Home » Public Forums » GMCnet » [GMCnet] Addition to fire prevention steps
| [GMCnet] Addition to fire prevention steps [message #132208] |
Mon, 27 June 2011 09:03  |
 |
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
|
Senior Member |
|
|
G'day,
As noted in earlier emails I am working on a treatise regarding GMC fires.
Gene posted a link to the quote below on his website in response to Pete's
question about coiling his power cord.
"An inductor is a coil of wire that will restrict/impede the flow of AC
current & will heat up the same as an equivalent resistor value (as in an
electric heater). Operating the coach at maximum load (80 amps) can be a bit
sporty with the shore power cable coiled up nicely in its electrical box
(creates an inductor). It has been reported at an FMCA rally, technical
seminar; that fires have occurred due to the coiling of the shore power
cable into a small electrical storage area. When I plug into shore power, I
always pull all the wire out of the storage area & lay it on the ground in a
straight line to prevent the coil effect. This will also minimize the
voltage drop (maximize the ac voltage available) of the shore power cable
while running under loads. Type "SO" wire/cable is a much better choice than
the OEM for the shore power cable, since it has a neoprene rubber jacket &
has very fine wire strands. Type "SO" is rated at a much broader range of
temperature operation w/o becoming stiff & brittle."
I'm a bit confused by the statement:
"Operating the coach at maximum load (80 amps) can be a bit sporty with the
shore power cable coiled up nicely in its electrical box (creates an
inductor)."
Is (80 amps) a typo; should it not be 50 amps? The power cord is rated for
50 amps and campsites have 50 amp circuit breakers on the sockets.
Has anyone ever heard of a GMC that caught fire because of this?
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
_______________________________________________
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
|
|
|
|
| Re: [GMCnet] [Bulk] Addition to fire prevention steps [message #132209 is a reply to message #132208] |
Mon, 27 June 2011 09:08  |
Wayne Newland
Messages: 75
Registered: February 2004
Karma: 0
|
Member |
|
|
It's my understanding that we only get two legs of 120 thru the big fat
shore cable, for a total of 40 watts, not 50. It's so stamped on my shore
cable.
Wayne Newland F9300 75 Palm Beach Sebastian, Fl
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Rob Mueller
Sent: Monday, June 27, 2011 10:04 AM
To: gmclist@temp.gmcnet.org
Subject: [Bulk] [GMCnet] Addition to fire prevention steps
G'day,
As noted in earlier emails I am working on a treatise regarding GMC fires.
Gene posted a link to the quote below on his website in response to Pete's
question about coiling his power cord.
"An inductor is a coil of wire that will restrict/impede the flow of AC
current & will heat up the same as an equivalent resistor value (as in an
electric heater). Operating the coach at maximum load (80 amps) can be a bit
sporty with the shore power cable coiled up nicely in its electrical box
(creates an inductor). It has been reported at an FMCA rally, technical
seminar; that fires have occurred due to the coiling of the shore power
cable into a small electrical storage area. When I plug into shore power, I
always pull all the wire out of the storage area & lay it on the ground in a
straight line to prevent the coil effect. This will also minimize the
voltage drop (maximize the ac voltage available) of the shore power cable
while running under loads. Type "SO" wire/cable is a much better choice than
the OEM for the shore power cable, since it has a neoprene rubber jacket &
has very fine wire strands. Type "SO" is rated at a much broader range of
temperature operation w/o becoming stiff & brittle."
I'm a bit confused by the statement:
"Operating the coach at maximum load (80 amps) can be a bit sporty with the
shore power cable coiled up nicely in its electrical box (creates an
inductor)."
Is (80 amps) a typo; should it not be 50 amps? The power cord is rated for
50 amps and campsites have 50 amp circuit breakers on the sockets.
Has anyone ever heard of a GMC that caught fire because of this?
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] Addition to fire prevention steps [message #132220 is a reply to message #132208] |
Mon, 27 June 2011 09:44 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
|
Senior Member |
|
|
WELLLL, YES, BUT!!
