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How do you wire a transfer switch


alan0043

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Hi Everyone,

 

I have been working on the interior of my truck. I have been working on the shore power part of the truck. The next step will be to re-install the invertor. I have new cables to come from the batteries for the invertor. The invertor I have is a Cobra 1500 watt. I want to use the same receptacles, whether the 120 volts comes from the shore power or the invertor. The 120 volts that comes from the invertor is to be primary power. Then when you plug in the shore power the receptacles will get there power from the shore power. I understand that I need a transfer switch to do this. I have a transfer switch that was given to me from Dave of Dave and Jenny on the forum. Thank You again Dave for the switch. I do not know how to wire the transfer switch. I can see that there is a shoe that can get pulled in. It looks like where the shoe pulls in, the power is being transferred to a different set of wires. I think that there is also a coil that pulls in the shoes. On this transfer switch there is a place for a total of 8 wires or 4 wires per side. The part of the shore power that I have been working on I have not laid out any wires yet. I am still working on the plan. The following question is part of the plan. The big question, is how do I wire the transfer switch. Does the shore power go to the coil on the transfer switch first and then to the breaker box ? Does anyone have a drawing showing the wires for a transfer switch.

 

Al

2012 Volvo VNL 630 w/ I-Shift; D13 engine; " Veeger "
  Redwood, model 3401R ; 5th Wheel Trailer, " Dead Wood "
    2006 Smart Car " Killer Frog "
 

 

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That type of inverter is generally not very ideal for "full house" wiring. Not that it can't be done, but it would really be better using it as a stand alone unit using the inverters built-in receptacles.

 

Just to be aware that it appears to be a MSW inverter and has a rating of 1500 watts max.. but only for 60 minutes before it needs a 15 minute cooling period (at lower wattages over temp shut-off may still be an issue). Surge is listed as 3000 watts for .1 seconds. As long as that is understood, then you can use a transfer switch (assuming that it's an auto TS), however, you would still want to wire the shore power to the primary connection and inverter to the secondary leg of the TS. The reason being.. when no power source (shore power) is detected on the primary, then the secondary (inverter) side will deliver your 120v current. If your inverter is wired as the primary source then you run the risk of plugging in to shore power.. but you left your inverter on.. so the TS will ignore the shore power and continue to pass current from the inverter.

 

For all intents and purposes, your inverter will be the "primary" power source unless shore power/genset is detected.

 

Yes. The TS can be installed with the inverter and shore power connections and then to your distribution panel. Depending on what is being powered by your DP though it might be best to take a different approach and install a subpanel if there are loads you don't want to be powered by your inverter. Ie., A/C, space heater, etc.

 

Ideally though, an "in-line" pass-through type inverter would be much better suited for this application. Make and model of your transfer switch would be helpful for specific wiring info.

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Al - The make and model of your transfer switch is needed to properly answer your wiring question. It sounds like you may have a 50 amp ATS but the connections for generator/inverter input can vary. Let us know the make and model.

 

Advice from Yarome is valid.

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Randy, Nancy and Oscar

"The Great White" - 2004 Volvo VNL670, D12, 10-speed, converted to single axle pulling a Keystone Cambridge 5th wheel, 40', 4 slides and about 19,000# with empty tanks.

ARS - WB4BZX, Electrical Engineer, Master Electrician, D.Ed., Professor Emeritus - Happily Retired!

 

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That type of inverter is generally not very ideal for "full house" wiring. Not that it can't be done, but it would really be better using it as a stand alone unit using the inverters built-in receptacles.

 

Just to be aware that it appears to be a MSW inverter and has a rating of 1500 watts max.. but only for 60 minutes before it needs a 15 minute cooling period (at lower wattages over temp shut-off may still be an issue). Surge is listed as 3000 watts for .1 seconds. As long as that is understood, then you can use a transfer switch (assuming that it's an auto TS), however, you would still want to wire the shore power to the primary connection and inverter to the secondary leg of the TS. The reason being.. when no power source (shore power) is detected on the primary, then the secondary (inverter) side will deliver your 120v current. If your inverter is wired as the primary source then you run the risk of plugging in to shore power.. but you left your inverter on.. so the TS will ignore the shore power and continue to pass current from the inverter.

