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RE: Running Generator while on shore power
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I have no argument with the folks who say that failures are rare and the risks are minimal. I happen to agree with them. What I take exception to are the comments that failure is impossible and there is no way for it to happen. There is always a way.
The manual for my transfer switch does not specifically warn against starting the generator with the shore power on. But it does contain the following, which goes to show that they acknowledge that failures are possible:
IOTA Engineering L.L.C. will not knowingly sell an ITS
Transfer Switch for any life-support application. It is
strongly recommended that you do not operate any life
support equipment from a transfer switch. If the switch
should malfunction, or fail to operate due to other external
conditions, it is possible that all connected appliances,
including any life support equipment, will also shut down,
resulting in a risk of medical complications and potential
loss of life.
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Ok, I'll agree that the probability of failure is not zero, although many of the failure modes you listed earlier (wiring overheating and insulation softening or becoming brittle, etc.) are a risk whether there is an ATS or not.
ATSs for life support equipment have a different set of standards they have to meet, UL 1008, I believe. I'm sure that $50 wouldn't cover the requirements for UL 1008.
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Bubby's RV
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02/12/10 12:13pm |
General RVing Issues
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RE: Running Generator while on shore power
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after the utility power drops out the generator (usually diesel powered) starts, there is always a period of time when AC power is off and only the battery powered emg lights are on, anywhere from 30sec to 3 minutes depending on the installed system avg time approx 90 seconds.
the commercial ATS are not subject to switching while the Utility/shore power is still HOT.
and the generator only supplies essential systems, NOT everything in the bldg or facility, when utility power returns, there is a timed response as loads are shifted from the generator to the utility power by sections
Usually true, but not necessarily. Some ATSs, called a Closed Transition Transfer Switch (CTTS) have make-before-break although they have circuitry to synchronize the power supplies. Those are required when loss of power for even an instant is not acceptable.
Also, ATSs in critical applications have the capability of being tested and are required to be tested to verify they work without having to shut off the power.
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Bubby's RV
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02/12/10 12:02pm |
General RVing Issues
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RE: Running Generator while on shore power
and your ATS cost thousands of $$ not $50, your ATS is mfg tested for this kind of service, the one in the typical RV is not rated this way, is designed as shore cord protection and convenience, NOT as a foll proof way to switch loads.
Please explain how these are for shore cord protection. I though thought that was the function of the breakers.
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Bubby's RV
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02/12/10 11:41am |
General RVing Issues
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RE: Battery summary – is this correct?
Hi Andy,
Yikes! I hope you make a speedy recovery.
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item #4 the alternator output, in most cases, may be governed by what is happening at the starter battery. As starter battery may be a much smaller capacity than a "house" battery bank, the likelihood of "over charging" the house bank is pretty small. Add to that, that often wire from the engine compartment is undersized and fused at 60 amps. DAMHIK.
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I second the hope for a speedy recovery!
Alternator output is not really driven by the starting battery. It's driven by alternator temperature, with output voltage going down as temperature increases, unless it's been modified somehow. The alternator doesn't "fill up" the starting battery and then "fill up" the house batteries, it fills them so they have the same state of charge, allowing for line losses.
You can increase the wire size to the house batteries (I have to #4) to improve current flow to the house batteries. I don't know your wiring specifically, but I don't have a fuse in the line to/from the house batteries from/to the alternator. My rig has a emergency start switch so I can start my engine from the house batteries and the several hundred amps to the starter would blow a 60-amp fuse.
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Bubby's RV
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02/11/10 07:48pm |
Tech Issues
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RE: California speed limits/restrictions
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Bubby's RV
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02/11/10 07:27pm |
General RVing Issues
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RE: RV Crime Statistics
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Bubby's RV
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02/11/10 07:23pm |
General RVing Issues
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RE: Running Generator while on shore power
There is no way that the transfer switch can fail and cause generator power to flow down the shore power cable. The transfer switch can connect to the shore power cable OR the generator, but NEVER both.
Murphy will always prove you wrong in the end. But by then you'll be to dead to really care.:S
Not me. I currently (no pun intended) have one of those "cheap" RVs that doesn't have an ATS. I have to unplug from shore power to connect to the generator.
It's just that ATSs are used for emergency load shifting in all kinds of homes and businesses, including medical facilities, and the NEC allows it. Not only are they allowed, they are tested with both power sources available to make sure they work. So if they were so dangerous, they wouldn't be installed elsewhere and the lawyers for ATS manufacturers (including those for RVs) would have all kinds of warnings saying not to do it. After looking at the manuals for several ATSs, there are no warnings to not start the generator while plugged into shore power.
