Which Surge Protector to use - 30A or 50A?

[PwrWgnWalt]

Have not been able to find the answer to this question, so thought I'd ask ...

Currently, the MH has:

5.0 KW Onan Generator,
30A Convertor/Charger (old Litton model; but a PowerMax Boondocker PM4B-75 is on "the list")
30A Shore Power line/cord/plug
2 A/C units - only one runs on shore power, the second one runs only on genny power
Manual switching from Shore to Generator power (insert shore plug into 30A receptacle box from Genny)
No surge protection (that I can find)

Am considering adding surge protection AND an Automatic Transfer Switch (ATS)...  but seems that many of the ATS's state the 30A models are for generators of less than 4.5KW, and the 50A models are for 4.5KW (or so) up to 12KW. To me, this is saying I need the 50A model (?)   Given the difference between what mfr's seem to be saying, and what the coach is wired for:

1. Can I use a 50A ATS in my MH without hassle?  (what ramifications would there be)

2. Should I just get separate units - a 30A Surge Protector and a 50A ATS?   What do you use???

Thanks everyone!
- Walt

[ClydesdaleKevin]

If you go with an external model, the kind you plug in first to the campground outlet, then plug your coach into it, go with the 30 amp.  You really shouldn't need a surge protector on the genny side.  If you go built in, I'd still say 30 amp is the way to go, even fed from the genny...but the external ones are a lot cheaper.  Auto transfer switches are convenient, but when mine literally blew up, I went with a simple plug instead...simple and effective and dummy proof...and cheap!

Kev

[DaveVA78Chieftain]

I suspect the 2nd AC is feed directly from the alternate (L2) set of generator leads.  The 30 amp plug you connect the shore power to uses the primary leads (L1).  I suspect each leg has it's own seperate 25 amp CB at the generator.  So, your are actually only switching between a 30 amp and a 25 amp circuit.  A 30 amp ATS would work fine.



Note: The neutral and Ground lead connection shown at the top of the drawing is in error.  The AC Neutral and ground leads should NEVER be connected together in the RV EXCEPT inside the generator.

[PwrWgnWalt]

Thanks Dave;

Good note about the 120VAC Neutral and Ground wires remaining separate...

The reason I was asking about using a 50 Amp Surge Protector in my 30 Amp MH is that a friend has one he said I could have (would need an adapter) but I don't want to hurt aything.

BTW - is that a special program you use to draw those nice electrical diagrams?
Is it available free somewhere?

[Elandan2]

I use a "Brick Wall" surge protector.  Although it is only 15 amp, I use it on the Convertor circuit to protect my Statpower charger.  When I lived in Ashcroft, the power was very unstable and I blew two chargers before I found out what was happening.  The Brick wall is an induction type surge protector.  Since putting it in (about 10 years ago), I have had no problems.  You can read about them at www.brickwall.com Very interesting information, even if they are trying to sell their system.  Rick

[DaveVA78Chieftain]

A 50 amp ATS is designed to switch 50 amp service which is actually 220VAC (4 conductor cable).  You would need to know which leg the control board is monitoring to perform the switch over from shore power to generator power.  You would only be using one leg (i.e. L1) of the unit.  The other Leg (i.e L2) would not have any connections to it.  Even though it is actually 220VAC service, almost all 50 amp RV's are only wired to use 2 independent 110VAC circuits.  There is no 220VAC appliances installed.

The drawing program is free.  I just use MS Paint that is bundled with MS Windows.

Dave

[Lefty]

Don't know a thing about surge protectors...

But... Don't they make a switch "thingy" that allows users with two A/C units to use both at the same time on a 30A circuit? I think they make the compressors alternate so that as one compressor kicks in, the other compressor kicks out. Hm?

[PwrWgnWalt]

Thanks Rick & Kev - I think I will stick with a manual "idiot-proof" method (I'm sure I'll prove that saying wrong!) for switching from shore to genny power.

Thanks Dave - that helps my understanding of a couple of things - one being how the genny could run both A/C units (and I always wondered how one could use the 220V feed of the 50 amp, and yet have a 110V house system...).  Assume then that 50A male to 30A female adapters one might use at the power box (at campsite) must be blocking one hot leg... interesting stuff.  Since I tend to do better using the KISS principle (Keep It Simple Stupid), I will likely forego my friend's generous offer and just stick with 30A stuff for my 30A MH.

Also - when you use MS Paint, are you using just the standard menu choices (square, line, circle, etc.) to make your squiggly lines and such, or is there some custom approach with pre-defined images I'm not seeing?

[DaveVA78Chieftain]

Also - when you use MS Paint, are you using just the standard menu choices (square, line, circle, etc.) to make your squiggly lines and such, or is there some custom approach with pre-defined images I'm not seeing?