The opposition to current "flow" in a coil with
AC applied is quite easily calclulated.
Using XL (the opposing inductive reactance),
L (inductance in Henrys), and F (frequency in
Hertz/cycles per second) the formula is:
XL = 2 x (Pi) x F x L
(sorry I don't know how to access the "pi" symbol.)
Since the inductance of the coil of power cable would
NOT be tremendously large (could be calculated by
somebody with more time than I want to spend), and the
frequency very low, I doubt there is a whole lot of
inductive reactance (XL) involved here.
I am quite sure that the simple resistance of the
copper wire itself would give the greatest voltage
drop and resultant heating of the cable conductors.
Would coiling the power cable (OUTSIDE the compartment)
offer SOME lightning protection? I would say yes. The
energy in lightning is supposedly almost totally AC
(actually at radio frequencies) and the inductive
reactance at RF frequencies would be tremendously
greater than at 60 Hz power frequency.
Even a single length of wire or a braided ground strap
has significant inductance and consequent inductive
reactance at RF frequencies (I.E., lightning-caused).
I have seen one of the braid straps that connected a
ham friend's radio tower to his 6-foot ground rod
VAPORIZED by a lightning stroke.
As always, your results may vary (YRMV).
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~~ ~ ~ (TZE166V101966) ~ ~ ~~
~ ~ ~ ex-Palm Beach, 76 ~ ~ ~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
P.S. Isn't the "in-coach" power system breakered
for 40 Amps total? 20 Amps on each of the two
blades of the Onan output?
> From: robmueller@iinet.net.au
> To: gmclist@temp.gmcnet.org
> Date: Tue, 28 Jun 2011 00:03:54 +1000
> Subject: [GMCnet] Addition to fire prevention steps
>
> G'day,
>
> As noted in earlier emails I am working on a treatise regarding GMC fires.
> Gene posted a link to the quote below on his website in response to Pete's
> question about coiling his power cord.
>
> "An inductor is a coil of wire that will restrict/impede the flow of AC
> current & will heat up the same as an equivalent resistor value (as in an
> electric heater). Operating the coach at maximum load (80 amps) can be a bit
> sporty with the shore power cable coiled up nicely in its electrical box
> (creates an inductor). It has been reported at an FMCA rally, technical
> seminar; that fires have occurred due to the coiling of the shore power
> cable into a small electrical storage area. When I plug into shore power, I
> always pull all the wire out of the storage area & lay it on the ground in a
> straight line to prevent the coil effect. This will also minimize the
> voltage drop (maximize the ac voltage available) of the shore power cable
> while running under loads. Type "SO" wire/cable is a much better choice than
> the OEM for the shore power cable, since it has a neoprene rubber jacket &
> has very fine wire strands. Type "SO" is rated at a much broader range of
> temperature operation w/o becoming stiff & brittle."
>
> I'm a bit confused by the statement:
>
> "Operating the coach at maximum load (80 amps) can be a bit sporty with the
> shore power cable coiled up nicely in its electrical box (creates an
> inductor)."
>
> Is (80 amps) a typo; should it not be 50 amps? The power cord is rated for
> 50 amps and campsites have 50 amp circuit breakers on the sockets.
>
> Has anyone ever heard of a GMC that caught fire because of this?
>
> Regards,
> Rob M.
> Sydney, Australia
> AUS '75 Avion-The Blue Streak TZE365V100428
> USA '75 Avion-Double Trouble TZE365V100426
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] [Bulk] Addition to fire prevention steps [message #132224 is a reply to message #132209] |
Mon, 27 June 2011 09:54 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
|
Senior Member |
|
|
That is 40 AMPS and NOT 40 Watts!
40 Amps x 120 Volts give you 4,800 vOLT-AMPS;
similar but not exactly equal to 4,800 Watts.
