a/c condenser

[westelectric]

I have an a/c condenser 3phase 208v with a fused disco. Hvac repairman told the building to replace the fuses because they dont look to good, whatever that means. I went to look at it and felt that they need more than new fuses. They need a new disco and new emt that actually connects to the sealtight not almost connects to it. So my question is do I have to put a fused disco or can I just put an exterior saftey sw. since its outside. The conductors ARE fused at the main panel. Also min. cir. amp is 89a and max fuse is 125a. #6's feeding disco and #8's load side in sealtight whip is what they have there now.

 

[peter d]

Also min. cir. amp is 89a and max fuse is 125a. #6's feeding disco and #8's load side in sealtight whip is what they have there now.

You have some trouble on your hands.

 

[augie47]

suprised things have not deteriorated beyond "not looking good". Your #6 is at least two sizes too small (depending on termination ratings). A more direct answer to your question, howver, if the protection at the main panel mets the criteria specified on the nameplate, then a properly sized non-fuse disconnect would be o.k. at the unit

 

[infinity]

You need to increase the conductor size to a minimum of 89 amps. 90-125 amp fuses at the panel would be code compliant. You would still need a means of disconnect at the unit. That could be unfused if you so choose.

 

[westelectric]

thanks but a little help sizing the conductors properly please.

 

[quogueelectric]

They got a good price on the original install.

 

[infinity]

thanks but a little help sizing the conductors properly please.

The conductors need to be sized according to the MCA on the nameplate. Since you said 89 amps you would need to choose a conductor from table 310.16 good for at least 89 amps.

 

[peter d]

They got a good price on the original install.

Maybe the cow did it?

 

[westelectric]

The conductors need to be sized according to the MCA on the nameplate. Since you said 89 amps you would need to choose a conductor from table 310.16 good for at least 89 amps.

Thanks Rob. Here we go again with "But it worked for all this time"

 

[LarryFine]

Thanks Rob. Here we go again with "But it worked for all this time"

Yeah, and with a built-in soft-start.

 

[noonan]

Yeah, and with a built-in soft-start.

Good one!!

 

[splinetto]

What is the benefit of a fused disco? Something to do with the wires feeding the disc? branch ckt/ feeders?

 

[augie47]

If you were to read Bussmann's literature or that of any fuse manfacturer, they will list advantages (in their eyes, of course).
Some equipment is "listed" using fuse protection only.
My experience has been that in many commercial HVAC applications, the exact nature (size & fuse vs breaker) of the protection is not clear until the units are installed...often after preliminary wiring & gear. The use of a fusible diaconnect makes it easy to provide the proper protection quickly when the "heat is on" to finish the job. Fuses are oft time quicker to obtain than an "off size" breaker.