Electric resistance water heater - how to?

Discussion about the FM100 AFCI Charge Controller
Post Reply
mosbergh
Forum Member
Posts: 14
Joined: Tue Mar 24, 2020 1:08 pm
My RE system: Flexpower Radian 8kW:
GS8048A
2x FM100-300DC
FN-DC FlexNet DC
Mate 3s
Batteries: 4 "BYD" LFPs 200AH at 24V nominal, 2 banks x 2 in series
Diesel generator FG Wilson 14 kVA (20 yrs old)
Location: Man-o-war cay, Bahamas
Contact:

Electric resistance water heater - how to?

Post by mosbergh »

For the time being, I manually turn on the 4.5kW water heater once I see that battery charging is complete - around 11am, when max. collector harvest is still an hour away. And I watch the power balance on Optics-Re to see if there is significant battery drain (if the day turns cloudy), n which case I would turn it off again.

I am aware of the various AUX relais options, but none of them appears to reflect what I do manually. There are a few particulars in my system:
- the LFP batteries maintain around 52.5 V once charging is over; there s no useful voltage set point to turn the water heater on/off
- the LFP batteries are not well suited for a long-term drain of 100A (5kW), and the BMS may turn off one of them, with the other string then collapsing completely.

So I would need a starting point for the heater tied into the possibility of PV production (high voltage?), although the actual charging has come to a halt, and turn-off if PV production is less than, e.g., 3kW.

Does anyone have recommendations on hoe to use the AUX relais for this purpose?

Thanks,
Hans
provo
Forum Czar
Posts: 630
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
Eight Rolls S-550 (2 strings, total ~800Ah @ 24V)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC and Trimetric
Honda EU3000is generator
Location: Sierra foothills

Re: Electric resistance water heater - how to?

Post by provo »

mosbergh wrote: Thu Apr 02, 2020 6:46 am
So I would need a starting point for the heater tied into the possibility of PV production (high voltage?), although the actual charging has come to a halt, and turn-off if PV production is less than, e.g., 3kW.

Does anyone have recommendations on how to use the AUX relays for this purpose?
I don't, but it's something I've thought about a lot for other purposes. It would be great if there was a way of sensing how bright the sun is from moment to moment and controlling other functions based on that, maybe with some programmable timers or even some "smart" (predictive) features. A great Arduino project!

The "photosensors" are there already, so it should be straightforward. My immediate use would be a sun-based version of HBX (rather than based on battery voltage, which lags and also depends on other factors.)
Last edited by provo on Thu Apr 02, 2020 9:37 am, edited 1 time in total.
mosbergh
Forum Member
Posts: 14
Joined: Tue Mar 24, 2020 1:08 pm
My RE system: Flexpower Radian 8kW:
GS8048A
2x FM100-300DC
FN-DC FlexNet DC
Mate 3s
Batteries: 4 "BYD" LFPs 200AH at 24V nominal, 2 banks x 2 in series
Diesel generator FG Wilson 14 kVA (20 yrs old)
Location: Man-o-war cay, Bahamas
Contact:

Re: Electric resistance water heater - how to?

Post by mosbergh »

I would hope that the Mate3(s) has all the computational functions needed - this should be just another mode for AUX control. I wouldn't want to install and maintain another (foreign) piece of hard/software that no-one else understands.
provo
Forum Czar
Posts: 630
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
Eight Rolls S-550 (2 strings, total ~800Ah @ 24V)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC and Trimetric
Honda EU3000is generator
Location: Sierra foothills

Re: Electric resistance water heater - how to?

Post by provo »

mosbergh wrote: Thu Apr 02, 2020 9:34 am I would hope that the Mate3(s) has all the computational functions needed - this should be just another mode for AUX control. I wouldn't want to install and maintain another (foreign) piece of hard/software that no-one else understands.
For sure, that would be best. But I don't believe the actual sun level is even known or used directly by anything in the OB system.
raysun
Forum Emperor
Posts: 3829
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Electric resistance water heater - how to?