 

For all intents and purposes, your inverter will be the "primary" power source unless shore power/genset is detected.

 

Yes. The TS can be installed with the inverter and shore power connections and then to your distribution panel. Depending on what is being powered by your DP though it might be best to take a different approach and install a subpanel if there are loads you don't want to be powered by your inverter. Ie., A/C, space heater, etc.

 

Ideally though, an "in-line" pass-through type inverter would be much better suited for this application. Make and model of your transfer switch would be helpful for specific wiring info.

 

Hi Guys,

 

First off I want to 'Thank' you guys for trying to help me. The following is the info that I found on the transfer switch it's self. Struthers - Dunn ; 425XBX ; coil 120v, 50/60 Hz; contact rating 1HP 30 amp 120 volts; 1 HP 30 amp 240 volts; 30 amp 28 VDC; 10 amp 600 volts. Total of 8 wires, 4 wires per side.

 

Yarome, I need help in understanding what you wrote. I do not understand the electronics field that good. Is the part of the transfer switch where the contacts are touching in a resting state the primary side ? And when the contacts pull in on those contacts the secondary side ? I want to wire this transfer switch as safe as possible.

 

Thank you guys for all of your help,

Al

2012 Volvo VNL 630 w/ I-Shift; D13 engine; " Veeger "
  Redwood, model 3401R ; 5th Wheel Trailer, " Dead Wood "
    2006 Smart Car " Killer Frog "
 

 

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https://www.google.ca/search?q=magnum+inverter+wiring+diagrams&biw=1093&bih=446&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjs9LvFv_fKAhUIymMKHZuDBw8Q7AkINQ#imgrc=M0Q7FeSLCMXlHM%3A

 

Could it be one of these?

 

I recently had the AC leg in my 2812 replaced x2 then the whole thing had to be replaced. The original installer had wired it in incorrectly. We bypassed the inverter for the 2 ac's and the hot water heater. Also installing a sub panel.

 

A generic example of what you want may be here. We installed an automatic transfer switch.

 

Roger

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What Yarome said ...

 

Wire it so when the contacts are in their resting state the inverter power passes through the transfer switch to the load, using the contacts that are engaged when the relay is NOT energized. Then wire the shore power to the contacts that engage when the relay is energized.

 

Connect the coil to the shore power input so it engages when shore power is present. Put a 3 - 5 amp fuse in line with the hot side of the coil for protection in case the coil shorts out.

 

This way shore power controls the relay. When shore power is present the relay engages and switches the load to shore power. When shore power is not present the load is connected to the inverter. It doesn't matter if the inverter is on or off.

 

Sometimes a picture helps ....

post-1427-0-38323500-1455478273_thumb.jpg

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What Yarome said ...

 

Wire it so when the contacts are in their resting state the inverter power passes through the transfer switch to the load, using the contacts that are engaged when the relay is NOT energized. Then wire the shore power to the contacts that engage when the relay is energized.

 

Connect the coil to the shore power input so it engages when shore power is present. Put a 3 - 5 amp fuse in line with the hot side of the coil for protection in case the coil shorts out.

 

This way shore power controls the relay. When shore power is present the relay engages and switches the load to shore power. When shore power is not present the load is connected to the inverter. It doesn't matter if the inverter is on or off.

 

Sometimes a picture helps ....

 

 

Hi Guys,

 

Thank you for the help. I am a little confused now. The following is a statement from Yarome wrote earlier in the post.

