# E-stop contactor in PVC box



## Bird dog (Oct 27, 2015)

Why not an Estop button & just break the coil ckt? The three pole contactor can sit fat, dumb & happy (protected) where it is.


----------



## hardworkingstiff (Jan 22, 2007)

Bird dog said:


> Why not an Estop button & just break the coil ckt? The three pole contactor can sit fat, dumb & happy (protected) where it is.


That is exactly what I'm doing. The question is not how to do this, the question is whether there is a problem in installing the contactor in a non metallic enclosure. I've done it in the past, but I've done a lot of things that later I found out were ...... wrong.  

In your presentation, what is the enclosure for the contactor made of, and why?


----------



## Bird dog (Oct 27, 2015)

PM MechDVR or Suncoast Power. I think they both have done Marina work.


----------



## hardworkingstiff (Jan 22, 2007)

Bird dog said:


> PM MechDVR or Suncoast Power. I think they both have done Marina work.


I must be horrible in communication. This is not about marina work (I guess I gave too much information), but are there UL or some other rules that prohibit installing a contactor in a non metallic box (because of heat generation or ...?)? 

Thanks for the tips though.


----------



## 99cents (Aug 20, 2012)

Bird dog said:


> PM MechDVR or Suncoast Power. I think they both have done Marina work.


No PM's. I want to see those two agree on something  .


----------



## Bird dog (Oct 27, 2015)

I think they could agree on electrical...maybe. :no:


----------



## MechanicalDVR (Dec 29, 2007)

hardworkingstiff said:


> I must be horrible in communication. This is not about marina work (I guess I gave too much information), but are there UL or some other rules that prohibit installing a contactor in a non metallic box (because of heat generation or ...?)?
> 
> Thanks for the tips though.


Can you put a contactor in a pvc electrical enclosure? Sure you can! 

Would I, nope. If it's going to generate any heat the pvc will end up getting dried out and brittle and crack easily. Fiberglass is fine, done that several times.

FWIW, I always ordered enclosures for this type stuff from McMaster-Carr

https://www.mcmaster.com/


----------



## Bird dog (Oct 27, 2015)

My understanding is that the coast is a harsh environment & you may want to consider a stainless steel Hoffman box.


----------



## MechanicalDVR (Dec 29, 2007)

Bird dog said:


> My understanding is that the coast is a harsh environment & you may want to consider a stainless steel Hoffman box.


Stainless is the best choice but cost can be prohibitive.


----------



## hardworkingstiff (Jan 22, 2007)

MechanicalDVR said:


> Would I, nope. If it's going to generate any heat the pvc will end up getting dried out and brittle and crack easily. Fiberglass is fine, done that several times.


Yea, that's kind of where my head was. I can't believe I let him (sales guy) talk me into that PVC box. I'll just return it next week.


----------



## hardworkingstiff (Jan 22, 2007)

MechanicalDVR said:


> Stainless is the best choice but cost can be prohibitive.


Best? IDK. Stainless steel still corrodes, just not so fast. IMO, fiberglass is better than SS in corrosive environments. 

But, there will be a couple of resi-grade panels installed in this dock house along with motor control equipment that comes in painted steel enclosures, so I don't know why I'm so concerned about what I'm supplying.,


----------



## Bird dog (Oct 27, 2015)

Because you don't want to have to come back in a year or two to address poor design issues. :thumbsup:


----------



## splatz (May 23, 2015)

I think you are right to be concerned you'd not want to mess up thermal overloads with an excessive temperature inside the enclosure or otherwise exceed the temperature rating of the equipment in the box. If you put it in an enclosure, I think you're on the hook to do the calculations and determine if heat is going to be an issue. When you do the calculations, the heat transfer of PVC is much slower than metal, like half. So you probably need double the surface area of the enclosure with PVC compared to metal, all other things being equal. You'd have to account for the current in the conductors and of course the power consumed by the coil holding the contacts.


----------



## nrp3 (Jan 24, 2009)

I'm assuming how an enclosure holds up depends upon where in the country you are? Seacoast aside, I wonder how the choice would be made in FL, vs NH. Would using a mechanically held contactor make a difference aside from cost?