Post by raysun »

mosbergh wrote: Thu Apr 02, 2020 9:34 am I would hope that the Mate3(s) has all the computational functions needed - this should be just another mode for AUX control. I wouldn't want to install and maintain another (foreign) piece of hard/software that no-one else understands.
It would seem, with those fancy FM100s and their enhanced set of Aux control parameters (don't ask me what they are, I just have a dirtbag old tech system), one would be able to find a trigger other than battery voltage.

I'd start by seeing if the FM100 has any sort of diversion trigger - able to service your "dump load".

Failing a direct parameter, there's two known events: Battery Charge Parsmeters Met in the FNDC, and instantaneous power on the FM100s that should be able to be leveraged somehow.

If you want to ship me your FM100s for 6 months or so, I'm sure I could configure a solution for you. 😁
provo
Forum Czar
Posts: 630
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
Eight Rolls S-550 (2 strings, total ~800Ah @ 24V)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC and Trimetric
Honda EU3000is generator
Location: Sierra foothills

Re: Electric resistance water heater - how to?

Post by provo »

raysun wrote: Thu Apr 02, 2020 10:27 am
Failing a direct parameter, there's two known events: Battery Charge Parsmeters Met in the FNDC, and instantaneous power on the FM100s that should be able to be leveraged somehow.
Well there you go :grin: -- the output of the FM into an A/D converter, and the Arduino does whatever you want with that!
JRHill
Forum Emperor
Posts: 1192
Joined: Thu Feb 17, 2011 11:12 am
My RE system: VFX 3648, FM80, 3k panels, Mate3, FNDC, 3ea 3.8 PHIs. And still, a wonderful wife.
Location: Not
Contact:

Re: Electric resistance water heater - how to?

Post by JRHill »

Kind'of off topic but:

My gosh in that location you are prime for passive HW heating. Why not? Even if it was an old well pressure tank with the bladder removed and painted black for preheat.... We're not near as advantageous as you in that location. For example we have an 80g tank like that in a tree for an outdoor shower in the summer. Its quite a delight. Sometimes way too hot. Sometimes way too cold. But it was inexpensive and fun to play with.
mosbergh
Forum Member
Posts: 14
Joined: Tue Mar 24, 2020 1:08 pm
My RE system: Flexpower Radian 8kW:
GS8048A
2x FM100-300DC
FN-DC FlexNet DC
Mate 3s
Batteries: 4 "BYD" LFPs 200AH at 24V nominal, 2 banks x 2 in series
Diesel generator FG Wilson 14 kVA (20 yrs old)
Location: Man-o-war cay, Bahamas
Contact:

Re: Electric resistance water heater - how to?

Post by mosbergh »

Yes, solar-thermal direct heat ... if t were so simple:

First,the domestic expectation is for hot water to flow on-demand out of faucets and showers - and that the water be of the same (hygienic) quality as the cold water. That rules out pressure-less systems with big volumes and stagnant water.
Second, the problem we have here is that the heat cannot be controlled. If we don't use hot water for any length of time, it would quickly come to a boil.
The solution to all this, of course, would be a secondary circulation of high boiling-point liquid (e.g., coolant) and heat exchangers. Can be done, but is really expensive and has limited system life due to all sorts of stress and corrosion (salt, UV).

Third - and most relevant here: the electric resistance 60 G heater is already in place, and I am making so much electric power that everything on a sunny day after 10:30 am could be used - and still, after 90 min or so, the heater and charge controllers turn off with half a day wasted.

My initial idea - and not having experienced the abundance of electricity - was to install a tankless LP gas heater: I have done so, and it works really well - but kept the electric heater in the system, and I now realize I get the heating energy free of charge (LP gas comes in 100 lbs tanks at more than $100).

Hope this explains why I am interested to automated my old heater.

Cheers,
Hans
raysun
Forum Emperor
Posts: 3829
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Electric resistance water heater - how to?

Post by raysun »

Plus, with engineering DNA, if you aren't working on a problem, you're likely creating a problem, or if like me, being a problem. LOL!

I think, without knowing, the answer lies in coulomb counting. Knowing what the charge controller knows, and triggering when the Battery Charged flag is set.

I understand the FM100 has beaucoup relay setting logic.

