The Combine Forum banner
1 - 17 of 17 Posts

·
Registered
Joined
·
1,168 Posts
Discussion Starter · #1 ·
Wanting to wire in some 3hp bin fans with underground wire. What size of wire do I need, was thinking #8. Wanting to pull 1 line up between 2 bins and run 2 fans of the 1 line.

Longest run will be 50ft from the panel.

The tags on the motors are:

PH -1
HZ-60
40C Continuous
14.9amps
230 Volts
SFA 21.0
 

·
Registered
Joined
·
3,616 Posts
Just to clarify, your intention is to run underground from a source which I assume is the transformer pole to a central location between these two grain bins. What will the length of the underground portion be as I took it to mean the 50 feet is a cord length required from the panel you will build to reach each fan ?
 

·
Registered
Joined
·
1,168 Posts
Discussion Starter · #3 ·
There is a panel with 200amp service to it already. Want to trench lines in from that panel to the bins to get rid of extension cords for the fans. Will have short 4ft cords off the fans then. The panel sits in the middle of my air bin row of 6 bins so only running 3 lines underground.
 

·
Registered
Joined
·
3,616 Posts
I've done a little bit of panel setting up and so forth for aeration fans in the past but have never split off in the way you have and if I was in your shoes I'd have some questions and possible scenarios in how I'd like to set it up directed at an electrician that understands the loads/constant loads of aeration fan motors and him tell me what makes the most sense.

Because you have the ample service supply already set up, I also assume you currently have 6 breakers running to 6 outlets OR you wired in each cord directly and have a mass pile of 6 cords laying there along the ground to each fan. If that is the case and lets say you want to run 1 underground rated 2 conductor, copper 8 gauge wire ( with ground wire in the cable ) to power up two fans, then I believe you would have to install a mini breaker box to split the power to two breakers which would then be wired to outlets for those two fans. Then back at the main breaker box ether a larger breaker would have to be installed to power up two fans or if it would meet code, to wire directly into the box bypassing the need for a breaker and the main breaker of the box ( assuming it has one ) will be the one you have to switch off to work on any portion of the system for any reason. Also I suspect an inspector would like to see a ground rod at each one of the three mini breaker boxes but again a question for someone in the know.

The other way and again not sure if this would be to code as I am only guessing, would be to in a sense mirror what you already have and run 2 separate 2 conductor cables in the same trench ( in this case possibly 10 gauge but could be 8 gauge for future fan upgrades ) to a little stand pole and each of the two cables would run to its respective outlet. So another words each of the six breakers back at the main box will power up one fan just as before only now its all underground. In this case I don't know if this might fly without the requirement of needing a ground rod at each mini tower because the breaker after all is back at the main box along with the grounds of each 6 cables just like it was when plugging into an outlet wired right at the main box.

Remember when measuring the wire length required, go from the top of the existing main box, down into the ground ( with down and then up loop for pole movement ) and then across to where the mini tower is and the same thing as it comes out of the ground. Its always a surprise as to how much more wire length it takes then first thought and that equates into voltage loss with length and so on too. If you have any inkling of putting larger fans on in the future, now is the time to put in large enough wiring so its all there ready to switch over to larger breakers and so forth with minimum hassle.

Hopefully you can follow what I meant as you can see if you are required to get three little breaker boxes and grounding each one of them, vs if its also to code going with separate cables for each outlet, double the wire underground might not seem all that bad cost and hassle wise in the end ... all questions to throw at an electrician that understands farm wiring needs and maybe he is kicking around on here !.
 

·
Registered
Joined
·
3,616 Posts
Keep in mind there are differences between free air ( over head lines ) amperage ratings for a given wire size and an underground wire of the same size and material. Also even though a given wire has a certain amperage rating, that does not mean its large enough to run a given load at a longer distance without severe voltage drop and has the ability to start the motor properly without a voltage drop so drastic that it may even cause motor damage or never get enough juice to spin up properly and the breaker that should have been sufficient isn't because it times out in a manor of speaking due to subsized wire for the job. I've seen expensive cord ends get melted simply because of undersized wire as it started the never ending chain reaction heating cycle and that can take days sometimes or just an increase in outside air temperature along with plug contacts that have some oxidization on them and good twist lock cord ends are expensive. Also have seen bluish looking overheated copper wire in the female outlet wiring or into the breaker itself all because of pushing the limits on wire size for the job, never mind the waste of power in the form of heat rejection and a fan that can't run to its full potential because of voltage loss. Not trying to step on anyones toes but just don't want to see you "9520deere" end up with less then you should expect when you are done wiring it up.
 

·
Registered
Joined
·
1,187 Posts
Hello 9520deere
You're not going to save much at all.:confused: Might cost you an extra $40.00 or $50.00 to run 100' of mnwu 10/2 (might even get away with 12/2 on a 50' run) & have each fan on it's own circuit verses running 50' of mnwu 8/2 & having both fans on 1 circuit.
 

·
Registered
Joined
·
3,616 Posts
I thought maybe there might be an electrician kicking around on here, probably is but hasn't noticed this thread. For sure I'd consult one or the supplier where you typically go to get the wire and so forth may have a licensed person on staff who has farm/commercial wiring knowledge.

