Direct to water heating.

[efficientPV]

PV hot water..........No place for crybabies!

This is my off grid summer home. Somewhere in there is a house and a garage. Some might think you couldn't have solar there. I have PV refrigeration, hot water, dishwasher with heated dry, clothes washer with its own 40-gallon hot water tank. All cycles are done with hot water, clothes come out steaming. Paid about a third of what others did for a system that doesn't do near as much. PV hot water since 2016 and waiting for the solar world to catch up in technology. Learn some engineering.

 

[curiouscarbon]

*cheers fervently for @efficientPV*

the sun shines every day, let's make the best of it ?

 

[sdj]

Does work well. My solar array is around 2.4KW @ 240VDC. I use a voltage sensitive relay and a thermo switch to sense battery bank volts and solar insolation. On hot days with battery above 95% the relay closes a DC SSR and connects the 240V hot water element directly across the solar array. Very simple, programmable, inexpensive, and reliable.

 

[offgriddave]

Does work well. My solar array is around 2.4KW @ 240VDC. I use a voltage sensitive relay and a thermo switch to sense battery bank volts and solar insolation. On hot days with battery above 95% the relay closes a DC SSR and connects the 240V hot water element directly across the solar array. Very simple, programmable, inexpensive, and reliable.

Are you running the hot water element on DC? Can you run DC into inductive heat coils that are designed for AC? Like a crock pot?

 

[Hedges]

Resistance wire that is coiled may have some inductance, but that is so small as to be negligible with either 60 Hz AC or DC.

The only "inductive heating coils" that operate by anything other than Ohm's Law would be RF induction coils used to cause circulating eddy currents in a piece of metal, heating it. For instance, some stove tops which remain cool while heating metal pots by magnetically coupling high frequency AC into them.

The problem with powering a crock pot or other heating appliance from DC is that the switches and thermostats designed for AC will fail to interrupt DC. When opened they will pull an arc, continue conducting, and burn up. It is possible they will function, likely get damaged much more rapidly than with AC. Or, they may just sit there burning the first time they are used.

There may be ways to re-engineer an AC heating appliance to run on DC, using the contacts for "pilot duty", e.g. for coil of a DC rated relay. But it ought to be fail-safe; not prone to failing in closed position and overheating.

 

[TRW]

Resistance wire that is coiled may have some inductance, but that is so small as to be negligible with either 60 Hz AC or DC.

The only "inductive heating coils" that operate by anything other than Ohm's Law would be RF induction coils used to cause circulating eddy currents in a piece of metal, heating it. For instance, some stove tops which remain cool while heating metal pots by magnetically coupling high frequency AC into them.

The problem with powering a crock pot or other heating appliance from DC is that the switches and thermostats designed for AC will fail to interrupt DC. When opened they will pull an arc, continue conducting, and burn up. It is possible they will function, likely get damaged much more rapidly than with AC. Or, they may just sit there burning the first time they are used.

There may be ways to re-engineer an AC heating appliance to run on DC, using the contacts for "pilot duty", e.g. for coil of a DC rated relay. But it ought to be fail-safe; not prone to failing in closed position and overheating.

I used to work on large DC contactors, and one of the biggest issues here is that in some percentage of contact failure, they weld closed, and will not shut off, leaving you with a dangerous overheating situation. How often that happens, I have no idea.

To give you a bit more info, these contactors had heavy-duty asbestos shields to keep the arc from causing damage.

 

[clockmanfr]

DC Water heaters at 4.8KW? , good luck on that one.

I have had small 1kw DC heaters but just not robust enough for proper domestic use.

All my stuff gets convertered to AC 230v for my 5KW water heaters. Far simpler in the long term and easy to repair and maintenance.

 

[Honuz]

Does work well. My solar array is around 2.4KW @ 240VDC. I use a voltage sensitive relay and a thermo switch to sense battery bank volts and solar insolation. On hot days with battery above 95% the relay closes a DC SSR and connects the 240V hot water element directly across the solar array. Very simple, programmable, inexpensive, and reliable.

You said not expensive, but you are cycling your battery pack isn't it ? (Edit : misread, forget it)
So .. if you use 220V in your house after the battery are full, it will draw the battery ?

 

[Tecnodave]

You said not expensive, but you are cycling your battery pack isn't it ?

If he is connecting directly to the solar array then the batteries and the charge controller are not in the loop, All the power to the water heater comes directly from the array, sized correctly there will be enough power left to top off the batteries

My system does it totally different, All my array’s feed directly to Midnight Classic 150’s , then to the battery banks. When the battery is 85-90 % charged the voltage rises and the Trace C-40 controllers set in diversion mode kick in and divert excess charge current to DC elements, which are at battery voltage.

4 arrays, 2200 watts ea. , 2 for full sun and the other 2 used when we have the coastal fog (I’m right on the left edge, I can see the Pacific Ocean, we get real fog here, pea soup vareity) 2 Midnight Classic 150’s 2 Trace C-40 in diversion mode and 2 banks of batteries not connected together. I do not need the extra power of two systems, Its all about redundancy.........20 years no system fails.....and yes the same Rolls-Surette S-530’s

I do not use high voltage array’s due to the very high voltage conversion ratio that would result, making the main charge controllers work harder and at less effencicy and as a result hotter, thereby reducing life.....heat is the enemy of electronics.

 

[Honuz]

If he is connecting directly to the solar array then the batteries and the charge controller are not in the loop, All the power to the water heater comes directly from the array, sized correctly there will be enough power left to top off the batteries

My system does it totally different, All my array’s feed directly to Midnight Classic 150’s , then to the battery banks. When the battery is 85-90 % charged the voltage rises and the Trace C-40 controllers set in diversion mode kick in and divert excess charge current to DC elements, which are at battery voltage.

4 arrays, 2200 watts ea. , 2 for full sun and the other 2 used when we have the coastal fog (I’m right on the left edge, I can see the Pacific Ocean, we get real fog here, pea soup vareity) 2 Midnight Classic 150’s 2 Trace C-40 in diversion mode and 2 banks of batteries not connected together. I do not need the extra power of two systems, Its all about redundancy.........20 years no system fails.....and yes the same Rolls-Surette S-530’s

I do not use high voltage array’s due to the very high voltage conversion ratio that would result, making the main charge controllers work harder and at less effencicy and as a result hotter, thereby reducing life.....heat is the enemy of electronics.

Hoo yea, i read it again, my bad .. i misread.