Iv'e decided to add a Automatic Transfer Switch to my Toy Hauler I installed a solar system with a 2000 watt Renogy Inverter several months ago. I purchased a 30amp Progressive Dynamics ATS. I also recently added a Progressive Dynamics 4 way charge controller in place of the OEM charger. The ATS will switch between Shore Power and the Inverter.Question.If plugged into shore power and the inverter is on at the same time which will the ATS select as priority?Q

1L243 wrote:BFL13 wrote:"On a sunny day my solar can produce as much as 26 amps and I think my refrigerator only about 8/10 amps. "My 6cu ft Norcold pulls about 350w on 120v so that is about 35 amps DC via inverter. I had lots of solar but it could not keep up with the fridge, even at high noon. Gave up on that and now leave the fridge on propane after trying that.You would only slow down the draw on the battery by running the fridge on inverter with whatever amps solar is doing at the time. A few more amps via 7-pin would help if only they were at the same voltage as the solar, but it would still not be enough to supply the fridge's inverter draw completely.I know the refrigerator uses alot of amps on startup not sure what my number is but much less once the refrigerator reaches cold. Then it depends on how much you access the fridge and maybe how hot it is outside. It could go hours before it cycles on and off while traveling.Down the road I may add a 40 amp DC to DC charger.Like I said I usually run the refrigerator on propane when towing if there is too much of a draw and it starts to drain down the batteries I will switch it back to propane.It will still be nice to have energized outlets when stopping for lunch or a break without having to go outside and plug into the Inverter.Absorbsion RV fridges (that can use propane or 120V) do not have any startup surge. Instead they use a little resistance heater module which can range from 275W to 325W at 120V depending on fridge size. So unlike a home fridge conversion you do not need to figure in for startup surge.The downfall of using 120V AC instead of propane in an absorbsion fridge is that 120V heater uses three times more power than if you simply swapped out to a home fridge.325W at 120V is 2.7A, run that through an inverter that turns into 27A at 12V not including inverter losses. Inverter will have about 80% or a bit more efficiency so add in an extra 2A at 12V or roughly 29A.Compare that to a home fridge conversion, if you watch you can find 10 cu ft apartment size home fridges that draw about 90W at 120V or .75A. That .75A would convert to 7.5A at 12V without inverter loss which would be around 1.5A for a total of 9A at 12V. A much more reasonable power draw.The startup surge for all intents and purposes do almost nothing to use up battery capacity even though they are on the order of 8x the run current because the startup surge lasts for only a few microseconds. You do however have to plan for the surge upfront with thick enough wire and a inverter above 1,000W.Your throwing good money at this for no real good reason other than to not use propane. If the propane operation while moving is a problem, then fix it. Generally propane operation while moving is not a problem. I personally never had an issue with propane operation while mobile and the fridge I had was a manual pilot light! Even during a severe storm with 60 MPH microburst straightline winds hitting the fridge side while driving.Otherwise, if it is you simply do not like propane at all, swap the RV fridge for a home fridge conversion.. My current TT, we did a home fridge conversion, just one pair of 6V GC2 batteries powers everything we use including the fridge for 24hrs without the need for solar or a generator..

The ATS has two inputs normally marked LINE and GENERATORTwo types of ATS One is a relay race (Whatever is first is only) But I doubt that's how yours works... More likely GENERATOR controls it.If there is power on the GENERATOR input. than that is used. NOTE: DO NOT SWITCH UNDER LOADTurn off all loads before plugging in or turn off main breaker so there is no 120 volt load when you plug in.

wa8yxm wrote:The ATS has two inputs normally marked LINE and GENERATORTwo types of ATS One is a relay race (Whatever is first is only) But I doubt that's how yours works... More likely GENERATOR controls it.If there is power on the GENERATOR input. than that is used. NOTE: DO NOT SWITCH UNDER LOADTurn off all loads before plugging in or turn off main breaker so there is no 120 volt load when you plug in.I have to disagree. Most likely if there is power on the line then it is used. When line power is not there then it will switch to the Gen position. There should be instructions with the switch that will tell you how it works.