If lets say for example you did go with 10 gauge two wire for all 6 fans/6 outlets, it would be a fair length you would need and some places will do better deals on spool lengths or what not ... even ordering in a specific spool length of wire.

Since I expect you won't be using teck cable, be sure to protect the wire before it reaches ground level and depending on what type of outlets/boxes you used it would make a very neat slick install by running each of the two cables up the one post in their respective PVC ( or steel conduit ) pipes and a threaded joint glued/fastened to the top of the pipe where it could enter the bottom of a weather proof aluminum outlet box and then capped off with a PVC flip up weather proof cover for instance. I'd also want to have a rain cap or mini shelter shielding over the outlets as no doubt if they are close at all to the bins the water just pours off bin roofs and having good sheltering will let the outlets stay good for many many years.
 

·
Registered
Joined
·
5 Posts
Hey 9520deere,
I am a JMan Electrician so i should be able to help you out.
I would go two runs in the trench each to a separate receptacle. Minimum according to code is 2c#12gauge with 2pole 20amp breakers, OR if you want too exceed code i would go 2C#10 with 2pole 30amp breakers.DO Not use 2C#14gauge as TSIPP has said as it does not meet canadian electrical code. Personally i would go with the second option of 2C#10 and 30amp breakers as the 20amp breaker may cause nuisance tripping during startup. Run either NMWU or TECK90 for your underground install and make sure it is mechanically protected as Northern Farmer has indicated in his recent post.
 

·
Registered
Joined
·
1,582 Posts
good thing I am not a sparky, but sometimes I do see sparks fly. the wire size calculator I used shows #16 at 50 feet and 15 amps.
Just some farm experience here but some of the best money you will ever spend is on BIGGER wire than code. What nobody is saying here is that a single phase motor draws up to seven times running amps called inrush current. Since a fan is starting under full load, and a single phase motor has to maintain high voltage to be able to charge the capacitors quickly, you need to think of what that voltage is at 16 amps x 7 = 112 amps momentarily
Otherwise your voltage drops and you will be replacing capacitors and worse. Trust me !
The suggestions here for #10 or even #8 would be my choice. What about #2 USEB I think it is called in 70% concentric neutral running to a small breaker box for 2 fans? That #2 aluminum is fairly cheap.
Another question is how long is the feed run to the 200 amp service and what is the load on that typically. It is all about maintaining voltage so the amps don't go so high.
Watts is the true measure of load and is found by volts x amps=watts. So therefore if the volts go down, esp on startup, then the amps go up to give you the true watts required.
So you see where this is going, the amp draw is 7x to start with which pulls the voltage down, which causes the amp draw to go higher and so on. There is good return on bigger wire.
Another consideration is to have some extra capacity to upsize fans or add heaters in the future. Cost would be much less to do it right the first time.
 

·
Registered
Joined
·
3,616 Posts
LOL, yup that must be it, you accidentally stumbled across the wiring chart that home owner do it yourselfers use and then wonder why insurance won't cover their burned down house :D

Here's an example of wiring that is to code and yet is inefficient in wire size to run the load properly because of voltage loss and a lot of us can relate to this scenario. Take a typical house in town, the exterior outlet that is wired with 14 gauge and a 15 amp breaker runs block heaters ok but come summer time and plug in one of the higher amperage rated electric mowers and the mower performs like crap, has no power. There are usually two problems with that picture, one is that their is a surprising amount of of voltage loss within the house from the breaker box to the outlet even though amperage wise its still safe and to code. Then to top it off I see these "townies" using what I call skipping rope for cord ... a hundred feet of 16 gauge cord and they wonder why the mower is bogging along as soon as there is any grass at all to amount to anything. Yet that 16 gauge cord will meet the maximum amperage rating of the mower motor. Ideally had a house been wired with 10 gauge to an outlet like that ( same 15 amp breaker ) and using a minimum of 12 gauge for the cord, it would perform much better.

That's why with aeration fans, always better to error on the side of larger wire and as its buried, its not so easy to change up later on if a higher HP fan was installed. I think a lot of farmers would get a surprise to know how much voltage drop they are getting to their fans because of wire distance from the transformer to a breaker box and then further underground wiring branching off from that ... then cord strung out to finally reach the fan.

I see Transaxial threw out many great comments in the time I was typing this, yes I totally agree with that whole concept of wiring heavy to reduce voltage lost as much as possible.
 

·
Registered
Joined
·
3,616 Posts
Just to add again to echo Transaxial's thoughts, "if" funding wasn't a problem then on the "good, better, best" scenario, going with number 2 aluminum and the three breaker boxes would be the ideal situation. That is, assuming that there are enough lugs within the current breaker box to accommodate direct hookup to the power bar.

Something to keep in mind when planning a wiring project, its to ensure that the wire used can physically fit into the breaker on the one end and also into the style of plug outlet used on the other end. Years ago I watched an electrician dad had hired to do some wiring in our yard for aeration take a number 2 aluminum underground cable and stuff it ... ok try to stuff it into a 40 amp breaker and finally started snipping off wires and mashing the remaining ones with plyers so that he could get it to fit. Yes, the 40 amp breaker was the limiting factor and in a safe sense it was still ok but what a mess when it came to doing wiring properly as what should have happened is that a larger splitter box was used that could accommodate larger sized breakers to begin with !.
 
1 - 17 of 17 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top