What size wires

[Alex_Blackwood]

The solenoid does draw an appreciable especially initially. They do (sometimes,/ usually, not sure which) have a pulling winding and a hold on winding, the pull in winding taking quite a high current. I was surprised how large when I measured it but I forget the actual figure.
A heavy duty switch or push button is therefore essential. A 60amps rating would not be inappropriate.
You'd not want the contacts in a switch of inadequate rating to weld themselves together

Without wishing to draw this out into a meaningless discussion. It just didn't go with 2.5mm cable. Paul's fuse would certainly help!

 

[PaulRainbow]

Without wishing to draw this out into a meaningless discussion. It just didn't go with 2.5mm cable. Paul's fuse would certainly help!

The MDI is wired with 1.5mm wire, rated at 21a, but needs a 60a switch ????

 

[rogerthebodger]

The MDI is wired with 1.5mm wire, rated at 21a, but needs a 60a switch ????

Is that 60 Amp rating AC if DC as DC ration seems to be less than AC due to possible larger arcing with switching DC

 

[PaulRainbow]

Is that 60 Amp rating AC if DC as DC ration seems to be less than AC due to possible larger arcing with switching DC

Not sure Roger, the OP didn't say.

 

[VicS]

The MDI is wired with 1.5mm wire, rated at 21a, but needs a 60a switch ????

The current rating for the wire is for a continuous current but the starter solenoid is only energised for a few seconds at a time hence a lighter gauge than that required for a contiuous current can be used especially for short runs where voltage drop will not be significant.
Earlier I quoted wire sizes gleaned from the schematics in the owners manuals. If you go back in time to the MD11C , which did not use a starter relay, you find that wiring between panel and the solenoid is 6mm². Presumably this gauge to avoid excessive voltage loss over a much longer length.

 

[rogerthebodger]

Not sure Roger, the OP didn't say.

I have a simular setuo with 20 Amp switched one as a run switch and a second spring return to operate the starter solenoid.

Like DB it only for use when working in the engine space.

Cannot remember what size cable I used eother 1.5 or 2.5 may be 2.5 as I standardized on 2.5 for most lighting and instrument power

 

[PaulRainbow]

The current rating for the wire is for a continuous current but the starter solenoid is only energised for a few seconds at a time hence a lighter gauge than that required for a contiuous current can be used especially for short runs where voltage drop will not be significant.

Oddly enough, i do know how current ratings for wire works Vic.

Earlier I quoted wire sizes gleaned from the schematics in the owners manuals. If you go back in time to the MD11C , which did not use a starter relay, you find that wiring between panel and the solenoid is 6mm². Presumably this gauge to avoid excessive voltage loss over a much longer length.

Not sure how going back in time answers the questions.

The OP has a new D1-30, this engine has been fitted with a starter relay for at least 10 years, hence the 1.5mm wiring. A 60a switch, whilst not doing any harm, is far from essential.

 

[Daydream believer]

I bought 60 amp because most of those on offer were 5 & 10 amp & not all for starters. I saw this one & it said it was for vehicle starter motors. I thought that for no more money it seemed a sensible option.
I did not know about fuses in the line & I bow to Paul Rainbow's experience. Particularly as I know SFA about electronics.
But Paul now poses another question!!
What size in line fuse? 5, 10, 20 ? I do not have a clue
Advice please.

 

[Daydream believer]

The OP has a new D1-30, this engine has been fitted with a starter relay for at least 10 years, hence the 1.5mm wiring. A 60a switch, whilst not doing any harm, is far from essential.

If the MD1 fails, will not switching across the terminals byepass the relay within it, thus meaning bigger cables needed?
As I see it, I am just shorting across the solenoid in the same way I did with a bare screw driver on my Lombardini engine in my last boat
I do not know- just asking.

 

[PaulRainbow]

If the MD1 fails, will not switching across the terminals byepass the relay within it, thus meaning bigger cables needed?
As I see it, I am just shorting across the solenoid in the same way I did with a bare screw driver on my Lombardini engine in my last boat
I do not know- just asking.

Unless Volvo have changed things recently, the start relay is 30a. So a 30a fuse should be fine.

Like i said, no harm whatsoever in fitting the 60a switch, i was just questioning that it was "essential".

 

[Chiara’s slave]

Unless Volvo have changed things recently, the start relay is 30a. So a 30a fuse should be fine.

Like i said, no harm whatsoever in fitting the 60a switch, i was just questioning that it was "essential".

now DDB has explained the switch choice, it surely needs to be at least as much as the fuse, so the choice was made for him. No 30A switch, only a 60.

 

[PaulRainbow]

now DDB has explained the switch choice, it surely needs to be at least as much as the fuse, so the choice was made for him. No 30A switch, only a 60.

Why fit a 60a fuse to protect 30a wiring and a switch ?

 

[Chiara’s slave]

I thought you’d said 30a. Hence he couldn’t really have fitted a 10 or 20a switch. There being no 30, he has, by default picked the best size available. To be fitted, as you say, with a 30a fuse.

 

[PaulRainbow]

I thought you’d said 30a. Hence he couldn’t really have fitted a 10 or 20a switch. There being no 30, he has, by default picked the best size available. To be fitted, as you say, with a 30a fuse.

For heavens sake, i answered the OPs question in post #2, post #34 and still going.

The starter relay is rated at 30a max, it is protected by a 16a circuit breaker.

The OP wants an emergency starter option in case of a failure within the MDI. I suggested 2.5mm cable, rated at 30a. A fuse should be fitted as close to the MDI as possible, to protect the wiring and whatever circuits/components the circuit passes through within the MDI. Ergo a 30a fuse. The switch would certainly be OK at 20a, possibly even 15a.

FYI there are multitudes of 30a switch options 30a momentary switch - Google Suche

 

[Daydream believer]

Paul
I was not trying to wind you up. Yes you did answer my original question in#2 & I am grateful for that. But you threw in the comment about the fuse size & that prompted my additional response. If I had known about fuses I would have asked at the start

But we have got there:-
I need 2.5m2 wire & a 30 amp in line fuse in the +ve wire. My switch is more than adequate.
Hopefully, I will never need it; but if I do it will be ready

Thanks

 

[PaulRainbow]

Paul
I was not trying to wind you up. Yes you did answer my original question in#2 & I am grateful for that. But you threw in the comment about the fuse size & that prompted my additional response. If I had known about fuses I would have asked at the start

But we have got there:-
I need 2.5m2 wire & a 30 amp in line fuse in the +ve wire. My switch is more than adequate.
Hopefully, I will never need it; but if I do it will be ready

Thanks

Didn't think you were winding me up.