Solenoid Project - Wire Size

[Clay Greene]

I am about to tackle adding a solenoid to the glow plug circuit.  I have reviewed the project page and other posts and have seen that it is recommended to use 8 AWG or even 6 AWG wire to run from the starter to the solenoid and from the solenoid to the glow plug.  We're planning to install an Cole-Hersee insulated solenoid in the wood frame above the engine compartment (running a separate ground wire to the engine ground).  I have not measured this exactly yet but I don't think that the round trip between the starter and the glow plug is more than 8 feet and certainly not more than 10.  The amp draw of the glow plugs is less than 30 amps.  Both wire size charts I have consulted (West Marine and Blue Sea Systems) indicate that the appropriate wire size is 10 AWG even if it is an engine room installation.  Is there a reason I am missing why I need to use 8 AWG or 6 AWG?  I know bigger is better when it comes to wire size due to resistance but we're talking a relatively short distance and not a huge amp draw.  8 AWG is challenge to work with because it falls between my lug crimper and my racheting crimper.  Thanks. 

[Stu Jackson]

When it comes to the heavy current producing glow plugs, I believe bigger is better.

[Ron Hill]

Clay : I used #6 wire for that job.  

If you mount that soleniod on the engine there is no need for an additional ground wire!!

I backed out the two bolts that hold the HX saddle to the top of the bell housing and used those bolts thru the feet of the soleniod an rescrewed them back in their threaded holes.  
You might have to elongate the holes on the soleniod's feet?

A thought

[Clay Greene]

I found some ready-made 6 AWG battery cables that worked well for the wires form the starter to the solenoid and the solenoid to the glow plug. The heat exchanger bracket was a perfect horizontal mounting location. 10 seconds of glow plug and she starts right up. That will be really nice when the air temperature goes down in September and October. As always, thanks much for the guidance.