Just another electrical question

outinthetalgrass · Oct 26, 2016

Background:
Putting up a 30' flagpole. In process of digging 4 foot round by 4 foot deep footing for it. I have an 8' ground rod to drive in below the footing and will run "bare copper wire up through the concrete and rebar to the anchor bolts so it will be grounded.

I am not going to bring power out to the pole at this time, but I want to plan for the future. I want install a 1" conduit from the top of the concrete down 24" to a sweeping 90 degree turn and out the house side of the concrete footing and cap it off for future power.

Now for the question. When I run the power does it have to be single wires, or can I run 8/3 w ground underground cable through the conduit? I have read that underground cable can't be put in conduit, that single wires have to be used if using conduit.
Same question for the other end when it comes up along the house, can I use conduit to protect it.
The codes are confusing me.
Thanks.

JerryK · Oct 26, 2016

I have not taken a code class in years, but you can run undergound cable for short distances in conduit... I think under 10 feet you should be OK, you have to protect the cable as it surfaces...

Inspector507 · Oct 26, 2016

According to the latest National Electrical Code there is no restriction on putting it in conduit all the way.

topbuilder · Oct 27, 2016

8/3? What are you powering?

LD1 · Oct 27, 2016

Seems like an extremely huge footer for a flag pole, and never heard of anyone driving a ground rod at one before? Whats the point of that? And what 240v light/appliance/fixture are you powering at this flagpole?

TemporaryKubotaOwnerMark · Oct 27, 2016

LD1 said:
Seems like an extremely huge footer for a flag pole,

Seems like massive overkill. That's almost two yards of concrete for a 30' pole. Massive overkill. So is the ground rod.

outinthetalgrass · Oct 27, 2016

LD1 said:
Seems like an extremely huge footer for a flag pole, and never heard of anyone driving a ground rod at one before? Whats the point of that? And what 240v light/appliance/fixture are you powering at this flagpole?

Well, as my grandpa said, better to overdo than under do it. Yes big footing but I'm sure it isn't going anywhere anytime soon. No matter what I tie to it.
As go the power issue, planning for lots of power needs in the future, maybe a sub panel ( besides lightning it's another reason for ground rod) I would like to hope that in the next 5 - 10 years (if swmbo allows) I can build up my 2 acres of front yard into one heck of animated Christmas light show.
I tend to over build I know that, but oh well.

Redlands Okie · Oct 27, 2016

Not a electrician by trade but done a LOT of concrete work. Telephone system back up power units concrete pads for instance. The pads for a back up generators that we have done have ground rods set in place UNDER the slab. The ground wire to the panels was protected from the concrete due to corrosion. There was a couple more ground wires from the panel that was attached to the rebar mat in the pad. I was told they were after as close to zero ohm reading for ground as they could get due to some type of switching equipment that was part of the project. The concrete attracts moisture and and is usually moist under the slab. The ground rods into the ground was about 10 feet long, i am use to seeing around 6 ft long for homes. Everything was copper, except for the rebar mat.

Cord · Oct 29, 2016

outinthetalgrass said:
Background:
Putting up a 30' flagpole. In process of digging 4 foot round by 4 foot deep footing for it. I have an 8' ground rod to drive in below the footing and will run "bare copper wire up through the concrete and rebar to the anchor bolts so it will be grounded.

I am not going to bring power out to the pole at this time, but I want to plan for the future. I want install a 1" conduit from the top of the concrete down 24" to a sweeping 90 degree turn and out the house side of the concrete footing and cap it off for future power.

Now for the question. When I run the power does it have to be single wires, or can I run 8/3 w ground underground cable through the conduit? I have read that underground cable can't be put in conduit, that single wires have to be used if using conduit.
Same question for the other end when it comes up along the house, can I use conduit to protect it.
The codes are confusing me.
Thanks.

Your design sounds pretty much spot on. I like the ground rod because it'll help ground a lighting strike and reduce the chance of current back feeding to the house. I too wonder why such a heavy wire? Must be quite the run to the flag pole. Honestly, if you just want a light and use a LED lamp you won't have more than a single amp. Even using 12g, you can get a several hundred foot run before the voltage drop becomes excessive. Lights are less sensitive to voltage drop than motors ago ir'a OK to exceed 3% drop for a lighting only circuit.

If the wires are 24" or deeper, they don't need to be in conduit. PUtting them in pipe let's you set them shallower, I believe at 18". However, where the wires turn up they need to be protected so the proposed 90 conduit is correct. Just be sure to deburr the end of the elbow so it doesn't damage the wire jacket when it's pulled through. A little time with a round file will work or you can glue a metallic box adapter on.

Cord · Oct 29, 2016

outinthetalgrass said:
Background:
Putting up a 30' flagpole. In process of digging 4 foot round by 4 foot deep footing for it. I have an 8' ground rod to drive in below the footing and will run "bare copper wire up through the concrete and rebar to the anchor bolts so it will be grounded.

I am not going to bring power out to the pole at this time, but I want to plan for the future. I want install a 1" conduit from the top of the concrete down 24" to a sweeping 90 degree turn and out the house side of the concrete footing and cap it off for future power.

Now for the question. When I run the power does it have to be single wires, or can I run 8/3 w ground underground cable through the conduit? I have read that underground cable can't be put in conduit, that single wires have to be used if using conduit.
Same question for the other end when it comes up along the house, can I use conduit to protect it.
The codes are confusing me.
Thanks.