Keep us posted!
sodamo
Forum Emperor
Posts: 1011
Joined: Mon Apr 03, 2006 1:55 am
My RE system: Totally off grid - Hamakua side, Big Island, Hi

36 Trina 280 & 16 Phono 250 in 48 volt array (fixed) 14080w
Radians GG8048/GS4048 w GSLCs
4 FM 80 charge controllers
Hub 10.3
FNDC w/3 shunts
Mate 3s
OpticsRE - MMKL - Ninole Hi
12 SimpliPhi 3.8
14Kw Kohler 14RESA Propane

Charging Only
2FX3048T
Hub
FNDC. - shared shunt feeds from Radian FNDC
Mate 3s
10Kw MEP 803a Military gen

Honda EU7000i

Davis VantagePro2 Wx Station
On line at: https://www.wunderground.com/dashboard/pws/KHININOL2
Location: Ninole, Hi

Re: Electric resistance water heater - how to?

Post by sodamo »

Maybe out in left field, but I have been curious if something like a wx station uv sensor could come into play.
David
Please visit http://vacation.ninolehawaii.com
mosbergh
Forum Member
Posts: 14
Joined: Tue Mar 24, 2020 1:08 pm
My RE system: Flexpower Radian 8kW:
GS8048A
2x FM100-300DC
FN-DC FlexNet DC
Mate 3s
Batteries: 4 "BYD" LFPs 200AH at 24V nominal, 2 banks x 2 in series
Diesel generator FG Wilson 14 kVA (20 yrs old)
Location: Man-o-war cay, Bahamas
Contact:

Re: Electric resistance water heater - how to?

Post by mosbergh »

Thank you all for your suggestions - yes, it looks like the system would have access to serviceable mechanisms, like PV array voltage and net charge (FN-DC).
But none of them is reflected in any of the available modes for AUX relay control. Most deal with battery voltage, which, in case of Lii, is a poor choice as stated above. I find it surprising that this topic - apparently - hasn't come up more commonly, I would have thought this to be quite typical once new solar disciples hook up an existing (old) house distribution.

My hope is that Outback engineering / software dev. may implement a lot more flexibility in the AUX logic.

I still have to string the wires and hook up an experimental contactor to try a few thing, will post a f/u when I get around to doing it.

Cheers,
Hans
raysun
Forum Emperor
Posts: 3829
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Electric resistance water heater - how to?

Post by raysun »

I'd think SoC would work. Though it doesn't really appear to track all that well for certain lithium batteries from what I've read here, it's still a measure of the net current flow. As long as SoC is at 99%-100% no net charge is being drawn from the battery.

I don't automate that, but use that metric to run optional loads. It could easily be automated from the Aux on the FNDC however.
provo
Forum Czar
Posts: 630
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
Eight Rolls S-550 (2 strings, total ~800Ah @ 24V)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC and Trimetric
Honda EU3000is generator
Location: Sierra foothills

Re: Electric resistance water heater - how to?

Post by provo »

raysun wrote: Sat Apr 04, 2020 9:18 am I'd think SoC would work.
But SOC is still awfully "sluggish". A brightness sensor would allow an HBX-like function (for example) to pop back and forth between utility power and PV as each cloud went past....
JRHill
Forum Emperor
Posts: 1192
Joined: Thu Feb 17, 2011 11:12 am
My RE system: VFX 3648, FM80, 3k panels, Mate3, FNDC, 3ea 3.8 PHIs. And still, a wonderful wife.
Location: Not
Contact:

Re: Electric resistance water heater - how to?

Post by JRHill »

Both Sodamo and I chimed in on this thread: viewtopic.php?f=46&t=13662

We and I suspect others have Davis systems of some model. "Us" user's would have welcomed this additional data a long time ago. And for uses just as this thread suggests

The purpose from Mr. Lebow was to get 3rd party app integration with OB and our input. The Davis line of weather stations is well established as is OB. I think it would be complimentary to the users but maybe not the organizations. I suspect a stand off as to who will do what and how it benefits the bottom line of either/both. But who knows?
provo
Forum Czar
Posts: 630
Joined: Thu Jul 27, 2006 4:34 pm
My RE system: Sixteen Evergreen EC-120
(4 strings, total 1920W)
Eight Rolls S-550 (2 strings, total ~800Ah @ 24V)
One FM80
One VFXR3524A
Hub 10
Mate3s
FNDC and Trimetric
Honda EU3000is generator
Location: Sierra foothills

Re: Electric resistance water heater - how to?

