electrical question

Wooly · Mar 2, 2011

I was looking at the installation instructions for my new to me cab and I see that I need a breaker/ on-line fuse and a relay. Anybody know what size breaker would work? I assume the relay is to shut off the cab power when the key is off. So, I know what a relay does I just don't know what kind to buy. Any help is appreciated.
Thanks, AL

droach77 · Mar 2, 2011

From what i can see from that sweet cab you have a radio, fan motor, and lights. Not sure of the load calculation of what each is drawing i would say you need to run atleast 12 gauge stranded wire and 20 amp fuse or breaker , or even maybey 10 gauge strsnded wire and 30 amp fuse, but without the wattage of each component u plan on runnning i cannot be 100% sure. You will be better off going up than down on wire and breaker or fuse size because it looks like each of your branch circuits has a seperate fuse in the cab distribution block. good luck :trink39:

dave

PA318Guy · Mar 2, 2011

Might want to PM Ken in NJ or D-Dogg, when it comes to electrical they are the ones I trust!

ksp · Mar 3, 2011

Wooly, is there a wire present on the cab that comes from the overhead console? If so that would determine the correct circuit breaker or fuse to use. On my 445 I took a Bosch relay and a circuti breaker and installed under the steering whel area behind the panels and fed the cab from there.
Below is a picture I got off internet.
You should be able to follow the intention of the diagram. In your case the pump would be the cab console and the trigger would be an ignition wire from you key switch. You will have to test wires to find one that is hot when ignition is one to trigger the relay.

Wooly · Mar 3, 2011

Thanks guys. There is existing wiring coming from the console. I'll see what size it is when I get home today.

Nouveau Redneck · Mar 3, 2011

ksp is exactly right. Size the fuse to protect the existing wiring on the circuit that is already there in the cab. It does no good to use a heavier fuse, and in fact it would be inviting a meltdown of the existing wires if the fuse allowed more current than the existing wire was designed to carry. You can always use heavier wire for any new wire that you are adding, but don't put in a larger fuse than would protect the existing wires.

oaker55 · Mar 3, 2011

Nouveau Redneck said:
ksp is exactly right. Size the fuse to protect the existing wiring on the circuit that is already there in the cab. It does no good to use a heavier fuse, and in fact it would be inviting a meltdown of the existing wires if the fuse allowed more current than the existing wire was designed to carry. You can always use heavier wire for any new wire that you are adding, but don't put in a larger fuse than would protect the existing wires.

:thThumbsU:thThumbsU:thThumbsU Excellent answer!

Wooly · Mar 3, 2011

It looks like I have 10 guage wire coming out of the console. I just did a quicky google search and it says that I can run up to a 30 amp breaker on 10ga. Does this sound right to you guys?

Tomadvanced · Mar 3, 2011

Then use ten guage wire. Check your consumers. Chances are a 30 amp would be fine. You could use a circiut breaker, but I would rather use a fuse. A circuit breaker in automotive applications is only used with wiper motors, seat motors and window motors as they can get hot and draw alot with excessive use. The breaker cools off and resets. If you decide to use a breaker, then get a manual reset style. ATC fuse holders only have 12 g wire. You could get a fuse holder without wires and make your own terminations. Or use a maxi fuse and holder. Be sure to install the breaker or fuse as close as you can to your power source. I would install an eye terminal on the supply side of your circuit breaker/fuse and attach it to the starter battery terminal. I have a picture of mine I will post when I get home.

UrbanTractor · Mar 3, 2011

Wooly,

Did you do an alternator upgrade, or are you on the stock 20 amp version?

Wooly · Mar 3, 2011

UrbanTractor said:
Wooly,

Did you do an alternator upgrade, or are you on the stock 20 amp version?

I have the upgrade kit still sitting on my workbench. I got it with the other cab but didn't install it yet. It's part of the electrical install that I hope to accomplish soon.

Wooly · Mar 3, 2011

Tomadvanced said:
Then use ten guage wire. Check your consumers. Chances are a 30 amp would be fine. You could use a circiut breaker, but I would rather use a fuse. A circuit breaker in automotive applications is only used with wiper motors, seat motors and window motors as they can get hot and draw alot with excessive use. The breaker cools off and resets. If you decide to use a breaker, then get a manual reset style. ATC fuse holders only have 12 g wire. You could get a fuse holder without wires and make your own terminations. Or use a maxi fuse and holder. Be sure to install the breaker or fuse as close as you can to your power source. I would install an eye terminal on the supply side of your circuit breaker/fuse and attach it to the starter battery terminal. I have a picture of mine I will post when I get home.

Thanks Tom. I checked out that site you gave me. Now I'm going to run down the street to NAPA and check what they have. I'm not in a hurry, ok, yes I am,:woohoo1: so I am hoping I can get something to work for a this weekend project.

SkipD · Mar 3, 2011

ksp said:
Wooly, is there a wire present on the cab that comes from the overhead console? If so that would determine the correct circuit breaker or fuse to use. On my 445 I took a Bosch relay and a circuti breaker and installed under the steering whel area behind the panels and fed the cab from there.
Below is a picture I got off internet.
You should be able to follow the intention of the diagram. In your case the pump would be the cab console and the trigger would be an ignition wire from you key switch. You will have to test wires to find one that is hot when ignition is one to trigger the relay.

That electrical drawing is all but useless for a novice and is quite questionable even for someone like me who has worked with electrical stuff for many decades.

The relay is quite improperly drawn, as there is no way to determine what connections are for the coil and what connections are for the contact. I could guess about the function of each terminal of the relay, but it would be purely a guess.

Tomadvanced · Mar 3, 2011

SkipD said:
That electrical drawing is all but useless for a novice and is quite questionable even for someone like me who has worked with electrical stuff for many decades.

