Electrical Question.... - Montana Owners Club

pbahlin · 05-11-2010, 01:18 PM

We are thinking of adding over counter lighting in our Big Sky and I was wondering if its possible to convert a 120 volt light fixture to 12v? If yes, how do you do it....change wiring and bulb fixture? Where would you get the parts required? Just thought I'd ask in case I find a 120V light I've just got have??

Have to have all the answers before I add this to my DH's honey do list!

Thanks again

Betty

helmick · 05-11-2010, 01:25 PM

Just change the bulb to 12v.

RCN.Stoker · 05-11-2010, 01:36 PM

I installed Xenon low voltage "Puck" lights in my last MH. They came with the transformer, all the required wiring and give a bright white light. They can be put on a dimmer on the low voltage side but I just switched mine using a standard wall switch. I took the power from the closest 120 volt wall plug. Any building supply store has them. I chose Xenon over Halogen as they produce less heat

pbahlin · 05-12-2010, 12:37 AM

Helmick....my Electrical Engineer (not an electrician and doesn't play one on TV either) DH said you cannot do that because the 12v bulb would blow up as it would be drawing 10 times the current it was designed for. Not sure it would fit in the socket either.

Maybe Ozz could jump in here with some help!

Thanks for your contribution to the subject!

Betty

NCFischers · 05-12-2010, 01:12 AM

Betty,
If you just want to change an existing ceiling light fixture with a different one, then any fixture will work as long as you use a 12 volt bulb. The power source for the ceiling lights is 12 volts.

pbahlin · 05-12-2010, 02:34 AM

Perhaps I wasn't clear in what I wanted to do....I'm looking to ADD a fixture over the "island/peninsula", preferably a pendant and I can't find what I want in 12v. Is the wiring on a 120V fixture different from the 12V fixture? I know the socket for the bulb probably is...
DH husband isn't signing up to rewire the 5er for aesthetics!

Thanks for your help, as always the MOC is terrific!

Betty

ARJ · 05-12-2010, 02:49 AM

Just use any 120v fixture you like and look here to get bulbs to fit.

http://www.go2marine.com/product.do?no=16170F

Here's another:

http://www.shipstore.com/SS/HTML/ANC/ANC531100.html

pbahlin · 05-12-2010, 03:02 AM

ARJ....you are my hero!!!!! How great is that....never knew these bulbs existed......Thank you so much! Wahoo!!!!!!!!!!!!!!!!!

Betty

**Rondo** · 05-12-2010, 03:19 AM

Betty-- When you are talking pendant light, are you talking free swinging pendant or solid bar pendant? I'd be leery of a free swinging pendant especially if you are on the road much do to the sway when moving down the road or around turns. I like your ideas however.

helmick · 05-12-2010, 03:51 AM

Quote:

quote:Originally posted by pbahlin

Helmick....my Electrical Engineer (not an electrician and doesn't play one on TV either) DH said you cannot do that because the 12v bulb would blow up as it would be drawing 10 times the current it was designed for. Not sure it would fit in the socket either.

Maybe Ozz could jump in here with some help!

Thanks for your contribution to the subject!

Betty

You asked about converting a 120v fixture to a 12v. If 12v was coming through the wiring it would not be ten times the voltage.
I have used 120v fixtures with 12v bulbs hundreds of times in the last 30 years and never had a problem.

pbahlin · 05-12-2010, 05:20 AM

Ron: Now, first I didn't know that 12v system fed all lighting in rig, but now that I have learned all this stuff....I could be increasing the honey do list

Rondo: I did figure out it had to be a fixed pendant, and this just gives me way more options!

ARJ: can't figure out how my reply shows up before your post?

I did reply after you posted!

Anyway, thank you all for the edu-macation!!!!!!

Betty

HamRad · 05-12-2010, 08:46 AM

Betty,
Not all ceiling lighting is 12 volt. At least not in my older 3295 trailer. It is a 2002 year model. Most of the ceiling lights are in fact 12 volt but we do have at least three lights that are 120 volts. Perhaps some models and or the newer trailers have only 12 volt lighting in the ceiling.

If you're adding a fixture then just find the nearest unswitched 12 volt OR 120 volt wiring and tap into that to add your new fixture.

12 volt and 120 volt are very different animals. The wiring is different and you do not want to "mix" them. You can use a 120 volt circuit to run a 12 volt fixture but you must have a transformer to step down the voltage from 120 to 12 volt.

There I've completely depleted my very limited knowledge of electricity.

