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| [GMCnet] Avion 120 VAC System [message #192455] |
Fri, 07 December 2012 06:20  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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G'day,
Would appreciate it if you guys could review what I wrote below and let me know if I've got it!
Thanks,
Rob M.
-----Original Message-----
From: Rob Mueller
Matt, Ken, Mike,
Here's what I think I understand.
Reference: http://www.gmcmhphotos.com/photos/avion-circuit-breaker-panel/p46677-double-trouble-cb-pane.html
The number on the single handled breaker is 40. It is the Main breaker as labeled.
Subsequent to this photo I removed the stickers above the C/B's put Dymo labels under them
From left to right they are:
1) Water Heater
2) Rear Air Conditioner
3 & 4) Main (Dual C/B)
5) Wall Plugs
6) Front Air Conditioner
Reference: http://www.gmcmhphotos.com/photos/member-galleries/p41975-avion-120vac-schematic.htm
On the schematic in the box that represents the Load Center there are three rows:
Row 1) A rectangle with five black dots and connecting white wires. From left to right the white wires connect to:
A/C - Front A/C
A/C - Rear A/C
Water heater
Power cable plug
Wall plugs
I understand this to be the Neutral.
Row 2) Two empty rectangles
I understand these to be the power busses.
Row 3) A row of black dots grouped in twos from left to right which are connected to black wires connecting to:
Water Heater
Rear A/C
Black wire from the Power Cable
Red wire from the Power Cable
Wall Plugs
Front A/C
The middle two are power input from the Power Cable or Onan when the Power Cable is plugged into the 50 AMP RECEPTACLE in the CORD
STORAGE BOX.
The Black wire from the Power Cable supplies 120vac to the left breaker of the Dual C/B. That side of the Dual C/B supplies up to 20
amps of 120vac to the Water Heater and Rear A/C.
The Red wire from the Power Cable supplies 120vac to the right breaker of the Dual C/B. That side of the Dual C/B supplies up to 20
amps of 120vac to the Wall Plugs and Front A/C.
Regards,
Rob M.
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Avion 120 VAC System [message #192461 is a reply to message #192458] |
Fri, 07 December 2012 06:55  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Matt,
Thanks!
And YOU too! ;-)
Frankly for the life of me I can not understand why my mind can grasp mechanical, hydraulic, pneumatic, etc things in a heart beat
but electrical stuff I struggle with.
Strange.
Regards,
Rob M.
-----Original Message-----
From: Matt Colie
Rob,
If I had found an issue with it, I would have brought it to your attention the first time you published it.
I know you believe yourself to be electrically challenged, but that is only because you are using KenB and KenH as a benchmark...
Matt
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Avion 120 VAC System [message #192467 is a reply to message #192455] |
Fri, 07 December 2012 08:31 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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| Robert Mueller wrote on Fri, 07 December 2012 04:20 |
G'day,
Would appreciate it if you guys could review what I wrote below and let me know if I've got it!
...
<< snipped >>
...
The Black wire from the Power Cable supplies 120vac to the left breaker of the Dual C/B. That side of the Dual C/B supplies up to 20 amps of 120vac to the Water Heater and Rear A/C.
The Red wire from the Power Cable supplies 120vac to the right breaker of the Dual C/B. That side of the Dual C/B supplies up to 20 amps of 120vac to the Wall Plugs and Front A/C.
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Not quite correct:
EACH SIDE of your 40 amp "dual" C/B can supply 40 amps. It is basicly TWO 40 amp breakers with a common lever. The ones in a GM up-fitted coach just have the handles (levers) connected together so they turn on and off at the same time.
So, it is POSSIBLE to supply 20 amps to the Water Heater, 20 amps to the Rear A/C, 20 amps to the Wall Plugs and 20 amps to the Front A/C. ALL AT THE SAME TIME.
And to really blow your mind: If you did get 20 amps to all your branch curcuits, when plugged into a 240v curcuit, the current on the neutral wire in the power cord would be ZERO amps!
But if you used a 120v system it would be 80 amps! (scarey)
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Avion 120 VAC System [message #192519 is a reply to message #192467] |
Fri, 07 December 2012 18:40 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Mike,
Thanks!
I understand the first two sentences but the third and fourth have confused me.
I'm talking about the 120 VAC / 60 Hz system in Double Trouble not the 240 VAC / 50 Hz system in The Blue Streak.
I'm going to do some Google searches about how A/C systems work to try and reach a better understanding of the way they work. Along
with that I'll read the GMC MM sections that relate to house A/C systems.
Regards,
Rob M.
-----Original Message-----
From: Mike Miller
EACH SIDE of your 40 amp "dual" C/B can supply 40 amps. It is basicly TWO 40 amp breakers with a common lever. The ones in a GM
up-fitted coach just have the handles (levers) connected together so they turn on and off at the same time.
