Is a 345A switch enough for my engine?

[Jammer]

Different beast. That is similar to these:


https://www.ohmite.com/assets/docs/c...es.pdf?r=false


That particular Ohmite product line isn't available in an off-a-both-b configuration but rotary switches of similar construction have been made that way and can be made on a special order basis in quantity. They also cost 5x as much as the typical marine battery switches being sold today.



The difference is in the contact materials, insulation material, wiping action, and spring action.

[Jammer]

Originally Posted by Bowdrie

I suppose you can get something like this that's going on ~100 years old.
Could break both the legs if the starter went wild.
You get extra points if the switch is labeled "General Electric" or "Westinghouse".

You can still get new ones. They are big and expensive and have the exposed conductive parts, but they are reliable, easy to troubleshoot, and easy to repair.


https://filnor.com/quality-products-...-switch-front/

[coopec43]

I'm sure when I installed the starting system for the 4-108 the solenoid was rated for 900A (intermittent)





5 May 2019 — Our marine version for Perkins 4.108 is a high quality, 12V solenoid rated to 100 amps continuous and 800 amp intermittent load, ...

[coopec43]

Originally Posted by gsalgado

My boat came with the engine starter wired to the battery via a Guest 2300A switch (rated to 600A momentary), but there's also a Guest 2111 switch (345A momentary) right next to the engine.

I'm now using the 2300A for my house bank, and plan to use the 2111 for the starter, but my engine's (Perkins 4.108) starter motor max current is 900A (according to the manual), so I'm wondering if it'd be safe to do so?

Thanks in advance

I just checked to see what a Guest 2300A switch was


Then to start the motor you have to go down below to the engine room?

I have a keyed switch in the center cockpit which energizes a 900A (intermittent) solenoid switch (attached to the starter motor) which starts the motor.

If the Perkins 4-108 starter motor draws 600A+ (intermittent) and you are trying to put that current through a switch rated at 345A (intermittent) the result would be obvious?


I just looked at the Passport 41 design and wondered how you start the motor. Where am I going wrong?

[LifesBetterWhenYoureBeating]

Originally Posted by coopec43

I just checked to see what a Guest 2300A switch was


Then to start the motor you have to go down below to the engine room?

I have a keyed switch in the center cockpit which energizes a 900A (intermittent) solenoid switch (attached to the starter motor) which starts the motor.

If the Perkins 4-108 starter motor draws 600A+ (intermittent) and you are trying to put that current through a switch rated at 345A (intermittent) the result would be obvious?


I just looked at the Passport 41 design and wondered how you start the motor. Where am I going wrong?

The switch is just so I can disconnect the battery from the starter. It stays on and I start the engine from the ignition panel on the cockpit -- which activates the solenoid just like in your setup

As others have pointed out, the starter motor doesn't draw 900A

[coopec43]

Originally Posted by Jammer

1) Regardless of what the manual may say, the starter will never draw 900 amps. It might perhaps draw as much as 300 amps on a really cold morning. I say this based on having owned several diesels and measured the starter current on them, with a meter.


2) The rotary battery switches, regardless of rating or manufacturer, are a fruitful source of electrical system failures and should not be installed gratuitously. If you really need a battery disconnect for the engine for reasons of safety then I would suggest using an Anderson Powerpole connector instead of a rotary switch. The powerpole connectors have better contact wiping action when connected and disconnected and can readily be inspected and cleaned as needed.

Are you aware the Perkins 4-108 diesel engine has a high compression ratio of 22:1?

Your comment above "I say this based on having owned several diesels and measured the starter current on them, with a meter." Unless those motors had high compression ratios too those observations would be irrelevant.

The compression ratio of a diesel has a lot to do with the load on a starter motor (as I'm sure you would be aware)

Perkins 4-108 compression ratio.

23 Feb 2013 — 22:1 is the compression ratio. It means the engine compresses the air mixture down to 1/22 of the volume of the cylinder at the bottom of the

What is the compression ratio of 4 stroke diesel engine?
14:1 to 22:1

The compression ratio varies from 14:1 to 22:1. The pressure at the end of the compression stroke ranges from 30 to 45 kg/cm2.

[Wotname]

Originally Posted by gsalgado

The switch is just so I can disconnect the battery from the starter. It stays on and I start the engine from the ignition panel on the cockpit -- which activates the solenoid just like in your setup

As others have pointed out, the starter motor doesn't draw 900A

The average starting current will around 200A to 300A but don't try starting your engine with a 300 or 400 CCA battery, you will be very lucky to get a start even with a band new fully charged battery.

