Please check my math/thinking/both

[DParker76020]

I have a livestock stable situated about 100 ft from the back of my house. I've been contemplating a small, simple solar setup for it so that I can power a few A/C devices, like LED lights in the stalls and the electric milking machine I plan to get eventually. But more important is the need to power about 75 ft. of self-regulating heater cable that I'll be attaching to the plumbing that runs to and through the length off the stall, branching to a couple of automatic waterers (for my goats), in order to keep it all from freezing in Winter (I just installed the plumbing this Spring so the need did not exist previously).

I live in N. Central Texas where the winters can get surprisingly cold for equally surprisingly long periods. It occasionally dips into the low teens F and can stay below freezing for a week at a time. I have no way of knowing how often the automatic heating cable would be on during such periods, so I have to assume the worst case scenario of it being on at all times, 24/7 while the air temperature is near/below freezing, even though that's probably very pessimistic (especially since I'll also be wrapping the pipes and cable with foam insulation tubing). The cables are most all rated at 5 W per foot of length. The cable closest to my needs is 80 ft long, so I'm looking at the possibility of consuming up to 400 W of continuous power around the clock for a few days at a stretch even if I don't run any other loads. Add in the fact that the skies are commonly partially-to-completely overcast for days at a time when inclement weather moves through and I'm going to need a ridiculously large battery bank to power the heater cables for 2-3 days at a stretch (just shy of 30 kWh worth). If in reality the heating cable only ran 20% of the time during even the worst conditions, that's about 6 kWh of storage needed, which is not terrible. But if I gambled on that and lost then the price would be burst plumbing and the need to manually haul water out to some thirsty goats until the weather warms and I can make repairs...something I very much want to avoid.

At this point the cost of the battery bank required for a safety margin, even ignoring the cost of all of the other equipment, makes it seem like it would be cheaper in both the short and long term to just pay an electrician to run electricity from the house to the stable. Or am I screwing something up somewhere along the way in my thinking here?

 

[sunshine_eggo]

At this point the cost of the battery bank required for a safety margin, even ignoring the cost of all of the other equipment, makes it seem like it would be cheaper in both the short and long term to just pay an electrician to run electricity from the house to the stable. Or am I screwing something up somewhere along the way in my thinking here?

This, particularly if you do your own trenching.

Or just get an extension cord and mark it, so you don't hit it with the lawn mower.

 

[Doggydogworld]

75 feet is a lot of exposed plumbing. There's no way to bury some of that?
In general batteries suck for events that happen a few days per year. Plus you'll need to keep the batteries warm for charging.
I'd first try to bury all I could and prevent freezing in the rest with insulation and drip-flow or drain-back.
Second choice would be run wire from the house.

 

[DParker76020]

This, particularly if you do your own trenching.

Or just get an extension cord and mark it, so you don't hit it with the lawn mower.

An extension cord is OK for occasional one-off uses, but isn't a long-term solution for what I need. But other than that it sounds like you agree with my assessment. Thanks.

 

[DParker76020]

75 feet is a lot of exposed plumbing. There's no way to bury some of that?
In general batteries suck for events that happen a few days per year. Plus you'll need to keep the batteries warm for charging.
I'd first try to bury all I could and prevent freezing in the rest with insulation and drip-flow or drain-back.
Second choice would be run wire from the house.

No, burying the pipes isn't a good option...for a number of reasons. I don't think keeping the batteries warm would be a problem, since I could easily build an insulated enclosure for them and even provide a little heating if need be. And as I said, I want power out there for other uses as well, so some sort of electrical solution is called for. I was just hoping initially that the small system that would meet my other needs could also work during times of hard freeze when I wouldn't be out there using it for anything else anyway. But the math seems to have quickly killed that hope.

 

[Warpspeed]

I would just run an extension cord across the ground for one winter, and monitor the actual power required to do the job.
You will then have a much more firm basis on deciding where to go from there.

Buried would be nice, but you could also string an overhead cable.

 

[Warpspeed]

A totally different solution to this would be to fit some kind of water heater, perhaps powered by propane ? You run all your cold water pipes in a continuous loop, and fit a very small circulating pump. It would not need much as there is negligible back pressure to pump against.
The whole thing starts up when air temperature falls below freezing. The pump could be 12v dc, and only a small battery would be required.
Just about all of the required energy comes from the propane. and propane stores very well.