The genset needs to be capable of more than
4.8 KW because of the inductive load, especially
at start-up, of up to TWO A/C units.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~~ ~ ~ (TZE166V101966) ~ ~ ~~
~ ~ ~ ex-Palm Beach, 76 ~ ~ ~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
----------------------------------------
> From: waynewland@bellsouth.net
> To: gmclist@temp.gmcnet.org
> Date: Mon, 27 Jun 2011 10:08:05 -0400
> Subject: Re: [GMCnet] [Bulk] Addition to fire prevention steps
>
> It's my understanding that we only get two legs of 120 thru the big fat
> shore cable, for a total of 40 watts, not 50. It's so stamped on my shore
> cable.
>
> Wayne Newland F9300 75 Palm Beach Sebastian, Fl
>
> -----Original Message-----
> From: gmclist-bounces@temp.gmcnet.org
> [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Rob Mueller
> Sent: Monday, June 27, 2011 10:04 AM
> To: gmclist@temp.gmcnet.org
> Subject: [Bulk] [GMCnet] Addition to fire prevention steps
>
> G'day,
>
> As noted in earlier emails I am working on a treatise regarding GMC fires.
> Gene posted a link to the quote below on his website in response to Pete's
> question about coiling his power cord.
>
> "An inductor is a coil of wire that will restrict/impede the flow of AC
> current & will heat up the same as an equivalent resistor value (as in an
> electric heater). Operating the coach at maximum load (80 amps) can be a bit
> sporty with the shore power cable coiled up nicely in its electrical box
> (creates an inductor). It has been reported at an FMCA rally, technical
> seminar; that fires have occurred due to the coiling of the shore power
> cable into a small electrical storage area. When I plug into shore power, I
> always pull all the wire out of the storage area & lay it on the ground in a
> straight line to prevent the coil effect. This will also minimize the
> voltage drop (maximize the ac voltage available) of the shore power cable
> while running under loads. Type "SO" wire/cable is a much better choice than
> the OEM for the shore power cable, since it has a neoprene rubber jacket &
> has very fine wire strands. Type "SO" is rated at a much broader range of
> temperature operation w/o becoming stiff & brittle."
>
> I'm a bit confused by the statement:
>
> "Operating the coach at maximum load (80 amps) can be a bit sporty with the
> shore power cable coiled up nicely in its electrical box (creates an
> inductor)."
>
> Is (80 amps) a typo; should it not be 50 amps? The power cord is rated for
> 50 amps and campsites have 50 amp circuit breakers on the sockets.
>
> Has anyone ever heard of a GMC that caught fire because of this?
>
> Regards,
> Rob M.
> Sydney, Australia
> AUS '75 Avion-The Blue Streak TZE365V100428
> USA '75 Avion-Double Trouble TZE365V100426
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] Addition to fire prevention steps [message #132227 is a reply to message #132220] |
Mon, 27 June 2011 10:08 |
|
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
|
Senior Member |
|
|
Mac,
If I understand what you're saying I should include it in steps to prevent
GMC fires but it's a long shot?
I just checked the Avion Operators Manual and you're correct, it says; "The
distribution panel . . . . . . provides a 40 amp main disconnect. . . ."
Keeping in mind that I'm electrically challenged this brings up another
question; do the RV parks actually supply 50 amps or are they too only 40
amps?
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of D C *Mac* Macdonald
Sent: Tuesday, 28 June 2011 12:45 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Addition to fire prevention steps
WELLLL, YES, BUT!!
The opposition to current "flow" in a coil with
AC applied is quite easily calclulated.
Using XL (the opposing inductive reactance),
L (inductance in Henrys), and F (frequency in
Hertz/cycles per second) the formula is:
XL = 2 x (Pi) x F x L
(sorry I don't know how to access the "pi" symbol.)
Since the inductance of the coil of power cable would
NOT be tremendously large (could be calculated by
somebody with more time than I want to spend), and the
frequency very low, I doubt there is a whole lot of
inductive reactance (XL) involved here.
