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Old 05-28-2021, 05:22 PM   #1
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Transfer switch priority

I noticed today that my WFCO transfer switch is “generator priority” and is “shore power pass through”. My inverter is wired to the transfer switch generator input and the shore power is wired to the shore power input.

This has 2 implications:
1) When both shore power and generator/inverter inputs are active, it always chooses the generator/inverter source. This is inefficient and wasteful. It is also limiting since the inverter has less capacity than the 30A shore power
2) The relay activates to select the generator/inverter input. Because it is “generator priority”, it is almost always using the generator/inverter input. This consumes a bit of battery

Has anyone swapped the generator and shore power inputs so that shore power has priority? It seems more intuitive to favour shore power over generator/inverter power.
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Old 05-28-2021, 07:01 PM   #2
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Originally Posted by M_canada View Post
I noticed today that my WFCO transfer switch is “generator priority” and is “shore power pass through”. My inverter is wired to the transfer switch generator input and the shore power is wired to the shore power input.

This has 2 implications:
1) When both shore power and generator/inverter inputs are active, it always chooses the generator/inverter source. This is inefficient and wasteful. It is also limiting since the inverter has less capacity than the 30A shore power
2) The relay activates to select the generator/inverter input. Because it is “generator priority”, it is almost always using the generator/inverter input. This consumes a bit of battery

Has anyone swapped the generator and shore power inputs so that shore power has priority? It seems more intuitive to favour shore power over generator/inverter power.
For our purposes here Shore power and generator are the same thing. Both external 120v power sources and use the same input to the Trailer. . The Inverter is wired directly to the battery (DC) for input and the Inverter AC output connected to the Xfer switch.

The xfer switch has two inputs. One from the Sub panel breaker (if multiple outlets) in the AC distribution panel and the other from the Inverter.. I don't know of a xfer switch that would select inverter over generator/shore power. It could be done but why , I haven't the foggiest. If the inverter 'sees' generator/shore power, that what it will use.

If generator/shore power fails and then comes back up after you have turned the inverter on, the xfer switch will switch back to generator/shore power. No intervention required.

The Inverter is still on, just not being used. It's up to you to turn it off.
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Old 05-28-2021, 07:04 PM   #3
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When not using the inverter it should be switched off, problem solved.
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Old 05-28-2021, 07:52 PM   #4
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Originally Posted by RangerMan View Post
For our purposes here Shore power and generator are the same thing. Both external 120v power sources and use the same input to the Trailer.
I would say, as M_canada is suggesting, that "generator" and "inverter" are equivalent - they are the alternative to shore power. Generators are routinely as internal to the RV as an inverter; it's not often (if ever) that anyone wires separate inputs to the outside of an RV, with one for shore power and the other for generator power.

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Originally Posted by RangerMan View Post
The xfer switch has two inputs. One from the Sub panel breaker (if multiple outlets) in the AC distribution panel and the other from the Inverter.. I don't know of a xfer switch that would select inverter over generator/shore power. It could be done but why , I haven't the foggiest. If the inverter 'sees' generator/shore power, that what it will use.

If generator/shore power fails and then comes back up after you have turned the inverter on, the xfer switch will switch back to generator/shore power. No intervention required.
What you're describing is what M_canada is suggesting would be desirable, and I agree. The issue is that M_canada is seeing the switch configured in the opposite way.
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Old 05-28-2021, 07:58 PM   #5
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Originally Posted by Brian B-P View Post
I would say, as M_canada is suggesting, that "generator" and "inverter" are equivalent - they are the alternative to shore power. Generators are routinely as internal to the RV as an inverter; it's not often (if ever) that anyone wires separate inputs to the outside of an RV, with one for shore power and the other for generator power.


What you're describing is what M_canada is suggesting would be desirable, and I agree. The issue is that M_canada is seeing the switch configured in the opposite way.
Are we not talking about Escapes here?
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Old 05-28-2021, 08:08 PM   #6
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Originally Posted by RangerMan View Post
For our purposes here Shore power and generator are the same thing. Both external 120v power sources and use the same input to the Trailer. . The Inverter is wired directly to the battery (DC) for input and the Inverter AC output connected to the Xfer switch.

The xfer switch has two inputs. One from the Sub panel breaker (if multiple outlets) in the AC distribution panel and the other from the Inverter.. I don't know of a xfer switch that would select inverter over generator/shore power. It could be done but why , I haven't the foggiest. If the inverter 'sees' generator/shore power, that what it will use.