 

"Just to be aware that it appears to be a MSW inverter and has a rating of 1500 watts max.. but only for 60 minutes before it needs a 15 minute cooling period (at lower wattages over temp shut-off may still be an issue). Surge is listed as 3000 watts for .1 seconds. As long as that is understood, then you can use a transfer switch (assuming that it's an auto TS), however, you would still want to wire the shore power to the primary connection and inverter to the secondary leg of the TS. The reason being.. when no power source (shore power) is detected on the primary, then the secondary (inverter) side will deliver your 120v current. If your inverter is wired as the primary source then you run the risk of plugging in to shore power.. but you left your inverter on.. so the TS will ignore the shore power and continue to pass current from the inverter."

 

When I read both suggestion for wiring I came up with two different answers. Maybe I am not reading something correct. Can some other folks read both statement and see what they come up with.

 

The picture is going to be a big help.

 

Al

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2012 Volvo VNL 630 w/ I-Shift; D13 engine; " Veeger "
  Redwood, model 3401R ; 5th Wheel Trailer, " Dead Wood "
    2006 Smart Car " Killer Frog "
 

 

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Hi Alan -

 

If you read "primary connection" as the one that takes precedence when both sources are available, Yarome and I are both saying the same thing.

 

When the relay coil is connected to shore power as shown in the diagram, the relay switches to shore power whenever it's available. Shore power takes precedence over inverter power, no matter if the inverter is on or off.

 

If you want to do it the other way, just reverse the Shore Power and Inverter labels on the diagram so the relay coil is connected to the inverter power. This makes the inverter the primary source and shore power is secondary to it. You won't be able to use shore power unless the inverter is off. If you plug into shore power with the inverter on, the relay stays in the inverter position and the inverter continues powering the loads until it's turned off. This is an easy way to accidentally drain your batteries - forget to turn off the inverter when plugging in and the loads will continue to run on it even though you're plugged into shore power.

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So far, all info given looks good to me. But, what you have is just a relay, not a full blown transfer switch. This type of relay may be safely used as the guts for a homebrewed transfer switch. The wiring diagram looks good, but I would encourage you to wire it as shown with shore power throughput as the default rather than the inverter. Using the relay "as is" will not give you any delay once the alternate voltage source is applied - not that you need a delay for an inverter - the delay in commercial transfer switches is really to allow an attached generator to come up to speed before connecting.

 

Your relay will, of course, need to be in an enclosed compartment. You can find some large (8" square) grey PVC electrical boxes with covers that will hold the relay and wires nicely. These are generic boxes and as such require drilling holes for the wiring. In our area you can buy these boxes at Lowe's.

 

Now to the inverter - and I will keep the why's brief. Install an in-line GFCI between the inverter and transfer switch. Mount the inverter on an insulated base (a piece of plywood or plastic cutting board) being sure no screws from the inverter case touch any part of the metal truck frame. Run ONLY the hot and neutral wires from the inverter to the GFCI (no grounding wire). At the GFCI output connect the grounding connection from the GFCI to the vehicle frame. Be sure the grounding wire from the shore power passes straight thru to the grounding bus in your breaker box and this bus is bonded to the truck frame. Why? Unlike shore power the output from the inverter has NO attachment to earth ground. There is really no "neutral" as both sides are at the same potential to earth ground. MSW manufacturers designate a side as hot and the other as "neutral" and then bond the designated neutral to the inverter case along with the grounding (safety) wire and the grounding lug on the inverter that goes to the frame. Internal bonding of the MSW inverter defeats the required isolated neutral from ground(ing) requirement for an RV. The method I described does not defeat the isolation or ground(ing) and neutral and using the GFCI provides safety that surpasses bonding. BTW - MSW inverters are bonded so a fuse will blow or CB trip should the hot wire short to ground. But, with the bond in place the frame of your truck will have a potential of 60 volts to earth ground any time it is on. No big deal as long as you are in the cab (like a bird sitting on a power line wire). But, hey, we live in an AC world and electrons are attracted to their opposites. You can receive a significant electric shock by touching the frame of a truck with a working inverter (that is bonded) while standing on earth ground. Same is true for an RV with a bond in the RV between neutral and ground if the grounding in the power pedestal is wired wrong or absent. Honest!

