50 amp transfer switch with 30 amp RV?

[Skwidward]

Hi,

I'm preparing to install solar on my 19ft RV. I have 4x 100W panels, a 150V/35 amp solar charge controller, 3x 100 ah lithium batteries, and a 2000W inverter/charger with a built-in 50 amp transfer switch (the victron multi compact).

My question is regarding the 50 amp transfer switch. The RV I have only uses a 30 amp system. Will this transfer switch work when I plug into 30 amp shore power? And will it also work if I use an adapter and plug into 50 amp shore power? (I plan to wire the shore power line into the "AC in" part of the inverter).

I'm thinking that plugging into 30 amp will be ok, and that the 50 amp transfer switch will allow the 30 amps to travel on in as it should. However, I'm concerned that if I use an adapter and plug into 50 amp (I'm new to RVing, and this seems like something folks have to do now and then), this will allow 50 amps into my system and flip a breaker somewhere or worse. Is that right? Or does the adapter restrict the amperage to 30?

[Ampster]

No worries, the 50 Amps will stay where they are until you tell them to come on over. However the devil is in the details since you could plug in something or turn on something that causes them to come over your shore power and cook your switch.

Therefore you should have some circuit protection device such as a fuse or circuit breaker to protect your Victon inverter charger. That may be built into the equipment.

[Skwidward]

No worries, the 50 Amps will stay where they are until you tell them to come on over. However the devil is in the details since you could plug in something or turn on something that causes them to come over your shore power and cook your switch.

Therefore you should have some circuit protection device such as a fuse or circuit breaker to protect your Victon inverter charger. That may be built into the equipment.

This is what Victron says about it:

"PowerControl - Dealing with limited generator, shore side or grid power
The MultiPlus is a very powerful battery charger. It will therefore draw a lot of current from the generator or shore side supply (nearly 10A per 5kVA Multi at 230VAC). With the Multi Control Panel a maximum generator or shore current can be set. The MultiPlus will then take account of other AC loads and use whatever is extra for charging, thus preventing the generator or shore supply from being overloaded."

I will always use a 30 amp surge protector when hooking up to shore power. I plan to put a breaker between the inverter and the battery bank.

[PNW_Steve]

Your RV power is 240volts if you have 50amp service. if you have 30amp service it is 120volts.

If the contactors in the 50amp transfer switch are 240volt then it will not work.

[Ampster]

Your RV power is 240volts if you have 50amp service. if you have 30amp service it is 120volts.

If the contactors in the 50amp transfer switch are 240volt then it will not work.

His earlier post about the tranfser switch said it was 30 Amps. His subsequent post said it was 230 v.

[Skwidward]

His earlier post aost about the tranfser switch said it was 30 Amps. His subsequent post said it was 230 v.

I'm confused. I'm sorry.

The transfer switch is 50 amps and is built-in to the inverter/charger. My concern was when I plug into 30 amp shore power, will this still charge my batteries and power my RV as if I am plugged in, even though the transfer switch is 50 amps?.....and, I was even more concerned about plugging into 50 amp shore power (with an adapter) and having the 50 amp transfer switch allow 50 amps to come waltzing in to my RV's 120V/30amp electrical system and cause a lot of trouble.

I hope that makes sense.

As for the 240V versus the 120V....that I don't understand. Imagine a 30 amp RV with no solar and no inverter, etc. that uses an adapter to plug into a 50 amp RV park outlet. That works, apparently, and people do it. I'm not sure why putting the inverter/charger inside that circuit would change things. Like I said, I'm confused.

[Skwidward]

So the inverter I have is 120 VAC. What I quoted earlier must have been a more general statement made by the manufacturer regarding their higher AC voltage units (hence the 230 VAC).

I've come to the conclusion that the built-in transfer switch will allow up to 50 amps to flow through it, meaning it will definitely allow 30 amps. No problem.

Where I'm confused is the idea of hooking a 30 amp/120V system up to a 50 amp/240V outlet with an adapter......whether you're passing through an inverter/charger or not....

[SunEagle]

i

So the inverter I have is 120 VAC. What I quoted earlier must have been a more general statement made by the manufacturer regarding their higher AC voltage units (hence the 230 VAC).

I've come to the conclusion that the built-in transfer switch will allow up to 50 amps to flow through it, meaning it will definitely allow 30 amps. No problem.

Where I'm confused is the idea of hooking a 30 amp/120V system up to a 50 amp/240V outlet with an adapter......whether you're passing through an inverter/charger or not....

