Transfer switch question???

[mbrower]

I finally got around to installing an inverter and have question concerning transfer switch. A little information on what I have. I bought a 50A progressive dynamics xfer switch that I wired with priority to shore power instead of inverter/generator. I took the time delay out so the switch will transfer power instantly with no loads dropping out. I ran the power for the AC's and hot water heater through a contactor that is actuated by shore power so when power is switched to inverter, both ACs and water heater are open circuits. I also ran a separate 30A marine plug to the front of the camper to power camper from portable generator and tied it into the inverter circuit via a 30A transfer switch with priority to inverter and a time delay switch to generator.

Everything works well configured this way but I do have concerns with the 50A relay switching loads backwards. Progressive dynamics have been little help as to drawbacks if any and I was seeking wisdom from fellow campers. Any information would be appreciated.

[happycamper002]

mbrower wrote:


I appreciate the concern and as I told my wife I was going for "idiot proof" especially where I was concerned. Power for the switching is coming from the feed itself and is operating the relay through electronic circuitry.

[COLOR=]This relay is energized by shore power that is fed to your battery charger via a branch circuit from the load center. In my RV it is the third breaker from the left.


After a lot of testing and metering, I have the belief that both electrical sources are operated by relay coils and not by mechanical springs.

These are electro-mechanical relays. As opposed to solid state relays, they have magnet coils to open or close the contacts. The springs are there to hold the contacts when deenergized. There are also three relays (if you include the time delay relay. Time delay relay is electronic no spring.

If I am on shore power and I power up the inverter or generator nothing happens. If while inverter or generator is powered up and I open the shore power breaker at the pedestal, I hear the relay operate for the alternate power and life goes on with out a blip.

The relay click that you hear is the isolation relay that isolates the shore power from any foreign power source that is introduced to the panel buss, that includes generator and/or inverter or any auxiliary power source. This is activated via time delay through a DC bridge to prevent chattering in case of voltage fluctuation from the generator. The time delay is there to allow the generator voltage to stabilize before energizing the relay.


If Neither alternate source is powered up and I loose shore power, nothing happens. Relay does not operate. If I am powered by the inverter and I close the shore power breaker, the relay will operate and power will transfer back to shore power.

[COLOR=]What is happening here is: when you throw the power on, you are activating the charging system through a third relay that is hidden in the charging module. It is an integral part of the Progressive Dynamics Converter that doesn't need maintenance. If it goes bad, PD would recommend changing the whole module. Although for a resourceful guy like you, could easily replace it with parts from eBay.

Leaving the inverter on will not run my batteries down except in extreme power outage. Exactly what I wanted.

You will not run your batteries down because you are continuously charging the battery. Also (you said) you are plugged in to the pedestal while running the inverter which means you are not drawing power from inverter. . . and instead from the PD converter. Remember that you have it configured to shore power priority. You can't have both because the way the isolation relay is configured.

Having said that, leads me to conclude that somewhere this is defying logic.

Why would you need to run the inverter when you are plugged in to pedestal? I hope you are not confused about INVERTER and CONVERTER.

Inverter you hookup to battery 12VDC to 120VAC

Converter you hookup to AC. 120VAC to 12 VDC

Had I wired transfer switch with priority to inverter, I would stay on inverter even with shore power available running my batteries down to inverter shut off, even if I regain shore power to the camper. Not what I wanted.

Checking with meter, there is no back feeding anywhere.

Everything I have bought is either rated for or exceeds the capacity of the loads, with breakers and fuses being the exception.

Mark

[mbrower]

First and foremost, thanks for the compliment.. .you just made my day. 🙂

Now back to the issue.

I think I'm following your line of thought. The inherent logic would certainly serve the projected goal. However, you did not say where you will get the control power to energize/deenergize the transfer switches.


Are you powering them from the shore power or from the inv/gen?

Since you stated that your dominant power would be shore power, I assume that both 30A transfer switch and 50A transfer switch are controlled by shore power. Being plugged in to the pedestal would ignore other available power source. Which is fine and dandy as long as there is power at the pedestal.

Now, here is the kicker: Although this instance is moot and hopefully won't ever happen in your case, the possibility still exist. If I can quote Murphy's Law: "Anything that can happen will happen".