 

Bottom line - use the GFCI after the inverter and before the transfer switch. Do not allow the built-in bond between the designated neutral and ground of the MSW inverter attach to the truck frame.

 

Are you planning on using a RV type converter/charger in your truck? If so, some additional wiring is needed to keep it from working off of the inverter power. More later if you need it.

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Randy, Nancy and Oscar

"The Great White" - 2004 Volvo VNL670, D12, 10-speed, converted to single axle pulling a Keystone Cambridge 5th wheel, 40', 4 slides and about 19,000# with empty tanks.

ARS - WB4BZX, Electrical Engineer, Master Electrician, D.Ed., Professor Emeritus - Happily Retired!

 

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Randy,

 

Can you please explain to me why a GFCI is needed before the transfer switch. I am trying to understand how the total system works together. I am working on my plan for the shore power and the invertor for the truck. I want to lay out any wires ahead of time before they go into the truck. I remember what you said one time about making a plan. It looks like a plug with a power cord will be needed to come from the invertor to go to the GFCI and then to the transfer switch. Am I on the right track ? I also understand that I should add a fuse in the power line that goes to the transfer switch from the shore power. What is the best way to add a fuse for this purpose ? I am thinking that I can use a Bussman box that has a the old style glass fuse. Is this a good option ? Or is there something better ?

 

Thank you again for your help,

Al

2012 Volvo VNL 630 w/ I-Shift; D13 engine; " Veeger "
  Redwood, model 3401R ; 5th Wheel Trailer, " Dead Wood "
    2006 Smart Car " Killer Frog "
 

 

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Yes, you are on the right track. The type of fuse for the input you referenced will work but it is sort of old school. You really do not need a fuse (or breaker) on the input as you are fused at the shore power connection. NEC will allow this for portable cord sets. But, as noted by Mark on another thread there is no rule to keep you from adding a fuse/breaker/disconnect before the transfer relay if you want one. I did not put one on my truck.

 

Now, for the inverter and GFCI question:

 

Back to the National Electrical Code (NEC) and requirements for RV's and branch circuits. Your RV is wired as a branch circuit and as such must have separate neutral and grounding connections. Just for reference, a 120 VAC circuit has 3 wires - one is considered hot as it does not have a connection to earth ground (black or red wire in most cables), one is called neutral because it does have a connection to earth ground (white wire in most cables), and a grounding wire (note the -ing) that has also been called the safety wire on this forum that normally carries no voltage and also connects to earth ground. This wire may be bare copper, green or green/yellow. By the NEC, this grounding wire can only connect to earth ground at the originating service entrance panel. This rule is to avoid additional ground paths, or loops, that can compromise safety should a fault occur. This is the same point where the neutral is also connected to earth ground by a copper clad 8' rod driven into moist earth (or other acceptable material/grounding method). So, we have two wires originating from the SEP that are bonded (tied together) and connected to earth that have NO OTHER CONNECTIONS to each other or earth ground all the way to your RV or truck, even at the park pedestal or other shore power connection. For some it seems silly to have two wires side-by-side connected to earth ground. But, remember one carries voltage and the other does not unless there is a fault. If a fault should occur you want to be sure the grounding wire is there and installed according to NEC rules. Unfortunately, this is the most common error made in park power connection pedestals as they may leave out the grounding wire (saves $$$) or only bond it to neutral in the pedestal.