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Bubby's RV
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02/11/10 07:19pm |
General RVing Issues
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RE: Monterey Bay KOA
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Bubby's RV
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02/11/10 12:47pm |
RV Parks, National Parks, State Campgrounds & More
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RE: Magnitude 3.8 Earthquake in ILLINOIS today
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Bubby's RV
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02/10/10 02:49pm |
Around the Campfire
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RE: Do you know dogs & behavior?
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Bubby's RV
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02/10/10 02:38pm |
Around the Campfire
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RE: Running Generator while on shore power
There is no way that the transfer switch can fail and cause generator power to flow down the shore power cable. The transfer switch can connect to the shore power cable OR the generator, but NEVER both.
I have to respectfully disagree. A 2-pole 50-amp service transfer switch has two contactors. One could fail to switch which would leave one pole of the shore power and one pole of the generator connected.
Forty-five years ago when training new help at a Bell System toll office a one leg of a manual 3-pole switch failed which ultimately caused 208-VAC to be placed on every 120-VAC circuit in the office. Besides a few small fires over $20,000 of damage occurred in the office which was built in 1932 and contained miles and miles of pulp insulated cable wiring.
When working with electrical power circuits one must always assume the worst can and will happen in some circumstance. Taking chances with anything electrical is just playing Russian roulette.I would love for you to be able to show me how that (or anything remotely similar) could happen today, with today's equipment, installed per code. I am always ready to learn something new.
I second Ron's request.
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Bubby's RV
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02/10/10 02:07pm |
General RVing Issues
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RE: Running Generator while on shore power
There is no way that the transfer switch can fail and cause generator power to flow down the shore power cable. The transfer switch can connect to the shore power cable OR the generator, but NEVER both.
That's how it's designed to work, but there is always a way for it to fail in an unexpected manner. Something may melt, short out, fuse, etc. The odds of it happening may be extremely remote, but strange stuff can happen.
While it's possible, I won't be losing any sleep over it. It's probably more likely that my rig will be destroyed by a meteor, or I'll get killed by a drunk driver the next time I get behind the wheel.
I have assumed that no one has used a screwdriver to short out the transfer switch.
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Bubby's RV
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02/09/10 06:17pm |
General RVing Issues
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RE: Running Generator while on shore power
The first and foremost reason and logic for unplugging the shore power is safety.
If, for some reason unknown to you, the landline power has been shut down by the power company and you connect a generator to your system, you are creating what is known as “feed back”.
You will be supplying the shore power circuit with 120 vac. This in turn feeds back to the main transformer at the pole, This in turn boosts the power from 120vac to what ever the transformer is rated. In most cases, this will be 37.5k.
If a lineman is working as close as a mile away on a broken power circuit and grabs hold of a line thinking that the power is “dead”. He gets fried to crisp, immediately.
A good practice to hold firm to is “always disconnect” from shore power, regardless of whether or not you have an auto transfer, manual transfer, or no transfer switch. The transfer switches can and will fail and you’ll never know it until its too late.
Not unless your transfer switch fails.
There is no way that the transfer switch can fail and cause generator power to flow down the shore power cable. The transfer switch can connect to the shore power cable OR the generator, but NEVER both.
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Bubby's RV
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02/09/10 12:05pm |
General RVing Issues
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RE: Do you drink the water....
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Bubby's RV
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02/08/10 04:29pm |
General RVing Issues
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RE: Another American rip off
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Bubby's RV
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02/08/10 03:30pm |
Around the Campfire
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RE: .....can constant cynicism be good for you.......??
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Bubby's RV
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02/08/10 03:21pm |
Around the Campfire
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RE: RV'ers dealt another blow
It's because Arizona can't balance their budget any better than California can.
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Bubby's RV
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02/04/10 06:57pm |
General RVing Issues
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RE: DMV renewal w/smog inspection while out of state
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Bubby's RV
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02/04/10 04:06pm |
General RVing Issues
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RE: Pole option to remedy the Dead Horse
... giving people the feeling that we are of lower maturity than we are. ...
A pretty long leap of faith if you ask me. :B
Most questions are not easily answered with a simple poll (or pole, unless it's "Would you touch a ___ with a 10-ft pole?").
In addition, one should learn the reason behind an answer, not just the answer, because there will be times when the standard answer doesn’t apply, or there is a twist on the problem. The discussion helps teach others how to think. It’s why we teach a guy how to fish, not just give him a fish. Yeh, I know, so he can sit in a boat all day and drink beer. :R
JMO
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Bubby's RV
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02/04/10 03:36pm |
General RVing Issues
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RE: ...what a motor SHOULD sound like.........
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Bubby's RV
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02/04/10 12:20pm |
Around the Campfire
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