Roger10378 wrote:wa8yxm wrote:The ATS has two inputs normally marked LINE and GENERATORTwo types of ATS One is a relay race (Whatever is first is only) But I doubt that's how yours works... More likely GENERATOR controls it.If there is power on the GENERATOR input. than that is used. NOTE: DO NOT SWITCH UNDER LOADTurn off all loads before plugging in or turn off main breaker so there is no 120 volt load when you plug in.I have to disagree. Most likely if there is power on the line then it is used. When line power is not there then it will switch to the Gen position. There should be instructions with the switch that will tell you how it works.I have to agree with wa8yxm. I have never seen one with LINE priority that wasn't mis-wired. Every one that I have ever seen, wired as the instructions call for, when the generator starts, the ATS switches to it regardless of what the shore power line has.

I concur, Generator is the primary input on mine. Can be connected to shore power, start the genny and it switches from shore to genny.

Automatic Transfer Switch | Good Sam Community

39 Replies

1L243
Explorer II
Jan 10, 2022
Automatic Transfer Switch is installed. As usual the estimated cost of $200 was more like $300. Primarily due to the cost of shielded 10ga copper cable.

I needed about 42 feet.The distance from the control panel to the ATS which is in the front pass through is about 13 feet. I had to run one 10ga cable from the control panel to the panel side of the ATS. A second cable from control panel to the Plug side of the ATS and a third cable from the Progressive Dynamics converter/charger (which is located below the control panel) to the Plug side of the ATS. A fourth cable from the Inverter to the Inverter or Generator side of the ATS. This distance was only about 2 feet.

Since I no longer need the the 15 amp dedicated breaker in the service panel for the Converter/Charger I added a 15 amp AGC fuse inside the ATS to protect the Charger.

How it works.

When plugged into shore power everything works as it should. When I want to run on the Inverter generally I will already be unplugged from Shore power. But, if not the Inverter will have priority . The batteries will only charge when plugged into shore power.

From inside the trailer I turn on the Inverter using the wired remote on/off switch. There is a 35 second delay. You can hear the ATS "click" and then everything comes to life inside the trailer.

I won't know till the next time I take it out on a sunny day when I have solar to see if turning on the refrigerator if I will be in the positive or negative.

Regardless it will be nice to have shore power at the flick of a switch wherever I am.
Gdetrailer
Explorer III
Dec 14, 2021
1L243 wrote:

I'm planning on running 10 gauge wire. Should I use stranded 10 gauge wire (more expensive) OR a 10/3 Romex? The Wire will be routed out the floor and along the frame to their termination points. Either one will be inside flexible plastic conduit.

Any thoughts?

Either stranded or solid wire is fine, Romex is not really rated for use inside conduit. "Single strand" stranded or solid building wire unlike Romex should be run in a conduit.

In the past, I was able to buy single strand at a lower cost per ft because of bulk pricing but when you add in the cost of conduit actually made it more expensive option than Romex. If the wiring is exposed to potential damage hazards then conduit might be better option over Romex.
Tom_M1
Explorer
Dec 14, 2021
Here's a schematic of my solution:

K1 is my existing ATS. K2 is a 120 VAC 30 amp relay. The output feeds all my 120 volt receptacles except the ones feeding my fridge and microwave. The converter is powered only when on shore or generator power.
1L243
Explorer II
Dec 14, 2021
All valid points.

As far as cost of this Mod goes it's actually pretty cheap compared to some of the mods I have done about $200.

If my current fridge draws too much power to run when towing with the solar I now have then so be it I will go back to Propane I simply want the option of energizing my outlets from the inside of the trailer with a flick of a switch.

If my refrigerator failed I would consider a residential fridge although I do like to use of propane when boondocking so that would be a hard choice.

At around $1400 that is an expensive option. As with a Victron inverter/charger running about the same price.

A question regarding wiring.

Most of my parts have come in and I am getting ready to wire. Not sure if the ATS will fit in the same cabinet behind the control panel. If it does it would be great as wiring would be shorter and easier. If not I will have to Put the ATS is a cabinet where the Park cable extension cord coils up.

This would add about 15 extra feet to my wire run. From the ATS I will need to run wire to the Inverter about 20 feet. I will also have to run wire from the ATS to the Converter Charger as it has to be wired to the ATS a distance of about 15 feet.

I'm planning on running 10 gauge wire. Should I use stranded 10 gauge wire (more expensive) OR a 10/3 Romex? The Wire will be routed out the floor and along the frame to their termination points. Either one will be inside flexible plastic conduit.