 

With AC the current in BOTH the neutral and hot wires should be equal at all times. If current is not equal it means there is a fault and current in one wire is going somewhere else. This could be to something like a metal appliance cabinet, or even the metal frame/skin of your RV. If the fault passes enough leakage current the fuse or circuit breaker should open. Unfortunately, enough leakage can occur and pass through your body to stop your heart and never open a fuse or circuit breaker. The GFCI can sense an extremely small leakage and open fast enough to keep electric current from passing through your body in a fault situation. Since the greatest danger to us in these situations is when we are standing on earth ground, concrete, or the like - and possibly in direct contact with ground through plumbing and water, GFCI's are required by the NEC in kitchens, bathrooms garages and outside (including your RV/truck).

 

(sorry if I am making this too long and wordy)

 

OK - now back to the NEC and even OSHA. Their rules require gensets and inverters used in vehicles to be bonded. This means the neutral and grounding are wired together at the device and if bolted to the vehicle frame actually negate the previous rule of NOT bonding the neutral and grounding in a branch circuit. ??????? This rule is in place believing that a fault between the hot wire and ground will open a fuse or breaker. And, in a stand alone install it usually does. I say usually because some fuses are slo-blow and some non-magnetic breakers rely on heat (thermal) to open and can actually take as much as 15 minutes to open.

 

Let's look at your inverter. It takes DC from a battery, uses transistors to switch DC back and forth so it emulates AC, and then increases the voltage through a transformer to 120 VAC. Where is the earth ground for neutral? Yep, it is not there. Actually BOTH wires coming out of the inverter are at the same potential. Add to that the practice of bonding the so called neutral to the case as a grounding point and the ground/neutral/grounding system has a 60 volt potential - with no earth ground. Under most circumstances this is OK since the vehicle is floating above earth ground. Notice I said most. You see, we live in an AC world with electrons all around us. You realize this when you get shocked from static electricity or see lightning. These events occur due to an electrical principal known as capacitance. This is where my recommendations for wiring an inverter or generator come in and actually go beyond NEC and OSHA practices for personal safety. First, you do not want to install any device that negates the isolation of neutral and the grounding (safety) wire in a RV or your truck. Many inverters and generators that do not have a floating neutral (no bond) will negate isolation. Second, we know from experience that someone standing on earth ground and touching the metal frame of a RV or truck that is connected to an operational power source that puts an electrical potential on the metal parts of the vehicle can shock the pee out of you and even under the right (or wrong) conditions kill you! It is that capacitance thing again.

 

So, old Dr. Professor Randy here determined a long time ago that the commonly accepted methods of installing bonded inverters and generators in trucks and RV's without the benefit of an earth ground imposed an unexpected danger. To avoid that danger we use a GFCI after the output of the inverter or generator. We also isolate/ insulate a bonded inverter from the vehicle frame. This is where the insulated mount and not bringing the grounding wire from the inverter to the GFCI comes in. We protect the integrity of the isolated neutral/grounding and still provide a reliable system to open the circuit if a fault occurs. The only component that remains that could hurt you is the case of the inverter - so do not make it a practice of touching the case of a working inverter while you are in contact with ground.

 

Currently, most upper end ($$$) inverters are now providing an option to choose between bonding or a floating neutral. Inverter generators are also providing isolation. I have been successful in getting the non-OSHA compliant imported synchronous generators sold under the name of Category 5 or Champion Power Equipment to provide a floating neutral with a bonding option. Many of the other imported (Chinese) synchronous generators have followed the practice. Unfortunately, CSA (Canada) still requires bonding on generators and inverters of any size.

 

I hope this makes sense. I don't have pictures with me that would help. Note that not everyone agrees my approach is necessary. I sincerely believe it should be the standard.

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Randy, Nancy and Oscar

"The Great White" - 2004 Volvo VNL670, D12, 10-speed, converted to single axle pulling a Keystone Cambridge 5th wheel, 40', 4 slides and about 19,000# with empty tanks.

ARS - WB4BZX, Electrical Engineer, Master Electrician, D.Ed., Professor Emeritus - Happily Retired!

