Connecting 24v DC device loads on 48v FP1 system

A place where users can meetup with other FlexPower One users and can find support for one another. A great place for people who have not purchased the FlexPower One yet to look up information.

Connecting 24v DC device loads on 48v FP1 system

Postby Jpro556 on Thu Apr 12, 2018 3:24 pm

Hi,

I'm upgrading a 24v Trace 3524 inverter system in an old cabin to an FP1 vfxr3648 system. Batteries are also upgraded. For the most part, there are no issues as just about everything is AC. However, there are 3 DC loads that have to continue to function and they are 24vdc. Two of them are 4 amp Shurflo water booster pumps, and one is a small 3W fan in the vent pipe of a composting toilet. I'd like to find the best solution to deal with this if someone with knowledge would be so kind to help me out.

The possibilities I've considered are:

1. replace the DC devices with something compatible with new system. Problem is that there are no 48v models of the devices and only the pumps, not the fan can be found in AC, and AC requires a difficult rewire. This isn't an option.

2. down convert a 48v circuit to 24v feeding something like a midnite solar MNEDC breaker box with some 5 and 10 amp DC breakers. QUESTION: how exactly do I do this? Where do I tap the 48v in the system such that I don't bypass or mess up the FNDC monitoring? I imagine then I'd take that circuit out to the downconverter and then into the MNEDC box to a bus and then to the breakers. If this is the best answer, and there is a good place to tap the 48v, does anyone have a recommendation for a good VDC downconverter?

3. The fp1 powers a small external AC load center. I suppose I could put in another breaker for a circuit to a 120vac to 24vdc power supply and connect my dc loads to that power supply. I found one that would do the trick, providing 10A continuous and 15A peak at 80% efficiency, from Schneider.

I feel like #3 is the best option, even though a little wasteful in terms of efficiency. However, I really want to know the best way to connect DC loads to the system in a way that plays well with the FP1 and the FNDC for future reference in any case.

As an aside, I think I can get a 12v fan, and was thinking I could just hook that up to the inverter's 12v aux terminals, since it runs all the time, as opposed to intermittently for the water booster pumps. That way I can set the inverter to turn it off when the batteries get low.

Can anyone give me some insight, feedback, or suggestions?

Thanks.
Jpro556
Forum Junior Member
 
Posts: 3
Joined: Thu Mar 22, 2018 7:19 pm

Re: Connecting 24v DC device loads on 48v FP1 system

Postby Mike Curran on Thu Apr 12, 2018 5:15 pm

Jpro556 wrote:2. down convert a 48v circuit to 24v feeding something like a midnite solar MNEDC breaker box with some 5 and 10 amp DC breakers. QUESTION: how exactly do I do this? Where do I tap the 48v in the system such that I don't bypass or mess up the FNDC monitoring? I imagine then I'd take that circuit out to the downconverter and then into the MNEDC box to a bus and then to the breakers. If this is the best answer, and there is a good place to tap the 48v, does anyone have a recommendation for a good VDC downconverter?

This is the route I took to power some 12V DC motored driven pumps and a thermostat from my 24V system. I tapped into the 24V on my positive and negative busses, and added an in line fuse in the positive leg. This fed a 24 to 12V DC buck converter - here's a link to 48 to 24V model, haven't experience with it so can't vouch for reliability (Amazon.com):
Screenshot_20180412-203501.jpg
There are others out there, just Google 48 to 24 volt converter. I feed several DC devices from the 12 volt side of the converter, just had to make sure current draw didn't exceed the converter capacity, and size the upstream fuse accordingly. Here's a photo, kinda messy:
152357820242115382046.jpg

Where mine is connected affects current measurement "from battery" so I think it accurately reflects its location electrically.