Since there are factory made 50A 4W (male) to 30A 3W (female) adapters out there that are made to power a 30A RV using a 50A plug. I would say they internally convert the 4W 240/120V plug to a 3W 120V plug successfully.

Which means you will only be getting 120V service to the RV and it's loads. I guess the 50amp transfer switch is a little overkill on a 30A service but it should work.

[NCmountainsOffgrid]

your 'internal' Inverter automatic transfer switch is designed to provide a 'flow thru' of 120v service when you are plugged into Shore Power... if it is a 50amp variety, then it also has a built-in 50amp breaker, which would limit any overuse of amperage thru it's system, whether you are plugged into 30amp RV shore power, or using a 30/50amp adapter when plugged into a 50amp 240v RV shore power outlet. The adapter used converts the 240v to 120v, and your RV's Main Panel breaker, which is 30amp, will provide protection if you try to 'use' too much(more than 30amps).
So, in essence, there's little to no way you can ever 'use' more than your RV is designed for.

I'm a motorcoach owner with a Magnum Inverter, with a 30amp limit, but on a 50amp 240v coach, though the main panel is not designed to use 240v, only 120v - it simply uses both 'sides' of the incoming 50amp power lines, without combining them. This is the standard for most any RV or motorhome - even though 50amp RV service is 240v, we only use 120v, which is really up to 100amps of usable power.(two hot lines of 50amps each)...

[littleharbor]

. This is the standard for most any RV or motorhome - even though 50amp RV service is 240v, we only use 120v, which is really up to 100amps of usable power.(two hot lines of 50amps each)...

Sure about that? I've been away from the RV scene for a while but 50 amps on one leg seems wrong. I was under the impression there was 30 amps , potentially, on each leg, 50 amps, max @120 volts. I could be completely wrong here.

[NCmountainsOffgrid]

Sure about that? I've been away from the RV scene for a while but 50 amps on one leg seems wrong. I was under the impression there was 30 amps , potentially, on each leg, 50 amps, max @120 volts. I could be completely wrong here.

yes, that's the general impression that many folks have, which is incorrect. 50amp RV service is 240v, just like at your home, which is why there is a DOUBLE-POLE 50amp breaker at the special 4-prong outlet that you are plugging into. This is TWO separate 50amp hot lines, which a shared/common NEUTRAL, making it 240v power.
The RV's Main Panel, though, doesn't allow these to be combined within the RV, making it essentially two 50amp incoming lines of power, each at 120v. Within the main panel, approximately 1/2 of the breakers use one 'side' of the power, while the other 1/2 of the breakers use the other 'side' of power. This is especially effective for coaches with TWO Roof Air Conditioners, since they each draw a substantial amount of amps. Add the microwave, residential fridge, battery charger, and electric water heater, and you can quickly gather why 50amp service is much more appropriate for these coaches.

Many folks do have the misconception, though, that 50amp service is only 50amps of power.... but it's double that.
While a very few higher-end coaches with residential 240v Clothes Dryers might have Main Panels that allow the use of double-pole breakers to make use of 240v power, this is really the rare exception within the RVing world. In those cases, the coach still makes use of mostly 120v power, with one double-pole 240v breaker for the clothes dryer. These coaches also have Generators capable of providing 240v power output, which is also rare for the RVing world, but needed for these RVs since they require 240v to power the dryer, of course. Most coaches have generators that only produce 120v power, since that's all they need.

[Ampster]

.....

Many folks do have the misconception, though, that 50amp service is only 50amps of power.... but it's double that.
.......m

I generally think of power in terms of Watts. 50 Amps at 240 volts is 12 000 Watts. Two 50 Amp legs at 120 volts is also 12,000 Watts.

[littleharbor]

Thanks for clearing that up. Makes sense.

[PNW_Steve]

If your transfer switch uses contactors with 240 volt coils it will not work on 120 volt service.

Again, 30 amp service is 120 volt and 50 amp service is 240volt

[Ampster]

If your transfer switch uses contactors with 240 volt coils it will not work on 120 volt service.

Again, 30 amp service is 120 volt and 50 amp service is 240volt

Just to be clear, you are talking about typical RV parks. Correct? There are a lot of 30 Amp receptacles that are 240 volt. E.G. 14-30 & 6-30. Unless you are talking about two wire receptacles the NEMA 5-30 is a grounded 30 A 120 V receptacle. Is that the one commonly found in RV Parks?

The important issue here is that the OP connect the correct voltage even though the original question was regarding Amps.