 

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Hi Randy,

 

' Thank You ' very much for your explanation. I did not think it was to wordy. I understand now what you where saying. I also think that this explanation will help other people working on and building their own trucks. To me it is safety first. When I was working the company that I worked for would have safety classes on different subjects every year. There was also a program of Lockout Tagout that was done annually. Everybody that worked in the labs fell under these programs.

 

I have most of the parts that I need to put the total system together. I have one more question. I would like to add a disconnect for the shore power before to goes to the transfer switch. What kind of disconnect would you use ?

 

Are you planning on going to the 2016 ECR ? If so, maybe you could check over what I have done.

 

Thank you again for all of your help,

Al

2012 Volvo VNL 630 w/ I-Shift; D13 engine; " Veeger "
  Redwood, model 3401R ; 5th Wheel Trailer, " Dead Wood "
    2006 Smart Car " Killer Frog "
 

 

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A small breaker panel with a single 20 amp or 30 amp breaker (depending on the size of your power cord and plug) between the shore power cord and the transfer relay would make a nice disconnect:

 

http://www.homedepot.com/p/PowerMark-Gold-40-Amp-2-Space-4-Circuit-Indoor-Single-Phase-Main-Lug-Circuit-Breaker-Panel-TL240SCUP/202978667

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Lou's suggestion for a main disconnect before the transfer relay would work well. It would also allow you to do as Mark suggested and cut off both the neutral and hot rather than just the hot. I'm not sure what type of breaker fits the Power Mark brand box (QO, Homeline, Murray, GE, etc.) but you should use a double space 30 amp breaker with a tie bar or single trip lever similar to the one in the pic below. Your grounding wire should attach to the metal box.

 

No, we will not be able to attend the ECR this year. Wish we could!

 

71fKqnt7X9S._SY450_.jpg

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Randy, Nancy and Oscar

"The Great White" - 2004 Volvo VNL670, D12, 10-speed, converted to single axle pulling a Keystone Cambridge 5th wheel, 40', 4 slides and about 19,000# with empty tanks.

ARS - WB4BZX, Electrical Engineer, Master Electrician, D.Ed., Professor Emeritus - Happily Retired!

 

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Lou's suggestion for a main disconnect before the transfer relay would work well. It would also allow you to do as Mark suggested and cut off both the neutral and hot rather than just the hot. I'm not sure what type of breaker fits the Power Mark brand box (QO, Homeline, Murray, GE, etc.) but you should use a double space 30 amp breaker with a tie bar or single trip lever similar to the one in the pic below. Your grounding wire should attach to the metal box.

 

No, we will not be able to attend the ECR this year. Wish we could!

 

71fKqnt7X9S._SY450_.jpg

 

 

Hi Randy,

 

I have another question or too. I am working on the wiring plan for the shore power and transfer switch. In previous post inside this thread there is talk about using a breaker before the transfer switch. The breaker box that I am planning on using has four breakers in it. I don't see for my use needing all four breakers. Breaker #1 & #3 come off of one of the hot leads that comes into the breaker box and breaker #2 & #4 come off of the other hot lead coming into the box. This brings me to my questions. I will only be using breaker #1 & #3 for power coming from the transfer switch. This includes power (120 volts) coming from the invertor thru the transfer switch. That leaves breaker #2 & #4 not in use. Can I use breaker # 2 or #4 for the breaker that is ahead of the transfer switch ? I also understand that if I use breaker #4 for this work, breaker #2 can not be used for anything else. I will also add a separate ground bar inside the box. The box is made of plastic. I hope I am making sense to you. It would save me room inside the storage compartment. The microwave for the truck needs to be inside of the storage compartment because of the size of my sleeper. I only have a 42" sleeper.

 

Thank you again for all of your help,

Al

2012 Volvo VNL 630 w/ I-Shift; D13 engine; " Veeger "
  Redwood, model 3401R ; 5th Wheel Trailer, " Dead Wood "
    2006 Smart Car " Killer Frog "
 

 

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I'll leave the detailed answer to Randy, since he started this ....

