Generator feeder questions

[LarryFine]

I'll be installing a Generac 16kw genny that has a 70a output breaker. How do I know whether I can use the 90-degree columns in Table 315/316?Presuming I must use the 75-degree column, can I use #6cu or #4al and the next-breaker size allowance?

Also, can the control wires be run in the same conduit if properly voltage-insulated and jacketed, or must they be run separately?

 

[augie47]

Other than for derating purposes (ambient, fill, etc) you can not use the 90° rating.
Likely your terminations are rated at 75° so you can use that rating (110.14) unless you are using Romex (and in some cases SE) then you are limited to 60°.
IMO, you can not use the "next size up" rule as the conductor must be sized to carry the load and it is possible, although not likely, that the conductors may be fully loaded.

As far as wire mix, check your install manual. At one time Generac called for separate raceways.
If not, I believe, it is permissible if you follow the rules in Art 725.

 

[LarryFine]

Thank you, so full-size conductors, and yes, the control wires may now occupy the same raceway, as long as they're suitably insulated.

 

[augie47]

If you are under the '17 Code you might check Art 336. Tray Cable is a possibility now also (with limitations).

 

[LarryFine]

We're not, but what would be the advantage? I'll be using 1" PVC with three #4 cu for power, one #8 cu EGC, and up to five #18 cu control.

The distance from the generator to the ATS will only be 12-15 feet, all outdoors, with the ATS nippled directly beside the existing main disco.

The 4-0 al line and load conductors will share the 2" nipple, so I should only need to use the #4 neutral between the ATS and the main disco.

 

[mkgrady]

We're not, but what would be the advantage? I'll be using 1" PVC with three #4 cu for power, one #8 cu EGC, and up to five #18 cu control.

The distance from the generator to the ATS will only be 12-15 feet, all outdoors, with the ATS nippled directly beside the existing main disco.

The 4-0 al line and load conductors will share the 2" nipple, so I should only need to use the #4 neutral between the ATS and the main disco.

I think Generac calls for six control wires. Three line voltage and three 12 volt. I run #14 thhn for all six. I can’t picture what #18 line voltage wire looks like. I have seen people use thermostat wire but obviously this is no good.

 

[LarryFine]

I might need all six, but if I do, I need smaller than 14 to avoid having to use 1-1/4" PVC. #18 is good for up to 115 ft.

 

[Cow]

I might need all six, but if I do, I need smaller than 14 to avoid having to use 1-1/4" PVC. #18 is good for up to 115 ft.

There's a problem with 1.25" pvc? We don't pull #4 in anything smaller than it.

 

[LarryFine]

The problem is that I need to bore a hole through these steps and my largest solid SDS-max bit is 1.5". I will get an SDS-max extension. The plan is to come out of the generator toward the steps, use an elbow to turn alongside the steps, use an LB to go through them, and an elbow up into the bottom of the ATS, which will be nippled into the disconnect under the meter.

Side view, Gen location, Step front, ATS location

 

[JFletcher]

personally, if I had to go through that step, I would use a concrete saw to cut a notch through the step, Roto chisel out a U-shaped trough, lay in the conduit, then backfill and form-in with new concrete. Either that or core drill as far as possible, knock out the slug, repeat until through.

You know if you get that Roto Hammer bit jammed in 3 foot of concrete, you're going to have a very bad day... also, if I remember correctly, you may need up to 10 control wires two more each for a battery tender and engine block heater.

Is there no way to go through the brick to the left of the steps, behind the steps and back out? Or under the steps?

 

[LarryFine]

personally, if I had to go through that step, I would use a concrete saw to cut a notch through the step, Roto chisel out a U-shaped trough, lay in the conduit, then backfill and form-in with new concrete. Either that or core drill as far as possible, knock out the slug, repeat until through.

That sounds too much like work! I have core bits, but the deeper you bore, the harder it is to break and extract the core.

You know if you get that Roto Hammer bit jammed in 3 foot of concrete, you're going to have a very bad day... also, if I remember correctly, you may need up to 10 control wires two more each for a battery tender and engine block heater.

I have drilled through solid brick with the 1.5" x 36" bit. It doesn't get stuck. The generator maintains the battery, and is air-cooled (16kw) so no block heater needed.

Is there no way to go through the brick to the left of the steps, behind the steps and back out? Or under the steps?

The brick wall is a concrete-floored porch, so no crawl space. Under would be harder than through, in my judgement.