Any thoughts?
CharlesinGA
Explorer
Dec 09, 2021
Some inverters, Victron, for instance, will pass thru the full amount of shore power and even synchronize the phasing so if shore drops off, the inverter takes over instantly "no break power transfer" as McDonnell Douglas called it on the MD-11. No need for a transfer switch at all.

Charles
Gdetrailer
Explorer III
Dec 06, 2021
pianotuna wrote:
Gdetrailer,

Nice choice of inverter/fridge. My Magnum has a standby mode--but ever few seconds it checks for a load. That causes the microwave to beep, as I run in a "whole house" mode.

Yes, the Tripplite does similar thing as your Magnum, it sends a quick pulse every few seconds in order to detect if there is a 120V load above my preset. Set mine to power on if it sees about 9W, this way I can plug in a 120V trouble light and it will turn on the inverter if I need the light.

I don't bother with MW on inverter, figure for that it doesn't take much effort to start the gen so to me it was a low priority item.

Since you don't need the microwave powered all the time, add a manual switch in a easy to get to location, switch the microwave off when not needed.. That would allow you to take advantage of the low power sleep mode you have.

I use a 20A DPDT toggle with center off to manually select shore or inverter for my Home fridge conversion. Saves plugging and unplugging.

Have been considering upgrading to the Tripplite APS versions which have built in ATS for the fridge which would simplify our setup and teardown list of things to do.
StirCrazy
Moderator
Dec 06, 2021
TechWriter wrote:

So OP will have to always remember to throw several switches or risk dead batteries.

Plus, if the ATS is generator preferred and the inverter is connected to the generator side of the ATS, then OP will have to remember to also turn off the inverter when shore power is applied.

Why not just use a manual transfer switch?

Or, though more expensive, it sounds eminently more practical to buy an inverter/charger with a built-in transfer switch and wire it like so (with or without a sub panel), especially is OP's wife or friend(s) will also be responsible for switch throwing:

no he won't nothing poweres up just because the breaker box is live.

the whole idea of using a transfer switch with an inverter is for boon docking so you do not use them at the same time and you turn it on when you need it. I have left mine running for an entire weekend but didn't use any 120V stuff and I used a whopping 5AH more per day due to the effiency of the inverter. now if you have your frifge on electric and such then ya you need more batteries than the four I have. when I plug in shore power with my inverter running it will actualy disconect my inverter and reansfter to the shore supply so that is how the factoy wires it when you don't have a genny.

Steve
pianotuna
Nomad III
Dec 06, 2021
Gdetrailer,

Nice choice of inverter/fridge. My Magnum has a standby mode--but ever few seconds it checks for a load. That causes the microwave to beep, as I run in a "whole house" mode.
Gdetrailer
Explorer III
Dec 06, 2021
pianotuna wrote:
Gdetrailer wrote:

Otherwise, if it is you simply do not like propane at all, swap the RV fridge for a home fridge conversion.. My current TT, we did a home fridge conversion, just one pair of 6V GC2 batteries powers everything we use including the fridge for 24hrs without the need for solar or a generator..

Gdetrailer,

Do you know the make and model of the fridge?

Haier 10 cu ft fridge, marketed as small apartment size, same manufacturer that makes Magic Chef and a few other well known brand names of that size.

I measured the current draw personally and average was right at 90W at 120V, compressor is marked as 1.1A draw.

Only downside to it is it is a frost free model so it does have a auto defrost cycle but that only happens once for 10 minutes for every 10 hrs of compressor operation. My timed tests gave average of 20-22 minutes compressor run per every hr from 50F all the way to 100F. Didn't bother testing below 50F as I am not a colder weather camper.

Paired that up with a Tripplite PV1250 MSW inverter which has a power save feature which puts the inverter into a deep low power sleep mode when it does not see a 120V AC load. That power save mode saves 24 Ahrs of battery capacity alone per 24hrs.

Since the fridge is pretty efficient the charge line from my vehicle is able to nearly support the fridge while driving unlike if I was attempting to run a absorbsion fridge off of 12V.
pianotuna
Nomad III
Dec 05, 2021
Gdetrailer wrote:

Otherwise, if it is you simply do not like propane at all, swap the RV fridge for a home fridge conversion.. My current TT, we did a home fridge conversion, just one pair of 6V GC2 batteries powers everything we use including the fridge for 24hrs without the need for solar or a generator..

Gdetrailer,

Do you know the make and model of the fridge?