If generator/shore power fails and then comes back up after you have turned the inverter on, the xfer switch will switch back to generator/shore power. No intervention required.

The Inverter is still on, just not being used. It's up to you to turn it off.

I just redid my tests to confirm the operation.

- Turn off the inverter and plug in to shore power and wait for the EMS
- Plug in a fan for an AC load
- Turn on the inverter. Initially, the inverter monitor display no AC load, but after 30 seconds, you can hear the transfer switch operate and the inverter monitor displays the AC load

At first this seemed strange to me too, but a quick google search with "RV transfer switch priority" confirms that RV transfer switches give priority to the generator input. An old WFCO T-30 manual says the same thing. My testing confirms this, so I'm pretty sure it is operating as designed. I'd be happier if it gave shore power priority.

I haven't wired up a remote on/off for the inverter, but maybe I should do that.
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Old 05-28-2021, 08:10 PM   #7
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Are we not talking about Escapes here?
Yep, I have a 2021 21NE optioned with lithium and the inverter is wired for all outlets. I've swapped the inverter for a Victron, but I haven't changed the transfer switch wiring.
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Old 05-28-2021, 08:22 PM   #8
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Originally Posted by M_canada View Post
I just redid my tests to confirm the operation.

- Turn off the inverter and plug in to shore power and wait for the EMS
- Plug in a fan for an AC load
- Turn on the inverter. Initially, the inverter monitor display no AC load, but after 30 seconds, you can hear the transfer switch operate and the inverter monitor displays the AC load

At first this seemed strange to me too, but a quick google search with "RV transfer switch priority" confirms that RV transfer switches give priority to the generator input. An old WFCO T-30 manual says the same thing. My testing confirms this, so I'm pretty sure it is operating as designed. I'd be happier if it gave shore power priority.

I haven't wired up a remote on/off for the inverter, but maybe I should do that.
The 'icon' displayed on the Go Power simply means the inverter is on. It does not mean there is a load on the inverter.

The inverter should be turned off when not in use as it uses battery power just by being on.

On our Escapes as they come from ETI the Xfer switch is shore power priority.
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Old 05-28-2021, 08:55 PM   #9
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The 'icon' displayed on the Go Power simply means the inverter is on. It does not mean there is a load on the inverter.

The inverter should be turned off when not in use as it uses battery power just by being on.
I’m not using the GoPower controller. My system consists of Victron inverter, solar controller, shunt and GX-based monitor. It displays the inverter AC load in watts. 30 seconds after the the inverter is turned on, the transfer switch clicks and the AC load changes from 0W to 145W. I’m very confident that the inverter is suppling the load.

This discussion has proved useful, thank you for the conversation. While considering the remote on/off switch, I just discovered a menu in my monitor panel to remotely control my inverter, so I don’t need to wire in a remote switch.

It has also reminded me other another drawback to the transfer switch having shore power designated as the ‘pass through’ input. My inverter has an ECO mode where it periodically turns on the AC output and checks for a minimum AC load. This can reduce idle power draw to less than 3W. The transfer switch needs the generator input to be active for 30 seconds and operates the relay to switch to the generator input, so ECO mode doesn’t work. I think if I swap the input connections at the transfer switch, I will be able to use the ECO mode and solve most of my issues.
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Old 05-28-2021, 08:55 PM   #10
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The wfco 30amp transfer switch was designed for rvs that have built in generators. A call to wfco should clear it up using it with an inverter . Escapes go power install with solar integrates an off on switch in the solar controller, at least in 2017. I would think you definitely want the remote switch if you are using a different brand. I’m planning on adding my inverter after the fact as we have solar only. I’ll use the progressive dynamics 2000 watt inverter that has a ts built in , granted only 20 amps. However my dual six volts are only cable of supporting a 2200 watt inverter any way. I will be adding the remote. Go power makes the same type of inverter with a ts, but it’s 200 plus dollars more versus installing a dedicated on off and monitor switch

The ts in the progressive dynamics will work as expected and shore power will be the priority. I’ve learned a lot from other members on this forum about various designs.
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Old 05-28-2021, 08:56 PM   #11
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Originally Posted by RangerMan View Post
The 'icon' displayed on the Go Power simply means the inverter is on. It does not mean there is a load on the inverter.