 

But the short answer is no - with a conventional breaker box you cannot do that without modification to the box. Which I don't recommend.

 

With a DIN breaker box and DIN breakers you can have multiple power sources, but not in a "conventional" breaker box as you would be using. That is why I like using DIN breakers and rails, as appropriate.

Jack & Danielle Mayer #60376 Lifetime Member
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PLEASE no PM's. Email me. jackdanmayer AT gmail
2016 DRV Houston 44' 5er (we still have it)
2022 New Horizons 43' 5er
2016 Itasca 27N 28' motorhome 
2019 Volvo 860, D13 455/1850, 236" wb, I-Shift, battery-based APU
No truck at the moment - we use one of our demo units
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-------------------------------------------------------------------------
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I'll leave the detailed answer to Randy, since he started this ....

 

But the short answer is no - with a conventional breaker box you cannot do that without modification to the box. Which I don't recommend.

 

With a DIN breaker box and DIN breakers you can have multiple power sources, but not in a "conventional" breaker box as you would be using. That is why I like using DIN breakers and rails, as appropriate.

 

Hello Jack,

 

Can you explain a DIN breaker to me ? Does the big box stores sell DIN breakers ? I will do some searches myself. Where would DIN breakers be used at ? Solar ? They seem to be industrial style breaker.

 

Thank you for any help that you can give,

Al

2012 Volvo VNL 630 w/ I-Shift; D13 engine; " Veeger "
  Redwood, model 3401R ; 5th Wheel Trailer, " Dead Wood "
    2006 Smart Car " Killer Frog "
 

 

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A DIN breaker has a totally different setup than what most people are used to. They basically have an input AND an output wire. They snap into a rail that's only function is to hold them - there is not a bus bar integrated into the rail. To power the breakers you either power them with an individual wire on the input side, OR you use a metal bus bar to jumper between them (if powering multiple breakers). For smaller projects they can sometimes be convenient.

 

The link shows DIN breakers in a small box being used for two independent functions. In this case, as disconnect devices as well as circuit protection of a solar controller. One is before and one is after the controller. If you examine the picture you can see that the breakers simply snap onto the rails.

 

This SECOND picture shows a similar box with breakers joined on their output side by a bus bar. This feeds to the solar controller, but could be anything.

Jack & Danielle Mayer #60376 Lifetime Member
Living on the road since 2000

PLEASE no PM's. Email me. jackdanmayer AT gmail
2016 DRV Houston 44' 5er (we still have it)
2022 New Horizons 43' 5er
2016 Itasca 27N 28' motorhome 
2019 Volvo 860, D13 455/1850, 236" wb, I-Shift, battery-based APU
No truck at the moment - we use one of our demo units
2016 smart Passion, piggyback on the truck
-------------------------------------------------------------------------
See our website for info on New Horizons 5th wheels, HDTs as tow vehicles, communications on the road, and use of solar power
www.jackdanmayer.com
Principal in RVH Lifestyles. RVH-Lifestyles.com

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Al - agreeing with Jack, don't use the box you have. Go back to the one Lou posted a link to and the full size breaker I gave you a picture of previously. Lou's reply shows a box for less than $12 that can be used for two separate inputs (neutral and hot) for 120 VAC or two independent hot legs of a 240 volt (40 amp) line. One can also place a jumper between the input lugs if they desire a 4 circuit 120 VAC box using 1/2 space size breakers. The same model of box is also available from Square D. Yes, the DIN standard is also a viable option but typically more expensive, not stocked in home stores and not really necessary for the scope of your project. This box will give you the same benefits of a DIN box and breakers.

 

0217f081-f089-4694-b71b-e993eabfd329_400

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Randy, Nancy and Oscar

"The Great White" - 2004 Volvo VNL670, D12, 10-speed, converted to single axle pulling a Keystone Cambridge 5th wheel, 40', 4 slides and about 19,000# with empty tanks.

