How many discos required?

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How many discos required?

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e57

e57

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Location
San Francisco, CA
I have this odd bird foreign job AC unit - as pictured below. It has a RTU with a disco on the roof... The evaporators - two of them are fed from here - and provide power to the units inside the building - both are in dropped cielings and not within sight of the disconnect.

Are disconnecting means required at each inside unit?
(Since they do not get the branch circuit directly - but through the RTU)

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Done many of these, condenser has to have a disco within site, and each evap has to have disco within site, so in you diagram, I would say 3, that disconnects all ungrounded conductors to each unit.

Keep in mind that many of these has a third conductor that is a control circuit, and depending upon the manufacture, that control conductor has 120 volts on it to ground when calling for cooling, so it needs to land on the disco also, I use a 30 or 20 amp 3-pole toggle switch for the ones I've done.

If they have protection for the feeds to the evap, I have seen were only a 12/3 was required and even in one case only a 14/3 where it was protected by a 15 amp breaker at the condenser, I have also seen where they can be fed from either end with just 120 volts, at 20 amps.
 
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430.102 is applicable for the evaporator units so each needs a disconnect in addition to the RTU disconnect.
 
Devils advocate here:

Now - what if I said (for instance) the fan units (an assembly of sensors and a few relays - with fans inside a housing attached.) did not have to have a disconnecting means - because the relays and sensors did not require one - AND the fans INSIDE them were cord and plug connected. ;) (They have little factory plug in connections inside to remove each fan individually.) And say those were the disconnecting means for the fans....

Would you buy that?

IMO it's a stretch...
 
e57 said:
Devils advocate here:

Now - what if I said (for instance) the fan units (an assembly of sensors and a few relays - with fans inside a housing attached.) did not have to have a disconnecting means - because the relays and sensors did not require one - AND the fans INSIDE them were cord and plug connected. ;) (They have little factory plug in connections inside to remove each fan individually.) And say those were the disconnecting means for the fans....

Would you buy that?

IMO it's a stretch...
Click to expand...

Nope I wouldn't buy that as you can still have power to the relays and sensors even when the fans are unplugged.

I voted for disconnects required.
 
Out of curiosity, what do the manufacturers instructions say?

In all non-NEC countries, there are no additional disconnects required, but under the NEC it insists on a disco within sight. This may be contrary to the manufacturers instructions, which, of course, form part of the listing of the plant...
 
dbuckley said:
Out of curiosity, what do the manufacturers instructions say?

In all non-NEC countries, there are no additional disconnects required, but under the NEC it insists on a disco within sight. This may be contrary to the manufacturers instructions, which, of course, form part of the listing of the plant...
Click to expand...
This is a Samsung unit/s _ it's just there on the job.... Piped and ducted - Rare for the HAVC guys to leave documents around - I can't even find it on-line... (The one below is about as close as I can get... But the one I have to deal with has two inside units.)


The indoor unit is powered from the outdoor unit via the connection cord.​
Remove the screw on the electrical component box and remove the cover
plate.​
1​
Route the connection cord through the side of the indoor unit and connect
the cable to terminals; refer to the figure below.​
2​
Route the other end of the cable to the outdoor unit through the ceiling &
the hole on the wall.​
3​
Reassemble the electrical component box cover, carefully tightening the​
screw.
Click to expand...
Pretty vague :roll: But shows no disco's in between them.

Ref:(See page 15-16 & again at 43-45)


Oh BTW - one Sunday I watched 'This Old House' put one of these in - also no disco inside... Not that I trust the opinions of TOH.... :roll:

Anyway - the reason I ask... This thing is snugged up in a TIGHT dropped cieling (as if they wrapped it in rock - can just barely wire it via a dental mirror and a lite.) - hardly anyplace to put a disco, HAVC guy couldn't be bothered, GC not interested in making room, and the district EI is well a little lazy... He won't look... And too many are getting complacent with that... BUT - if his boss shows (the District Senior Inspector) damn sure he will....
 
If you remove a few tiles, the unit is now within sight, you can't work on it without removing tiles, so , IMO no local disco required, the panel within sight would suffice.



EDIT: I read the op wrong, I thought he said in a dropped ceiling and in sight, but NO.

A disconnect is required
 
e57 said:
Devils advocate here:

Now - what if I said (for instance) the fan units (an assembly of sensors and a few relays - with fans inside a housing attached.) did not have to have a disconnecting means - because the relays and sensors did not require one - AND the fans INSIDE them were cord and plug connected. ;) (They have little factory plug in connections inside to remove each fan individually.) And say those were the disconnecting means for the fans....

Would you buy that?

IMO it's a stretch...
Click to expand...

If you went back to just the fans, the factory plugs might not be much of a stretch, but, taking 430.108 and 430.109 into account it wuld still be "No".
With the realys and sensors there 430.102(a) would also make it necessary to add a disconnect.
 
nhfire77 said:
How about a DP motor rated switch? Fairly small.
Click to expand...
Nearly had to wire the unit with a dental mirror... The access is great for the refridgerant piping connections that still need to be made up - but the access to the terminations are in though that - and found out the 'framer' who put the short section of duct in, and the framing with the access - screwed the access cover to the terminations shut by screwing to the unit willy nilly. Had to pry it open, then fold it over to get in.

As for the disco - it may have to be a cut-in box in the ceiling - no room to get a 1900 with a cover in there behind the 'access' panel.... :roll:
 
I checked no, meaning that no other disconnect is required. However, I was assuming that the roof top was a knife style disconnect capable of being locked out. If this is the case, you're not required to add another disconnect.
 
paul said:
I checked no, meaning that no other disconnect is required. However, I was assuming that the roof top was a knife style disconnect capable of being locked out. If this is the case, you're not required to add another disconnect.
Click to expand...

perhaps where you are, but here, lockable would not count unless you complied with 430.102(B)(2) exception
 
paul said:
The exception allows you to install a lockable disconnect. That's what I said in my previous post.
Click to expand...

More precisely:
Exception to (1) and (2): The disconnecting means for the motor shall not be required under either condition (a) or condition (b), provided the controller disconnecting means required in accordance with 430.102(A) is individually capable of being locked in the open position. The provision for locking or adding a lock to the controller disconnecting means shall be installed on or at the switch or circuit breaker used as the disconnecting means and shall remain in place with or without the lock installed.
(a) Where such a location of the disconnecting means for the motor is impracticable or introduces additional or increased hazards to persons or property
(b) In industrial installations, with written safety procedures, where conditions of maintenance and supervision ensure that only qualified persons service the equipment

I will admit that there is a possibility that the OPs situation falls under "b", but from the info given, it is doubtful.
Unless condition "a" or "b" exists, the lockable disconnect is not relevant.
 
augie47 said:
More precisely:
Exception to (1) and (2): The disconnecting means for the motor shall not be required under either condition (a) or condition (b), provided the controller disconnecting means required in accordance with 430.102(A) is individually capable of being locked in the open position. The provision for locking or adding a lock to the controller disconnecting means shall be installed on or at the switch or circuit breaker used as the disconnecting means and shall remain in place with or without the lock installed.
(a) Where such a location of the disconnecting means for the motor is impracticable or introduces additional or increased hazards to persons or property
(b) In industrial installations, with written safety procedures, where conditions of maintenance and supervision ensure that only qualified persons service the equipment

I will admit that there is a possibility that the OPs situation falls under "b", but from the info given, it is doubtful.
Unless condition "a" or "b" exists, the lockable disconnect is not relevant.[/QUOTE



I agree with Augie, I've never seen an inspector allow a SFD to fall under "b"
Click to expand...
 
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