leaving chassis system on while plugged into shore power

[Tenor]

Kind of an odd question here.  There are times when it is advantageous to leave the chassis system connected to the house bank, while parked and on a pole to run the inverter.  Such as wanting the bay lights to come on, or working on some other aspect of the chassis electrical. 

Since I reinstalled the 50DN and it's regulator, I realized that the regulator gets warm under these scenarios.  Will this cause any damage?  Should I worry about this?  Thanks!

Glenn

[Geoff]

I see a few problems, first of all is your house battery bank 24v instead of 12V?

Second of all, I would never "splice" the starting batteries to the house batteries.  They need to be separate and on their own system.  I gather you have a way of switching this off, so it may work for you.

Three, if you are set up with a 24v house system with a center tap or equalizer to get your 12v you are just asking for problems.

Also, if you have a generator it should be on it own start battery.

If you have gone the route of 24v is the best system for house and start system please take my advice with that in mind.  Two schools of thought.

--Geoff

[Tenor]

I guess I need to be more specific. 

I have my bus wired so that the 50DN runs the bus chassis systems and only charges the house battery bank.  This battery bank can be disconnected using the original master disconnect.  I have a separate battery bank and alternator to charge the start batteries. 

When parked, not running but plugged into a pole (or running generator), if I leave the house batteries tied to the bus chassis systems the voltage regulator for the 50DN gets warm.  Is this a problem?

Glenn

[Sean]

... When parked, not running but plugged into a pole (or running generator), if I leave the house batteries tied to the bus chassis systems the voltage regulator for the 50DN gets warm.  Is this a problem?
...

Yes.

connecting the house batteries to the chassis batteries should not do anything different to the regulator than the chassis batteries alone.  If you think about it, it just makes a bigger chassis battery.  I would say you have something else mis-wired.  Perhaps whatever you are using to make the connection is back-feeding the regulator or the Relay terminal on the alternator.

Do you have a schematic of how you have everything hooked up?

-Sean
http://OurOdyssey.BlogSpot.com

[Tenor]

Sean,
You are on to it. 

Bus is parked.
House batteries are charging from the inverter.
House batteries are connected to the chassis system.
Inverter is back feeding to the alternator and regulator. 

Will that back-feeding cause a problem?  (I should have said it that way in the first place!) 

Thanks!

Glenn

[Sean]

Glenn,

What I am saying is that simply connecting the batteries together, even with another charger in parallel, should not cause this problem.  The regulator should be off when the ignition is off.

If your regulator gets warmer with the batteries bridged than it does without, you likely have a different problem.

What are you using to bridge the batteries, and how is it connected?

-Sean
http://OurOdyssey.BlogSpot.com

[Tenor]

I know what I did wrong. When I reinstalled the regulator, I used a wire direct from a bus bar that is constantly hot to send to the "bat"  terminal on the regulator.  As if on a car, I need to get that current from a "switched" source.

Glenn

[Sean]

... I used a wire direct from a bus bar that is constantly hot to send to the "bat"  terminal on the regulator.

Actually, that should not be a problem.  In fact, the BAT terminal should be wired directly to the battery positive on the chassis batteries, as this is the regulator sense lead.  However:

As if on a car, I need to get that current from a "switched" source.

The regulator terminal you want "switched" is labeled IGN or I.  This is the terminal that tells the regulator to turn on.  So if you have it wire now so that the IGN terminal is hot all the time, or hot when the batteries are bridged, that would be your problem.

-Sean

[Tenor]

Just an update to this thread.  I pulled the electrical diagram and found that the field contact on the regulator should have been sent to the field relay that closes once the ignition switch is turned on.  Originally, the relay was activated by a Penn switch that closed at 60 lbs, allowing the relay to be grounded.  The Penn switch has been bypassed. Is there any reason to restore that ground system?  Currently, the field relay has a ground wire. Thanks!

Glenn

[Sean]

...  I pulled the electrical diagram and found that the field contact on the regulator should have been sent to the field relay that closes once the ignition switch is turned on.  Originally, the relay was activated by a Penn switch that closed at 60 lbs, allowing the relay to be grounded. ...

OK, so I confess I am not all that familiar with the MC-7, but this sounds strange to me.

Are you sure you are not confusing the field (FLD, F, or F1) terminal with the relay (RLY or R) terminal?

The relay terminal is a half-wave rectified take-off from one of the three windings, about half the nominal output voltage of the alternator.  It is used as a signal that the alternator is producing output, and typically drives a relay that is then used to operate accessories that should only run when the alternator is charging (such as the HVAC blowers) and also to deactivate the charging system tell-tale.  On many MCIs, the relay signal is run through an air pressure switch on its way to the relay; this is to ensure that enough air has built to supply any air-operated belt tensioners, as well as to give the engine a chance to warm up a bit before placing a ~10-12 hp load through the alternator.

If you post the model or part number of your regulator I can tell you how it ought to be connected.  Typically, the connections are as follows:

G or GND: frame ground
B or BAT: battery positive (AT the batteries)
I or IGN: switched positive from the master switch, key switch, or "ignition" switch
F or FLD: direct to the F, F1, or FLD terminal on the alternator.  No other connections at either end.
R or RLY: to a half-voltage relay controlling blowers and charge lamp.  May be gated by an air pressure switch.

I suppose it is possible that there would be a relay between the field terminal on the alternator and the field terminal on the regulator, gated by an air pressure switch, that would serve to keep the alternator from charging when the pressure is low, but this seems like a bad idea to me -- it would mean a compressor or air system failure under way would also kill the charging system.  In any case, interrupting the field connection in this manner should still not lead to the symptom you describe.

It sure sounds to me like whatever you use to interconnect the two battery systems is backfeeding either the IGN or RLY terminals, either of which could cause the regulator to get warm.  You may also be damaging the alternator itself, so you really want to track this down.

-Sean
http://OurOdyssey.BlogSpot.com

[Tenor]

Well, I blew that last post Sean!  I should have written that the Field relay engages the Positive terminal on the regulator with the battery via a bus bar.  Sorry!

I agree with you about the Penn switch design being strange.  I wonder if that is why it has been disengaged.  I cannot think of a reason to reduce the load off of the alternator (since the original air conditioning is gone) during a low air situation.  Even at engine start-up, the inverter would not drawing enough power to put a drag on the starter.  As you pointed out, if the alternator kicked out due to low air, electrical could still be needed.

Thanks!

Glenn

[buswarrior]

Remember, air tensioners for the alternator drive belts were part of the intended design execution.

Low air means loose belts, means slipping or throwing belts under load...

Not to mention whatever other air powered controls may be present for HVAC or other systems that the manufacturer wants the air system up to strength before engaging the big alternator.

happy coaching!
buswarrior