The inverter should be turned off when not in use as it uses battery power just by being on.

On our Escapes as they come from ETI the Xfer switch is shore power priority.
I wonder if they changed the wiring or mis-wired mine?
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Old 05-28-2021, 09:04 PM   #12
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Originally Posted by M_canada View Post
I noticed today that my WFCO transfer switch is “generator priority” and is “shore power pass through”. My inverter is wired to the transfer switch generator input and the shore power is wired to the shore power input.

This has 2 implications:
1) When both shore power and generator/inverter inputs are active, it always chooses the generator/inverter source. This is inefficient and wasteful. It is also limiting since the inverter has less capacity than the 30A shore power
2) The relay activates to select the generator/inverter input. Because it is “generator priority”, it is almost always using the generator/inverter input. This consumes a bit of battery

Has anyone swapped the generator and shore power inputs so that shore power has priority? It seems more intuitive to favour shore power over generator/inverter power.
I assume that this is the WFCO T-30 transfer switch. I don't see anything in the product web page, brochure, or current manual, which indicates that this has generator-priority logic... but it doesn't mention priority at all, so that doesn't mean it isn't generator-priority.

The “shore power pass through” feature is good - it means that relays are not energized when on shore power. Assuming that shore power is connected for more time than the inverter is on, that extends the life of the transfer switch.

I agree that it makes no sense in this case to use the inverter when shore power is available. It is nonsensical, if the inverter is accidentally left on, to convert shore power from 120 V AC to 12 V DC in the WFCO converter just to invert it back to 120 V AC in the inverter. But there's a reason for inverter/generator priority: it allows the user to get reliable or clean power from their own generator or inverter when there are problems with shore power, without unplugging anything.

To avoid unnecessarily using the inverter (or generator) - assuming generator/inverter priority - it just need to be turned off, as already mentioned. As already explained, you typically don't want the inverter on unnecessarily even if it isn't delivering any power, as it has idle power consumption whenever it is turned on. If accidentally leaving the inverter on is an issue, maybe a highly visible inverter-on indication would help, or an indicator (or even an alarm) to show when the inverter is on while shore power is available (which could be done with a couple of relays).
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Old 05-28-2021, 09:05 PM   #13
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Originally Posted by RangerMan View Post
Are we not talking about Escapes here?
Yes, but the transfer switch is not unique to Escape - it is labelled for typical applications, which are more commonly generators than inverters. I was just explaining that "shore power" and "generator" are not interchangeable in the context of this transfer switch, and why the input for the inverter is labelled "generator".
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Old 05-28-2021, 09:06 PM   #14
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Originally Posted by RangerMan View Post
Are we not talking about Escapes here?
Quote:
Originally Posted by M_canada View Post
Yep, I have a 2021 21NE optioned with lithium and the inverter is wired for all outlets.
RangerMan's remark was directed to me, because I mentioned RVs with onboard generators (which Escapes don't have).
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Old 05-28-2021, 09:07 PM   #15
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The wfco 30amp transfer switch was designed for rvs that have built in generators. A call to wfco should clear it up using it with an inverter . Escapes go power install with solar integrates an off on switch in the solar controller, at least in 2017. I would think you definitely want the remote switch if you are using a different brand. I’m planning on adding my inverter after the fact as we have solar only. I’ll use the progressive dynamics 2000 watt inverter that has a ts built in , granted only 20 amps. However my dual six volts are only cable of supporting a 2200 watt inverter any way. I will be adding the remote. Go power makes the same type of inverter with a ts, but it’s 200 plus dollars more versus installing a dedicated on off and monitor switch

The ts in the progressive dynamics will work as expected and shore power will be the priority. I’ve learned a lot from other members on this forum about various designs.
I may give WFCO a call on Monday. I dealt with them on another question and was impressed with their commitment to answering my question. I was just hoping that it was common to wire the inputs to the transfer to meet the application.
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Old 05-28-2021, 09:08 PM   #16
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Originally Posted by Brian B-P View Post
RangerMan's remark was directed to me, because I mentioned RVs with onboard generators (which Escapes don't have).
Oops, sorry about that. Thanks for the clarification.
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Old 05-28-2021, 09:31 PM   #17
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Originally Posted by Brian B-P View Post
I assume that this is the WFCO T-30 transfer switch. I don't see anything in the product web page, brochure, or current manual, which indicates that this has generator-priority logic... but it doesn't mention priority at all, so that doesn't mean it isn't generator-priority.