Just the out of the box selections.  The squiggly line is done with the Curve tool which is beside the line tool.  It allows you to make 2 adjustments to the line which is how I make the fuse symbol.

Here is is an detailed example that shows both 30 and 50 amp RV distribution from the light pole through the house breaker to the RV.

Dave
PS: As you can see you can get fairly fancy with MS Paint   

But... Don't they make a switch "thingy" that allows users with two A/C units to use both at the same time on a 30A circuit? I think they make the compressors alternate so that as one compressor kicks in, the other compressor kicks out.

Most Coach Mfg's used a front or back AC selector that allowed you to run either unit off shore power connection.  WHen front was selected, you could also run the rear AC from the generator.  You just could not run both from Shore power.

Another option did allow the option to alternate between front and back AC's while on shore power.  I forget the name of the company that produced the controller however I do know they are no longer in business.

[PwrWgnWalt]

I went ahead and picked up the 50 Amp Electrical Management System (more than a "Surge Protector", as I called it before)...
Was looking at a 30Amp EMS-HW30C, but the "price was right" on this unit. It is a Progressive Industries (PI) EMS-PT50C, which plugs directly into the shore power service at a campground  http://www.progressiveindustries.net/ems_pt50c.htm 
It is large and appears to be very well-made. When I called PI (great service, BTW), they said all the features would remain intact if using 30Amp adapter(s), so am confident this will work just fine with our MH as it now exists. 

So much for the background info - now a question...
Since I am re-doing the MH electrical from original and questionable PO mods anyway... is it feasible to update the entire system to 50 Amp service? (like Dave's drawing above, but without an ATS)

I understand I will need to:
   Replace the 30A Shore Power line with a 50A line; and
   Replace the 2 x 30A breaker boxes with a 50A breaker box (& maybe new Circuit Breakers) and do some rewiring/tidying there.
   Could also wire this EMS unit in-house when doing all this, to prevent theft and keep out of weather.
What am I missing?

(The PowerMax Boondocker 75A Converter/Charger, refer and other house service will still plug into 15A power from the breaker box; but am thinking this upgrade may possibly allow for both front and rear A/C to run simultaneously on shore power?)

Thanks for all the help, everyone!  You all are making our "new" MH turn out to be GREAT!
- Walt

[DaveVA78Chieftain]

As long as you understand at a minimum house wiring basics, you can accomplish most anything.  First thing is to makea plan simular to the following (I only use MS Paint to do this stuff)



That drawing was one of several iterations I did to assist someone with an older diesel pusher that had some 1990's era components in it.  As you can see by this next one, it evolved.




In the 2nd drawing that is a 2500W inverter/Charger which performs both as an AC inverter as well as a DC converter/charger.

Even so, there a basics you have to follow much of which is the same as 110VAC house wiring.  220VAC connections or appliances are not realy used in an RV even though the 50 amp shore power supply cable is actually a 220VAC supply.

There are many options for a power panel.  A combination AC and DC power center is the best option simular to the one I used on this thread is the best way to go: http://www.classicwinnebagos.com/forum/index.php/topic,5326.0.html

From my web page: http://dave78chieftain.zxq.net/ConverterInfo.html#Progressive


For this sort of project the first step is to decide what you want and then make yourself a drawing so you know how it all connects together.

Dave

[PwrWgnWalt]

This is too much fun!        

Here's my plan for what we either have now or are planning.  Not shown are the 120VAC Ground lines, which will run back to the subpanel Ground Bus.  This graphic does not include an inverter setup; we're going to wait and see how we get along without one (perhaps a Samlex SSW, and a Transfer Switch, in the future).


(click image to open larger size for details)

I am open to thoughts or suggestions, so please don't hesitate... (want to do it right the first time).
Thanks!
- Walt

[DaveVA78Chieftain]

1. Does your rig have an AUX Start switch and relay?  Cross connects house and chassis batteries so that the house battery can be used to assist the chassis battery if necessary.

2.  Using a diode isolator is not the best alternator charging approach.  They do not allow full alternator voltage to be applied to either the battery (undercharged).  Modern method is to use a battery isolator relay that is controlled by a Bi-Directional Relay Delay Controller (B.I.R.D).
http://www.randkproducts.com/bird-gas-wlow-threshold-p-232.html?osCsid=8kmu0luufnb1dmvdpalv0v2e55
You can also wire in a AUX start switch to the relay so the relay performs doulbe duty.  This has been a standard setup in almost all of todays new rigs.