 

[JFletcher]

Very well then. Your plans seem solid, however I feel like I would be remiss in not pointing out any potential options that may have saved you labor, time, or aggravation.

Please post pictures of the finished product!!

 

[Cow]

Based on the width of the meter being around 12 inches, eyeballing it, I'd say you don't have the required 30" wide working clearance in front of all that equipment. Adding an ATS might open a can of worms...

 

[Dennis Alwon]

Depending on the class wiring the control wires may need to be run in a separate conduit. I know years ago Generac controls needed separate conduit.

Also drill the step with your solid bit then use the hole saw core bit

 

[kwired]

I can’t picture what #18 line voltage wire looks like.

It looks pretty much the same as 14 AWG line voltage wire just with smaller diameter. Many don't have the need to use much of it and just use 14 AWG where they could have used 16 or 18.

 

[Jamesco]

The problem is that I need to bore a hole through these steps and my largest solid SDS-max bit is 1.5". I will get an SDS-max extension. The plan is to come out of the generator toward the steps, use an elbow to turn alongside the steps, use an LB to go through them, and an elbow up into the bottom of the ATS, which will be nippled into the disconnect under the meter.

Side view, Gen location, Step front, ATS location

View attachment 19876 View attachment 19875 View attachment 19877 View attachment 19878

Are those brick pavers sitting on a sand bed? Pavers just, set, installed, on the sand bed installed against one another with loose sand filled between them?
Because of where you live, no frost footings are needed? It looks like the steps are setting on grade. Did you look at possibly removing some of the pavers, as shown in the picture showing the entire side elevation of the steps, to see if you could push a piece of 1" PVC under the steps out to the other side them?

As for the steps themselves. The methods used for forming and pouring concrete steps vary. Looking at the steps they appear to be pretty old.
In my area one of the methods that was used 30, 40, 50, ??, years ago was to mound compacted dirt inside of where the steps would be sitting. The dirt would be sloped from the top of the steps to the bottom making sure when the steps are poured there will be enough empty space for concrete at the back of each set. The sides of the mounded dirt was cut away as needed making the inside form to hold the poured concrete. The outside form(s) were then installed along with the step riser forms.
Worth noting, inside along with the dirt to hold the poured concrete in place until it set up and cured, was any type of filler laying around on the construction project. Bricks, cement block, you name it.

So where am I going with all of this? Depending on how low below the step riser of the step you will be drilling the outside of the step maybe only 6", 8", ??" thick. Great right? Yes, unless beyond that is solid filler.

Also keep in mind the thickness of the concrete step at the back of the step might only be a few inches thick.

Later years to present time the inside form was cut from a wood product plywood or OSB making the inside forms for the steps. Basically a reversed stair riser stringer. An inside filler was still/is used. Dirt, sand, busted cement block, bricks, ect.

You might want to drill a pilot hole first using a 1/2" or 3/4" bit first before trying the 1-1/2" bit. If you hit a hollow spot try pushing/hammering a piece of 3/8" rebar or 1/2" conduit into the hole and see how easily it passes through the filler.


.

 

[jap]

I was thinking that since this is an Automatic Transfer Switch that it would need to be sized for the full load so it wouldn't possibly fall on its face.

I'd have to read up on it though.

As far as getting through the step, I'd have to do the cut and re-pour myself but it looks like a tight spot to begin with.


Tough deal all the way around.

JAP>

 

[LarryFine]

Depending on the class wiring the control wires may need to be run in a separate conduit. I know years ago Generac controls needed separate conduit.

The Generac manual calls them Class 1 circuit conductors.

Also drill the step with your solid bit then use the hole saw core bit

I still don's see the advantage of the core bit here.

 

[LarryFine]

Is there no way to go through the brick to the left of the steps, behind the steps and back out? Or under the steps?

If I go through the wall behind the generator and back out after passing behind the steps, will a disconnect be required behind the generator?

 

[JFletcher]

If I go through the wall behind the generator and back out after passing behind the steps, will a disconnect be required behind the generator?

702.11... I thought the circuit breaker on the generator could serve as the disconnecting means, unless the generator is not within sight of the building. I do not remember installing or seeing any external disconnects for any of the Generacs we've installed at residences.

If I am reading and interpreting that section correctly, the generator has to be able to be seen from the building, not where its conduit penetrates into the building, to avoid a second disconnecting means at the building where the penetration is made.

Eta: upon rereading 702.11 again, I may be in error in regards to the generator breaker. However if a external disconnect for the generator is visible from the house, you would not need one on the house