yet another diversion load question . . .

[crtr]

I'm sorry if this had been answered already. I searched the forum a few times but couldn't find a clear answer. I'm relatively new to this topic (I've had grid-tied home solar for 17-18 years) and not familiar with all the newer components and related issues.

I lucked out and am buying a set of new solar system components from a friend at a big discount. He had some bad luck with a 4x4 Sprinter lemon and aborted his conversion plans before he even started! Here are the major components:
2X Rich 335watt solar panels
Growatt 24V SPF 3000TL LVM - inverter/charger
EG4 24V 200AH LiFePo4 - battery
Sterling BB122470 - B2B charger

I also just bought a Surecal 12v/120v calorifier w/heat exchanger and would love to use it as a "dump load". The 12v element is 300W. The 120v is 700W.

Over the past couple weeks, I've viewed countless posts about diversion load setups on this and other sites, YouTube videos, etc etc etc and my head is about to explode! Seems there are >100 different ways to set this sort of thing up and each way has it's own pros/cons. My first thought was to setup a voltage sensitive relay to monitor battery and divert when fully charged. The issue here is that it would drain the battery (to the extent I set up the monitor) when no PV or alternator charging available. Another I heard mentioned was to add an addition PMW charge controller (Xantrax) between the chargers and battery (Growatt and Sterling) and divert at this point.

I think my requirements/goals are pretty simple:
1. heat my water when battery is full
2. ONLY heat water when either solar output and/or B2B charger output are adequate: no sun or parked, do not heat water, regardless of battery state
3. simple design and set up
4. automatic and reliable -- set it and forget it!

Given my "wish-list" above, is there a reaonably easy way to set this up?!?

 

[kanelr]

Exactly my wish list , and similar approach. Am wanting to do the same, does your inverter have "extra" relays?
relay- works as switch to turn on whatever smaller wire you run through it.

 

[Rednecktek]

What about getting a wind turbine or water turbine controller that's already built for providing dump loads and just parallel that into the system? It only comes on when voltage > setpoint, outputs to a resistor/element, pretty much set up out of the box.

Hit up the Wind and Water sub sections and see if there are any good pointers in there.

 

[pollenface]

I believe the easiest way to use diversion control is with a controller that is built for the task, eg Xantrax C-series

 

[OzSolar]

My 2 cents is that dump/diversion load set ups tend to break pretty much all of my KISS tests. So I would start off with using a manual 120v timer that runs that 700 watt element for 30 (or so) minutes then shuts off. If I found that didn't work I might look at doing a dump load.

Outback's Flexmax charge controllers have programmable contacts that can used to do what you're wanting to do. The instructions start on page page 38. Not that I'm suggesting that product , rather it's some good reading about the what all has to go into setting it up.

 

[crtr]

Thanks to all for the thoughtful replies.

What about getting a wind turbine or water turbine controller that's already built for providing dump loads and just parallel that into the system? It only comes on when voltage > setpoint, outputs to a resistor/element, pretty much set up out of the box.

Hit up the Wind and Water sub sections and see if there are any good pointers in there.

Thanks and wish I'd had your thoughts a few months ago . . . would have saved me a few hours. In the end, that's basically what I did. I found a voltage sensitive relay on Ebay for $12.

 

[crtr]

Exactly my wish list , and similar approach. Am wanting to do the same, does your inverter have "extra" relays?
relay- works as switch to turn on whatever smaller wire you run through it.

The inverter has some dry contacts and those are what I used initially. I ran a 24v lead to them and used a simple SPDT relay to power the heating coil. The issue was that didn't allow for using the Sterling B2B as well. Ultimately, what I did: I found a cheap voltage sensing relay on EBay and wired directly off my bus bars. It works like a champ!!

There were only 2 challenging parts to this. 1. deciphering the Chinese written "English" directions on how to program the unit. 2. I had to play around a little to get the on/off voltage settings right. Been using it for a couple months now and it keeps the calorifier water hot 24/7. The real test is coming up when I start using the AC in the van . . . .

 

[crtr]

I believe the easiest way to use diversion control is with a controller that is built for the task, eg Xantrax C-series

Well, that would've been a great option if I didn't already have my controller.

 

[crtr]

My 2 cents is that dump/diversion load set ups tend to break pretty much all of my KISS tests. So I would start off with using a manual 120v timer that runs that 700 watt element for 30 (or so) minutes then shuts off. If I found that didn't work I might look at doing a dump load.

Outback's Flexmax charge controllers have programmable contacts that can used to do what you're wanting to do. The instructions start on page page 38. Not that I'm suggesting that product , rather it's some good reading about the what all has to go into setting it up.


View attachment 97514

I used the dry contacts on the Growatt initially and that worked fine. The issue was that it didn't include the B2B charging option. In the end, I found a simple, cheap relay on EBay that solved everything.