----------



## telsa (May 22, 2015)

hardworkingstiff said:


> I need to install a 3-pole contactor to act as an E-Stop for a marina fuel system. The supply house suggested I install it in a PVC box (for corrosion issues, being it's out over the water, but still in a building on a floating dock).
> 
> I have concerns that there may be something not OK with this from a heat generation issue, but I don't know if I'm being over concerned, or if there are other reasons to not do this. I was thinking of a fiberglass enclosure, but he didn't have any so his salesman side came out pushing the PVC box.
> 
> ...


You should run this by the boy at Big Box Hardware.

He'll know, fur sure.


----------



## splatz (May 23, 2015)

nrp3 said:


> I'm assuming how an enclosure holds up depends upon where in the country you are? Seacoast aside, I wonder how the choice would be made in FL, vs NH. Would using a mechanically held contactor make a difference aside from cost?


Since it's an E stop you'd probably wire it to the NO contacts so that it would fail safe. 

With magnetic coil it's drawing all the time and generating heat. With mechanically held, it's only drawing when it switches, and therefore heat is diminished, but would it fail safe?


----------



## MechanicalDVR (Dec 29, 2007)

nrp3 said:


> I'm assuming how an enclosure holds up depends upon where in the country you are? Seacoast aside, I wonder how the choice would be made in FL, vs NH. Would using a mechanically held contactor make a difference aside from cost?


Environmental factors do cause a difference. I've seen pvc boxes on roofs in locations away from salt air that hold up well to sunlight. Then I have seen the same brand boxes in salt environments exposed to less sunlight due to shading and basically turn to chalky powder. 

When I read the first post here I envisioned an 18" square grey pvc box mounted in an exterior panel closet that you could see two 'melted' looking distorted spots on the cover directly in front of the two contactors inside. It made me cringe everytime i went there for a service call. The marina was in bankruptcy and only did absolute break down repairs.


----------



## nrp3 (Jan 24, 2009)

Ah the reasoning behind that (mechanical vs electrical), not just cost.


----------



## foothillselectrical (Mar 17, 2013)

Considering that it's an E-Stop circuit and not a motor control circuit, I can't see where heat would cause any issues with tripping thermals because you shouldn't need any. I didn't see a current rating on the circuit, but I have 20A 3-pole contractors mounted all over the place in 6x6x6 PVC boxes and have never had an issue. I use these for controlling ventilation and evaporative cooling systems in poultry houses and swine barns from low low voltage controllers. If box material and corrosion is a concern, why not install the contractor adjacent to the MDP, and put the E-Stop button in a PVC box at the pumps with a two wire circuit?


----------



## splatz (May 23, 2015)

foothillselectrical said:


> Considering that it's an E-Stop circuit and not a motor control circuit, I can't see where heat would cause any issues with tripping thermals because you shouldn't need any. I didn't see a current rating on the circuit, but I have 20A 3-pole contractors mounted all over the place in 6x6x6 PVC boxes and have never had an issue. I use these for controlling ventilation and evaporative cooling systems in poultry houses and swine barns from low low voltage controllers. If box material and corrosion is a concern, why not install the contractor adjacent to the MDP, and put the E-Stop button in a PVC box at the pumps with a two wire circuit?


This makes sense but the OP asks that we forget the specifics of his application and just address putting a contactor in a PVC enclosure.


----------



## foothillselectrical (Mar 17, 2013)

You're right. I musta missed that. I have them all over the place in corrosive farm environments, and have never had a service call. Some of those go back 12 - 15 years I suppose.


----------



## hardworkingstiff (Jan 22, 2007)

splatz said:


> This makes sense but the OP asks that we forget the specifics of his application and just address putting a contactor in a PVC enclosure.


I wasn't trying to be a jerk, I just am not open to changing how we are going to do this. A 3-pole contactor to break L1,L2,N feeding a sub panel that will feed the (4) fuel dispensers and (3) electric hose reels. So the continuous load is minimal (I think those dispenser pull less than 2-amps) and the hose reels will work for about 30 seconds to a minute when the hose gets rewound. The pumps will be fed out of a different panel.