I am quite sure that the simple resistance of the
copper wire itself would give the greatest voltage
drop and resultant heating of the cable conductors.
Would coiling the power cable (OUTSIDE the compartment)
offer SOME lightning protection? I would say yes. The
energy in lightning is supposedly almost totally AC
(actually at radio frequencies) and the inductive
reactance at RF frequencies would be tremendously
greater than at 60 Hz power frequency.
Even a single length of wire or a braided ground strap
has significant inductance and consequent inductive
reactance at RF frequencies (I.E., lightning-caused).
I have seen one of the braid straps that connected a
ham friend's radio tower to his 6-foot ground rod
VAPORIZED by a lightning stroke.
As always, your results may vary (YRMV).
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~~ ~ ~ (TZE166V101966) ~ ~ ~~
~ ~ ~ ex-Palm Beach, 76 ~ ~ ~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
P.S. Isn't the "in-coach" power system breakered
for 40 Amps total? 20 Amps on each of the two
blades of the Onan output?
_______________________________________________
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
|
|
|
|
| Re: [GMCnet] [Bulk] Addition to fire prevention steps [message #132233 is a reply to message #132224] |
Mon, 27 June 2011 10:31 |
|
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
|
Senior Member |
|
|
Mac,
So 50 amps x 120 volts = 6000 VOLT-AMPS?
6000 watts is what the Onan is rated at so why don't they have a 50 amp C/B
in the panel?
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of D C *Mac* Macdonald
Sent: Tuesday, 28 June 2011 12:54 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] [Bulk] Addition to fire prevention steps
That is 40 AMPS and NOT 40 Watts!
40 Amps x 120 Volts give you 4,800 vOLT-AMPS;
similar but not exactly equal to 4,800 Watts.
The genset needs to be capable of more than
4.8 KW because of the inductive load, especially
at start-up, of up to TWO A/C units.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~~ ~ ~ (TZE166V101966) ~ ~ ~~
~ ~ ~ ex-Palm Beach, 76 ~ ~ ~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
_______________________________________________
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
|
|
|
|
| Re: [GMCnet] Addition to fire prevention steps [message #132238 is a reply to message #132208] |
Mon, 27 June 2011 10:40 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
|
Senior Member |
|
|
| Robert Mueller wrote on Mon, 27 June 2011 09:03 |
G'day,
As noted in earlier emails I am working on a treatise regarding GMC fires.
Gene posted a link to the quote below on his website in response to Pete's question about coiling his power cord.
"An inductor is a coil of wire that will restrict/impede the flow of AC current & will heat up the same as an equivalent resistor value (as in an electric heater). Operating the coach at maximum load (80 amps) can be a bit sporty with the shore power cable coiled up nicely in its electrical box (creates an inductor). It has been reported at an FMCA rally, technical seminar; that fires have occurred due to the coiling of the shore power cable into a small electrical storage area. When I plug into shore power, I always pull all the wire out of the storage area & lay it on the ground in a straight line to prevent the coil effect. This will also minimize the voltage drop (maximize the ac voltage available) of the shore power cable while running under loads. Type "SO" wire/cable is a much better choice than the OEM for the shore power cable, since it has a neoprene rubber jacket & has very fine wire strands. Type "SO" is rated at a much broader range of temperature operation w/o becoming stiff & brittle."
I'm a bit confused by the statement:
"Operating the coach at maximum load (80 amps) can be a bit sporty with the shore power cable coiled up nicely in its electrical box (creates an inductor)."
Is (80 amps) a typo; should it not be 50 amps? The power cord is rated for 50 amps and campsites have 50 amp circuit breakers on the sockets.
Has anyone ever heard of a GMC that caught fire because of this?
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
|
Any fires that might be caused by coiling the cord have nothing to do with inductance (which has no resistance and therefore cannot create any heat). If the inductance introduces enough impedance, it would LOWER the current and therefore LOWER the amount of heat in the cord. That might cause appliances problems, and THEY might get hot. I dunno. Also, I doubt that the small number of coils in rolling up that cord could introduce enough inductance to amount to anything. It would be interesting to measure the inductance of a tightly coiled cord.