Post by provo »

JRHill wrote: Sat Apr 04, 2020 10:36 am
Both Sodamo and I chimed in on this thread: viewtopic.php?f=46&t=13662
VERY interesting, I had no idea you guys had been talking about this for what, two years! I actually thought about getting a weather station at my place, but there are already a LOT around here -- Weather Underground is all about those, and Davis is one of the most popular.

Anyway, maybe someday it'll all come together....
sodamo
Forum Emperor
Posts: 1011
Joined: Mon Apr 03, 2006 1:55 am
My RE system: Totally off grid - Hamakua side, Big Island, Hi

36 Trina 280 & 16 Phono 250 in 48 volt array (fixed) 14080w
Radians GG8048/GS4048 w GSLCs
4 FM 80 charge controllers
Hub 10.3
FNDC w/3 shunts
Mate 3s
OpticsRE - MMKL - Ninole Hi
12 SimpliPhi 3.8
14Kw Kohler 14RESA Propane

Charging Only
2FX3048T
Hub
FNDC. - shared shunt feeds from Radian FNDC
Mate 3s
10Kw MEP 803a Military gen

Honda EU7000i

Davis VantagePro2 Wx Station
On line at: https://www.wunderground.com/dashboard/pws/KHININOL2
Location: Ninole, Hi

Re: Electric resistance water heater - how to?

Post by sodamo »

To my thinking this integration is available From Davis, but am guessing OB doesn’t see a value there. On the Davis side there seems to be a push for $$ with the latest software. I would willing do the Pro upgrade if that meant connection to my OB stuff.

Seems like someone really smart at OB could turn such a feature into a marketing feature.

Still listening to us, David :grin:
David
Please visit http://vacation.ninolehawaii.com
JRHill
Forum Emperor
Posts: 1192
Joined: Thu Feb 17, 2011 11:12 am
My RE system: VFX 3648, FM80, 3k panels, Mate3, FNDC, 3ea 3.8 PHIs. And still, a wonderful wife.
Location: Not
Contact:

Re: Electric resistance water heater - how to?

Post by JRHill »

Yup, I saw that Davis had a software development (SDK) kit available. This stuff isn't easy. Nor is security these days. Nor are the business details. But if it is to the benefit of both it would happen.

Who drives that? We do 'cause we will pay for it. It just takes enough demand. I don't think there was anything in the $2T stimulus that covers this project.
sodamo
Forum Emperor
Posts: 1011
Joined: Mon Apr 03, 2006 1:55 am
My RE system: Totally off grid - Hamakua side, Big Island, Hi

36 Trina 280 & 16 Phono 250 in 48 volt array (fixed) 14080w
Radians GG8048/GS4048 w GSLCs
4 FM 80 charge controllers
Hub 10.3
FNDC w/3 shunts
Mate 3s
OpticsRE - MMKL - Ninole Hi
12 SimpliPhi 3.8
14Kw Kohler 14RESA Propane

Charging Only
2FX3048T
Hub
FNDC. - shared shunt feeds from Radian FNDC
Mate 3s
10Kw MEP 803a Military gen

Honda EU7000i

Davis VantagePro2 Wx Station
On line at: https://www.wunderground.com/dashboard/pws/KHININOL2
Location: Ninole, Hi

Re: Electric resistance water heater - how to?

Post by sodamo »

Yup, left out of the stay at home package.

OpticsRE has (or had) a wx link built in. Don’t know if free or OB paid for it, but it indicates to me the possibility. Of course I shut it off after complaining to David that it was near worthless to me. Not sure its data source but no where chose to what I was experiencing and I’m not meaning details, I mean what I was reading didn’t match what I was seeing out the window. Wx for me is very very local, hence why I have my Davis.
David
Please visit http://vacation.ninolehawaii.com
Post Reply