Hope this helps. - Mike
Mike Curran
Forum Czar
 
Posts: 607
Joined: Sat Aug 28, 2004 6:28 pm
Location: Chagrin Falls, Ohio
My RE system: Outback:
- 8 (2x4) Evergreen 180's into one MX60
- 6 (2×3) ALEO S79-300's into one FM80
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC
- 12 Surrette/Rolls 2V x 1766Ah
- Hub10.3, Mate3, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar:
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied.

Re: Connecting 24v DC device loads on 48v FP1 system

Postby Jpro556 on Fri Apr 13, 2018 1:47 pm

Thank you Mike,

Did you connect directly to the +/- terminals for the battery on the inverter with 5/16" lugs or elsewhere?

I'm an engineering type and just starting to get hands-on with this. Studied a lot, had some training, but just now digging in and installing my own stuff to start with.

That is one particularly cheap 48v-24v converter. Seems like converters are priced all over the place, even when looking at same power ratings. Happy to try the cheapest first.
Jpro556
Forum Junior Member
 
Posts: 3
Joined: Thu Mar 22, 2018 7:19 pm

Re: Connecting 24v DC device loads on 48v FP1 system

Postby Mike Curran on Fri Apr 13, 2018 3:03 pm

Jpro556 wrote:Did you connect directly to the +/- terminals for the battery on the inverter with 5/16" lugs or elsewhere?

That's a particularly cheap 48v-24v converter. Seems like converters are priced all over the place, even when looking at same power ratings. Happy to try the cheapest first.

Jpro - I have an older Outback DC enclosure with positive and negative busses inside. The connections were made to these busses, as shown by the red arrows in this photo:
20180413_175320.jpg
Note the fuse near the positive connection.

Yeah, these buck converters are cheap, I paid $5 for my 24->12V converter, it's been running 2 winters in a row without a hitch. - Mike
Mike Curran
Forum Czar
 
Posts: 607
Joined: Sat Aug 28, 2004 6:28 pm
Location: Chagrin Falls, Ohio
My RE system: Outback:
- 8 (2x4) Evergreen 180's into one MX60
- 6 (2×3) ALEO S79-300's into one FM80
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC
- 12 Surrette/Rolls 2V x 1766Ah
- Hub10.3, Mate3, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar:
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied.

Re: Connecting 24v DC device loads on 48v FP1 system

Postby Jpro556 on Fri Apr 13, 2018 7:26 pm

Mike,

Thanks for the photo, that is convenient having those busses.

So, based on the photo I have included below of the DC neg shunt at the inverter, does it matter where I attach to? The options are clear in the photo...left side of shunt, right side, or at inverter terminal. I imagine I need to attach either at right side of shunt or inverter terminal to get on the "other side" of the FNDC metering wires seen here in gr/gr-wh. What do you think? Battery neg attaches on left side of shunt, fyi.

Thanks,
Jason

IMG_2161.jpg
Jpro556
Forum Junior Member
 
Posts: 3
Joined: Thu Mar 22, 2018 7:19 pm

Re: Connecting 24v DC device loads on 48v FP1 system

Postby Mike Curran on Sat Apr 14, 2018 4:52 am

You should connect on the inverter side of shunt. It looks like there's a couple of tapped holes in the shunt "block" on the right side, you might be able to use one of them if your DC loads are small. - Mike
Mike Curran
Forum Czar
 
Posts: 607
Joined: Sat Aug 28, 2004 6:28 pm
Location: Chagrin Falls, Ohio
My RE system: Outback:
- 8 (2x4) Evergreen 180's into one MX60
- 6 (2×3) ALEO S79-300's into one FM80
- 2 grid-tied GVFX3524's classic stacked for 120/240VAC
- 12 Surrette/Rolls 2V x 1766Ah
- Hub10.3, Mate3, FNDC, RTS, OpticsRE. Tigo Energy ES maximizers on each PV module.

Westinghouse Solar:
- 30 (2x15) 235W panels with Enphase M215 microinverters, grid-tied.


Return to Flex Power One

Who is online

Users browsing this forum: No registered users and 2 guests