Back up system for natural gas furnace - Help with bypass

[Sneruh]

I am designing a system to ensure that we have backup power for a high efficiency natural gas furnace (mainly-I will likely also include a receptacle to provide current elsewhere if needed). I plan on using a Victron Multiplus 24V2000A -50 inverter/charger with two 12V100Ah LiFePO4 batteries in parallel. I am looking at connecting the AC IN side of the inverter to my basement subpanel on 15A breaker, then the AC OUT to the furnace with an emergency shut off switch (required by code here) at the foot of my stairs. I think this part is fairly straight forward. But the Victron Wiring Unlimited book suggest adding a bypass so that - in the event I need to take out the inverter (or decide to feed the furnace directly from the panel) - the furnace can continue to be online. How is this done while making sure there is no possibility for backfeed? In particular what kind of switch is required and how is it tied into the circuit?

 

[Ampster]

How is this done while making sure there is no possibility for backfeed? In particular what kind of switch is required and how is it tied into the circuit?

The simplest bypass is interconnected breakers with an interlock device. Midnite Solar makes a device that costs more but does that in a separate box.

 

[Sneruh]

After some more research I found that there is an alternative to an interlock for my particular set up. Reliance Controls and EZ Generator both have a switch that includes a generator connection point. I think I've solved my bypass issue. Appreciate any comments, in particular with respect to making sure that this is a safe plan (and especially to avoid any potential for backfeed) and 2) in accordance to code (or at least nothing that is glaring a no go). Thanks in advance.

 

[Ampster]

After some more research I found that there is an alternative to an interlock for my particular set up. Reliance Controls and EZ Generator both have a switch that includes a generator connection point.

i just installed a Reliance Controls generator switch for my Nephew. I to not know which switch you are looking at, but I don't think it is a good device to use to use as a bypass. The one I installed has breakers for individual circuits and may duplicate what you already have in your critical loads sub panel. If I understand your application correctly, you just want to be able to switch the feed to your critical loads panel between your inverter and your main panel. That is the concept of a bypass switch which toggles between those two sources for your sub panel.
EDIT:
I just looked at the diagram and if the Transfer switch you are referring to above, that diagram will not let you bypass the Multiplex.

 

[Rednecktek]

Replace the emergency switch with a switched outlet, replace the power wire with a plug. Plug furnace power into switched outlet.

When power goes out, shut off switch and plug furnace into solar generator/inverter/whatever.

No house rewiring, no tearing apart walls, impossible to back feed, safety switch still in place.

 

[time2roll]

No need to automate the removal or bypassing of the Victron. In the very unlikely event there needs to be service simply disconnect power and remove.

And the 12v batteries need to be in series for a 24v Multiplus.

 

[RV10flyer]

Replace the emergency switch with a switched outlet, replace the power wire with a plug. Plug furnace power into switched outlet.

When power goes out, shut off switch and plug furnace into solar generator/inverter/whatever.

No house rewiring, no tearing apart walls, impossible to back feed, safety switch still in place.

All of my furnace installs get an appliance cord then plugged into a single receptacle. Easy to plug into a generator or backup power source when needed. Easy for me when servicing.

 

[Sneruh]

i just installed a Reliance Controls generator switch for my Nephew. I to not know which switch you are looking at, but I don't think it is a good device to use to use as a bypass. The one I installed has breakers for individual circuits and may duplicate what you already have in your critical loads sub panel. If I understand your application correctly, you just want to be able to switch the feed to your critical loads panel between your inverter and your main panel. That is the concept of a bypass switch which toggles between those two sources for your sub panel.
EDIT:
I just looked at the diagram and if the Transfer switch you are referring to above, that diagram will not let you bypass the Multiplex.