So, it is POSSIBLE to supply 20 amps to the Water Heater, 20 amps to the Rear A/C, 20 amps to the Wall Plugs and 20 amps to the
Front A/C. ALL AT THE SAME TIME.
And to really blow your mind: If you did get 20 amps to all your branch curcuits, when plugged into a 240v curcuit, the current on
the neutral wire in the power cord would be ZERO amps!
But if you used a 120v system it would be 80 amps! (scarey)
Mike
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GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Avion 120 VAC System [message #192538 is a reply to message #192519] |
Sat, 08 December 2012 00:34 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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Senior Member |
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| Robert Mueller wrote on Fri, 07 December 2012 16:40 |
Mike,
Thanks!
I understand the first two sentences but the third and fourth have confused me.
I'm talking about the 120 VAC / 60 Hz system in Double Trouble not the 240 VAC / 50 Hz system in The Blue Streak.
I'm going to do some Google searches about how A/C systems work to try and reach a better understanding of the way they work. Along with that I'll read the GMC MM sections that relate to house A/C systems.
-----Original Message-----
From: Mike Miller
EACH SIDE of your 40 amp "dual" C/B can supply 40 amps. It is basicly TWO 40 amp breakers with a common lever. The ones in a GM up-fitted coach just have the handles (levers) connected together so they turn on and off at the same time.
So, it is POSSIBLE to supply 20 amps to the Water Heater, 20 amps to the Rear A/C, 20 amps to the Wall Plugs and 20 amps to the Front A/C. ALL AT THE SAME TIME.
And to really blow your mind: If you did get 20 amps to all your branch curcuits, when plugged into a 240v curcuit, the current on
the neutral wire in the power cord would be ZERO amps!
But if you used a 120v system it would be 80 amps! (scarey)
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Rob,
I was talking about the 120 VAC / 60 Hz system, used in Double Trouble and most other GMC's. (But not Coachman 30 amp systems.)
I looked for a web-site that explains our 240v system simply enough for our purposes. Most that I found compared our “U.S., single split-phase, 240 V system” with other systems used else-where that only complicated the issue. But I did find this statement:
"The most common residential and small commercial service in the U.S., single split-phase, 240 V, features a neutral and two hot legs, 240 V to each other, and 120 V each to the neutral."
OK, but what does that mean?
I found a wikipedia entry that had a few good statements but LOTS of additional statements that just confused the issue. ( I put a quote and a link at the end of this message. It MIGHT make more sense after my explanation.) Something that I did not know was that this system has its roots back with Thomas Edison's DC power distribution systems.
The main advantage of the system is: If you double the voltage, you can get more power through a smaller conductor with lower line loss. (I.E. Less money/more power.)
Keep in mind that in an AC system there isn't any "fixed" positive and negative... it changes many times a second. (In the US, 60 complete cycles every second.)
AND...
While there ARE differences in how AC and DC react, but not much difference for purely resistive loads (like light bulbs)... so using light bulb loads, I will use a DC system and try to explain "just enough."
Let us use a DC power system "for instructional proposes only”. (It will not be a practical system but that is not the point.) We will power our system with two 12v batteries through a special jumper cable or cord with three conductors with amp gauges on each wire. The three wires will be called “hot A”, “hot B” and “common”.
Side “A” will be powered by “hot A” and Side “B” will be powered by “hot B.” Both sides share the “common” wire.
Situation #1 will simulate a connection to the “U.S., single split-phase, 240 V system.” The battery on side “A” will be connected with the positive side connected to the “hot A” wire and the negative connected to the “common” wire. Side “B” battery will be connected with the positive connected to the “common” wire and the negative connected to the “hot B” wire.
This provides 12v between each “hot” and the “common” wire. (Granted “Hot B” is negative (-12v) in relation to common.) This system also provides 24v between the two “hots.”
You would notice that:
-- With a 12v 12 watt light bulb on the “hot A” side you would have 1 amp flowing on the “hot A” and common wires, with nothing flowing on the “hot B” wire.
-- With a 12v 12 watt light bulb on the “hot B” side you would have 1 amp flowing on the “hot B” and common wires, with nothing flowing on the “hot A” wire.
-- With a balanced load of a 12v 12 watt light bulb on EACH “hot A” and a 12v 12 watt light bulb on “hot B” side you would have 1 amp flowing in the “hot A” and “hot B” wires, but NO current in the common wire. (Note that this one amp is providing a total of 24 watts.)
-- With a non- balanced load of two 12v 12 watt light bulbs on “hot A” and “hot B” sides you would have 2 amps flowing in the “hot A,” and 1 amp flowing on “hot B,” and ONLY 1 amp on the common wire. (This totals of 36 watts.)
-- Now to use the full voltage, with a 24v 24 watt light bulb load between the two hot wires, it will draw 1 amp through both hots but no current in the common wire. (This one amp is providing a total of 24 watts.)
