Transfer Switches - They're Nothing But Trouble Waiting to Happen
- Thread starter rsalhus
- Start date
The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
OP
OP
rsalhus
Well-known member
- Joined
- Jul 20, 2006
- Posts
- 1,335
I have never heard you recommend not being connected to shore power when switching from generator to shore power or vice versa. In fact, I don't think I've ever heard anyone make such a recommendation in here besides Lou Schneider. That's the point.
Rolf, I would venture a guess that every recommendation you have ever read here on this subject has included the admonition that it is better to err on the side of caution when switching power sources.
I agree with Lou's first point in that switching power sources under load is a bad idea. No one has said anything different.
As for statement number two,
"Second, AC power switches from Positive to Negative and back again 60 times per second. There's nothing to make the generator synchronize with shore power, so the instant the switch transfers you could have +120 volts on the shore power and -120 volts on the generator. This will send a surge through everything that's turned on at that time, which will likewise shorten it's life."
The contacts of the transfer switch are break before make and take an eternity to switch, compared to the 60 times a second swing of the ac voltage, (and the -120 doesn't just sit there waiting for the +120 to show up) so the probability of an unreasonable or unusual surge damaging circuitry, from this phenomenon, during a simple controlled switch in power source is extremely remote and no more probable than damaging something every time you apply power through any switch.
I realize I'm not a staff member, but I think forty-plus years of electrical engineering and practical application experience qualifies me to at least have an opinion on the subject.
I thought earlier on that some of the banter here was done, tongue in cheek, but I'm beginning to believe you have a definite agenda on this subject.
I hope you still have enough of a sense of humor to appreciate the comment that your dunce cap would make a good looking accessory to Lou's outfit of belt and suspenders.
I agree with Lou's first point in that switching power sources under load is a bad idea. No one has said anything different.
As for statement number two,
"Second, AC power switches from Positive to Negative and back again 60 times per second. There's nothing to make the generator synchronize with shore power, so the instant the switch transfers you could have +120 volts on the shore power and -120 volts on the generator. This will send a surge through everything that's turned on at that time, which will likewise shorten it's life."
The contacts of the transfer switch are break before make and take an eternity to switch, compared to the 60 times a second swing of the ac voltage, (and the -120 doesn't just sit there waiting for the +120 to show up) so the probability of an unreasonable or unusual surge damaging circuitry, from this phenomenon, during a simple controlled switch in power source is extremely remote and no more probable than damaging something every time you apply power through any switch.
I realize I'm not a staff member, but I think forty-plus years of electrical engineering and practical application experience qualifies me to at least have an opinion on the subject.
I thought earlier on that some of the banter here was done, tongue in cheek, but I'm beginning to believe you have a definite agenda on this subject.
I hope you still have enough of a sense of humor to appreciate the comment that your dunce cap would make a good looking accessory to Lou's outfit of belt and suspenders.
OP
OP
rsalhus
Well-known member
- Joined
- Jul 20, 2006
- Posts
- 1,335
Lou, no agenda here. But honestly, it's been my philosophy to always disconnect shore power before switching power and Lou Schneider's recommendation just confirmed what I have always practiced, although I could never explain the 'why' of it as he did. I do it because it seems safer. That's it. And like you say, caution has always been recommended here when switching power sources while under a modest load, but I don't recall anyone else recommending always disconnecting from shore power before actually switching. I could be wrong, and will gladly don my dunce cap and sit in the corner again if proven so.
I hope so too. You know, that comment I made about the dunce cap was borrowed here from Shayne, who's posts always made me laugh. I still crack up whenever I think of him accidentally leaving his wife at a fuel stop.
I certainly miss his humor, I'll tell you that. :'(Rolf, you are not the only one who misses Shayne, but I'm pleased to hear that I'm not either.. What a delight it was to sign on and see posts from him. He could tell it like it was....
As for disconnecting from shore power before switching to an alternate source, I haven't found a way to react fast enough to disconnect shore power, before my whole house inverter takes over, during an unscheduled power outage. I suppose I could run outside into the rain to unplug from shore power so there would be no automatic switch back, when power was restored. Seems a little counter intuitive since I designed it to be automatic. My inverter does wait for two minutes after sensing power to switch back after an outage to protect it self from unstable power and/or multiple emergency switches. I am perfectly content to allow that automatic transfer to take place.
Different strokes...
As for disconnecting from shore power before switching to an alternate source, I haven't found a way to react fast enough to disconnect shore power, before my whole house inverter takes over, during an unscheduled power outage. I suppose I could run outside into the rain to unplug from shore power so there would be no automatic switch back, when power was restored. Seems a little counter intuitive since I designed it to be automatic. My inverter does wait for two minutes after sensing power to switch back after an outage to protect it self from unstable power and/or multiple emergency switches. I am perfectly content to allow that automatic transfer to take place.
Different strokes...