The devil is in the detail - the starter motor will draw something close to 900A but only for a very short time i.e. its maximum starting current will be close to what the manual states.

Your starting circuit (battery, fusing, switching, wiring, solenoid and motor) design should consider peak (maximum) and cranking average (intermittent) currents and the relevant period of operation (duty cycle).

[coopec43]

Originally Posted by gsalgado

The switch is just so I can disconnect the battery from the starter. It stays on and I start the engine from the ignition panel on the cockpit -- which activates the solenoid just like in your setup

As others have pointed out, the starter motor doesn't draw 900A

Why does the Perkins 4-108 manual say you need a 900A (intermittent) solenoid switch?

Perkins 4 108 diesel engines have quite a high compression ratios so I don't think "general advice" is relevant.

I agree with Wotname (comment above)

Originally Posted by Wotname

I would caution against using the Guest 2111 switch in your starting application.

Every time you start the engine, you will overloading (i.e. heating) the switch contacts beyond their designed rating. The more times you cause damage to the contacts, the worse the problem becomes. At some stage in the future, the switch will fail and will either prevent the engine from starting or start a fire or both.

[wingssail]

bump

Originally Posted by wingssail

This makes me wonder. My battery control switch is a single Marinetics rotary switch on the Master Power Control Panel (see photo). It switches all power to and from my batteries including to the engine starter which is essentially on the house side of the switch. I have additional distribution panels and other switches and meters but this is the only battery switch I have.

This switch and this panel have been on the boat for 40 years. As far as I know the rotary switch has never been changed or serviced in any way. (there are no log entries for Battery Switch or marinetics, etc).

I wonder if this switch is worn out or causing a voltage drop when starting amps for my yanmar are going through it. Can these switches last forever?

Maybe I should ask, is this switch adequate? It has been in use for 40 + plus years and I have never been aware of any deficiency.

[Wotname]

^^ 40+ years is a good field test. This is a case of don't fix it if it ain't broke

Unless you have some evidence of a failing switch like slow cranking speed or the switch getting warm, it will likely outlive you.

[coopec43]

Originally Posted by Wotname

^^ 40+ years is a good field test. This is a case of don't fix it if it ain't broke

Unless you have some evidence of a failing switch like slow cranking speed or the switch getting warm, it will likely outlive you.

I hope the "slow cranking speed" doesn't occur as a 200,000 oil tanker bares down on you!

[Ballsnall]

Originally Posted by gsalgado

The main reason for the switch was so that I could disconnect the battery in case the starter motor gets stuck -- someone mentioned that in another thread and it scared the hell out of me.

Internet forum's are pretty good at scaring people yet I have never heard of anyone dying from a starter motor (well one guy, but it fell on him attached to a motor)
Unless you are extremely unlucky, you will never encounter a stuck starter. Out of all those extremely unlucky people the worst that would happen is the starter would just keep spinning with the idling engine and although making a hell of a racket, you will have plenty of time to disconnect the cable or battery terminal without any damage occuring.

[Ballsnall]

Originally Posted by coopec43

I hope the "slow cranking speed" doesn't occur as a 200,000 oil tanker bares down on you!

Best to change the switch, and the starter, hmmmm maybe the engine too. Them tankers are scary as.

[wingssail]

Actually, let's talk about a stuck starters:

If, for some reason the starter stays engaged after the key is released, and it is turned by the engine, you have a problem. It will be noisy and may get hot, really hot. If the starter is not energized but still stays engaged by the engine, then you're going to have to stop the engine. A switch will not solve that problem (other then an engine stop switch). This is an uncommon problem.

If the key gets stuck and electricity stays on to the starter solenoid, then before too long you will need to disconnect that electricity because otherwise you have an electrical problem, maybe a fire. In this case a switch will be of use. Possibly a fuse will be of use.

So, an engine stop switch and a battery switch for the start system are both good ideas.

Make sure you have both and stop obsessing about it. Chances are neither situation will ever occur but if it does, you're prepared.

Is a 345A switch enough? Maybe not. I have no idea what my switch's capacity is, it looks smaller that your 345A and it has worked for 38 years but nobody on this forum has yet said anything about it. So get a bigger switch and move on.

[wingssail]

Originally Posted by coopec43

I hope the "slow cranking speed" doesn't occur as a 200,000 oil tanker bares down on you!

Yes, and I also worry about an asteroid falling on me. So far my cranking speed has been sufficient.

Oh and ask Lodestar. They never will bear down on me, but if they do, it's my fault.