The contactor will be mounted inside of a framed building on the floating dock, so a Nema 1 enclosure will actually suffice.


----------



## glen1971 (Oct 10, 2012)

If you are worried about heat, why not add a vent?
http://www.alliedelec.com/bud-industries-ipv-1115/70368863/

http://www.cooperindustries.com/con...ures/enclosure-accessories-breather-drain.pdf

I know there are a few different styles out there and have used them in the past to help get rid of any heat..

So long as the metal back plate is bonded, I wouldn't see any issues..

As was mentioned, there shouldn't be any issue of added heat affecting thermal overloads, as this is a contactor, and not a starter..


----------



## sbrn33 (Mar 15, 2007)

I would and have done this. The heat is a non issue IMO. Really the only heat generated is going to be from the coil anyway. The hard part is mounting something decent inside as there are ribs and nothing to screw to.


----------



## Cow (Jan 16, 2008)

Just my personal preference, I would rather use a fiberglass enclosure, because I know I can get them with a hinged cover and a backpanel. The pvc boxes over here wouldn't come that way. 

The small amount of heat generated is a nonissue, a contactor does not put out enough heat to even remotely consider it being a problem.

For reference, I've installed contactors in fiberglass enclosures before, we are in an area where it gets to 106 degrees. I've never seen an enclosure show any signs of being heat deformed from the equipment inside it.

I also think breaking the power to the entire sub is clean way to do it if you have several circuits you need to control.

Keep going, you're on the right track...


----------



## splatz (May 23, 2015)

sbrn33 said:


> I would and have done this. The heat is a non issue IMO. Really the only heat generated is going to be from the coil anyway. The hard part is mounting something decent inside as there are ribs and nothing to screw to.


You can buy a back plate for a lot of the enclosures, the Hoffman and Sceptre ones...

They also make DIN mount kits for some contactors, not a lot of money.


----------



## MechanicalDVR (Dec 29, 2007)

foothillselectrical said:


> Considering that it's an E-Stop circuit and not a motor control circuit, I can't see where heat would cause any issues with tripping thermals because you shouldn't need any. I didn't see a current rating on the circuit, but I have 20A 3-pole contractors mounted all over the place in 6x6x6 PVC boxes and have never had an issue. I use these for controlling ventilation and evaporative cooling systems in poultry houses and swine barns from low low voltage controllers. If box material and corrosion is a concern, why not install the contractor adjacent to the MDP, and put the E-Stop button in a PVC box at the pumps with a two wire circuit?


The ammonia in poultry houses doesn't mess with pvc?


----------



## sbrn33 (Mar 15, 2007)

splatz said:


> You can buy a back plate for a lot of the enclosures, the Hoffman and Sceptre ones...
> 
> They also make DIN mount kits for some contactors, not a lot of money.


I don't think you can for the cheap? Carlon ones they are trying to sell him. Could be wrong though.


----------



## nrp3 (Jan 24, 2009)

I don't remember much from chemistry, but i dont think ammonia is a problem with pvc. Solvents, maybe petroleum products, not sure.


----------



## splatz (May 23, 2015)

sbrn33 said:


> I don't think you can for the cheap? Carlon ones they are trying to sell him. Could be wrong though.


Well Hoffman is generally the most you can spend on whatever they're selling, although I found their fiberglass at a pretty competitive price last year. I might not be shaking the right tree for good pricing. 

Sceptre if I remember right looked like a great value but their hinged lid stuff was a few months out, I planned to try them next time it came up.


----------



## splatz (May 23, 2015)

Here is Scepter, I think this is pretty reasonable, and I think they are made in USA or Canada 

Hinged cover 8x8x4 box for $26.55 
http://www.springfieldelectric.com/index.jsp?path=product&part=2680553

Back panel $9 
https://www.springfieldelectric.com/index.jsp?path=product&part=2680565


----------



## hardworkingstiff (Jan 22, 2007)

splatz said:


> Here is Scepter, I think this is pretty reasonable, and I think they are made in USA or Canada
> 
> Hinged cover 8x8x4 box for $26.55
> http://www.springfieldelectric.com/index.jsp?path=product&part=2680553
> ...