What's gonna happen if (God forbid) you lost power completely or experience a prolonged power outage, your battery is down while the auxiliary is setting idle. Whatever state you transfer switch is in prior to the power failure will remain that way. Firing up the Auxiliary power would not do any good either because the transfer switches are looking for the pedestal power which of course God knows when it's coming back.

I just hope it won't coincide with Jesus's Second Coming. 🙂

Cheers!

I appreciate the concern and as I told my wife I was going for "idiot proof" especially where I was concerned. Power for the switching is coming from the feed itself and is operating the relay through electronic circuitry. After a lot of testing and metering, I have the belief that both electrical sources are operated by relay coils and not by mechanical springs.

If I am on shore power and I power up the inverter or generator nothing happens. If while inverter or generator is powered up and I open the shore power breaker at the pedestal, I hear the relay operate for the alternate power and life goes on with out a blip. If Neither alternate source is powered up and I loose shore power, nothing happens. Relay does not operate. If I am powered by the inverter and I close the shore power breaker, the relay will operate and power will transfer back to shore power. Leaving the inverter on will not run my batteries down except in extreme power outage. Exactly what I wanted. Had I wired transfer switch with priority to inverter, I would stay on inverter even with shore power available running my batteries down to inverter shut off, even if I regain shore power to the camper. Not what I wanted.

Checking with meter, there is no back feeding anywhere.

Everything I have bought is either rated for or exceeds the capacity of the loads, with breakers and fuses being the exception.

Mark

[DrewE]

mbrower wrote:

Excellent response! Love this kind of feedback.

I currently have 2 transfer switches. One is a 50A with priority to shore power (as stated before) that will stay on shore power regardless whether the inverter or generator is on. It will only switch if shore power is off. Once shore power is returned, the switch will transfer power back to shore power. Alternate power should never backfeed to shore power as long as the transfer switch is working correctly.

The generator and inverter are on the alternate power feed and is being switched by a 30A transfer switch. Priority is given to generator after 40 second time delay.

I think you may believe the generator and shore power feed one input side of the transfer switch and this is not the case. Shore power feeds one input and inverter/generator feeds the other input though a separate 30A transfer switch. All inputs are separated from one another so no backfeeding is possible with properly operating transfer switches. Am I still missing something?

Mark

This is how I understood your setup (though the initial description wasn't as clear as it might have been). The setup is fine in concept, and should be safe and workable in practice provided everything is appropriately specified and wired properly.

I probably would not set things up quite this way (in particular, I don't think I would want shore power to have priority over the generator), but that's a question of personal preference rather than safety.

[happycamper002]

mbrower wrote:


Excellent response! Love this kind of feedback.

I currently have 2 transfer switches. One is a 50A with priority to shore power (as stated before) that will stay on shore power regardless whether the inverter or generator is on. It will only switch if shore power is off. Once shore power is returned, the switch will transfer power back to shore power. Alternate power should never backfeed to shore power as long as the transfer switch is working correctly.

The generator and inverter are on the alternate power feed and is being switched by a 30A transfer switch. Priority is given to generator after 40 second time delay.

I think you may believe the generator and shore power feed one input side of the transfer switch and this is not the case. Shore power feeds one input and inverter/generator feeds the other input though a separate 30A transfer switch. All inputs are separated from one another so no backfeeding is possible with properly operating transfer switches. Am I still missing something?

Mark

First and foremost, thanks for the compliment.. .you just made my day. 🙂

Now back to the issue.

I think I'm following your line of thought. The inherent logic would certainly serve the projected goal. However, you did not say where you will get the control power to energize/deenergize the transfer switches.


Are you powering them from the shore power or from the inv/gen?

Since you stated that your dominant power would be shore power, I assume that both 30A transfer switch and 50A transfer switch are controlled by shore power. Being plugged in to the pedestal would ignore other available power source. Which is fine and dandy as long as there is power at the pedestal.

Now, here is the kicker: Although this instance is moot and hopefully won't ever happen in your case, the possibility still exist. If I can quote Murphy's Law: "Anything that can happen will happen".

