How to wire my hot water heater to two AC sources?

[Brendan]

Hi All,

Am hoping someone will be able to offer me some advice about how to wire up my hot water heater so it can be powered either by the generator, when it is running, or by my inverter using a 30 min countdown timer switch.

Current set-up:
1,200 amp hour LiFePo4 house bank connected to a Victron Quattro 5000 inverter charger. Hot water heater is currently wired up to one of the Quattro's AC outputs that is only live when Quattro receives AC power from either shore power or generator. This is wired so as to avoid accidently draining the house bank if one forgets to turn off the hot water heater at the switchboard.

Target Set-Up:
Since I have 1,600 watts of solar and the water gets hot after about only 30 min of shore or generator power, I bought a mechanical 30-min countdown timer switch (https://www.amazon.com/dp/B003FIYZRI...roduct_details). I'd like to wire this up to the Quattro's other AC output that is fed by the inverter and so live even when there is no shore power and the generator is not running. The idea is to avoid needing to fire up the genset just to heat hot water and instead simply turn the knob on this countdown timre to 30 min to get hot water without the risk of accidently draining my house bank.

What I'm wondering about is if it would be safe and wise to simply wire up the imersion heather to both output circults at the same time, or if that would risk doubling up the AC voltage and frying my impersion heater (or damagaing the Quattro)? Is there a smarter way to get to the same outcome?

I could obviously disconnect the imersion heater from the Quattro's output that is live when shore power / genset is available, and have the imersion heater only wired to the countdown timer, but then I'd need to remember to turn on the count down timer for hot water even when I am on shore power or the genset is running.

Thanks in advance for any advice an appologies if this is a dumb question, AC power is mysterious to me.

[s/v Jedi]

Originally Posted by Brendan

Hi All,

Am hoping someone will be able to offer me some advice about how to wire up my hot water heater so it can be powered either by the generator, when it is running, or by my inverter using a 30 min countdown timer switch.

Current set-up:
1,200 amp hour LiFePo4 house bank connected to a Victron Quattro 5000 inverter charger. Hot water heater is currently wired up to one of the Quattro's AC outputs that is only live when Quattro receives AC power from either shore power or generator. This is wired so as to avoid accidently draining the house bank if one forgets to turn off the hot water heater at the switchboard.

Target Set-Up:
Since I have 1,600 watts of solar and the water gets hot after about only 30 min of shore or generator power, I bought a mechanical 30-min countdown timer switch (https://www.amazon.com/dp/B003FIYZRI...roduct_details). I'd like to wire this up to the Quattro's other AC output that is fed by the inverter and so live even when there is no shore power and the generator is not running. The idea is to avoid needing to fire up the genset just to heat hot water and instead simply turn the knob on this countdown timre to 30 min to get hot water without the risk of accidently draining my house bank.

What I'm wondering about is if it would be safe and wise to simply wire up the imersion heather to both output circults at the same time, or if that would risk doubling up the AC voltage and frying my impersion heater (or damagaing the Quattro)? Is there a smarter way to get to the same outcome?

I could obviously disconnect the imersion heater from the Quattro's output that is live when shore power / genset is available, and have the imersion heater only wired to the countdown timer, but then I'd need to remember to turn on the count down timer for hot water even when I am on shore power or the genset is running.

Thanks in advance for any advice an appologies if this is a dumb question, AC power is mysterious to me.

If you connect it to both outputs, you short the outputs, undoubtedly leading to expensive repair bills.

You already bought the timer switch so that’s what you have. If it doesn’t have an always-on position then you don’t have that.

I would have bought a Shelly relay that uses an app or even a browser to control it over wifi. There are many options.

[Brendan]

Originally Posted by s/v Jedi

If you connect it to both outputs, you short the outputs, undoubtedly leading to expensive repair bills.

You already bought the timer switch so that’s what you have. If it doesn’t have an always-on position then you don’t have that.

I would have bought a Shelly relay that uses an app or even a browser to control it over wifi. There are many options.

Thanks very much! I definately won't wire up both AC outputs then. Checked out Shelly switches, interesting. Fundamentally though, it appears as if I can only use one of the AC sources, unless I used a relay and a third switch to toggle between the two sources, making things even more complicated. Sigh.

[s/v Jedi]

Originally Posted by Brendan

Thanks very much! I definately won't wire up both AC outputs then. Checked out Shelly switches, interesting. Fundamentally though, it appears as if I can only use one of the AC sources, unless I used a relay and a third switch to toggle between the two sources, making things even more complicated. Sigh.

A Shelly relay, as well as many smart outlet adapters, let’s program you an automatic shut down after a set time. Also it allows you to program schedules etc.

At worst case, when it isn’t smart enough, you have to tap the screen on your phone or tablet to switch from timer to always on or off mode.

Of course this requires knowledge on programming such devices, connecting them etc. You can even drive the on/off function based on a signal from the battery monitor when that has a programmable relay, like the Victron BMV. For exmp,e, when battery SOC is more than 90% etc. Also, solar MPPT controllers often have relay outputs to control such things.

[PippaB]

A simple double-pole, double-throw relay (even a single-pole, double-throw if you are not running split-phase and your neutrals are all common) with an AC coil to match your shore power voltage would do the trick.

Wire the common to the water heater. Wire the normally closed to the timer, which then goes back to the inverter output (as you already have it). Wire the normally open to the shore/gen output from the inverter. Wire the coil also to the shore/gen connection.

When the gen/shore is live the coil will be energized, the contacts will pull in, and power will flow from gen/shore through the NO contacts (that are now being held closed by the coil) and to the heater element. The inverter output will be disconnected from the heater. When shore/gen goes away the coil will release, the contacts will transition, and the heater will be connected to the output of your timer switch, which you can then turn to run when the solar is abundant and the batteries are tapering their charge.

All automatic except for turning the timer whenever you want to heat from the inverter. You are basically making a small scale automatic transfer switch.

They cost a bit more, but I personally prefer hermetically sealed relays on the boat. Will depend on the current requirements of your heater whether they are a viable option.

Edit:

No affiliation, and I have not reviewed it for details (for instance, is your boat 120V? or 240V?), but if you just want to buy something...

https://www.amazon.com/gp/product/B0...JJFWBFD7&psc=1