Coiling the cord in a confined space would limit the amount of heat that could be dissipated, as opposed to leaving it uncoiled in open air. The HEAT from the RESISTANCE of the conductors in the cord, if it is seriously overloaded, MIGHT cause materials in the cord to become flammable. IMHO, that is the real risk.
As I have said before, other views of the universe may vary. Bottom line: Uncoiling the cord where it can dissipate heat is safer whether you blame the risk on inductance or on RESISTIVE heat.
|
|
|
|
| Re: [GMCnet] [Bulk] Addition to fire prevention steps [message #132240 is a reply to message #132233] |
Mon, 27 June 2011 10:46 |
Dave Mumert
Messages: 272
Registered: February 2004
Location: Olds, AB, Canada
Karma: 0
|
Senior Member |
|
|
Hi
The Onan feeds both 40 amp breakers in parallel so the coach is running on
120 volts when powered by the Onan and 240 volts when connected with the 50
amp 240 volt cable.
Dave
> -----Original Message-----
> Subject: Re: [GMCnet] [Bulk] Addition to fire prevention steps
>
> Mac,
>
> So 50 amps x 120 volts = 6000 VOLT-AMPS?
>
> 6000 watts is what the Onan is rated at so why don't they have a 50 amp
C/B
> in the panel?
>
> Regards,
> Rob M.
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] Addition to fire prevention steps [message #132244 is a reply to message #132227] |
Mon, 27 June 2011 11:19 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
[Keeping in mind that I'm electrically challenged this brings up another
question; do the RV parks actually supply 50 amps or are they too only 40
amps?
More food for thought. My favorite RV park which I admit is a bit primitive has a 70 amp breaker feeding 12 campsites with 50&30 amp reciprocals, a few 40 ft monsters sucking power and poof no power for the lot.
Roy
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
|
| Re: [GMCnet] [Bulk] Addition to fire prevention steps [message #132245 is a reply to message #132233] |
Mon, 27 June 2011 11:28 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
|
Senior Member |
|
|
Rob (and others), I am NOT an electrician, but Watts
is the unit of measurement for ACTUAL power (work done).
Volt-amps (IIRC) refers to "apparent" power being
generated/used. This includes "non-useful" power
in things such as motors and other "inductive" loads.
These currents are "out of phase" with your "main"
and usefull power. These out-of-phase components
are at a 90 degree angle to the main power. Depending
upon whether they are inductive (motors, compressors,
etc.) or capacitive (can't think of any right now)
compensation needs to be added at the device. Since
most motors are heavy inductive loads to the power,
RUN and START capacitors are needed for operation.
I think larger motors even use separate start and
run capacitors. They are harder to get running than
to keep running.
Usually, that will be a larger amount than the "true"
power. It is referred to by "power factor" which is
some sort of measure of how efficient your device
is putting the eletricity being supplied to work.
I am well aware that the above info is likely a
gross simplification and make NO claim to its
exact accuracy, but I hope it illuminates rather
than hides.
Regarding the safety question, I think it is highly
doubtful that there would be any problem in that
heavy duty power cable itself. Based on history
of electically-caused fires on boats, the trouble
spot is FAR more likely to reside at ANY connector.
Corrosion or simply wear on the contact points
will develop a high resistance. Whenever current
passes through a resistance, a voltage drop will
occur and heat will arise IN that connection. This
is by far the most common origination of fires
of an electrical nature.
I believe that many generators are specified in
Volt-Amps. This is to allow for the lowered TRUE
power to be supplies and takes into account the
power factor and "wasted" power.
I assume that the breakers in the GMC are chosen
to provide a safe margin for the devices that were
or could be installed in the coach. The wiring
would also (hopefully) have been corrected to give
a safe margin of operation.
