Transitioning couplings

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Steel coupling and PVC male adapter or just a PVC female adapter. The former is probably stronger.
 

kwired

Electron manager
Location
NE Nebraska
Take advice from the plumbers on this one. On a metal to plastic connection, always plastic male to metal female.

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But they deal with the pipe/fitting needing to contain pressure, we don't. Other stress factors are what comes to play. That said if the transition is below grade, those stresses probably are somewhat minimal other than possibly frost heave or settling if you didn't account for them when you installed it.
 

MAC702

Senior Member
Location
Clark County, NV
And there is the age old technical issue of the MA only being listed to be used with a locknut. Petty, but real.
Do you have a source for this?

They don't even come with a locknut when you buy it. And many go into a hub. Yes, I do realize not to expect listings to be accurate or make sense, but I'd still like to verify this one.
 
Do you have a source for this?

They don't even come with a locknut when you buy it. And many go into a hub. Yes, I do realize not to expect listings to be accurate or make sense, but I'd still like to verify this one.
This from carlon doesnt say locknuts only for TA's:

https://carlonsales.com/techinfo/brochures/conduit/Conduit_Fittings_Schedule_40_and_80.pdf

For adapting nonmetallic conduits to boxes, threaded fittings, metallic systems. Male threads on one end, socket end on other
Im not saying that is the last word, maybe there is something in the listing documents or product standards?
 

Cow

Senior Member
Location
Eastern Oregon
MA's are much more failure prone in my opinion, the plastic is thinner at the thread connection on an MA than on an FA. We can't have a connection fail for the sake of $1.00 part.
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
This from carlon doesnt say locknuts only for TA's:

https://carlonsales.com/techinfo/bro..._40_and_80.pdf



Im not saying that is the last word, maybe there is something in the listing documents or product standards?
You may be correct per that Carlon page. I would normally look this up on UL Product Spec but it has been retired. It is now called product IQ and needs a login which I have but have not yet looked it over enough to be proficient using it yet. It is a lot different than it used to be.
I made my comment based on the past fact that conduit connectors (such as am EMT connector) were only listed for use with locknuts. That may not be the case for a PVC MA.
 

Russs57

Senior Member
As a plumber by trade.....and assuming you are running schedule 80 PVC conduit.....I'd suggest a 6" threaded PVC nipple, cut it in half, and glued on with a coupling. I can't comment on the "code compliance" of it. They also make FA's with a metal band around the threaded side but they are a lot more money.
 

MAC702

Senior Member
Location
Clark County, NV
MA's are much more failure prone in my opinion, the plastic is thinner at the thread connection on an MA than on an FA. We can't have a connection fail for the sake of $1.00 part.
How is the MA likely to fail? I've split FA's before I learned to be careful when I use them. I can't even think of a way to make an MA fail.
 

MAC702

Senior Member
Location
Clark County, NV
...I made my comment based on the past fact that conduit connectors (such as am EMT connector) were only listed for use with locknuts. That may not be the case for a PVC MA.
Indeed, this would technically preclude PVC FAs when the metallic raceway is going to be EMT? Something I've seen, done, etc, etc. In fact, this is the method I learned as an apprentice from all the old hands.

EMT connectors typically have looser threads than threaded GRC (like in the OP), so wouldn't be nearly as big a splitting issue for FAs, either.
 

kwired

Electron manager
Location
NE Nebraska
How is the MA likely to fail? I've split FA's before I learned to be careful when I use them. I can't even think of a way to make an MA fail.
I've seen many, especially in small sizes where force from the side will shear the male threads away from the point the attach to the socket. Body of the fitting is thinner at the threads than at the socket and is the weak point. Not all female adapters are entirely alike but is possible to make heavier wall at threads than it is with a male adapter, if you want to maintain internal dimension anyway.

EMT connectors typically have looser threads than threaded GRC (like in the OP), so wouldn't be nearly as big a splitting issue for FAs, either.
EMT connectors and most other fittings have straight threads, the PVC FA probably has straight threads also. Threaded GRC has tapered threads, the more you tighten it the more outward force on the FA because of the tapered thread inserted into it.
 

Cow

Senior Member
Location
Eastern Oregon
How is the MA likely to fail? I've split FA's before I learned to be careful when I use them. I can't even think of a way to make an MA fail.

Someone installs a 90 down into a ditch but doesn't rest the conduit on the ditch bottom for one reason or another. Over time the ditch settles and the dirt puts pressure on the horizontal pvc coming off the steel 90, and the ma being thinner at the threads, cracks or breaks.

Ma's are thinner than fa's. Secondly, it takes 2 parts to use an ma, (coupling and ma), where an fa only takes one. So most of this conversation is a moot point anyway since I don't know anyone who would use two parts where one will suffice, especially when the one is superior to the two.
 

kwired

Electron manager
Location
NE Nebraska
Someone installs a 90 down into a ditch but doesn't rest the conduit on the ditch bottom for one reason or another. Over time the ditch settles and the dirt puts pressure on the horizontal pvc coming off the steel 90, and the ma being thinner at the threads, cracks or breaks.

Ma's are thinner than fa's. Secondly, it takes 2 parts to use an ma, (coupling and ma), where an fa only takes one. So most of this conversation is a moot point anyway since I don't know anyone who would use two parts where one will suffice, especially when the one is superior to the two.
I prefer to use a FA, but do not always have one handy when needed, especially sizes larger than 3/4", supply house is ~40 miles from my shop. Makeshift is cheaper than not having what you want when you need it sometimes.
 

oldsparky52

Senior Member
My FA over TA underground is from experience installing 3/4" conduit at gas stations. I've seen a TA break off (where the threads come out of the fitting body). IMO, a PVC coupling driven onto a 3/4" rigid conduit (threaded) is a stronger connection than a TA screwed into a RGS coupling.

Just my 2 cents.

BTW, is it just me or is the posting time still excessive?
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
My FA over TA underground is from experience installing 3/4" conduit at gas stations. I've seen a TA break off (where the threads come out of the fitting body). IMO, a PVC coupling driven onto a 3/4" rigid conduit (threaded) is a stronger connection than a TA screwed into a RGS coupling.

Just my 2 cents.

BTW, is it just me or is the posting time still excessive?
It must be you, mine only take 10 to 30 seconds, give or take. :D
 
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