Your animals might appreciate the extra heat.
Even if the final solution is something completely different, this might make for a useful backup that one day you might be really glad you had.

 

[OffGridForGood]

If you have an interest in Solar - even if right now is not the right time - you can plan a complete system for the barn and house. Building the buried wire part now may be the first step, with that same wire later becoming the power feed to the house from a future solar installation (for example). It may make good sense to over-size that cable, run 3C to suit the future solar generated AC that will feed the house. For now it can power the barn with utility power and be ready for your future plans. Consider where (the house or the barn) the solar installation would be best built, then plan it out from there. (this worked well for my set up, my only complaint - should have buried bigger wire!)

 

[OffGridForGood]

Actually my advice - if you plan the solar to be at the Barn, bury twin lines now from the house to the barn, one can be used for solar from the barn to the house, and the other could be utility back up from the house to the barn. Figure every possible load that you 'could' need to calculate the wire size and then double that size to be sure ! (I did bury twin 3C lines, but I Wish I went bigger cable. yeah) It may be a good idea to bury a communication cable as well. I set up a dedicated LAN router instead, but it may have been a better idea to have some small wire buried in the same trench while that was available. If in doubt, run empty conduit pipe instead, what size? = bigger.

 

[Warpspeed]

Big fat copper cable gets expensive really fast, but large diameter plastic conduit is dirt cheap.
Just be sure to fit a strong steel "pull through" and large smooth radius bends so that its easy to add or upgrade whatever you have later on.

Seventy five feet is getting a bit long for a single run, perhaps a cable pit half way might make things a bit easier in the future.

 

[Pinto Yates]

I’m south of Waco and I paid $2.50 per foot to have a guy trench (and bury) a wire 125 Ft so I could run a 30A. 240v wire to my well house. Used 10/3 direct burial wire (UF-B) and it cost $1,70 per foot at Home Depot Today. At less than $5 per foot that’s half the cost of the cheapest 5 kWh battery you’ll find.

 

[DParker76020]

Big fat copper cable gets expensive really fast, but large diameter plastic conduit is dirt cheap.
Just be sure to fit a strong steel "pull through" and large smooth radius bends so that its easy to add or upgrade whatever you have later on.

Seventy five feet is getting a bit long for a single run, perhaps a cable pit half way might make things a bit easier in the future.

75 ft is the length of water pipe I need to prevent freezing in, not the distance electrical wire would need to be run. If I'm able to tap into the wiring from my detached garage, which sits midway between the house and the stable and is on its own meter, the wiring run would be no more than 30-40 ft.

 

[Pinto Yates]

75 ft is the length of water pipe I need to prevent freezing in, not the distance electrical wire would need to be run. If I'm able to tap into the wiring from my detached garage, which sits midway between the house and the stable and is on its own meter, the wiring run would be no more than 30-40 ft.

It sounds like grid wiring to the barn is the most efficient and cheapest option, but if you are planning to spend big bucks in the future to take the whole farm to solar, I agree with others and would design the system now, then run conduit with plenty of room and extra pull strings to each connection point.

 

[DParker76020]

It sounds like grid wiring to the barn is the most efficient and cheapest option, but if you are planning to spend big bucks in the future to take the whole farm to solar, I agree with others and would design the system now, then run conduit with plenty of room and extra pull strings to each connection point.

Yeah, that all makes sense to me.

And just for clarification, I don't have a farm (though we do sometimes affectionately refer to the place as "the ranch"). It's just a 2.5 acre property in an unincorporated part of the county, and that has a few out buildings (a detached garage, 2 storage sheds, a steel hay barn and a 4-stall stable, one stall of which has been sectioned off and is used for storage and has a work bench, which is where I'd be running electrical to from the garage, and then branching off a line from there down the length of the stable for some outlets and light hookups.) The former owners kept a few cows and donkeys back there, but I've since sectioned that part off as a goat paddock. The rest is used for a huge vegetable garden and an excuse to buy a subcompact tractor as a lawn mower on steroids. (insert Tim Allen grunt here)