PDA

View Full Version : 3 LV Xformers along a drive question


cooper5114
06-23-2008, 10:35 AM
I would like to get an opinion on the best way to run 120V wiring along a long driveway. I'd like to have 3 recepticles along the way -- one at 250', 500' and 750' (the drive is about 850' long) each one used to power a LV xformer.

My thoughts are to run these in series and i'd allow 600W (5Amps) for each transfer. So the first run would need to carry 15A, the next 10A and the last 5A. If i just use a voltage drop calculator...it says i need to run #4 for the first 250' then #6 for the next and then #10.

Does this seem reasonable? Also i cannot seem to find specs on transformers as to what an allowable input voltage range they will operate with?

Any help is surely appreciated.

JoeyD
06-23-2008, 11:13 AM
You will need to consult with a liscensed electrician. I dont think any of the guys that participate here are liscensed EC's. The onkly thing I can say is that it will be the most expensive part of your lighting install running the 120v that far.

I can tell you that mist LV 12v transformers operate on a 10-1 ration so if you have 120v incoming you have 12v at your 12v tap. 130v you have 13v at your 12v tap......you can do the math from there.

Our units can operate with as little 60v incoming I believe, but anything less and you begin to put a strain on the unit and can cause an unwanted humming noise. You should try and provide as close to 120v as possible...and again i am speaking in regards to our units, I dont know how others would do.

I will also throw out that we have a 24v system which would allow you to put the transformer closer to the home and just run LV cable down along the drive.

http://www.lawnsite.com/showthread.php?t=235477

cooper5114
06-23-2008, 01:12 PM
i do plan on talking to an electrician but i would think that this is somewhat of a common scenario folks here encounter. How do the distances compare between 12V and 24V?

David Gretzmier
06-23-2008, 01:23 PM
A transformer with multiple taps up to 22, 24 volts allow you to go much further from the transformer than ones with only 12-14 volt taps. I'm not sure you can go 850 feet away from a trans even on a 24 volt tap, or how much load you can put on that wire. my charts for low voltage only go to 300 feet away. with very low loads, maybe just a few lights per wire run, it might be possible to stick to low voltage only. I asked an electrician many years ago before copper wire prices tripled to do outlets along a 1000 foot driveway as you described. The price was in the 2-3 thousand range. nowadays I would expect 5-7500- but it will make it way easier for low voltage to go in. it may very well be cheaper to do it as Joey descibed. good luck.

Pro-Scapes
06-23-2008, 03:22 PM
If you do irrigation and such and can pull the trench for him your cost will come way down if all they gotta do is lay the wire and hook it up. We just did one about 650 ft from the home. We had an open trench on site and I know it brought the cost down to less than half if the EC had to pull the trench.

Its not about cost its about doing it right. Running the line voltage would be the most effecient way for your client. You could however do line voltage half way and use Uniques 24v system and depending on your loads be ok.

JoeyD
06-23-2008, 06:03 PM
With a 24v system I can go 850ft on 10/2, and power up 105w. This would require the 30v tap. I guarantee this would be cheaper and easier to do than pulling 120v......But that is up to you to decide if you want to run a 24v system......

Pro-Scapes
06-23-2008, 07:53 PM
With a 24v system I can go 850ft on 10/2, and power up 105w. This would require the 30v tap. I guarantee this would be cheaper and easier to do than pulling 120v......But that is up to you to decide if you want to run a 24v system......

I dont know Joey. He is talking about putting a 600w trans out there. The drive is 1000 ft long. Thats alot of runs of 8 or 10ga wire to get 600w capability in that far zone. 6 runs out to a 1000 ft area is 6k ft of 10ga wire That alone could cost over 3k and thats just for the one zone. This isnt even factoring in the low voltage lines to run the mid section or the upper section.

You can pick up 1000 ft of 10/2 UF for under $1k... Rent the trencher if you dont have one for say 100 bucks... couple man hours have it all installed then have the EC come out for a couple of hours to hook it all up and still be under your LV wire cost not to mention to bury 6 10ga wires to just that far area your going to need to dig a pretty nice trench anyways.

Make the job or break it. 1000 ft drive is not going to be cheap. I personally would do line voltage all the way out. Now if a deep trech is not possible you got a whole different ball game.

NightScenes
06-23-2008, 08:02 PM
Why would you run the 120v circuit in series??? You should be installing a 20 amp circuit in parallel and the load that you will be placing on it will help determine the size of the wire that you will need.

cooper5114
06-23-2008, 11:09 PM
using a calculator that limits loss to 3% yields this

parallel
250' carrying 5 Amps needs #10
500' carrying 5 Amps needs #8
750' carrying 5 Amps needs #6

serial
250' carrying 15 Amps needs #6
250' carrying 10 Amps needs #8
250' carrying 5 Amps needs #10

so running this stuff serially and stepping it down is a good bit cheaper than running three seperate circuits.