What's gonna happen if (God forbid) you lost power completely or experience a prolonged power outage, your battery is down while the auxiliary is setting idle. Whatever state you transfer switch is in prior to the power failure will remain that way. Firing up the Auxiliary power would not do any good either because the transfer switches are looking for the pedestal power which of course God knows when it's coming back.

I just hope it won't coincide with Jesus's Second Coming. 🙂

Cheers!

[mbrower]

happycamper002 wrote:

mbrower wrote:
I finally got around to installing an inverter and have question concerning transfer switch. A little information on what I have. I bought a 50A progressive dynamics xfer switch that I wired with priority to shore power instead of inverter/generator. I took the time delay out so the switch will transfer power instantly with no loads dropping out. I ran the power for the AC's and hot water heater through a contactor that is actuated by shore power so when power is switched to inverter, both ACs and water heater are open circuits. I also ran a separate 30A marine plug to the front of the camper to power camper from portable generator and tied it into the inverter circuit via a 30A transfer switch with priority to inverter and a time delay switch to generator.

Everything works well configured this way but I do have concerns with the 50A relay switching loads backwards. Progressive dynamics have been little help as to drawbacks if any and I was seeking wisdom from fellow campers. Any information would be appreciated.

You are defeating the purpose of the transfer switch.

You said that you wired with "priority to shore power" which makes me think that you wired it differently from Progressive Dynamics design criteria. Your configuration will work by having the option of whether you want the power priority to be applied as in inverter/generator over shore power. By having a NO/NC contactor, you can only have one or other--not both at any given time . . .which is fine.

However, I'm concerned when you added a separate power input from a portable generator with a 30A plug. Power distribution systems designers take the time to figure out every scenario that can happen when their product hit the consumer. It would be a big mistake to oversimplify something that took considerable time for experts to examine every angle that might happen should their product are subjected to abuse. Unauthorized modification is one of them.

This is one reason engineers at Progressive Dynamics are not willing to commit. Say what you may but these are professionals who could be held accountable should their product cause harm or worse.

One scenario that could be catastrophic is: although you can be sure (after a good night's sleep and you haven't had one drink too many) that shore power is not applied when using the separate 30A marine plug.
What will happen if you forgot by having both sources applied to the rig?

The above could happen because you are using one NC contactor and a separate NO contactor feeding one common input.

If you have the marine 30A plug energized (along with the shore power plug) you will end up energizing the shore power distribution lines which could be deadly to utility workers.

This is where transfer switch becomes mandatory.



The above is just one scenario, but there could be more... cross feeding could also be a possibility.

Excellent response! Love this kind of feedback.

I currently have 2 transfer switches. One is a 50A with priority to shore power (as stated before) that will stay on shore power regardless whether the inverter or generator is on. It will only switch if shore power is off. Once shore power is returned, the switch will transfer power back to shore power. Alternate power should never backfeed to shore power as long as the transfer switch is working correctly.

The generator and inverter are on the alternate power feed and is being switched by a 30A transfer switch. Priority is given to generator after 40 second time delay.

I think you may believe the generator and shore power feed one input side of the transfer switch and this is not the case. Shore power feeds one input and inverter/generator feeds the other input though a separate 30A transfer switch. All inputs are separated from one another so no backfeeding is possible with properly operating transfer switches. Am I still missing something?

Mark

[happycamper002]

mbrower wrote:
I finally got around to installing an inverter and have question concerning transfer switch. A little information on what I have. I bought a 50A progressive dynamics xfer switch that I wired with priority to shore power instead of inverter/generator. I took the time delay out so the switch will transfer power instantly with no loads dropping out. I ran the power for the AC's and hot water heater through a contactor that is actuated by shore power so when power is switched to inverter, both ACs and water heater are open circuits. I also ran a separate 30A marine plug to the front of the camper to power camper from portable generator and tied it into the inverter circuit via a 30A transfer switch with priority to inverter and a time delay switch to generator.

Everything works well configured this way but I do have concerns with the 50A relay switching loads backwards. Progressive dynamics have been little help as to drawbacks if any and I was seeking wisdom from fellow campers. Any information would be appreciated.

You are defeating the purpose of the transfer switch.

