m 151 heater

[jim0311]

Installed my heater according to the diagram on the Garbee web site, my 5ohm 25watt resistor cooked. Is this the right resistor? I can not find a resistor thats labeld 5 ohm 24 volts. Can someone tell me the wattage of the resistor used?
Please help.
jim

[Monkey Man]

Resistors, unless used on very high voltage applications are not voltage rated or dependant, a resistor value at a particular wattage is all you need to know. If the resistor is correct value and wattage for the install a short circuit may have destroyed it by causing excessive current flow, if of insufficient wattage it'll cook up by over heating as there will be too much current flowing and heat generated through it for it's construction type. I am sure one of the guys on here can give you the info you need as to the correct wattage of 5 Ohm resistor required or even if that Ohmage is correct, Ohms law is the tool you need to work out the value of the resistor and the wattage you require

MM

[T. Highway]

Here is a simple way to do your own calculations along with examples.

If you know R the resistance and E the voltage, the formula for finding I current (Amps) is I = E/R.
24 DC Volts (E) divided by 5 Ohms (R) = 4.8 Amps (I)

If you know E the voltage and I the current, the formula for finding R resistance (Ohms) is R = E/I.
24 DC Volts (E) divided by 4.8 Amps (I) = 5 Ohms (R)

If you know I the current and R the resistance, the formula for finding E voltage (Volts) is E = IR.
4.8 Amps (I) multiplied by 5 Ohms (R) = 24 DC Volts (E)

If you know I the current and E the voltage, the formula for finding P power (Watts) is P =EI.
24 DC Volts (E) multiplied by 4.8 Amps (I) = 115.2 Watts (P)

I hope this helps you.

Bert

[jim0311]

Thank you. After diving into an old electronics book with those long forgotton formulas I managed to come up with the same answers as you. Now I know why the 25 watt resistor cooked. I really appreciate your response, you seem to be the go to guy for the M37.
Jim

[k8icu]

Having owned several M151s in the past I know that the resistor is big. About 3 inches long and about 3/8 inch thick. A hollow ceramic tube. All the resistor does is drop the voltage from 24V to about 14-16v on the blower motor. This gives you high and low bloser speeds. If you don't want the slower speed then just wire it up with a single toggle switch and it will blow out like crazy. If you want to drop the voltage for slower speed then you'll need that big fat resistor.

[Monkey Man]

Here is a simple way to do your own calculations along with examples.

If you know R the resistance and E the voltage, the formula for finding I current (Amps) is I = E/R.
24 DC Volts (E) divided by 5 Ohms (R) = 4.8 Amps (I)

If you know E the voltage and I the current, the formula for finding R resistance (Ohms) is R = E/I.
24 DC Volts (E) divided by 4.8 Amps (I) = 5 Ohms (R)

If you know I the current and R the resistance, the formula for finding E voltage (Volts) is E = IR.
4.8 Amps (I) multiplied by 5 Ohms (R) = 24 DC Volts (E)

If you know I the current and E the voltage, the formula for finding P power (Watts) is P =EI.
24 DC Volts (E) multiplied by 4.8 Amps (I) = 115.2 Watts (P)
I hope this helps you.
Bert

Now if a bloke like me was a kind and considerate type I would have included the formula in my post as opposed to saying "Go get it lad....."
Duh, not much of a help huh?? Thanks Bert for making me realise my stupidity, I will try harder to be useful next time

MM

[T. Highway]

Jim,

No problem, but I'm a not the go to guy for the M37. I'm new to this just like you.
I was taught Ohms Law when I was about 9 or 10 years old because I wanted to build a shortwave radio to listen to people from around the world, it has stuck with me and I use it often.


MM,

What's with the name calling?
Kind and considerate type, that makes me sound like a tree hugger.

Just kidding.......MM

Bert