Good luck with your project.
Dennis

Wild Horse · 05-12-2010, 10:27 AM

Betty,
I took out 5 12v fixures recently and replaced with 120v fixtures....then I got 12v screw in medium base bulbs, which work fine. I have also ordered 13watt cfl bulbs (12v) that I will put in some of the fixtures.

You are not limited by the fixtures, but rather by the bulbs.

Also, take a look on ebay...there are quite a number of 12v light fixtures there, including pendants from time to time...and a heck of a lot cheaper than buying 120v fixtures at retail.

Hope this helps.
Bill

RCN.Stoker · 05-12-2010, 11:41 AM

Just a small note of caution. Check the rating of the spade fuse for the 12 volt circuit to which you are adding lights. Add up the watts of existing lamps and other equipment on that circuit and divide by 12. This is very close to the existing current draw in amps for that circuit. Take the total watts of the fixtures you are adding and divide by 12. If the total of the two results is greater than 0.5 amps less than the rating of the fuse then you need to do some more homework on the wire gauge of the circuit. It takes much less wattage to exceed a low voltage DC circuit's capacity than in a 120 volt AC circuit. A 25 watt DC 12 Volt bulb pulls over 2 amps of current while a 100 watt 120 volt AC bulb only pulls 0.83 amps. There are many references available online. Here is one that should help. BTW the wire gauge is printed on the wire. You can ignore the voltage and temperature information as this isn't relevant.

http://www.rbeelectronics.com/wtable.htm

Wild Horse · 05-13-2010, 01:39 AM

Thanks RCN....I forgot to mention that. I actually computed it out, then to be on the safe side, after mounting the lights, I took out the 15 amp fuse and put in a 10 amp to see if it would blow. I figured better safe than sorry, and it would tell me if I was too close to max. They ran fine with a 5 amp less fuse.

ARJ · 05-13-2010, 04:27 AM

Quote:

quote:Originally posted by RCN.Stoker

Just a small note of caution. Check the rating of the spade fuse for the 12 volt circuit to which you are adding lights. Add up the watts of existing lamps and other equipment on that circuit and divide by 12. This is very close to the existing current draw in amps for that circuit. Take the total watts of the fixtures you are adding and divide by 12. If the total of the two results is greater than 0.5 amps less than the rating of the fuse then you need to do some more homework on the wire gauge of the circuit. It takes much less wattage to exceed a low voltage DC circuit's capacity than in a 120 volt AC circuit. A 25 watt DC 12 Volt bulb pulls over 2 amps of current while a 100 watt 120 volt AC bulb only pulls 0.83 amps. There are many references available online. Here is one that should help. BTW the wire gauge is printed on the wire. You can ignore the voltage and temperature information as this isn't relevant.

http://www.rbeelectronics.com/wtable.htm

I agree with you about wire size concerns, however the table you referenced is kind of weird (or is it me). As an example, the entry for 12v @ 10a is different than the entry for 12v/120w (???).

Easy way to determine max load for the circuit is to multiply the fuse size x 12v (15a x 12vdc = 180watts) and limit the number of fixtures/bulbs/etc to something reasonably less than the max wattage.

For instance three 50 watt bulbs would allow for an ~15% safety margin in this circuit IF the factory used decent wire guage with respect to the fuse size (hopefully nothing smaller than 12ga).

RCN.Stoker · 05-13-2010, 09:30 AM

ARJ Your approach is simpler and works just as well. My ready reference guide for vehicle wiring (checked when I got in the office today) says allow a 35% margin. I guess the message is that vehicle wiring is exposed to a more severe service environment and therefore has to be more robust as a result e.g stranded rather than solid wire.

ARJ · 05-13-2010, 10:11 AM

Quote:

quote:Originally posted by RCN.Stoker

ARJ Your approach is simpler and works just as well. My ready reference guide for vehicle wiring (checked when I got in the office today) says allow a 35% margin. I guess the message is that vehicle wiring is exposed to a more severe service environment and therefore has to be more robust as a result e.g stranded rather than solid wire.

Problem is that there are so many parameters to consider when sizing wire that it is probably easier to just hook the stuff up and see how hot it gets. (Only kidding) If you search for dc wire sizing, you will probably find that every table out there specifies different values. Stranded vs solid, bundled, in a conduit, insulation values, etc, etc.

I prefer this approach!

RonT · 05-15-2010, 03:58 PM

I just ordered two 2010 Montana 12V pendant lights from my local dealer at the cost of $33 each plus shipping. This is another option open to anyone who wants to add island lights.

You may also like: