Hi everyone,
After the last batch of storms here in Illinois with power outages I plan on installing a 1800w Xantrex freedom hf with 2 gel marine batteries for lighting and small loads. It has a built in 30 amp transfer switch and 40 amp charger and is made to be hardwired. I will install a 30 amp breaker from the AC panel to supply the inverter power and have a sub panel(2 space 4 circuit). I purchased slim line breakers which have 2 20 amp circuits on each breaker. The circuits I plan on powering are necessities such as fridge and kitchen lighting and outlets, no high load items.
I have been planning this out for a while and have most of the items, just waiting on a t-fuse and battery cables to arrive. I have installed many transfer switches with generators and am very comfortable with wiring. The reason for home battery backup is because the wife can't start a generator and to be honest am afraid she would blow up the house. So a built in transfer switch to save the fridge and give her lighting is my main goal. Question I have is about the sub panel since I never wired one. The inverter output will have 10 awg 3 wire(line neutral ground) which I will wire to the sub panel.
The sub panel has two lugs. one supplying each breaker I presume. The inverter has only one output lug(3 wire). Does the sub panel provide power to both breakers if I wire one lug? Are both lugs in there for 240? It doesn't look like they are bonded to each other. I want to supply power to both breakers(120v) but will have the inverter output to one lug. Hope this makes sense. Everything else looks very straight forward. Thanks for any input...
You can remove the 240 volt feed from the subpanel lugs and then connect the single 120 volt inverter feed to both hot lugs of the subpanel to power all of the breakers in which case any 240 volt equipment will get zero volts.
The transfer switch cannot be in the inverter unit with just one cable coming out. There must be a transfer switch in the current path from the main panel to the subpanel if you are going to power that subpanel with the inverter.
The common terminals of the (double pole) transfer switch are attached to the subpanel top feed. The side of the transfer switch (two sides; double throw) that accepts the inverter has two lugs for the two hot poles. Connect the hot lugs together (bridge them; bond them to each other) at this side and attach the single hot for the inverter feed. (Connect the inverter neutral to the neutral lug. Connect the original feed from the main panel to the subpanel to the other side of the transfer switch.)
Hey Allan,
Thanks for the reply. After reading your response, can you tell me why the transfer switch will not work in that configuration? The main panel is not attached per say because the built in transfer switch sees there is no power coming from the main ac panel. Once power is restored, then the transfer switch cuts off the battery side and the main ac panel is now supplying power to those circuits as well as charging the batteries. That is the intended use per Xantrex for hardwiring the inverter? All other Xantrex inverters have the same configuration. This transfer switch is the same as generator transfer switches,but automatic and both prevent backfeeding to the ac panel.(i.e no injured workers) At no time is power coming from both sources.(batteries versus ac grid) I understand both lugs providing 240 volt and each side is 120 volt, my question is if I wire one lug, are both sides receiving 120volt? Could you please explain? Thanks!
Thanks Allan,
You must have been editing your post while I was typing. I think we are both on the same page now. I am going to wire one lug of the sub panel with the inverter output so both sides of the sub panel are getting 120 volts. there will be no need for 240 volts. The transfer switch is between the sub panel and the main ac panel, there will be no backfeeding of power to the ac panel. Thanks again for taking the time!
You will be backfeeding the entire electrical system with 120 volts by doing what you are proposing.
The power from the inverter will be going into the subpanel and on through it via the conductors and te breaker feeding ths sub panel from the main panel.
A transfer switch is required to isolate the utility power from the emergency power. The inverter transfer switch does not do this.
Perfect, that's all you need to prevent backfeeding the utility lines. The inverter is also connected to this transfer switch (and not directly to the subpanel) in a manner that the subpanel can get power from the inverter or from the main panel but that the main panel and inverter can never be connected together.
You may not connect the inverter output directly to the subpanel without first unscrewing and removing the wires going to the main panel.
Exception: The National Electric Code does allow separate breakers or switches to connect the main panel feed or the inverter feed to the subpanel but with cams and/or levers and/or sliders that prevent both sets of breakers/switches from being on at the same time.
One option would be a GE TM830CUGEN manual transfer switch. About $100.00. You install it as a sub panel with the circuits you want to have for back-up power. The inverter is also fed to the switch. It prevents utility power and back-up power from being connected at the same time.
Hey Br, Allan
Thanks again for the time to answer these questions! Let me take another stab at this..Brr,after looking at the manual again I don't see how this will backfeed into the main ac panel. The 30 amp breaker from main ac goes to power inverter for power. internal transfer switch looks for power on either side so no backfeeding there. If main ac panel loses power, transfer switch sees this and transfers to batteries and inverter output supplies sub panel(4 circuits). These 4 circuits were removed off the main ac panel and relocated to sub panel. so when power is restored, main breaker supplying power inverter is also supplying those 4 circuits and when power is lost "only" those 4 circuits are being powered by the batteries. There is no tie between those 4 circuits and the rest of the ac panel. Does that make sense? I'm trying to visualize this and type in a coherent manner at the same time
Hey Br, Allan
Thanks again for the time to answer these questions! Let me take another stab at this..Brr,after looking at the manual again I don't see how this will backfeed into the main ac panel. The 30 amp breaker from main ac goes to power inverter for power. internal transfer switch looks for power on either side so no backfeeding there. If main ac panel loses power, transfer switch sees this and transfers to batteries and inverter output supplies sub panel(4 circuits). These 4 circuits were removed off the main ac panel and relocated to sub panel. so when power is restored, main breaker supplying power inverter is also supplying those 4 circuits and when power is lost "only" those 4 circuits are being powered by the batteries. There is no tie between those 4 circuits and the rest of the ac panel. Does that make sense? I'm trying to visualize this and type in a coherent manner at the same time
I see what you are saying. I must be unclear about how that unit operates. Are you sure that normal utility power is fed through the unit during normal cicumstances. If so your plan sounds ok. I was thinking the power to the inverter only monotors power and keeps the batteries charged until there is a power failure and then transfers to battery power. If it operates as you say then your plan might be ok. Is there a URL which shows the inverter manual?
Hey Brr,
Yes, here is the link... 3rd document installation instructions page 1-7. When A/C power is up it charges the batteries and passes power to ac loads in sub panel. Sub panel circuits are completely isolated from main breaker panel.
Hey Allan,
I would take the necessary circuits off the main panel and relocate them to the sub panel via twist nut ties which are approved in my area. So the main panel is still supplying these circuits via the 30 amp breaker to the inverter, but once power is lost the inverter transfer switch only allows power from the batteries and doesn't allow back flow via the 30 amp breaker. Since the 4 circuits were relocated from the main to sub panel, there are no ties to allow back flow.
Just found the part in the Xantrex manual allowing a hard wired cable from the inverter output as the sole feed to the subpanel, in lieu of cord and plug to the inverter front panel receptacles and allowing a power usage of nearly 30 amps with utility power on. (This is not the same cable that comes out the back of the inverter to go to the main panel)
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