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Re: [GMCnet] 28SI Alternator vs 27SI [message #360290 is a reply to message #360281] Wed, 25 November 2020 09:59 Go to previous messageGo to previous message
Matt Colie is currently offline  Matt Colie   Canada
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
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Ken Burton
Yes, but it will not compensate for the rest of the losses in the system. The fusible link is an example of only one of the voltage loss culprits. IIRC the remote sense is connected to the terminal on either the horn or fan relay. Both of these are after the fusible link.

Yes a combiner will fix the isolator drop problem but not anything else like cables losses at a 150 or so amps.

I think a installing a one wire alternator is looking for low voltage problems in several places on the coach.
Ken Henderson
All true, Ken, which is why I worded the comment as I did. However, he's indicated that he intends to replace the existing wiring with new, larger, conductors. He seems knowledgeable enough to correct those other voltage issues too. They're really not all that troublesome in a well maintained system -- witness the many millions of one-wire alternators running today.

Ken H.
Hey Guys,

The last thing I really want to do is get between you two when you are throwing lightning bolts around, but you both just stepped into a mud hole that has been a problem for me for years in the boat electrics business (now gone).

Problem, You are Both Correct (no surprise there), but so many do not understand is that the life of a 12VDC (nominal) system only about ~2VDC. Too many unsuspecting owners look at the tables (like Ancor's) that say use this wire size for either (pick one) a 3% or a 10% voltage drop at X Amperes for that distance.....
This is compounded by the fact (still a big issue in fiberglass boats) even more that they have only considered half of the circuit.

So, if you size for the 10% (1.2~1.5) loss, you are headed for a lot of stuff not working the way that they hoped. This is more of an issue than most believe. One of the big hits is that it can make it near impossible to get a lead/acid battery to a 100%SOC.

What I have (had) to keep impressing the owners with when putting together a proposal is that while copper is expensive, you only have to buy it once. If you don't buy it then, it will cost you forever....

It would be my contention that unless you plan to rewire the entire Alternator to Batteries part of the system that staying with a remote sense is just about the only really good option. This is from personal (very personal) experience.

I really don't remember when it was, but we were in Louisiana when I noticed that the engine battery voltage was sagging. We did the standard in-flight fix with the generator and I started looking for an auto electric shop. He was a good guy, but said it was too hot for him to deal with. I'm a steam engineer, so I took it out and brought it in to him. He broke it down and put parts one specialized testers. The regulator was bad and one of the diodes in the trio was not reading right. He noticed the part number of the regulator and remarked that it was for remote excitation. I lost his context there. That was unfortunate. The regulator he put back in was a type for a passcar one wire. You might not expect the level of irritation that was for the next two weeks and couple thousand miles. While it did beat no alternator, everything was a problem. I went so far as to strap out the isolator to the engine bank and (it's a 73) leave the boost switch on a lot. When we got home, I got the right regulator.

The wire weights are different in the later coaches, but I still firmly believe that the remote sense is well worth the effort for a coach with multiple banks and loads all over the place.

Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

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