The “shore power pass through” feature is good - it means that relays are not energized when on shore power. Assuming that shore power is connected for more time than the inverter is on, that extends the life of the transfer switch.

I agree that it makes no sense in this case to use the inverter when shore power is available. It is nonsensical, if the inverter is accidentally left on, to convert shore power from 120 V AC to 12 V DC in the WFCO converter just to invert it back to 120 V AC in the inverter. But there's a reason for inverter/generator priority: it allows the user to get reliable or clean power from their own generator or inverter when there are problems with shore power, without unplugging anything.

To avoid unnecessarily using the inverter (or generator) - assuming generator/inverter priority - it just need to be turned off, as already mentioned. As already explained, you typically don't want the inverter on unnecessarily even if it isn't delivering any power, as it has idle power consumption whenever it is turned on. If accidentally leaving the inverter on is an issue, maybe a highly visible inverter-on indication would help, or an indicator (or even an alarm) to show when the inverter is on while shore power is available (which could be done with a couple of relays).
The reference I found was from the older T-30 user manual (https://wfcoelectronics.com/wp-conte...57R-Manual.pdf). In one section it sort of implies generator priority:
“Shore Power to Generator Power Transfer Time Delay
Time delay (30 sec. nominal) allows gensets to complete self-diagnostics before power is transferred”
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Old 05-28-2021, 09:33 PM   #18
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Originally Posted by M_canada View Post
I’m not using the GoPower controller. My system consists of Victron inverter, solar controller, shunt and GX-based monitor. It displays the inverter AC load in watts. 30 seconds after the the inverter is turned on, the transfer switch clicks and the AC load changes from 0W to 145W. I’m very confident that the inverter is suppling the load.

This discussion has proved useful, thank you for the conversation. While considering the remote on/off switch, I just discovered a menu in my monitor panel to remotely control my inverter, so I don’t need to wire in a remote switch.

It has also reminded me other another drawback to the transfer switch having shore power designated as the ‘pass through’ input. My inverter has an ECO mode where it periodically turns on the AC output and checks for a minimum AC load. This can reduce idle power draw to less than 3W. The transfer switch needs the generator input to be active for 30 seconds and operates the relay to switch to the generator input, so ECO mode doesn’t work. I think if I swap the input connections at the transfer switch, I will be able to use the ECO mode and solve most of my issues.
Ah I ve read about those hybrid inverters that augment the load of a small generator to help start an ac that has a large capacitor load upon initial power. Is that what this mode is for ? Sounds like a nice system . I have looked at the Victron stuff and it seemed to me it was very large fixed solar centric for their inverters, and it was hard for me to discern the obvious equipment for mobile use, though many here use their solar controllers.

Let us know what Waco says, as I am finishing my design for this fall and would like to hear what the sander is.
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Old 05-28-2021, 09:44 PM   #19
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Ah I ve read about those hybrid inverters that augment the load of a small generator to help start an ac that has a large capacitor load upon initial power. Is that what this mode is for ? Sounds like a nice system . I have looked at the Victron stuff and it seemed to me it was very large fixed solar centric for their inverters, and it was hard for me to discern the obvious equipment for mobile use, though many here use their solar controllers.

Let us know what Waco says, as I am finishing my design for this fall and would like to hear what the sander is.
I don’t want to derail this thread too much and it’s fine if this response is moved to a new thread, but very briefly, I am quite happy with most aspects of the Victron stuff. I find it easy to figure out and one of the only solutions that provide complete system monitoring using through a single display as opposed instead of multiple monitor panels. Here is the display I used which showed me my inverter AC load. Unfortunately, the load measurement on my inverter isn’t very accurate, but it’s sufficient, but I’ve got faint hopes that a firmware update will fix it.
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Old 05-28-2021, 09:53 PM   #20
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I don’t want to derail this thread too much and it’s fine if this response is moved to a new thread, but very briefly, I am quite happy with most aspects of the Victron stuff. I find it easy to figure out and one of the only solutions that provide complete system monitoring using through a single display as opposed instead of multiple monitor panels. Here is the display I used which showed me my inverter AC load. Unfortunately, the load measurement on my inverter isn’t very accurate, but it’s sufficient, but I’ve got faint hopes that a firmware update will fix it.
Thanks. Hope you get the ts straightened out.
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