Scepter is what I bought. The 8x8x7. Glad to see a link to that back plate though (they didn't have one), thanks!


----------



## Paulusgnome (Mar 28, 2009)

I wouldn't expect any issues from heat from a contactor causing any problems from a PVC box.
I would, however, expect problems if the PVC box was exposed to sunlight - it will get very brittle as the UV from the sunlight degrades the PVC.
I would look for a glass-reinforced polyester box, GE's APO boxes spring to mind. These soak up much UV without failing, and believe me we do get plenty of UV down here in the south Pacific.


----------



## foothillselectrical (Mar 17, 2013)

MechanicalDVR said:


> The ammonia in poultry houses doesn't mess with pvc?


I haven't had any issues. I've opened the boxes in the past when troubleshooting, and everything was as good as when I installed them. Most of the control products we buy from poultry and swine suppliers (QC Supply and Hogslat) are in PVC enclosures.


----------



## MechanicalDVR (Dec 29, 2007)

foothillselectrical said:


> I haven't had any issues. I've opened the boxes in the past when troubleshooting, and everything was as good as when I installed them. Most of the control products we buy from poultry and swine suppliers (QC Supply and Hogslat) are in PVC enclosures.


I've lived around chicken houses and smell the ammonia in the air but never been inside to look at the equipment.

I know ammonia refrigerant leaks are brutal on everything they contact but they are very acidic if I recall correctly.


----------



## inetdog (Apr 13, 2016)

Ammonia in water (even from moisture in the air) is ammonium hydroxide, and is a strong base, not an acid.
It does react strongly with many metals and leads to their eventual destruction.

mobile


----------



## splatz (May 23, 2015)

I was looking for something a little more definitive about whether the heat should be a problem, so I geeked up ... 

Lets say you're going to use a PVC box 8*8*4 and want it to stay below 120*F in there, and your outdoor temperatures get to 100*F ambient temperature, and you keep the box out of the sun. 

Surface area of 8x8x4 box
(4*4 +4*8+8*8)*2 = 224 square inches
224/144 = 1.55 square feet 

Lets say operating temperature for contactor is 120*F and maximum outdoor temperature is 100*f
120-100=20

.62 heat transfer coefficient for PVC for units in square feet, *F, and BTUs/hr 

Heat load transfer is 
.62 * 1.55 * 20 = 19 BTU/hr

19 BTU/hr 
0.29307107 watts = 1 BTU/hr 
19 * .02930717 = 5.65 watts 

For an E Stop the coil will be in continuous operation, if the coil draws 5W or less, you should be OK. Just barely. (It won't be in the sun.)


----------



## splatz (May 23, 2015)

I was thinking that's a lot to get right for just installing a contactor, so I looked at an instruction sheet out of curiosity. 

So I just picked a random small contactor from Schneider, 8910DPA42V02










... looked at the instruction sheet ...

Instruction sheet for 8910DPA42V02 

The instructions tell you 



> Use the following devices with an
> enclosure that is greater than or
> equal to the dimensions shown in
> Table 1. For additional information,
> consult the factory


see table below.

So for an 8x8x7 box, you'd be at 448 cubic inches, a little small. 

They might assume you're using a metal box, too - if it's PVC, you need about twice the surface area, so it might be the additional information you get when you "consult the factory."


----------



## hardworkingstiff (Jan 22, 2007)

FYI, the box would be installed inside a building with AC. The AC won't be run all the time, but in the summer I'm sure it would be.


----------



## Cow (Jan 16, 2008)

Damn Splatz! You went above and beyond!:thumbsup:


----------



## MechanicalDVR (Dec 29, 2007)

hardworkingstiff said:


> FYI, the box would be installed inside a building with AC. The AC won't be run all the time, but in the summer I'm sure it would be.


That makes a huge difference, originally sounded like it was going to be outside.


----------