Your design sounds pretty much spot on. I like the ground rod because it'll help ground a lighting strike and reduce the chance of current back feeding to the house. I too wonder why such a heavy wire? Must be quite the run to the flag pole. Honestly, if you just want a light and use a LED lamp you won't have more than a single amp. Even using 12g, you can get a several hundred foot run before the voltage drop becomes excessive. Lights are less sensitive to voltage drop than motors ago ir'a OK to exceed 3% drop for a lighting only circuit.

If the wires are 24" or deeper, they don't need to be in conduit. PUtting them in pipe let's you set them shallower, I believe at 18". However, where the wires turn up they need to be protected so the proposed 90 conduit is correct. Just be sure to deburr the end of the elbow so it doesn't damage the wire jacket when it's pulled through. A little time with a round file will work or you can glue a metallic box adapter on.

Cord · Oct 29, 2016

Now I see that you are trying to design for a future light show. The idea of setting a panel out there is a good one for distribution purposes, however, the panel needs to be 36" above ground. Very unsightly. Instead of a permanent install, I'd suggest using temporary equipment which is mobile. Being a seasonal display this would be appropriate and then the rules start to relax.

EddieWalker · Oct 29, 2016

I disagree with some of the others on the footing. At 30 feet, with a flat, during a severe storm, you will have a lot of force pulling at that pole. Assuming that you are using a pole designed for flags, and not just a pipe of some kind, I wonder if you are deep enough? If it was me, I think deeper and not as wide would be a lot better. Just a 12 inch hole 6 feet deep would give you more strength, and 8 foot deep would be even better.

I have several street lights that are cemented into the ground over three feet deep from my 12 inch auger that sway in the wind. They are twelve feet in the air and made from 4 inch galvanized pipe.

Of course, before doing anything, I would contact the flag pole company and do what they say. If they say four foot deep by four foot square, then that wold be the best thing to do.

Redlands Okie · Oct 29, 2016

A rule of thumb often seen with such items as telephone poles or light poles is that they are placeded at 10% of the length of the pole plus 2 feet. So the 30 ft pole would be at least 5 feet deep.

JerryK · Oct 29, 2016

Depends on how big of a flag, too... I have put in several with about a 3' by 12" wide hole with about a 3' dia cement pad around it to help with mowing. Poles about 25' high and 3' by 5' flag.... no problems in many, many, many years...

TemporaryKubotaOwnerMark · Oct 29, 2016

Redlands Okie said:
A rule of thumb often seen with such items as telephone poles or light poles is that they are placeded at 10% of the length of the pole plus 2 feet. So the 30 ft pole would be at least 5 feet deep.

Not when you have such a massive diameter footing in relation to the pole. No need to go deeper with all that concrete in place.

On the other hand, an 18" hole 5 feet deep with a 4' diameter pad (say, 6" deep) would actually be better and take FAR less concrete.

EddieWalker · Oct 30, 2016

TemporaryKubotaOwnerMark said:
Not when you have such a massive diameter footing in relation to the pole. No need to go deeper with all that concrete in place.

On the other hand, an 18" hole 5 feet deep with a 4' diameter pad (say, 6" deep) would actually be better and take FAR less concrete.

I disagree. You are focusing all the stress of the pole on 18 inches. While the amount of concrete might be sufficient to hold a 30 foot pole in the air, the amount of surface area of the pole in contact with the concrete, or side walls of a hole needs to be sufficient to withstand the forces applied to the end of the pole farthest away.

A 30 foot pole is over 3 stories high including the roof!!!! That's a lot of height, and a lot of leverage.

JerryK · Oct 30, 2016

All the stress on the poles is at the point the pipe exits the concrete... There is not much stress on the pole, say 1' into the concrete... I put my poles in with two 4" channel cemented into the concrete, with the pole sandwiched in between these two pieces bolted thru with stainless bolts. That way I can lower them to paint/fix rope/etc. All you need concrete wise in enough mass stuck into the ground deep enough that the soil will keep it from shifting. Depending on pole height, size of flag, etc... with a proper pad around it so you can zoom by with your ZTR.

TemporaryKubotaOwnerMark · Oct 30, 2016

150' steel monopolies and electrical transmission towers are mounted with NONE of the pole in contact with the concrete. They bore a hole just a bit bigger than the diameter of the base of the pole, and a rebar cage is set in place and concrete poured on that. The tops of some of the vertical rebar pieces are threaded, and after curing, nuts are run down on the threads. The pole is set on those nuts (which are carefully leveled first) and then more nuts go on top of the pole base.

Scaled up to 150' from 30', the equivalent of 18" would be 5 * 1.5', or 7.5 feet, which is about what those monster poles have. But they have FAR more weight and loading on them than any 30' flagpole ever will.

EddieWalker · Oct 31, 2016

TemporaryKubotaOwnerMark said:
150' steel monopolies and electrical transmission towers are mounted with NONE of the pole in contact with the concrete. They bore a hole just a bit bigger than the diameter of the base of the pole, and a rebar cage is set in place and concrete poured on that. The tops of some of the vertical rebar pieces are threaded, and after curing, nuts are run down on the threads. The pole is set on those nuts (which are carefully leveled first) and then more nuts go on top of the pole base.

Scaled up to 150' from 30', the equivalent of 18" would be 5 * 1.5', or 7.5 feet, which is about what those monster poles have. But they have FAR more weight and loading on them than any 30' flagpole ever will.

But how deep do the bore that hole into the ground?

TemporaryKubotaOwnerMark · Oct 31, 2016

Same 10% of pole height, in normal conditions. Of course, really sandy soil, bedrock, lots of variables can change that.

I saw one that was on sand that went down basically forever. Very loose. Not good. They poured something like a 20x20 slab about 8 feet thick. This was for a big monopole, but I don't remember the height. The point is, soil conditions mean a lot.