ARS - WB4BZX, Electrical Engineer, Master Electrician, D.Ed., Professor Emeritus - Happily Retired!

 

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Al - agreeing with Jack, don't use the box you have. Go back to the one Lou posted a link to and the full size breaker I gave you a picture of previously. Lou's reply shows a box for less than $12 that can be used for two separate inputs (neutral and hot) for 120 VAC or two independent hot legs of a 240 volt (40 amp) line. One can also place a jumper between the input lugs if they desire a 4 circuit 120 VAC box using 1/2 space size breakers. The same model of box is also available from Square D. Yes, the DIN standard is also a viable option but typically more expensive, not stocked in home stores and not really necessary for the scope of your project. This box will give you the same benefits of a DIN box and breakers.

 

0217f081-f089-4694-b71b-e993eabfd329_400

I totally agree......I use those boxes all the time for projects like this. I only brought the DIN box up for general info and because it satisfies the "mounting of independently powered breakers". The DIN boxes cost more but are useful for some projects.

Jack & Danielle Mayer #60376 Lifetime Member
Living on the road since 2000

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Hi Randy,

 

Thank You for all of your help. All of the info that you posted will be a big help to me. I also think that this info is going to be a big help for someone else adding shore power to their own truck.

 

Hope to see you down the road,

Al

2012 Volvo VNL 630 w/ I-Shift; D13 engine; " Veeger "
  Redwood, model 3401R ; 5th Wheel Trailer, " Dead Wood "
    2006 Smart Car " Killer Frog "
 

 

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DIN products are commonly available at electrical supply houses. Not all will sell to non-contractors, so you may need to buy through an electrical contractor. Know the pricing, if you go this route, as walk-in traffic typically gets the highest mark-up.

I have been wrong before, I'll probably be wrong again. 

2000 Kenworth T 2000 w/N-14 and 10 speed Gen1 Autoshift, deck built by Star Fabrication
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2007 32.5' Fleetwood Quantum


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  • 1 month later...

You are just building a smallish 15 amp setup for the cab of the truck.

The extension cord you use will be plugged into a current protected circuit no matter what.

So having a separate breaker panel is a little redundant as has been mentioned.

Simple is good. Your outlets in the truck go to the armature (my industry calls it the heal).

When the relay is not activated the power goes from the inverter and when shore power is

available, it picks up the relay and sends that shore power to the outlet. The simplest DPDT

(double pole double throw) circuit you can build.

I should have most everything to help should you need it at ECR, as am building one for another also.

Drive safe.

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I did not read through this thread, sorry if I missed something. A powered relay is not a good idea to use as a transfer switch. Transfer switches can be mechanical, on-off-on. Or automatic. Automatic work as latching relays. Power is pulsed to make the switch-over.

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While it might be a benefit fior some folks to have an auto transfer switch in the truck I found that a simple set up was best for me.

 

I have all the outlets on one wire (light loads not using two items together like MW and Kettle) this wire has a plug on it.

 

It is plugged into inverter if on batts. Then if on shore power, it's plugged into an outlet near inverter that is powered by shore power. It has a male ended Ext cord on it that hangs tie wrapped in batt area. I just connect an Ext cord to it from shore power.

 

Protected by shore supply breaker or inverter.

 

I call it redneck shore power. Works fine for my uses.

 

I also can power my Batery Minder that lives near the inverter area and just plug into shore power for that. Minder stays connected to batt bank all the time.

 

I do have a remote inverter SW in cab.

 

Cost was minimal.

 

Can show this at ECR if anyone interested.

Bill and Joan and 3 Collie pups

2001 Volvo VNL 770 "The Doghouse" Singled short, "ET" hItch VED12 465HP Gen 1 Autoshift 3.58 ratio  2005 Mobile Suite 38RL3  2011 Smart Passion loaded piggybacK

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