Couple of electrical questions if you please?

Soupy sails

Member I
I'm committing to the glow plug switch to the solenoid to glow plugs project and I need to know.

In the diagram provided by marinehowto.com I have:

A) A 10 AWG min fuse from the starter post to the solenoid. Fuses are good I like them, AWG = 10 amps minimum? yes? can a larger fuse be used in this position? How large, Max amperage?
Three questions for one.

B) How about a large amperage fuse, say 150 amps between the "I" side of the solenoid switch to the Glow Plugs ? Would a fuse that large be overkill?

P.S. One last question please I don't see any power coming from the alternator? or Batts? so all the power travelling through the switch is coming from the Starter Post during crank?
A two fer.

Amazon is offering a Cole Hersee (24059 BP) including two of these 150 amp fuses and I'm thinking this can work. Open to any comments or suggestions,

Thanks,

Dan
 

Frank Langer

1984 Ericson 30+, Nanaimo, BC
Hi,
I'm not an electrician, but I would determine how many amps of current will be flowing through that circuit. Then I would use a slightly larger fuse for some "wiggle room", as an undersized fuse will burn out frequently. But I wouldn't use too large a fuse, cause then it won't protect the circuit by burning out when it should. To me a 150 fuse sounds way too large. I would be inclined to use a 30 amp fuse, but best to calculate how much current will run in that circuit.
Just my thoughts... I'll be interested in what others suggest.
Frank
 
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fool

Member III
Snip... best to calculate how much current will run in that circuit.
Frank is onto something here and there is a tool that will help with your inquiry.

http://circuitwizard.bluesea.com/#

Highlighting a field popups a window of explanation/definition. Insert the data as best you can and you'll get a recommendation for wire and over circuit protection (read fuse or breaker).

Over circuit protection is not for the device, but to protect the wire and insulation from turning into a toxic lightbulb and burning down the house. Use of the calculator is highly recommended.

Max
 

Tin Kicker

Member III
As Frank and Max wrote, the protection is sized for the wire and the wire is sized to the device on the end, in this case the glow plugs. So the first step is to know how many amps they pull and that should be in the owners manual.
https://www.westerbeke.com/technical manual/200151_m15-m25-5411-5421_technical_man.pdf

Page 19 has the plugs so multiply 7A times three plugs and get 21 amps. Uprate that by a third for corrosion resistance and other real life factors and you are at about 32 amps.
Enter that 32A in the Blue Sea calculator and your 10 ga cable should be fine for an estimated 10 feet of total circuit length. (battery to solenoid PLUS solenoid to plugs; the plugs themselves are the ground)

Now in the calculator add your circuit protection data and it will give you a chart which shows a variety of choices for the optimal protection device. For example, this suggested 50A fuse will give you more than double the 21A needed by the plugs yet is going to trip at half what the cable can carry:
https://www.bluesea.com/products/5177/MRBF_Terminal_Fuse_-_50A

Note that your proposed 150A fuse is not going to protect the cable. The cable will burn before the fuse blows. (Wouldn't you rather have a breaker?) For example if the cable rubs on the engine and a dead short develops. (ALWAYS assume a dead short like this will happen as it is the most conservative case.) Just to show why over-rating the protection is such a bad idea, below is the info for a 150A breaker and it shows the device will take 5,000 amps for 1 full second. (Really it'll just go to whatever the battery could provide.) At that point the cable can become an ignitor for any nearby fumes or wood it may have been touching and it would have destroyed/shorted/overloaded any wires routed with it.
https://www.bluesea.com/products/7048/187-Series_Circuit_Breaker_-_Panel_Mount_150A

If doing this in the future and if you want a good reference to keep on the boat for when out of touch with the internet, print a copy of a wire chart like this:
https://www.marinco.com/~/media/Websites/Resources/Ancor/three-percent-voltage-drop.png

If sizing for a new device on the end of a wire, the rule of thumb is 3 times the amperage for the load on the wire and a breaker or fuse sized to that. For your case you can see that tripling the load of the 3 glow plugs (7A each) comes to 96A for the 10 ft cable and 100A just so happens to be what the chart and calculator both arrive at.
 
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Soupy sails

Member I
Thanks Frank, Max and Tin this was excellent information indeed!

Frank yes you just saved me the cost of these fuses that would have been too much for the load indicated. Also thank you Max for the link to the "tool" and to Tin Knocker for doing the calcs. I did check your numbers and they agree.

I feel far better armed with this information,

Thanks to all of you.

Dan
 

Tin Kicker

Member III
Frank yes you just saved me the cost of these fuses that would have been too much for the load indicated. Also thank you Max for the link to the "tool" and to Tin Knocker for doing the calcs. I did check your numbers and they agree.

