--overthink it. Don't over-think it. Keep it simple. I'd imagine if you tried to get sexy with it, they'll eliminate unit #1, which everything seems to need to continue on, and your wires'll be too short to make it to the second disconnect on their own, and dogs'll hump cats...

Keep it simple. Just some friendly advice... :)
 
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