Though this is a long drive i really don't need a lot of lighting along it...maybe a total of 10-15 lights...if that helps on the approach.

David Gretzmier
06-24-2008, 12:15 AM
10-15 lights total? to light a 1000 foot long driveway? am I figuring this right, one light every 80-100 feet? or 10-15 lights for every 250 ft ?

if you go with a 24 volt trans, 850ft of 10guage to run 105 watts, you'll need several runs of that, and that isn't gonna be cheap either, but cheaper overall than 120 volt option, as low voltage does not need to be buried as deep.

Lite4
06-24-2008, 12:26 AM
Are there any trees along this driveway that they may want to hang Christmas lights in? If so running 120 all the way with available outlets would not be too hard of a sell for this additional perk.

cooper5114
06-24-2008, 12:35 AM
the drive itself actually is closer to 750' but yea i was thinking a fairly conservative amount of lighting along the drive. I don't want to illuminate the whole thing as much as give you some light as you drive through the woods. I haven't thought too much on exactly how many lights yet as i thougth 3 xformers woudl be give me plenty of headroom but if i decide to do a 24V system and have a single xformer i know i'd need to decide this sooner rathere than later.

cooper5114
06-24-2008, 12:47 AM
trees...oh yea. it's very heavily wooded. Here's a couple pic's looking from the house towards the street and an autocad drawing if i can fit it.

INTEGRA Bespoke Lighting
06-24-2008, 01:04 AM
Looks like an awesome project there... lots of great 'moonlighting' potential.

I would seriously consider using LED MR16 Lamps at 4w each instead of 20w Halogens, this will greatly reduce your transformer loads and wire requirements. I have just the lamp for this application if you want more information send me a PM.

I do this scale and scope of project regularly... the line voltage should not be anywhere near as expensive to pull as some here claim. Billy had the right idea there.

Have a great day.

Pro-Scapes
06-24-2008, 05:11 AM
They also will never complain about having some line voltage out there. We are working on one similar that will end up with 24 tree lights up a long wooded driveway.

JoeyD
06-24-2008, 09:48 AM
Sounds like you have a good idea of what you need to do...lots of guys with different opinions....I know for sure I could knock this out faster and cheaper with Low Voltage regardless of what anyone else says........10ga at a thousand feet in low voltage burried 6" in the soil is a heck of a lot cheaper to pull and install than 120v burried 16"+ in conduit, anyone who argues is in denial.....But there are some good points..there is nothing wrong with haveing a few 120v outlets out there...you could use direct burial transformers as well if you pulled the 120v.......but it would be nice to just have a couple 1120 24v trans at the house and pull all the runs you want down the drive and put the extra money into some nice lights or extra lights.....I think you owe it to yourself to price both of them out and decide which option works best for you and your client.

I only like the 120v for the fact that you have power out along the drive but if you want ease of install then a 24v system is definitley the way to go.....Tim had a good point about holiday lighting as well which would cause me to lean to the 120v side if they planned on doing holiday lighting.

If you want to dig deaper into the 24v idea let me know and we can actually put some real wire measurments and wattage counts into our calculator and establish exactly what you would need to do....you can contact me if you want to do this, I would be more than happy to help.

Pro-Scapes
06-24-2008, 09:53 AM
Joey would you really wanna dig 6 inches in thoes tree roots wide enough to bury multiple runs ? use a blower to blow back the leaves... ditch witch it... UF romex no conduit... either post mount behind the trees so its hidden or us Direct burials.

Human nature and the terrain when coupled with the summer heat tells us they wont hit 6 inches all the way down with thoes tree roots for 1000 ft.

It also shouldnt be based soley on the price. It should be based on which is a better idea and a beter value in the long run. It will NEVER bite them to have line voltage out there but if they had to install the line voltage later they could mangle the low voltage wires.

Nice project but discuss it with your client. We just did a 400ft wooded walkway with the unique tree lights but we placed line voltage in the middle behind some bushes.

JoeyD
06-24-2008, 09:55 AM
so your saying that trenching the 120v is easier to do? I have worked in hot summer heat, so cal isnt all bikinis and waves my friend......I will just leave it at that I know I could put LV in quicker and cheaper than 120v...............