I feel far better armed with this information,

Thanks to all of you.

Dan
np.
LOL - Hadn't about a Tin Knocker (metal boob?). A Tin Kicker is an accident investigator.
https://howitbroke.com
cheers
:egrin:
 

supersailor

Sustaining Member
A solionid is not really the right application here. a relay is more appropiate. The relay on Terra Nova has been working well for five years now. The total run from the battery to glow plug is under 6 feet. The voltage increase at the plugs compared to before (9.7 volts at the plugs to 11.9 volts at the plugs). The Universal sure likes to start now compared to before.
 

Tom Metzger

Sustaining Partner
Lots of good advice here and lots not so good.

Fusing to protect the wire is a great concept, and that is a requirement, but it is not the be all/end all. It's great that the wire doesn't cause a fire, but do you want the device at the end of the circuit to cause a fire?

Fusing for the wire size is the way to go if you are fusing from a source and will be splitting into branch circuits that will be protected with fuses or breakers. Think battery to DC panel. Those branch circuits should be sized for the load unless the load is also fused.

With the glow plugs, 3 of them at 7 amps you want to use #10 AWG wire and I would fuse the wire near the starter solenoid at 30 amps, 21 amps + 25% next highest size. The 25% is a factor of safety to avoid false blown fuses or bkr trips, not because of corrosion which would reduce the current. A fuse or breaker will carry approximately 125% of rating forever, 37.5 amps in this case.

If sizing for a new device on the end of a wire, the rule of thumb is 3 times the amperage for the load on the wire and a breaker or fuse sized to that. For your case you can see that tripling the load of the 3 glow plugs (7A each) comes to 96A for the 10 ft cable and 100A just so happens to be what the chart and calculator both arrive at.
I have a problem with the methodology. 100 amps through #10 wire equals fire. Three times the load current makes no sense as it would increase the required wire size. According to the charts on the Blue Seas site my solution works. 50 amps would be the largest fuse allowed in an engine compartment for #10 wire.

http://assets.bluesea.com/files/resources/reference/20010.pdf


P.S. One last question please I don't see any power coming from the alternator? or Batts? so all the power traveling through the switch is coming from the Starter Post during crank?
A two fer.
The current comes from the battery, and the charger if you are plugged in. Those are the only sources there are until the engine starts.
 

supersailor

Sustaining Member
Hey Tom, thanks. I really sat down and read this one. This proposed system needs to go back to the drawing boards. You cannot pull the power off the starter solenoid for the glow plugs. They must be activated prior to the use of the starter. A solenoid is the wrong equipment to use to energize the system and a high amperage fuse is a fire waiting to happen. This is a high amperage circuit that can easily burn your boat to the waterline. Don't commit to this project until you are sure exactly what you are doing.
 

Tom Metzger

Sustaining Partner
This proposed system needs to go back to the drawing boards. You cannot pull the power off the starter solenoid for the glow plugs. They must be activated prior to the use of the starter. A solenoid is the wrong equipment to use to energize the system and a high amperage fuse is a fire waiting to happen. This is a high amperage circuit that can easily burn your boat to the waterline. Don't commit to this project until you are sure exactly what you are doing.
OK, it's after cocktail time in the east, but... The gazinta post of the starter solenoid is always energized. A solenoid is a simple relay intended for high current low voltage applications. Could any 30 amp relay or contactor do the job? Yes, of course, but an automotive starter solenoid is cheap, easy to mount, and can certainly do the job.

BTW, all the people who rewired their engine panel per my Universal Engine Wiring Upgrade, or whatever I called it, powered their engines off of the starter solenoid. It works.
 
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Parrothead

Member II
I did not see any mention of circuit length anywhere in the thread and without it voltage drop cannot be accurately determined.
 

Tin Kicker

Member III
With the glow plugs, 3 of them at 7 amps you want to use #10 AWG wire and I would fuse the wire near the starter solenoid at 30 amps, 21 amps + 25% next highest size. The 25% is a factor of safety to avoid false blown fuses or bkr trips, not because of corrosion which would reduce the current. A fuse or breaker will carry approximately 125% of rating forever, 37.5 amps in this case.
We're coming at the 25% and 33% (third) from different standpoints of a design engineer and designing a repair. The 25% is more efficient and normal for a production installation while using thirds is normal in the field. For either, the 10 ga wire works.

I think my intent about the cable size was lost in how I worded the sentence you objected to and I certainly was not implying that 100A should be run through 10ga. My point was simply about uprating the wire to more than the fuse or breaker was rated for.