The relay is quite improperly drawn, as there is no way to determine what connections are for the coil and what connections are for the contact. I could guess about the function of each terminal of the relay, but it would be purely a guess.

That is an industry standard relay that has been used for at least 30 years.
87- consumer
86- input for relay contactor(coil pos)
85 -output of coil contactor(coil neg)
30- battery power

I do not have anything to illustrate the relay. KSP could you draw the relay coil and contacts for the novices please?

Wooly · Mar 3, 2011

So, I just looked over the schematic in the instructions http://www.800cabline.com/store/images/manuals/05-10408.pdf on page 19. According to that, all the wiring is 14 ga. from the factory. Maybe the PO beefed up the wires to the power source with 10 ga. That being the case, I don't want to use a 30 amp breaker/ fuse do I?

droach77 · Mar 3, 2011

Wooly if u are concerned with what fuse size you need u can do whats called a load calculation it's really easy to do. Look at every component in the cab such as radio, lights , blower motor and what ever alse is in there. Add up all the watts like your lights and radio will be measured in watts , and motors usually have the amp draw rating on them. Add all the watt measurments and divide by 12 volts and then add amp rating off the blower motor and u will have your answer. For example....3 35 watt lights add up to be 105 watts plus the radio which might be 50 watts, so u have 155 watts divde be 12 volts and you have 13 amps.....then add the amp draw on the blower which might be 5 amps and add that to the 13 amps and you have a total of 18 amps total draw of cab just remeber to upsize the wire incase you add stuff which it sounds like PO already did....hope this helps :trink39:

dave

SkipD · Mar 3, 2011

Tomadvanced said:
That is an industry standard relay that has been used for at least 30 years.
87- consumer
86- input for relay contactor(coil pos)
85 -output of coil contactor(coil neg)
30- battery power

I do not have anything to illustrate the relay. KSP could you draw the relay coil and contacts for the novices please?

Your terminology isn't at all familiar to me, and just last year I just retired from a 39-year career as a technician and systems designer in industrial process control systems.

I presume that the terminals labeled 85-86 in the drawing are the relay coil and the terminals labeled 87 and 30 are a normally open contact. That would make the relay a SPST relay, probably with a 12VDC coil if I am guessing correctly. I suspect the numbering relates to wire numbers from some piece of equipment (maybe a tractor?), as no relay I have ever seen has numbering like that on its terminals.

Tomadvanced · Mar 3, 2011

SkipD said:
Your terminology isn't at all familiar to me, and just last year I just retired from a 39-year career as a technician and systems designer in industrial process control systems.

I presume that the terminals labeled 85-86 in the drawing are the relay coil and the terminals labeled 87 and 30 are a normally open contact. That would make the relay a SPST relay, probably with a 12VDC coil if I am guessing correctly. I suspect the numbering relates to wire numbers from some piece of equipment (maybe a tractor?), as no relay I have ever seen has numbering like that on its terminals.

Skip, your description of that relay is correct. I should have been more clear and stated that it is an automotive industry standard. (standard in my industry not yours!). Any relay on any Euro car and some newer domestics will have a standard terminal designation. Not only are the terminals numbered, there is usually a diagram of the relay on the relay case. So when diagnosing you can quickly see what should be where and what you are missing (power, ground etc).

ksp · Mar 4, 2011

Here you go Tom. I found this and thought it explained things rather well:

SPDT Relay : (Single Pole Double Throw Relay) an electromagnetic switch, consist of a coil (terminals 85 & 86), 1 common terminal (30), 1 normally closed terminal (87a), and one normally open terminal (87) (Figure 1).

When the coil of an SPDT relay (Figure 1) is at rest (not energized), the common terminal (30) and the normally closed terminal (87a) have continuity. When the coil is energized, the common terminal (30) and the normally open terminal (87) have continuity.

The diagram below center (Figure 2) shows an SPDT relay at rest, with the coil not energized. The diagram below right (Figure 3) shows the relay with the coil energized. As you can see, the coil is an electromagnet that causes the arm that is always connected to the common (30) to pivot when energized whereby contact is broken from the normally closed terminal (87a) and made with the normally open terminal (87).

When energizing the coil of a relay, polarity of the coil does not matter unless there is a diode across the coil. If a diode is not present, you may attach positive voltage to either terminal of the coil and negative voltage to the other, otherwise you must connect positive to the side of the coil that the cathode side (side with stripe) of the diode is connected and negative to side of the coil that the anode side of the diode is connected.

SPST Relay : (Single Pole Single Throw Relay) an electromagnetic switch, consist of a coil (terminals 85 & 86), 1 common terminal (30), and one normally open terminal (87). It does not have a normally closed terminal like the SPDT relay, but may be used in place of SPDT relays in all diagrams shown on this site where terminal 87a is not used.

Tomadvanced · Mar 4, 2011

Thanks KSP.
Wooly, it looks like Cozy is using 14 ga wire in the whole circuit, including the power supply from starter to the relay, breaker and to the the aux fuse box. I am sure that would be ok, but Its a bit light for me. I would use 10 ga instead on that part.
As far as loads here is what I measured on mine. 55w halogens 9 amps. Wiper 3.7 amps. Dome lamp with 1156 bulb 2.3 amps. Heater with computer style fan 1.9 amps on high.

electrical question

Wooly

droach77

PA318Guy

ksp

Attachments

Wooly

Nouveau Redneck

oaker55

Wooly

Tomadvanced

UrbanTractor

Wooly

Wooly

SkipD

Tomadvanced

Wooly

droach77

SkipD

Tomadvanced

ksp

Attachments

Tomadvanced

Top Contributors this Month

Recommended Communities