Cable Sizing for the Belize Jungle!

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belize

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Hello, I am hoping some of you may be able to offer some advice and expertise to someone who has a far from comprehensive Electrical knowledge!!

Unfortunately, down here in Belize, sound Electrical know-how is difficult to find. As a result with any help you may be able to give, I want to try and grasp the full extent of the situation I have before me.

My ?problem? is based around needing to supply 2 large Houses (under construction) with mains power. The nearest house is 600' from a dedicated 25kVA transformer - the furthest 900'. In between the two is a Utility Building housing a Laundry room - 1 Washer and 1 Gas/Electric Dryer. The two houses are split into an independent self contained upper and lower level units. Without Aircon, electric cooking, and Hot water heating, or any electric motors other than the odd power tool now and again leads me to estimate that the max peak is unlikely to be higher than 50A for the whole site.

I am currently in the process of sizing the Cable required to bring the Mains electricity to the site. As you might guess, my main concern is that of Voltage drop along that length of line and disparities in the Voltage between the two houses. The Electric company says it can boost my voltage supply up to 130V and supply a up to 125A from my transformer.

My issues are:

1) On a 110V supply, at what voltage drop level would I start to noticeably experience appliance problems, lights dimming, etc. I believe 2% is generally used but is that practical?/reasonable?/necessary?

2) With the advice of the Electric company (whose advice is not consistently good!) I am anticipating using copper 00 cable which by my calcs using the online calculators leads to a VD of 8.7V at the furthest house equating to 7.3%

3) The Electric company only considers the one length 900' and NOT the return so say the VD will be about ?4V? and therefore fine!

4) I originally wanted to take the supply to the centrally located Utility Building and supply each house from there equalizing the Voltage somewhat but this could now add to the problem by adding a longer line plus the cost of 00 Cable is high here in such quantities

5) I guess what I would like to know is how sensitive to supply voltages will Lights/Fans/Fridges be? My current thought, open to alteration is to run a 00 spine through the site, branching off from it to supply the two apartments in House 1, then the Utility Building and then the apartments in House 2, accepting the fact that House 1 and 2 will have different supply Voltages.

6) If the above is feasible what size cable can I branch off the 00 spine and which would be the best way to branch it?

7) Does the Neutral Line HAVE to be the same size as the Hots? If not how small can I reasonably go?


I realize I am probably not using the correct terminology in much of this so please excuse my ignorance. I am happy for anyone to point out the errors of my thinking or approach and very grateful to receive any constructive suggestions from you electrical bods!

Thank you
 
Re: Cable Sizing for the Belize Jungle!

I know this may sound absurd but why don't you ask the utility to extend their line and put a transformer at each house? Trying to provide service to a load 900 ft away will only bring problems.
 
Re: Cable Sizing for the Belize Jungle!

Originally posted by bob:
I know this may sound absurd but why don't you ask the utility to extend their line and put a transformer at each house? Trying to provide service to a load 900 ft away will only bring problems.
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It does not sound absurd, it makes sense. However, there are two factors which do not make this an attractive option:

The first is that the Utility insists on a 20' clearing each side of their lines. The access road to the site is barely 20' wide in total, follows a little creek and is surrounded by attractive jungle flora. which I would be loathe to clear cut.

The second is that of cost. Getting the utility to do anything here that they have not already chosen to do is extremely expensive, particularly when linked to individual constructions. The $$$ possibilities blur their sensibilities!

Incidentally the Utility is controlled by Fortis the Canadian company.
 
Re: Cable Sizing for the Belize Jungle!

Boosting the voltage up could help but it will not overcome the voltage drop, as resistance is current limiting, and you still will have dimming lights when a heavy load is turned on and motors will still be starved when starting up. increasing wire size or paralleling conductors is the only true answer or using a step up transformer then a step down at each location. Which any or all of these options would have to be weighed against cost to see which one would provide the most benefit.
 
Re: Cable Sizing for the Belize Jungle!

I recently took a tour through parts of Central and South America to see how electrical systems are being developed and implemented throughout rural and isolated sections of the countries. As with large cities here in the US, the availability of good contractors and services unfortunately depends on the demographic of the area.

The electrical authority in Belize (I believe it was either BEL or BECOL?) sent a representative to host our visit and show us some of the projects and works in progress. We went to a hydroelectric dam in Mollejon and flew over some DOE projects extending electrical power in the jungle. The host went well out of his way to express how great his company is and how they are responsible for the betterment of Belize and its people. I definitely got the sense they would be difficult to work with and get assistance from.

We also met with some other organizations that seemed more inclined to help the individual person or community. I believe one group was called the Belize Development Trust. It was my understanding that most if not all electrical contractors and engineers register through these organization and can be reached through them. Maybe they can help you locate someone that can provide you with some assistance and that has a better working relationship with the electrical utility.

Good luck to you and I hope it works out.
 
Re: Cable Sizing for the Belize Jungle!

Originally posted by hurk27:
Boosting the voltage up could help but it will not overcome the voltage drop, as resistance is current limiting, and you still will have dimming lights when a heavy load is turned on and motors will still be starved when starting up. increasing wire size or paralleling conductors is the only true answer or using a step up transformer then a step down at each location.
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Thanks for the suggestions. The step up/step down transformer idea sounds interesting. My knowledge of them is weak so perhaps could you explain if it is feasible to step up the Voltage AT the houses, why not just step it up to 110V and avoid stepping it down again immediately?

My initial thought with your suggestion is that just one set could be located on the centrally located Utility building from where it is only 150' to each house.

If I assume the max load is split and each house then draws a max 25A then even using 4AWG over 150' gives less than a 2% VD - Am I missing something?

How big would these transformers be? Are they combined in one package? Any idea on price? - I will multiply it x3 and that's what it will cost here in Belize!!

Thanks
 
Re: Cable Sizing for the Belize Jungle!

Originally posted by bphgravity:
It was my understanding that most if not all electrical contractors and engineers register through these organization and can be reached through them. Maybe they can help you locate someone that can provide you with some assistance and that has a better working relationship with the electrical utility.
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Haven't done the overflight yet but I bet the view was good!

Yes, unco-operative utilities is an unfortunate fact of life here. In order for new connections to the grid to be made they need to be signed off by an Electrician licenced with the Public Utilities Commission. Unfortunately this means little. The licenced Electrician originally working on this project installed single insulated wiring through wooden rafters and specified 4AWG to supply the service over 900'

I am putting 2+2 and possibly making 5 but I am using the fact that I know the Utility as a rule uses a 50kVA transformer off the grid to supply up to an 800' line of 00AWG for about 20/25 houses in an urban area.

Places like Belize also makes one realize that there are the theoretical way things should or shouldn't work and then there is reality! I need a healthy splash of the former and a good dollop of the latter!!

Thanks
 
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