Again, this is simplification and very possibly
OVER-simplification.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~~ ~ ~ (TZE166V101966) ~ ~ ~~
~ ~ ~ ex-Palm Beach, 76 ~ ~ ~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
> From: robmueller@iinet.net.au
> To: gmclist@temp.gmcnet.org
> Date: Tue, 28 Jun 2011 01:31:48 +1000
> Subject: Re: [GMCnet] [Bulk] Addition to fire prevention steps
>
> Mac,
>
> So 50 amps x 120 volts = 6000 VOLT-AMPS?
>
> 6000 watts is what the Onan is rated at so why don't they have a 50 amp C/B
> in the panel?
>
> Regards,
> Rob M.
> Sydney, Australia
> AUS '75 Avion-The Blue Streak TZE365V100428
> USA '75 Avion-Double Trouble TZE365V100426
>
>
> -----Original Message-----
> From: gmclist-bounces@temp.gmcnet.org
> [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of D C *Mac* Macdonald
> Sent: Tuesday, 28 June 2011 12:54 AM
> To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] [Bulk] Addition to fire prevention steps
>
>
> That is 40 AMPS and NOT 40 Watts!
>
> 40 Amps x 120 Volts give you 4,800 vOLT-AMPS;
> similar but not exactly equal to 4,800 Watts.
> The genset needs to be capable of more than
> 4.8 KW because of the inductive load, especially
> at start-up, of up to TWO A/C units.
>
> ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
> ~~ ~ D C "Mac" Macdonald ~ ~~
> ~ ~ Amateur Radio - K2GKK ~ ~
> ~ ~ USAF and FAA, Retired ~ ~
> ~ ~ ~ Oklahoma City, OK ~ ~ ~
> ~~ ~ ~ "The Money Pit" ~ ~ ~~
> ~~ ~ ~ (TZE166V101966) ~ ~ ~~
> ~ ~ ~ ex-Palm Beach, 76 ~ ~ ~
> ~ www.gmcmhphotos.com/okclb ~
> ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] [Bulk] Addition to fire prevention steps [message #132246 is a reply to message #132240] |
Mon, 27 June 2011 11:31 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
|
|
Induced electromagnetic radiation or magnetic field strength is greater the
number of electrons (amps) that pass by a given point in a coil. Also
affected by the voltage, and the number of turns in the coil. In order for
a coil of wire lying on the ground or for that matter in a closed space to
do anything except maybe make your hair stand on end or interfere with what
ever radio equipment might be operating in the near vicinity, there would
have to be considerable electron flow. If your power cord is heating up, the
load on it is too great, or the internal resistance of the conductors is too
high. Too large a conductor is always a good idea vs too small. Two rooftop
ACs draw a lot of amps. If the cord is too small you can expect some heating
to occur. The Royales equipped with two Rooftop units usually power one from
the shore power and one from the Onan because of the load involved. That is
why most of them only have a 30 amp cord instead of the 50 amp one. Your
experiences with GMCs may differ. Lots of combinations exist out there.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Mon, Jun 27, 2011 at 8:46 AM, Dave Mumert <dave@mumert.com> wrote:
> Hi
>
> The Onan feeds both 40 amp breakers in parallel so the coach is running on
> 120 volts when powered by the Onan and 240 volts when connected with the 50
> amp 240 volt cable.
>
> Dave
>
> > -----Original Message-----
> > Subject: Re: [GMCnet] [Bulk] Addition to fire prevention steps
> >
> > Mac,
> >
> > So 50 amps x 120 volts = 6000 VOLT-AMPS?
> >
> > 6000 watts is what the Onan is rated at so why don't they have a 50 amp
> C/B
> > in the panel?
> >
> > Regards,
> > Rob M.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] Addition to fire prevention steps [message #132260 is a reply to message #132238] |
Mon, 27 June 2011 12:02 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
True dat - but th safest thing to do is determine what is drawing so much current the cord is getting hot in the first place and fix it. It's like about #6 wire, why is it getting hot???