Thx Ampster. I think the way I described it may not be accurate. I don't want to install a "bypass switch". What I want to do is be able to bypass the inverter/charger if I needed to. On my diagram, the DPDT switch on the left side receives current from either my sub-panel (15A breaker there) OR from the AC Out side of the inverter. The switch on the AC In side of the inverter, if from Reliance Controls, is their TF151W Easy/Tran transfer switch. Alternatively, I could install another DPDT switch with one IN coming from a dedicated breaker on my sub-panel, the other IN coming from a wired receptacle outside my house for the generator plug and the OUT side going into the AC IN side of the inverter. So here is what I think happens (or what I want to happen): Scenario 1: Winter Set Up: Transfer switch on the AC In side of the inverter set to connect AC IN to Sub panel 20 breaker; DPDT switch on AC Out side set to link AC Out to the furnace (no current flowing from the 15A breaker at the sub-panel (this would be my current breaker that feeds the furnace directly). Under this scenario, if there is a power outage, the furnace gets powered by my battery bank OR if I want by the generator if the battery bank gets depleted. Scenario 2: Summer: I don't need the gas furnace to provide heat, but I do need the furnace control system for the air conditioning system. Here, I would turn off my inverter/charger and switch the DPDT to provide current to the furnace from the 15A breaker at the sub-panel. FYI, I live in Ottawa, Canada where in winter temperatures can go down to -20 to -30F regularly. So heating is my main concern. Apologies for the long winded reply but hopefully ity clarifies what my objective is.

 

[Sneruh]

Replace the emergency switch with a switched outlet, replace the power wire with a plug. Plug furnace power into switched outlet.

When power goes out, shut off switch and plug furnace into solar generator/inverter/whatever.

No house rewiring, no tearing apart walls, impossible to back feed, safety switch still in place.

Thx Rednecktek. Living in Canada, my set up needs to kick in if I am not at home in winter. Otherwise, yes, this would be much simpler.

 

[Sneruh]

Thx Rednecktek. Living in Canada, my set up needs to kick in if I am not at home in winter. Otherwise, yes, this would be much simpler.

And thx RV10Flyer.

 

[Sneruh]

No need to automate the removal or bypassing of the Victron. In the very unlikely event there needs to be service simply disconnect power and remove.

And the 12v batteries need to be in series for a 24v Multiplus.

My initial post was using a 12V inverter then I decided to go with a 24V one. Thanks for the clarification..

 

[jbird526]

@Sneruh have you considered a transfer panel with a few more circuits? I installed this one, which is 4 circuits. Wanted to power some lights along with my furnace. It says its a Goal Zero but its just a PRO/TRAN 2 that they are branding.

Transfer Switch

 

[Rednecktek]

Thx Rednecktek. Living in Canada, my set up needs to kick in if I am not at home in winter. Otherwise, yes, this would be much simpler.

Plug in a UPS? That should buy you enough time to get home and get the extension cord run to the bigger inverter system.

I can see where that would be an issue though. It was a thought. ?

 

[jbird526]

@Sneruh have you considered a transfer panel with a few more circuits? I installed this one, which is 4 circuits. Wanted to power some lights along with my furnace. It says its a Goal Zero but its just a PRO/TRAN 2 that they are branding.

Transfer Switch

View attachment 140484

OH just saw this comment, which would be an issue.

Living in Canada, my set up needs to kick in if I am not at home in winter.

 

[Ampster]

have you considered a transfer panel with a few more circuits?

That panel would not suit his need for something that switches automatically. As I mentioned earlier, I just installed one of those and it is a good solution for manually switching some circuits over to a generator

 

[time2roll]

The bypass is called 3 wire nuts. Remove H-N-G from the Multiplus and connect in-out directly to complete the circuit.

 

[Grimmster]

Replace the emergency switch with a switched outlet, replace the power wire with a plug. Plug furnace power into switched outlet.

When power goes out, shut off switch and plug furnace into solar generator/inverter/whatever.

No house rewiring, no tearing apart walls, impossible to back feed, safety switch still in place.

That is fine if the furnace is all you want to power. For me I want to power more circuits.

 

[Sirtate]

Thx Rednecktek. Living in Canada, my set up needs to kick in if I am not at home in winter. Otherwise, yes, this would be much simpler.

What if the MultiPlus was plugged in, in-between?

Utility fuse panel-- Furnace power outlet--Multiplus--MTP outlet--furnace...
If you want to bypass the MultiPlus, you just unplug the furnace and plug it directly into the utility power outlet.
In normal operations, the MultiPlus would work like a big UPS.

 

[Grimmster]

That panel would not suit his need for something that switches automatically.

It can, just leave the circuit switches of the manual transfer switch in the Gen position. When grid is lost the Victron will auto transfer to battery. I would of course only do that for the circuits that I want UPS functionality.

 

[Ampster]

It can, just leave the circuit switches of the manual transfer switch in the Gen position. When grid is lost the Victron will auto transfer to battery.

Okay, I must have misunderstood his goals.