What device can replace the light bulb?

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  #1  
Old 03-26-07, 05:46 PM
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What device can replace the light bulb?

I'm a newbie to the forum and hopefully someone on this forum might be able to help me find a solution to a problem I'm having with my 1998 Lance slide in camper.

I'll try to be succinct:

I purchased a used 1998 camper which had a failed 6300 Magnatec charger/converter as well as a working Generac NP3400 series L/P propane Generator.

I replaced the old charger/converter with a new solid state-3-stage charger/converter, however the electronics on the generator will not run properly.

Apparently the problem is because the Generac's computer controller likes to see a very clear and clean signal at its output (it is a closed loop feedback system). When the generator is under no load (battery fully charged, and nothing using 12 V.) This confuses the Generator controller circuit, causing the gen to go to high rpm and then shut off.

At Magnatec's suggestion, loading the 110 circuit with a 60 watt light bulb solved problem and the generator works great with the light on. However, I would like to find a better option than the light bulb when I have my generator running.

On a recreational vehicle forum, one of the members recommended installing some kind of resistor, but the reply was the following:

"I believe it is INDUCTANCE that the Generac wants to see at the output. I don't think a resistor would provide that. I think the light bulb (being a coil as well as a resistor) provides both. I was hoping to find a coil I could install instead of the transformer, but I wouldn't know what size (in Henrys) to get or where to purchase it. Good thought though."

I was thinking about going to Radio Shack or an auto supply store...... but I don't know what to ask for to replace the light bulb solution. My preference would be to install a device to put a proper load on my 110 volt circuit . I would certainly appreciate any recommendations. Thank you.
 

Last edited by 56Nomad; 03-26-07 at 06:16 PM.
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  #2  
Old 03-26-07, 06:19 PM
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The inductance of an incandescent light bulb is negligible. The incandescent light bulb is almost a purely resistive load. What you want to do is to try progressively smaller light bulbs until your generator again is unstable and then go back to the next higher size. This may indeed be the 60 watt bulb you are presently using.

You then need to calculate the resistance of the bulb (when operating) and then you may substitute a fixed resistor of the same (or slightly higher) resistance and also of the same (or higher) wattage power handling capability.

For the 60 watt bulb it works out to be approximately 240 ohms resistance and no less than 60 watts (you may need to go to 100 watts) power capacity resistor.

The resistor will get warm, or even hot, when the generator is running, it will decrease the generator's usable output (in the above example by about 60 watts) and it will need to be mounted where it can dissipate the heat and also be protected from accidental damage or contact.

Such a resistor new may be a bit pricey so you may want to check surplus outlets via a Google search.
 
  #3  
Old 03-26-07, 06:35 PM
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It's been a long time since I did electric motor repair so those with better knowledge can help my memory but I'm thinking one or more of the heaters used in electric motors to help keep the windings dry in damp conditions might do the trick. IIRC they were available in various wattages.
 
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Old 03-26-07, 06:36 PM
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Originally Posted by furd View Post
The inductance of an incandescent light bulb is negligible. The incandescent light bulb is almost a purely resistive load. What you want to do is to try progressively smaller light bulbs until your generator again is unstable and then go back to the next higher size. This may indeed be the 60 watt bulb you are presently using.

You then need to calculate the resistance of the bulb (when operating) and then you may substitute a fixed resistor of the same (or slightly higher) resistance and also of the same (or higher) wattage power handling capability.

For the 60 watt bulb it works out to be approximately 240 ohms resistance and no less than 60 watts (you may need to go to 100 watts) power capacity resistor.

The resistor will get warm, or even hot, when the generator is running, it will decrease the generator's usable output (in the above example by about 60 watts) and it will need to be mounted where it can dissipate the heat and also be protected from accidental damage or contact.

Such a resistor new may be a bit pricey so you may want to check surplus outlets via a Google search.
Furd,

Thank you. I actually find that a 75 watt bulb works better than the 60 watt bulb. So I think you are suggesting I look for a 100 watt/240 ohm resistor
 
  #5  
Old 03-26-07, 07:53 PM
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No. The wattage of the resistor is the power handling capacity of the device, the wattage of the light bulb is an indirect measurement of the amount of amperage it consumes.

For the 75 watt lamp you would need a 192 ohm resistor with a power rating in excess of 75 watts.

The formulas are:

Bulb watt rating divided by the applied voltage equals the current in amperes drawn by the light bulb.

[75 divided by 120 = 0.63]

Applied voltage divided by current draw equals resistance

[120 divided by 0.63 = 192]

Watts power rating must be equal or greater than the voltage times the current [120 x 0.63 = 75] which in this application will always be the same as the size of the light bulb in the test.

The resistance rating is critical within +/- 10 to 20% and the power rating must always equal or exceed the power (watts) drawn by the component.
 
  #6  
Old 03-26-07, 08:44 PM
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Talking

furd wrote,

"For the 75 watt lamp you would need a 192 ohm resistor with a power rating in excess of 75 watts."

Thank you again:

Now.... I just need to find out who might sell this resistor :- )
 
  #7  
Old 03-26-07, 09:37 PM
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furd,

Would this work? please open this link: http://************/22ocaz
 
  #8  
Old 03-26-07, 09:40 PM
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A quick Google search turned up this:

http://theelectrostore.com/shopsite_sc/store/html/resistor-100-watt-100-ohm-dale-rh-100.html

You would need two of them wired in series (end to end) with the remaining ends connected to your circuit. Be sure to install a low-rated fuse or circuit breaker, 1 or 2 amp size, in series with one lead.

Like this:

line...CB...resistor...resistor...(other) line

Do a Google search for power resistor. Be sure to get resistors with a 100 watt or greater rating and you may mix the ohm rating to approximate the 192 figure by connecting them in series. You do NOT need exactly 192 ohms, the ones I linked to will do just fine.
 
  #9  
Old 03-26-07, 09:42 PM
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Originally Posted by 56Nomad View Post
furd,

Would this work? please open this link: http://************/22ocaz
Yes, that should do just fine. Remember that it will get hot when in operation and don't forget the circuit breaker or fuse.
 
  #10  
Old 03-26-07, 09:55 PM
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Originally Posted by furd View Post
Yes, that should do just fine. Remember that it will get hot when in operation and don't forget the circuit breaker or fuse.
So I will run a short length of 2 wire romex from the generator junction box
to the resistor.

I will put the 2 amp circuit breaker or fuse on the black wire which would then be connected to one end of the resistor. The other end of the resistor will be connected to the white wire.

This all will be housed in the generator compartment and have lots of room to dissipate the heat given off from the resistor. I'll be mounting it on a piece of ceramic tile.

Here is a diagram I made:
http://i2.photobucket.com/albums/y3/56Nomad/Generatorcopy-1.jpg

Thanks for all the help
 

Last edited by 56Nomad; 03-27-07 at 09:48 PM.
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