--johnny
--- On Mon, 6/27/11, A. <markbb1@netzero.com> wrote:
From: A. <markbb1@netzero.com>
Subject: Re: [GMCnet] Addition to fire prevention steps
To: gmclist@temp.gmcnet.org
Date: Monday, June 27, 2011, 3:40 PM
Robert Mueller wrote on Mon, 27 June 2011 09:03
> G'day,
>
> As noted in earlier emails I am working on a treatise regarding GMC fires.
> Gene posted a link to the quote below on his website in response to Pete's question about coiling his power cord.
>
> "An inductor is a coil of wire that will restrict/impede the flow of AC current & will heat up the same as an equivalent resistor value (as in an electric heater). Operating the coach at maximum load (80 amps) can be a bit sporty with the shore power cable coiled up nicely in its electrical box (creates an inductor). It has been reported at an FMCA rally, technical seminar; that fires have occurred due to the coiling of the shore power cable into a small electrical storage area. When I plug into shore power, I always pull all the wire out of the storage area & lay it on the ground in a straight line to prevent the coil effect. This will also minimize the voltage drop (maximize the ac voltage available) of the shore power cable while running under loads. Type "SO" wire/cable is a much better choice than the OEM for the shore power cable, since it has a neoprene rubber jacket & has very fine wire strands. Type "SO" is rated at a much broader range of
temperature operation w/o becoming stiff & brittle."
>
> I'm a bit confused by the statement:
>
> "Operating the coach at maximum load (80 amps) can be a bit sporty with the shore power cable coiled up nicely in its electrical box (creates an inductor)."
>
> Is (80 amps) a typo; should it not be 50 amps? The power cord is rated for 50 amps and campsites have 50 amp circuit breakers on the sockets.
>
> Has anyone ever heard of a GMC that caught fire because of this?
>
> Regards,
> Rob M.
> Sydney, Australia
> AUS '75 Avion-The Blue Streak TZE365V100428
> USA '75 Avion-Double Trouble TZE365V100426
Any fires that might be caused by coiling the cord have nothing to do with inductance (which has no resistance and therefore cannot create any heat). If the inductance introduces enough impedance, it would LOWER the current and therefore LOWER the amount of heat in the cord. That might cause appliances problems, and THEY might get hot. I dunno. Also, I doubt that the small number of coils in rolling up that cord could introduce enough inductance to amount to anything. It would be interesting to measure the inductance of a tightly coiled cord.
Coiling the cord in a confined space would limit the amount of heat that could be dissipated, as opposed to leaving it uncoiled in open air. The HEAT from the RESISTANCE of the conductors in the cord, if it is seriously overloaded, MIGHT cause materials in the cord to become flammable. IMHO, that is the real risk.
As I have said before, other views of the universe may vary. Bottom line: Uncoiling the cord where it can dissipate heat is safer whether you blame the risk on inductance or on RESISTIVE heat.
--
'73 23' CanyonLands
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
|
|
|
| Re: [GMCnet] Addition to fire prevention steps [message #132339 is a reply to message #132260] |
Mon, 27 June 2011 19:20 |
|
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
|
Senior Member |
|
|
G'day,
I appreciate all the responses to this question.
I have decided not to include "Uncoil the shore power cable" in the fire
prevention steps as it appears that in a GMC the chances that the cable
starting a fire is remote.
In an Avion there is a socket in the box that houses the cable that you plug
it into to feed Onan power to the C/B box. I have driven long distances with
the Onan running powering the front A/C, fridge, hot water heater, etc. and
never noticed the cable being hot when I uncoiled it from the box upon
parking for the evening.
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
_______________________________________________
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
|
|
|
|
Goto Forum:
Current Time: Tue Oct 15 09:29:27 CDT 2024
Total time taken to generate the page: 0.00961 seconds
|
GMCforum
Search
Help
Register
Login
Home