Situation #2 will simulate a connection to the “single phase, 120 V to both hot wire system” (like when connected to your generator) the battery on side “A” will still be connected with the positive side connected to the “hot A” wire and the negative connected to the “common” wire. Side “B” battery will be changed to connect with the positive connected to the “hot B” wire and the negative connected to the “common” wire. (Just like side “A.”)
This also provides 12v between each “hot” and the “common” wire BUT with both hots being positive (+12v) in relation to common. This system has 0v between the two “hots.” You would notice that:
-- With a 12v 12 watt light bulb on the “hot A” side you would have 1 amp flowing on the “hot A” and common wires, with nothing flowing on the “hot B” wire. (Just like situation #1.)
-- With a 12v 12 watt light bulb on the “hot B” side you would have 1 amp flowing on the “hot B” and common wires, with nothing flowing on the “hot A” wire. (Just like situation #1.)
-- With a balanced load of a 12v 12 watt light bulb on EACH “hot A” and a 12v 12 watt light bulb on “hot B” side you would have 1 amp flowing in the “hot A” and “hot B” wires, but 2 amps current in the common wire. (Just like situation #1, this a total of 24 watts.
Unlike situation #1 ALL current returns through the common wire.)
-- With a non- balanced load of two 12v 12 watt light bulbs on “hot A” and “hot B” sides you would have 2 amps flowing in the “hot A,” and 1 amp flowing on “hot B,” and 3 amps on the common wire. (Just like situation #1, this a total of 36 watts.
Unlike situation #1 ALL current returns through the common wire.)
-- As there is NOT 24 volts available across the hot sides, a 24v 24 watt light bulb (or any load) between the two hot wires, it will not give any current. (This why it isn't a good idea to install 240v equipment in our (US based) coaches, unless you wish to do other changes.)
Now applying what we have discussed:
In situation #1 when using current from each side, you get more actual POWER (watts) from each amp flowing through the cord. Also the current on the common wire is ALWAYS the difference between the current in the hot legs. So if you expect to always have some current on each side, you can use a smaller gauge wire for the common. (Saving money.)
In situation #2 the current on the common wire is ALWAYS the TOTAL of the current in the hot legs. So if you'll need to have a LARGER gauge wire for the common. (Costing more money.) You also only get to use each amp "once" increasing the total current for the same power (or watts.)
The promised quote/link:
<http://en.wikipedia.org/wiki/Split-phase_electric_power>
| Quote: |
In countries whose standard phase to neutral voltage is 120 V, lighting and small appliances are connected between a live wire and the neutral. Large appliances, such as cooking equipment, space heating, water pumps, clothes dryers, and air conditioners are connected across the two live conductors and operate at 240 V, requiring less current and smaller conductors than would be needed if the appliances were designed for 120 V operation.
No individual conductor will be at more than 120 V potential with respect to ground (earth), reducing the earth fault current when compared to a 240 V, 2-wire system that has one leg (the neutral) earthed.
Split-phase systems require less copper for the same voltage drop, final utilization voltage, and power transmitted than single phase systems. (Voltage drop tends to be the dominant design consideration in the sizing of long power distribution cable runs.) Just how much depends on the situation. However, the extra conductor may require more insulation material and more complex processing, reducing the cost saving for lower power runs.
Fig. 4
In the United States, the practice originated with the DC distribution system developed by Thomas Edison. By dividing a lighting load into two equal groups of lamps connected in series, the total supply voltage can be doubled and the size of conductors reduced substantially.
Fig. 5
If the load were guaranteed to be balanced, then the neutral conductor would not carry any current and the system would be equivalent to a single ended system of twice the voltage with the live cables taking half the current. This would not need a neutral conductor at all, but would be wildly impractical for varying loads; just connecting the groups in series would result in excessive voltage and brightness variation as lamps are switched on and off.
By connecting the two lamp groups to a neutral, intermediate in potential between the two live legs, any imbalance of the load will be supplied by a current in the neutral, giving substantially constant voltage across both groups. The total current carried in all three wires (including the neutral) will always be twice the supply current of the most heavily loaded half.
For short wiring runs limited by conductor ampacity, this allows three half-sized conductors to be substituted for two full-sized ones, using 75% of the copper of an equivalent single-phase system.
Longer wiring runs are more limited by voltage drop in the conductors. Because the supply voltage is doubled, a balanced load can tolerate double the voltage drop, allowing quarter-sized conductors to be used; this uses 3/8 the copper of an equivalent single-phase system.
In practice, some intermediate value is chosen. For example, if the imbalance is limited to 25% of the total load (half of one half) rather than the absolute worst-case 50%, then conductors 3/8 of the single-phase size will guarantee the same maximum voltage drop, totaling 9/8 of one single-phase conductor, 56% of the copper of the two single-phase conductors.
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Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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