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Hey everyone! Question about feeding commercial roof top equipment. Im fairly new to this so i was hoping to find some good help on here, Roof has the rubber membrane finish.

Equipment list:
MUA
RTU
Kitchen Exhaust Fan x 2
Condenser Units x 2
Service plug


Now I know I can stub pvc up with rubber cones and switch to liquid tight flex and strap to units to mount each disconnect, but I have been told its a waste of time you can feed most equipment without doing this and that you can drill down inside the unit to feed it later. And while ive seen this done on MUA's, how can I make sure I can with this particular MUA as well as other equipment.

I am suppose to prep my my stub ups before they put the membrane down so I just wondering how I can make sure I can feed the equipment after or should I just go feed everything with the pvc+rubber cone+ after liquid tight flex. Or is it that you can feed some equipment from inside after and some you cant.

If you have some pics id love to see! Thanks so much!
 

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Estwing magic
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Landlord may require that you hire a roofing guy. Most landlords I deal with have a specific company they deal with. If I got caught punching my own holes in a roof, it would be a bad day.

I normally have liquid tight whips ready underneath for when the roofing guy arrives. I’m not sure why they want stub ups prior to the membrane going down. It’s easy enough for the roofing guy to punch the hole and install the cone in one visit. I coordinate with the tin basher so all roof openings are done at the same time.
 

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If it's all new...there may be a roof warranty...usually we would use a curb and box approach instead of roof jack .Easier to seal to membrane ...Cables leave box horizontally. Roof Jacks with electrical often leak ....and then it's your problem .
 

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Get with the HVAC guy and verify placement of the stubs. Feeding them from inside the units is a royal pain. Take a 4s blank w/K.O., for power knock it out to 3/4". Take a 12" nipple, locknut, and a rigid coup. and put the blank on it. Drill your holes in the proper location and screw the blank over the hole with the coup. in the bldg. Ask the roofers if they need a metal flashing, and just drop it over the nipple no need to nail it down. Let the roofers do their thing, then you do yours. L.B.'s and seal-tite to the disco, conduit underneath.
 

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I pretwist and then use wire nuts. Solder pots rule.
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Welcome to ET

Please finish filling out your profile.


Yes I use the internal KO’s on larger rooftop units. Get the cut sheets, that will determine what you can do and what size things are.

A receptacle should be provided on the AC unit, separate feed or it may have an internal transformer to provide for one.

Once again, get the cut sheets.
 

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Old Grumpy Bastard
GOV/MIL contracting
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Welcome aboard @NfgGfi!

Please fill out your profile.

I never tell anyone to do their own roof penetrations, it isn't worth the call backs for leaks.

I agree with wirenutting, get the unit cut sheets that show electrical entrances in the base of the unit.
 

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It sounds sweet, but coming up inside the curb, feeding the units from below usually translates into a co-ordination nightmare. Yes, don't expect ANY co-operation from the HVAC dudes. It's the safe assumption to make.

I've seen HVAC clowns deliver RTU with the wrong voltage. Yes!

You want your jacks to come up diagonally -- that is, not along any face of the units. If they block access -- then you get to move them on your dime.

Membrane roofs are VERY expensive to repair. I've seen $2,000 charge-backs due to a 3 sq ft patch. I'd rather Sealtite all the around a RTU rather than punch a new hole.

Watch out for the auxiliary circuits: 20A GFCI for the HVAC dudes.
 

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Old Grumpy Bastard
GOV/MIL contracting
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It sounds sweet, but coming up inside the curb, feeding the units from below usually translates into a co-ordination nightmare. Yes, don't expect ANY co-operation from the HVAC dudes. It's the safe assumption to make.

I've seen HVAC clowns deliver RTU with the wrong voltage. Yes!

You want your jacks to come up diagonally -- that is, not along any face of the units. If they block access -- then you get to move them on your dime.

Membrane roofs are VERY expensive to repair. I've seen $2,000 charge-backs due to a 3 sq ft patch. I'd rather Sealtite all the around a RTU rather than punch a new hole.

Watch out for the auxiliary circuits: 20A GFCI for the HVAC dudes.

If I had a dime for every RTU I've wired up inside the curb after thevfact I'd have a new yacht.

Unless they leave excess metal roof deck in place they are fairly easy to get to. Some of the smaller units have sheetmetal plates on top of the curbs under the unit but you can often slide the unit to drill a hole in the blocking.
 

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MechanicalDVR;5228146[COLOR=Sienna said:
]If I had a dime for every RTU I've wired up inside the curb after thevfact I'd have a new yacht.[/COLOR]

Unless they leave excess metal roof deck in place they are fairly easy to get to. Some of the smaller units have sheetmetal plates on top of the curbs under the unit but you can often slide the unit to drill a hole in the blocking.
Yeah, but your knees would be shot.

As an experienced HVAC man, yourself, you're willing to shift units in a way I don't.

I've been burned by so many idiot HVAC contractors -- typically with troops high on something -- that hand me rotten cut-sheets// not cut sheets.

If I were to detail all of the screw-ups I've run across in RTUs over the years -- it's amazing that the boys unzip to relieve themselves.

What would you think of a NEMA1 controller ordered and delivered -- for a RTU suite?

Yeah, it was a riot.

I never found the internals of RTUs as favorable as you have.
 

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The guy above was absolutely right about the roofing guy. Landlords simply don't allow you to fix anything on the roof and sometimes it becomes really annoying. There are some basic things which you can really fix without any help, but instead of doing everything on your own you have to hire a roofing guy. The problem is that you can barely find a real professional roofer in US today. Lucky for me, I was able to find interesting information about the situation in this field that helped me find a good roofing company. You can visit here their website and read it on your own.
 

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Old Grumpy Bastard
GOV/MIL contracting
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Yeah, but your knees would be shot.

As an experienced HVAC man, yourself, you're willing to shift units in a way I don't.

I've been burned by so many idiot HVAC contractors -- typically with troops high on something -- that hand me rotten cut-sheets// not cut sheets.

If I were to detail all of the screw-ups I've run across in RTUs over the years -- it's amazing that the boys unzip to relieve themselves.

What would you think of a NEMA1 controller ordered and delivered -- for a RTU suite?

Yeah, it was a riot.

I never found the internals of RTUs as favorable as you have.
Long pilot bits, holesaw extensions, and a little ingenuity make wiring RTUs through the curb fairly easy.

I don't want to play around with any roofing myself.
 

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Elechicken!
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The guy above was absolutely right about the roofing guy. Landlords simply don't allow you to fix anything on the roof and sometimes it becomes really annoying. There are some basic things which you can really fix without any help, but instead of doing everything on your own you have to hire a roofing guy. :mad:
Welcome to the forum, Please take a few minutes to fill out your profile. It's required and only takes a few minutes to do. I have included a link below to assist you with this.

 

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Electrical contractor 37 years. Electrical inspector 2 years
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Several things to keep in mind. Do not drill out the bottom pan of any equipment. Use the internal provisions if they come with it. I worked on one unit where the EC drilled his own hole and it always leaked. For the long term, think about using rigid conduit for the stub up. They won't rust or crack. Make sure the stub ups are in the right spot. Nothing worse than having the stub up on the wrong side of the unit. Don't forget about the control wiring.
 
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