Below is the Blue Seas chart showing the 50A is called to be nominal. Using the lower current for 25%, the 30A c/b would acceptably be on the low side of what they show as nominal.

 

Tom Metzger

Sustaining Partner
Did I miss it or has wire gauge / length / load / voltage drop been completely ignored?
21 amp load plus a margin of safety makes #12 AWG 105*C wire the minimum acceptable size for use in the engine compartment with a 30 amp Maxi fuse. This per the Blue Seas chart I referenced and their on-line calculator. I don't know why they don't use a 30 amp ATC fuse in the engine compartment for #12 wire; they do for #14. http://circuitwizard.bluesea.com/

FWIW, Maine Sail recommends #10. Either would work for short runs. I would probably use #10 because I have it.
 

supersailor

Sustaining Member
The power for the glow plugs can be pulled off the hot side of the starter solenoid but that is a less than ideal situation. When the starter is engaged, the circuit is already pulling 21 amps. This means a big voltage drop when the high amperage of the starter (50 amps+) kicks in, the glow plugs dim significantly and the starter spins slower. Also, a lot of heat develops in the wiring. The original Universal wiring is a prime example of how not to wire an engine with long high amperage runs and switching high amperage through too many switches all of those switches failed multiple times on my boat before the redesign. It was easy to install the engine for the first time, though.

The question of where to pull the power from is the next question. The original wiring scheme doesn't have a good spot. In my case, the problem was solved by adding a battery post about a foot away from the batteries and distributing from there. Loren came up with a really neat Blue Seas distribution system complete with fuses. I don't seem to have it in my shrunken photos selection. Maybe Loren wouldn't mind retrieving it? Loren put his distributer directly on the battery post. I put mine just outside the battery box.

I also separated the glow plug switch from the starter switch. There is no need for the glow plugs when the engine is still warm. it is a lot easier to reach down and push one button than two. This is done automatically on my big 'ole 6 liter van but you need an onboard computer to do that. I understand why universal connected the two. Many people can't sense when the plugs are needed or not. Either way works.
 

Christian Williams

E381 - Los Angeles
Moderator
Blogs Author
Personal message

Dan, who started this thread, refers to marinehowto.com.

That's "Maine Sail," "Rod Collins," "R.C. Collins," and "Compass Marine."

Whatever entity, R. C. Collins has helped many of us with tutorials and explanations from an independent slant and based on experience. Like the Ericson Forum, he accepts no advertising. (I've never met him and have no affiliation with him...or anybody, for that matter).

Allow me, as you consider who to support when buying stuff, to excerpt this from his site:

As of Jan 1, 2018 MHT is still nearly $5440.00 in the red. What does that mean? It means I have essentially donated $5440.00 of my own money (my families money really) into this site so that it can remain free to the readers. My goal is to someday buy my self a hamburger with some of the money I hopefully earn, from all the work I’ve put into MarineHowTo.com.

Christian
 
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Soupy sails

Member I
First off,

Sorry Tin Kicker, I come from the architectural finishing trades and a tin knocker is a sheet metal worker or HVAC. Didn't mean to mis-classify your work. The conversation between Bob and Tom has been a really useful one and although I think I do have a pretty good idea about how to go about this project I have modified a few things that I think will make it successful.

I'm much clearer on the wiring size and fusing size and placement. Thanks Tom, and really everyone who's added to this thread.

A) Power will be pulled from the pos. side of the house bat. (these bats are close) (using a remote post located inside the engine compartment) via a 10AWG wire to a 50 amp ATC fuse. Then to the Cole/Herseey solenoid.

B) A smaller fuse (TBD) once I rewire the from the glow plug push button switch will be installed between the glow plug switch and the solenoid activation post.

C) Rewire (replace) from the solenoid to the number 1 glow plug wire size TBD by load (checked with a DVM)

One more question for Tom. What the hell is a "gazinta post"? I've grown up here mostly in the west so my Yiddish is a little weak.

Bob,

This project won't commence until I'm pretty sure it will be safe and successful I have no desire to see my boat catch fire. That's the reason I've started this very thread and I appreciate every comment made herein. So please keep adding your input but rest assured it won't go forward until I'm as certain as I can be, that it will work. If I leave things the way I found them, the odds of a fire will certainly be much higher. Frankly, I was shocked at how bad the wiring is laid out on this boat and this project is only the beginning.

Dan
 

Soupy sails

Member I
Hey Christian

Yes,

I agree 100 percent Christian, I have donated to that site and I do buy and will buy from his site as often as I can.

I would also strongly encourage other people to patronize his site since the resource is so very valuable. I had no idea that site existed until I ran across the link here so the only dog I have in this hunt is the hound I need to fix my boat.

Thanks,

Dan
 
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