Pro-Scapes
06-24-2008, 10:04 AM
you grab your shovel I will grab the ditch witch. You know I hand install just about everything Joey but this is a scenario I would be on a machine. Its not a debate about which is faster or cheaper. Its about which is a better choice. I agree your 24v system could definatly help here but its just not feesible for 1000 ft runs especially when it comes to adding lights in the future or like someone mentioned holiday lights or anything else.

Lite4
06-24-2008, 10:20 AM
If it were me, I would go rent a big ditch witch ride on trencher and pop me a nice deep trench right dead center on that dirt road. Most of the tree roots will have been removed with the trees when the road was constructed. Just pop out a few lateral lines off the main trench line there and yahoo you have your trench for your 120 and low volt all in one. I am with Billy on this one. I would just put line voltage down there. They may like the initial lighting you install so much that they may want to add more, then what? would be good to have a few additional power sources to rely on in close proximity to the trees.

JoeyD
06-24-2008, 10:25 AM
wells thats BS, why cant I have a machine to dig? but whatever.......I am giving an option, I agree that 120v is better because it allows for future 120v appliances or holiday lights but you give me the same ditch witch and I would SMOKE you installing my 24v and you would have to pay an EC to install your 120v......By the time he is done putting in his 120v wiring for you to put your lights in I would be tested and collecting a check..:weightlifter:..and for the record I never said LV is BETTER here, I just offered it as an OPTION to pulling 120v down that long driveway increasing the cost by who knows how much.....but I lose you win...:cry::cry:

Pro-Scapes
06-24-2008, 11:05 AM
Its not a win or lose situation. There are 2 different ways to do it. 1 is more economical and easier to do (line voltage) and the other is possible if your scared of line voltage or need a "unique" way of doing things.

JoeyD
06-24-2008, 11:10 AM
ohhhhhh ok well thanks for enlightening me Mr Bradford...I am glad to know that pulling 120v (paying an EC to wire it up) 1000ft is easier than pulling direct burial LV cable.......That humidity must be messing with your brain! I will succeed the argument to you but you and I both know I would smoke you!

INTEGRA Bespoke Lighting
06-24-2008, 09:01 PM
Joey, Around here (for branch circuits) we would simply have NMWU pulled in at a depth of 18", no conduit required. If the terrain does not allow for 18" of depth then we would pull Teck armoured cable in at whatever depth can be achieved. It really isnt any more expensive then purchasing the appropriate cable and then contracting out the installation to a friendly EC.

In that application, I would be tempted to do as Tim suggested, use a vibe. plow right down the gravel driveway. Fast, and right.

I am a firm believer in having appropriate line voltage installed on large sites. It might be a bit more expensive in the end, however the clients don't seem to mind having it done right, and the multiple 120V circuits throughout the property provides for a lot more design flexibility and future expansion. Why is everyone always trying to 'race to the bottom' on system price? I just don't get that ideology at all. Do it right, charge appropriately. What is the big deal?

cooper5114
06-24-2008, 10:19 PM
hey...i appreciate the passion. So (1) if i went 24V and wanted headroom for some additional lights how far from the end (street) of the drive would i need to install a 120V recepticle...this is assuming i don't run 24V all ~850' from the panel. (2) if i were to run 120V down the drive what size wire would you guys pull?

Lite4
06-24-2008, 10:44 PM
The size of wire is going to depend upon the size of the circuit. Most circuits are 20 amp. If you EC poppped in a 50 you could put a heck of a lot of jboxes out there, but again if you are only talking 10-15 lights, this would be overkill. Probably just 12/2 with a ground wire and a 20 amp circuit. I would have probably 4-5 jboxes spread evenly down the length of the driveway, but thats just me.

cooper5114
06-24-2008, 11:25 PM
well you'd think that would work but 12/2 won't get close if you want to even push 10Amps 1000'. The voltage drop would be about 40 Volts.

if you really tried to send that 10Amps that far and wanted to lose < 3% (ideal) you'd have to run #1 wire that far. Though #6 doesn't do too bad.

Naturally if you want to send more current...the wire size just goes up; that's what's led me to carry 15Amps to the first, 10Amps between the first and second and 5Amps from second to the third. Now if i go w/24V system maybe i can get by with just running out a few 100 feet rather than 800 or so.

Here's links to a couple voltage drop calculators that i've been using when thinking about this problem.

http://www.electrician2.com/vd_calculator.htm
http://www.elec-toolbox.com/calculators/voltdrop.htm

Pro-Scapes
06-25-2008, 09:33 AM
Sure. Why not just run line voltage to the middle then a 24v system ? That should work.

Did you actually measure the drive or are you rough guessing it ? An accurate measurement of the actual path you intend to bury the wire in is a good idea.

