Input wanted on plan to rewire 21NE Transfer Switch for larger battery bank

[RambleOn]

Using the diagram provided by @tdf-texas I wanted to run this basic approach past some folks more expert than I am. Focusing on the Inverter and Transfer switch, I'm thinking I'll remove the 30 AMP lead to the WFCO AC Distribution and run the AC input directly to the Transfer Switch inpu. I'll then run from the Transfer Switch output to the WFCO AC Distribution. In my thinking this will run all AC connected loads in the camper off of shore or inverted battery, as determined by the Transfer Switch. I also plan to add a Contactor Switch so the DC loads run directly off the battery bank even when the Inverter is powering the AC.

Do you see any issues with this basic approach?

 

[wackyburggeezer]

The 30 amp breaker in the WFCO panel that sees the incoming 'hot' protects everything in the downstream circuitry as an 'overcurrent device'. I haven't looked at the current electrical code section regarding RVs, but I personally would not make that change, regardless of the current code requirements.

 

[Centex]

First a question: What 120VAC load that you would want to support with inverted battery power are you unable to support now (without making any changes)?

If I'm reading your proposal correctly, there's a risk that you could inadvertently power your water heater 120VAC element off of your batteries when not connected to shore power?

Is your fridge a compressor or gas/electric model? IF the latter, it would always 'see' 120VAC power available even when not connected to shore-power, so would not default to propane operation in the absence of a true shore-power connection.

Maybe I'm missing something, but I don't see any benefit, only downside-risk of inadvertent battery depletion, in your proposal?

 

[RambleOn]

Thanks guys! My goal was to make it as simple as possible but….

I’m thinking I could deal with the protection issue by inserting a breaker or fuse,.? I’m not concerned about turning on the hot water heater on AC, unless it’s not manually controllable, but if the fridge defaults to AC that’s another issue (we do have the 3-way fridge). I’m surprised that the default is AC.

All that said, any suggestions on how to do this better, safely and effectively?

 

[RambleOn]

The 30 amp breaker in the WFCO panel that sees the incoming 'hot' protects everything in the downstream circuitry as an 'overcurrent device'. I haven't looked at the current electrical code section regarding RVs, but I personally would not make that change, regardless of the current code requirements.

Does the EMS perform a similar function? The EMS and breaker are “next” to each other in the circuit. Are they redundant? Learning as I go. Thanks

 

[Centex]

All that said, any suggestions on how to do this better, safely and effectively?

This question stands:

First a question: What 120VAC load that you would want to support with inverted battery power are you unable to support now (without making any changes)?

What are you trying to accomplish functionally that you can't accomplish without making any change to the wiring?

IMO you don't achieve 'simplification' when you introduce more components (contactor switch, more breakers/fuses) and the need for manual intervention to prevent unintended battery depletion.

Ask yourself .... Is this a 'solution' looking for a problem?

 

[RambleOn]

Thanks Alan. The main goal is to power the AC via battery. I thought it would be easier to use the wiring structure that ETI had already put in place than to break out or move components/appliances t other circuits, hence the changes at the front end, leaving all else intact. In my (simple) mind it was less complex this way.

All suggestions welcome.

 

[Centex]

The main goal is to power the AC via battery.

Ah, I missed the dual-use of "AC" in your first post (AC = Air Conditioning in some cases, Alternating Current in others).

IMO the most appropriate manner for accomplishing that is in fact to move the Air Conditioner (I'm going to refer to that as "A/C", distinct from "AC") to a dedicated breaker in the inverter sub-panel. IMO that's a simple approach that preserves all of the desirable attributes of the existing scheme.

Understanding that you plan to increase your battery-bank Ah capacity, will you also need to increase the amp-capacity of your inverter to handle that A/C load?

 

[RambleOn]

Adding a dedicated breaker to the inverter sub panel sounds good - and simple. Our camper will be delivered in 2 weeks and I’m hoping there’s space for a new breaker in the existing box

Yes, we’re planning on an 3000w inverter and new cables for the battery connections.

Thanks for your help!

 

[Centex]

It'll be interesting to see how closely the current ETI wiring and component details correspond to those shown in @tdf-texas' wonderful but somewhat dated diagrams.

In any case, congrats on your impending delivery and Have Fun with your mods!

Please do keep us posted on what you finally work-out.

 

[RambleOn]

Yes, I’m wondering how close they will be too. We’ll see and I’ll let you know,

I’m sure to have more questions- I’ve done mods, electrical and otherwise, in a Roadtrek van and a T@B 400 but they are all a bit different. I’m looking forward to a busy winter!

Thanks again and I’ll let you know how it works out.