Hey all, I work for a small installer company and we have a client that needs to have 2 single phase water heaters working exclusively with excess PV energy.
Previously, he had a Fronius with an Ohmpilot that did the job for one of them. Now, he has added an ESS with Victron Multiplus. So now, since the Ohmpilot only works with a Fronius smart meter (I’ve been told it can work without but it has not for me, ive tried a bunch of things) the water heater is not working exclusively with excess PV energy.
My question is:
Are there any devices compatible with Victron that support 2 or 3 single phase water heaters on a single phase home that also work exclusively with excess PV energy?
I have seen the AC-Thor / 9s and that could be a solution but… the AC Thor can only work one heater at a time or the second one to be on at all times which is not ideal. Or the 9s with load priority, but for that I think you need a three phase input from the AC Out of the Victron, which is single phase and not viable afaik. Unless there is a workaround, which would be great.
Are there any similar devices that can work with 2 or more water heaters on a single phase environment? Or is there a way to use relays? I’ve seen people on forums enable heaters with relays when SOC is almost full. Do you recommend this?
An external device that controls it like the AC Thor would be optimal. But I’m up for anything at this point. Kind of weird how Victron doesnt have their own device that does this sort of load management, but maybe its easy to do it another way.
If you could explain in detail that would be fantastic, I am fairly new to Victron.
Thank you in advance
The single phase AC-Thor can control two elements, it has a regulated output which can supply between 0-3000W and a 16A relay. It has several operating modes, one of which will use the regulated output until there is >3000W available, then enable the relay controlled element and use the regulated output for the remaining available power. This is operating mode M3 which you can read more about in the AC-Thor manual - https://download.my-pv.com/acthor/acthor_doc_en_a0021800.pdf
You can also have multiple AC-Thor networked together and set the priority individually in each one which would allow two fully regulated outputs if that’s what you need.
So if I undertstand this correctly, with the AC Thor, you can use the first heating element from 0-3000W and then the second one will activate via relay when the excess energy is greater than 3000W and also starts from “0W”? Or does it need a certain amount to also activate the second one?
Does this setup need the my-PV meter? On the connection diagram it says it is recommended. Or will the built in Victron passthrough meter work? I dont want there to be conflicts in consumption measurement with the ESS
The relay controlled element is always at full power if it is active as it is just being switched on and off, only the regulated output varies between 0-3000W. For example:
2500W available → regulated output = 2500W → Relay = Off
4000W available → regulated output = 1000W → Relay = On (3000W)
6000W available → regulated output = 3000W → Relay = On (3000W)
The actual power levels can be configured to suit the elements being used, for example you could use 2 x 2000W elements.
my-PV do recommend using their meter for grid monitoring in systems running mode M3, but I have several systems with the Victron meter as the control source working fine. You will require an actual grid meter in the Victron system, this doesn’t work if you are using the Victron inverter internal input current measurement as your grid metering.
The AC-Thor will only log the power from the relay controlled element if it is monitored by a my-PV meter, so if you want the info displayed on the AC-Thor itself to be accurate then that is required.
Depending on the power of the heaters, there might be a relatively cost-effective solution:
In my ess-extension, I’ve included a Service called SolarOverhead Distributer. It calculates (in Grid-Tie-Situations) how much excess solar is available and therefore can generated “allowances” for subscribing consumers.
A tiny extra feature (“NPC Consumer”) is that it is able to control devices through http-calls directly, without the need to implement external control-logic. (On / off, based on priority and configured power)
This could be used along with shelly devices, so, if a single shelly would be enough for one heater, could be used.
Also a battery reservation can be configured, so you can say “chargerate should be 4000 Watts, before additional consumers are turned on” (can even be an equation based on SoC)
If you want to check it out, see here and follow the link to the documentation / examples on github.