3.  Diaster fuses.
    A.  Boondocker converter output is already fused so move the diaster fuse over to between the house battery B+ and the house junction block.  Used to prevent mega current flow from battery if there is a short in a house load.
    B. Engine starter pulls up to 400 amps so having to account for that will negate any usefulness of the fuse in the B- battery leg.  A smaller fuse in B- would blow when you hit the start switch.   The only major house side fuse you need is the one I just told you to move to the house battery B+ leg.
    C.  I prefer resetable circuit breakers for this function http://www.ebay.com/sch/i.html?_odkw=(150%2C175%2C200)%20amp%20car%20circuit%20breaker&_osacat=0&_from=R40&_nkw=%28100%2C125%2C150%2C175%2C200%29+amp+car+circuit+breaker&_sacat=0&_trksid=m194&ssPageName=STRK:MEFSRCHX:SRCH.  You can easily isolate the circuit when working on it.  Never have to worry about trying to locate a large replacement fuse.  Works great for inverter connections.  You can isolate a inverter when not in use.
    D.  All major fuses CB's, or fusible links of this type should be mounted within 1ft of the battery.

Dave

[PwrWgnWalt]

Thanks Dave - as always, a wealth of good information.

1. I have not found an AUX switch, or MOM. I haven't found a relay/solenoid anywhere, so far (except on the starter). Here's a picture of the switch panel above the driver's left knee... this is the only thing I have found that approaches some of the capabilities listed on others' RV's. (click for larger image)

{while we're here...  from left to right this is what I know - or think I know}
  ACC - (unknown)
  Quartz Lights - two driving lights on front bumper
  Def. Fans - two round fans on each side of dash (like on school buses)
  Wind. Wash. - assume this will be for the windshield washer fluid squirter (untested, it's unhooked)
  C/O Main / Aux. - fuel tank selector (what's the "C/O" stand for?)
  Gauge Main / Aux. - dash gauge reads fuel level in tank

2. Am aware of the disadvantage of the diode-style battery isolator, but am planning to move the Voltage Regulator sense wire to the "B+"  (starting battery) post (I will use heavier wire than the 18 ga. stock, either 16 or 14 ga.). In theory this should help it 'see' the actual voltage to battery, after the drop for ~15' distance and from the diode isolator, and the Regulator will tell the Alternator to produce a little more juice to compensate for the drop.  The B.I.R.D. sounds intriguing, and I may look into that... looks like I'll need the BIRD unit ($60), plus the solenoid ($68); anything more beside wire?
{Have considered the AUX switch too; can the BIRD use a similar solenoid, or does it need to be theirs?
Might go with AUX switch and a constant-duty solenoid for now, adding the BIRD later if my plan does not work as intended}

3. Disaster Fuse/CB:  thanks for clearing that up & great tip on isolating lines with CB!  What rating should that "B+"  Circuit Breaker be?  {Think I read that it should be <= 125% of high current draw?}

3D. Battery box (under steps) is limited in size and the outside is exposed to road... suggestions on where to mount CB and House Junction Block, with minimal fuss? 

Appreciate you taking the time to share your knowledge!
- Walt

[DaveVA78Chieftain]

If you go with a AUX relay, then connect the house battery directly to it.
 

Then tap the Disaster fuse/CB directly to the house battery B+ post such that it is not in the AUX solinoid circuit.  That way all house components are protected but the fuse does not see engine starter current.

Here is a modern day setup.  Even though you do not have the battery disconnects, you can see how the "AUX Start" switch is integrated with a BIRD relay controller from this drawing.



Dave

[DaveVA78Chieftain]

Walt asked about the size of a disaster fuse so I thought I would answer here for everyones benefit.

Actually, I feel the best approach, in my opinion, is dividing the protection across multiple fuses rather than one single fuse.  Problem with a single fuse is it has to be so large that in effect it really doesn't provide protection.  The 400-500 amp starter amperage is one issue that has to be taken into account.

Use a short cable to either the isolation (Aux Start) solinoid or a isolated standoff that can be used as a distribution point for each fused leg.



The fuse (or CB) for each leg should be located close to the "distribution post".  This way provides more effective protection as each leg has a built in "diasaster fuse" sized appropriately for the actaul load in that leg.

Dave

[Oz]

(I think we should open a  "Dave Bailey Electro-Schematic Art Museum" to display his work....)

[PwrWgnWalt]

     My thanks to all of you for sharing your information, ideas and pictures - especially Dave and his magnificent drawings!

I have almost completed re-doing the 12V systems, incorprating many of the ideas & methods many of you have used or recommended - and avoided a few pitfalls in the process, too. 

In short, it was a very simple system (which I applaud) - but it was limited.
Now, I have Coach/Chassis Battery isolation, Battery Monitoring, and an Automatic Charging Relay to allow both the Coach and Chassis battery to charge whenever either one of them is receiveing a charge (converter/charger, or alternator, or whatever). 

I've loaded several pictures on my 'refurbish' posting/blog here: http://www.classicwinnebagos.com/forum/index.php/topic,6765.msg32397.html#msg32397

Again, thanks to all for your contributions to this effort!  We're getting closer to enjoying our first campout in the Ol' Beast.

- Walt & Tina