Also I probably wouldnt use a line ward (vibe plow) on this one. I would trench but not in the driveway itself due to when you backfill it things are going to settle alot.

No matter what you do its going to be a ton of work and ALOT of wire. We pulled almost 4k ft yesterday in a residential prewire and about 3500 more ft to go in Thursday. REALLY nice being able to prewire with the irrigation altho it still involved a good amount of digging and some rather long conduit pulls.

Lite4
06-25-2008, 09:48 AM
well you'd think that would work but 12/2 won't get close if you want to even push 10Amps 1000'. The voltage drop would be about 40 Volts.

if you really tried to send that 10Amps that far and wanted to lose < 3% (ideal) you'd have to run #1 wire that far. Though #6 doesn't do too bad.

Naturally if you want to send more current...the wire size just goes up; that's what's led me to carry 15Amps to the first, 10Amps between the first and second and 5Amps from second to the third. Now if i go w/24V system maybe i can get by with just running out a few 100 feet rather than 800 or so.

Here's links to a couple voltage drop calculators that i've been using when thinking about this problem.

http://www.electrician2.com/vd_calculator.htm
http://www.elec-toolbox.com/calculators/voltdrop.htm

Ok, Roger that, I hadn't run the numbers yet. I guess always plan on maxing out the circuit at some time down the road even if you don't do it now.

cooper5114
06-25-2008, 09:52 AM
i know the path and the lenghs even though my original post (1000') was kind of generic. From the panel box to the street is about 860' so i'd like to figure out the minimum distance up the drive i should go and still have pretty good flexability towards the end of the drive. For example....can i stop 300' short and put a receptible there and have room for expansion? Maybe another way to ask the same quesion is "for a 24V system, what's the length of a wooded driveway one could lite up...putting the xformer in the middle and running lights out from there? Maybe have to answer this for small, medium, heavy lighting"? I'm thinking a majority of the lites would be used for moonlighting.

JoeyD
06-25-2008, 11:02 AM
Once you figure out what you want to do with the 120v side let me know and I will be more than happy to help you with the sizing of your transformers and vd calculations on your LV side.

Pro-Scapes
06-25-2008, 05:04 PM
i know the path and the lenghs even though my original post (1000') was kind of generic. From the panel box to the street is about 860' so i'd like to figure out the minimum distance up the drive i should go and still have pretty good flexability towards the end of the drive. For example....can i stop 300' short and put a receptible there and have room for expansion? Maybe another way to ask the same quesion is "for a 24V system, what's the length of a wooded driveway one could lite up...putting the xformer in the middle and running lights out from there? Maybe have to answer this for small, medium, heavy lighting"? I'm thinking a majority of the lites would be used for moonlighting.

There really would only be a limit on how much lighting you could install by how much power you can get out there. I mean if you trenched in some heavy ga line voltage and put a small panel out there you could make it like a circus. Its better to plan how much you want and how much you anticipate as far as additions.

Before you continue to rack your brain with this is the client even in the ballpark on the price ? Do they have a budget ?

Where is Matt from firefly atlanta when you need him... he is a line voltage guy

cooper5114
06-25-2008, 10:00 PM
Joey...i'll try and give you a call next week.
Billy...well in this case i'm the homeowner and possibly the installer...my goal is just to get the 120V installed now for future lighting install.

JoeyD
06-25-2008, 11:32 PM
the homeowner duped us!!! LOL

Sounds good Cooper

Pro-Scapes
06-26-2008, 05:57 AM
Are you an electrician ? Do you know electricity enough to do the install by taking amp readings and such ?

If its your home its a no brainer. Run the line voltage. It really wont be that much more expensive and it will save you on your power bill as having the transformers closer will be more effecient.

cooper5114
06-26-2008, 08:51 AM
i'm not an electrician but i am an electrical engineer. Believe it or not being an EE doesn't really help much as they teach you zilch about code...most everything i deal w/5 volts or less.

running 120V down about 80% of the drive and putting out a few taps along the way was the original approach and i figured i could probably run 12/2 the whole way. But when i looked at these voltage calculators i kind of freaked out when it said i'd need like #1 wire to carry much amperage all the way to the end. That's when i talked to one electrician and he said the way he does it is to start w/really thick wire and drop it down as you get past each tap.

Also...didn't mean to dupe you guys as i hope i'm not the typical homeowner. I contracted thsi house and built a lot myself. doing the irrigation right now (got trenches everywhere) and while i've got the trenches (before the grass) i'd like to wire for at least the 120V part of the lighting solution.