Minimum current ampacity

[jim dungar]

Unless you are controlling the outdoor temperature and the supply voltage during your testing, no matter how hard you try you are not forcing the worst case operating conditions that the MCA has to account for.

Also don't forget to make the measurements during a brownout voltage condition.

 

[kwired]

Also don't forget to make the measurements during a brownout voltage condition.

They take brownout voltage conditions into rating?

I thought they mostly are rated for 208-240 volts and that a brownout voltage of say 165 is going to result in higher than normal current on any induction type motor and unless it is demanding pretty low torque at the time is likely going to result in motor overload protection doing what it was supposed to do.

 

[jim dungar]

They take brownout voltage conditions into rating?

If you are trying to find 'worst case'
A motor anf VFD have +/- voltage tolerances. Do you know which conditions are used by the manufacturer in order to determine machine nameplate values?

 

[AC\DC]

If you are trying to find 'worst case'
A motor anf VFD have +/- voltage tolerances. Do you know which conditions are used by the manufacturer in order to determine machine nameplate values?

Do we go off worst case scenarios or they go off normal operations
If you go off, worst case scenarios then there’s endless possibilities you could add. There’s gotta be a point when you say enough it’s enough. I was under the assumption. It was normal operations of course I’m not an engineer. I’m just a moron that install stuffs

Though for some of these Hvac guys, the engineers for Mitsubishi I’ve talked to I’d almost class myself as an engineer, then cause some of them are dumb as rocks
Or maybe they’re just technicians that are labeled engineers , our power company does that hire someone off the street and slap engineer on them

 

[jim dungar]

There’s gotta be a point when you say enough it’s enough.

Yep, enough is enough.
Why not just use the nameplate amps and stop trying to reengineer everything. This way any eventual replacement device can be compared to the original and its wiring, without someone trying to figure out what assumptions you made.

 

[winnie]

IMHO in this case the 'worst case' we are discussing is the maximum current drawn at the worst extreme of normal operation. Note: this is my assumption/guess.

So the lowest still in tolerance voltage, not a random brownout voltage, and the worst combination of rated outdoor temperature, indoor temperature, and required BTU/hr.

 

[AC\DC]

Yep, enough is enough.
Why not just use the nameplate amps and stop trying to reengineer everything. This way any eventual replacement device can be compared to the original and its wiring, without someone trying to figure out what assumptions you made.

lol- now you sound like an inspector that just wants it done cause that the way it always has been—- I am swapping it out so lay off- it’s still wrong in my opinion and a couple other guys hear think the same. so what’s wrong with that
Majority ruled- so I must follow the mob

Winnie point of 208- 240 makes a great point—- so it’s either sized to high for 240 or to low for 208 but the numbers not the same

 

[jim dungar]

it’s still wrong in my opinion and a couple other guys hear think the same. so what’s wrong with that
Majority ruled- so I must follow the mob

So what is the mob's opinion?
I believe you can put in whatever minimum size OCPD you want. The MCA is about the conductors.

My point was the nameplate values are what they are, there is no point trying to justify them.

 

[AC\DC]

- 440 states how you can find what they gave you if you do the math— all I was saying is I bet they just through a number out such as I would for a 100 amp service and just put in 200 just cause it’s the norm around here-

I did not say I was going to do the math and fight it I just wanted to do it and I bet it’s lower by alot

 

[AC\DC]

So what is the mob's opinion?
I believe you can put in whatever minimum size OCPD you want. The MCA is about the conductors.

My point was the nameplate values are what they are, there is no point trying to justify them.

And mob rules was cause most said I am wrong so I caved some said I was right but majority aka the mob- ruled and I was wrong- you know that is how most thing are that why.