Complex Service Entrance Mast in RMC

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jkcowboy

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Background: I am upgrading service on a residential canal home built on cinder block colums with all walls considered break away (i.e don't mount anything on or over the walls). The new service will replace the old on the same colum. The mounting surface is 12" inset off the vertical wall run to the roof were the mast will penetrate and rise an additional three feet to the weather head.

Problem 1: If I use 2" RMC from the Meter box to the Roof I am faced with the need for an offset exactly 12" in the run. I can find no listed fitting to make this turn. 45 degree galvanized plumbing fittings would physically do it, have the strength, and I'm sure conduct just fine. Is this allowed? If not, what is the correct way to get this bend. None of the hardward stores or electrical supply stores nearboy will bend the 10 foot lengths to custom dimensions. There has to be an easy way.

Problem 2: If I chose to put a 2" RMC mast at the roofline joined to PVC. I am still having problems locating a listed joint, making the precise 12" bend and now am also faced with how you bond the "floating" RMC at the top. I don't see any common methods or attempts at bonding this section in a few examples of other's work where... they inserted 1.5" PVC into the RMC with no fitting and did not bond the RMC at all.

This is an unusual project and would appreciate any suggestions from the group. Thanks in advance.

Additional Info: 2/0 Cu wiring, Run crosses the street so I have to go through the roof to get the required vertical height, no other good place for the meter box or exterior load center, 18" vertical from meterbox to the wall ledge (12" horizontal) then a 10' run along wall to roof line then another 3' to weather head.

Current plan: have custom 2" RMC nipples manufactured for use with two plumbing 45 degree elbows.

John King
 
John,

Welcome to the forum. First of all you cannot use plumbing fittings for an electrical raceway. Did you measure two RMC 45 degree elbows coupled together to see what the offset would end up being?
 
Trevor, The NEC states that all service raceway components (and I'm sure all others as well) have to be listed so I expected that response. But... it still leaves me with the problem of how to get this done correctly. For your question, a 17.5" nipple inserted between the two plumbing 45 elbows would make the 12 inch horizontal move to wall surface.
 
You need to get two RMC 45 degree elbows and couple them together. Now measure your offset. If less than 12" you'll need to buy a nipple to insert between the elbows. The nipple length should be 1.41 X the additional depth of the offset needed.
 
Trevor, I think I might see an answer in your last response. Is there such a thing as a listed RMC 45 elbow? None of the electrical supply stores (3) in my area had one and each wanted to sell RMC sweeps which don't make the precise offset that I need. I also looked on the web for any company that made RMC elbows. After following maybe 50 links with no results, I came to the forum, looked for old questions, found none and posted the question.
 
jkcowboy said:
Is there such a thing as a listed RMC 45 elbow?
Click to expand...

I would assume so, I would even expect to find a 22 if I asked.

I can get both a 45 and 22 for EMT off the shelf.

Heck, I can get 5 (Five) degree 4" PVC couplings.

You need to find the large supply house that normally supplies RMC to the small supply houses.

Or find a friendly electrical contractor that can bend the pipe up for a six pack.....any large commercial jobs going on around you?
 
Bob, I totally agree on EMT and PVC. I thought the same about RMC until I started looking for a 45 elbow. So far I haven't found any elbow for RMC, only sweeps. Oh, and as a sidenote... The local Lowes stopped threading 2" RMC because they said it is thinner than plumbing galvanized and broke their machine. That is a new one for me.
 
All, thanks for the websites links. I went to each and found what they call elbows are what I call sweeps. The problem with the 2" sweeps is that the offset is not 12" (for the selectable radius') and that the stub height is about 30" (for two) which would put the meter box around my belly and the load center on the ground. Are there any true elbows (think PVC type 45 and 90 elbows) for threaded metal raceway? Perhaps there is a common thread here that I'm missing.
 
Celtic, Standing the box out would be so much easier but probably not feasible in this instance (looks and the type of home). I enjoy working on old houses but sometimes the problems that look easy to solve at first get a bit bigger as the day goes on.
 
Why don't you just connect two 45* sweeps together, and roll them to the left or right to "shorten" the total makeup to a 12" offset? (I call this a "rolling offset", but I'm not sure if that's what other people call it or not.)
 
You could always try to bend it yourself. Look for a tree with a stout fork in the trunk. Use it like a hickey bender. If you try this, better have a few sticks of conduit because the first couple/three will look like crap.
 
Marc, The rolling offset works great except that the cumulative stub height for 2" pipe is about 30 inches. Since the box is located on a colum, using a sweep is very difficult in that it lowers the mounting location of both the meter box and load center too low. Specifically the meter box will be below the 5 foot specification (pwr company) and the 200 A exterior load center will be on the ground. Being a canal home, flooding is likely and on the ground is bad.
 
If you can't get two 45* sweeps to be "short" enough (30" of room above the can), it's unlikely that you'd be able to bend anything much more compact. You're faced with the (ugly) option of connecting two LB's and rolling that assembly to one side or the other. This sure is a weird service, isn't it?
 
Here's a couple of offsets in service masts from my album. Neither of these are my work. I take pics of work I want to make fun of. This won't help you, but it is on topic.

HPIM0543.jpg

HPIM0542.jpg
 
Marc, you hit that one on the head. There aren't many houses that do not have a smooth wall to run on. The existing installation is run in 1 " pipe with a small can and smaller load center. They bent the pipe for the offset. Upgrading to 200A and 2" pipe may create a problem for which there is no easy solution. There just isn't much room to work with here. That is the only reason I was looking at any way of making a hard 45. Which would work and then... just barely satisfactorily. Still thinking.
 
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