automate power on/off of water heater

[LordGarak]

I'm working on programming a microcontroller(Arduino likely) to poll an EG4 3000EHV inverter for the battery state and PV input. When the battery is above something like 95% and the PV input is above something like 2000W(of a 4360W array) it will then turn on a SSR that powers the 1500w water heater up. I'm also thinking I might poll for inverter load as well. So if the inverter has say more than 500watts on top of the 1500watt water heater, the water heater will turn off to free up inverter capacity. There will also be a 3 way override switch off-auto-on. So when we want to run larger loads we can force it off or if we need hot water at night we can force it on.

Haven't made much progress yet, been trying to find some information on the serial port protocol. I may have to do some serial port captures of the communication between the wifi dongle thing that comes with the inverter and reverse engineer the protocol from there. I've done that before for other things.

Once the serial protocol is figured out the rest of the code is pretty simple and wiring it up is fairly straight forward. I will share the source code and a wiring diagram. Parts wise is will all be from aliexpress: Arduino clone, RS232 level converter, 3 pos switch, SSR. I might even design up a little 3d printed box to put it all in.

I'm not sure if Growwatt uses the same protocols. Are they make by Voltronic like the EG4?

 

[zeeman]

Yes you do it indirectly by using the battery/mppt V. I don't understand all the confusion. You dump load with a relay at float or a bit below. If it can float from solar, you dump. If not, you dip, relay opens, and no dump. What am I missing?

you are correct. I was overthinking it.

 

[zeeman]

this is the relay i use with our system.....

Solid State Relays with AC or DC Control Inputs | Omega

The solid state relays used to control large resistance heaters with temperature controllers, up to 100 Amps, Control ac Lines to 660 Vac.

www.omega.ca

interesting approach. how would you turn the relay on at specific battery voltage?

 

[pollenface]

You can use the streetlight function and an NC relay. Streetlight function works on pv voltage and interrupts the NC relay.

I the streetlight function. It triggers many things in my shed to turn on/off between dawn and dusk.

Having multiple mppts allows different trigger points for different applications.

 

[42OhmsPA]

@zeeman might want to check out this very helpful post from @dougbert
Post in thread 'Need a way to bottle or can excess solar production.' https://diysolarforum.com/threads/n...an-excess-solar-production.82302/post-1066092

 

[Daddy Tanuki]

If this is a resistance heat water heater... consider moving to a heat pump style water heater. Uses 1/3 power for same BTU.

I was looking into HPWH's but they reportedly do not work well in cold climates. kinda negates the purpose as winter is when I really want a lot of hot water.

 

[kommando]

DIY build solution for 230v 50htz

Accueil -

MK2 PV Router Maitriser et optimiser la consommation de votre installation PV en pilotant votre flux d’énergie au cours de la journée … Le MK2 PV Router est l’accessoire indispensable lorsque l’on souhaite optimiser son autoconsommation. Particulièrement adapté à l’alimentation de résistances...

mk2pvrouter.com

This is what I run to divert excess to a dedicated immersion heater element.

This is a Chinese version, do not have experience but should work

https://www.aliexpress.com/item/1005004829132599.html?spm=a2g0o.productlist.main.9.979dURP0URP0Pq&algo_pvid=ad88b1d5-59b7-440c-b9ba-ff82d4364ebc&algo_exp_id=ad88b1d5-59b7-440c-b9ba-ff82d4364ebc-4&pdp_npi=4%40dis%21GBP%21104.87%21104.87%21%21%21920.70%21920.70%21%402103867617131799172984001e2b6f%2112000030644160055%21sea%21UK%21226801%21&curPageLogUid=yq6lYq7gefhb&utparam-url=scene%3Asearch%7Cquery_from%3A

 

[time2roll]

I was looking into HPWH's but they reportedly do not work well in cold climates. kinda negates the purpose as winter is when I really want a lot of hot water.

82F today, 60s and 70s in the rest of the 10 day forecast in Belgrade, Serbia.
Does the WH sit outside in the snow?

 

[Daddy Tanuki]

82F today, 60s and 70s in the rest of the 10 day forecast in Belgrade, Serbia.
Does the WH sit outside in the snow?

I never bought one once I some of the issues were explained to me. the plan was to build a small shack to put it in but even then the cold air it puts out would make it fight itself if enclosed. i think they work fine in any place that does not dip below 40 on a regular basis

 

[yodamota]

interesting approach. how would you turn the relay on at specific battery voltage?

using victrons charge controllers programmable relay, my outback charge controller will also work via voltage as well.

 

[The Terrible Triplett]

Here is an idea ...

Solar water heater

So its still running. had to use all the hot water the other day at 12:00 o clock, by 17:30 the water was at 68 degrees. i have only used 30 units on my electrical bill this month. so a big middle finger for our eskom from my side!!

diysolarforum.com