You said that you wired with "priority to shore power" which makes me think that you wired it differently from Progressive Dynamics design criteria. Your configuration will work by having the option of whether you want the power priority to be applied as in inverter/generator over shore power. By having a NO/NC contactor, you can only have one or other--not both at any given time . . .which is fine.

However, I'm concerned when you added a separate power input from a portable generator with a 30A plug. Power distribution systems designers take the time to figure out every scenario that can happen when their product hit the consumer. It would be a big mistake to oversimplify something that took considerable time for experts to examine every angle that might happen should their product are subjected to abuse. Unauthorized modification is one of them.

This is one reason engineers at Progressive Dynamics are not willing to commit. Say what you may but these are professionals who could be held accountable should their product cause harm or worse.

One scenario that could be catastrophic is: although you can be sure (after a good night's sleep and you haven't had one drink too many) that shore power is not applied when using the separate 30A marine plug.
What will happen if you forgot by having both sources applied to the rig?

The above could happen because you are using one NC contactor and a separate NO contactor feeding one common input.

If you have the marine 30A plug energized (along with the shore power plug) you will end up energizing the shore power distribution lines which could be deadly to utility workers.

This is where transfer switch becomes mandatory.

The above is just one scenario, but there could be more... cross feeding could also be a possibility.

[time2roll]

The 100 amp PD transfer switch is contactor based so that either side is held closed with a coil.

[mbrower]

brulaz wrote:

mbrower wrote:

...
That is correct, I have shore power running through the "designated generator " side of the relay (NO) and generator running through the "shore power" side of the relay (NC). I keep power on my camper 24/7 and was nervous about the relay coil staying energized.

Although I don't have a PD transfer switch, mine is wired this way as well. When on shore power the coil is activated closing the shore power contacts. When not on shore power, a spring keeps the other contacts closed.

I've been told that the electromagnetic coil will keep the contacts closed tighter than the spring allowing greater current. This is appropriate for me as shore power should handle the full 30 A (50A in your case), but my inverter can only generate a very max of 15A.
Also when using the inverter, I don't want to waste energy for the coil.

But when on shore power the coil is always energized, and it does generate heat, and I noticed a faint hum recently. Otherwise it's worked well over the last year or two.

This is exactly what I was thinking but could not find a relay that operated this way. Didn't make sense to me but I'm no electrical engineer

Thanks to all that took the time to reply! I really appreciate it.
Mark

[brulaz]

mbrower wrote:

...
That is correct, I have shore power running through the "designated generator " side of the relay (NO) and generator running through the "shore power" side of the relay (NC). I keep power on my camper 24/7 and was nervous about the relay coil staying energized.

Although I don't have a PD transfer switch, mine is wired this way as well. When on shore power the coil is activated closing the shore power contacts. When not on shore power, a spring keeps the other contacts closed.

I've been told that the electromagnetic coil will keep the contacts closed tighter than the spring allowing greater current. This is appropriate for me as shore power should handle the full 30 A (50A in your case), but my inverter can only generate a very max of 15A.

Also when using the inverter, I don't want to waste energy for the coil.

But when on shore power the coil is always energized, and it does generate heat, and I noticed a faint hum recently. Otherwise it's worked well over the last year or two.

[MrWizard]

no problems with what you have done

in fact I think it is Normal to use the NC side for shore power
and NO for generator.. I would do it that way

[mbrower]

smkettner wrote:

mbrower wrote:
Everything works well configured this way but I do have concerns with the 50A relay switching loads backwards.

If you mean Normally Open vs Normally Closed sides it is not an issue.

Even going the other way does not matter if you are switching power between two output paths.

As long as power goes one direction you are fine. Must travel from source to the load only.

That is correct, I have shore power running through the "designated generator " side of the relay (NO) and generator running through the "shore power" side of the relay (NC). I keep power on my camper 24/7 and was nervous about the relay coil staying energized.

[time2roll]

mbrower wrote:
Everything works well configured this way but I do have concerns with the 50A relay switching loads backwards.

If you mean Normally Open vs Normally Closed sides it is not an issue.

Even going the other way does not matter if you are switching power between two output paths.

As long as power goes one direction you are fine. Must travel from source to the load only.