A Question Regarding Excess Charge....

[Lagoon4us]

Yes i understand that we both have 240 elements for now :-)

[monte]

ok so I heated the HWS last night and had a fast luke warm shower this morning, Not really usefull.
Can I have the best of both worlds? A diverter that diverts excess solar to the HWS as well as being able to turn it on when needed as well as having 220 at the dock?
Or ... do I need 240 at the dock or just running it from the batteries will suffice? If it takes 30 mins to heat on 220, does that mean it takes 300 mins to heat on 12V?
Is there a twin element HWS I could use or a replacement element that does both 220 and 12v? I guess there is because some RV's have 2 or 3 way systems.
Also would be nice to be able to switch on the 12v at bedtime if my batteries are 100% and know that I will have hot water in the morning and still 90% charge.
When I did a power budget I allowed for 250Ah/day but at anchor Im just using 100, mostlly the fridge. I had in mind the power to run the watermaker and the water pump and allowed enough for nav gear when on passage, so I have a large excess.
Maybe the simplest is to replace the element with 12v and wire it directly to the batteries and us the switch on the power board to heat when I feel its necessary/available power?

[noelex 77]

Originally Posted by monte

ok so I heated the HWS last night and had a fast luke warm shower this morning, Not really usefull.
Can I have the best of both worlds? A diverter that diverts excess solar to the HWS as well as being able to turn it on when needed as well as having 220 at the dock?
Or ... do I need 240 at the dock or just running it from the batteries will suffice? If it takes 30 mins to heat on 220, does that mean it takes 300 mins to heat on 12V?
Is there a twin element HWS I could use or a replacement element that does both 220 and 12v? I guess there is because some RV's have 2 or 3 way systems.
Also would be nice to be able to switch on the 12v at bedtime if my batteries are 100% and know that I will have hot water in the morning and still 90% charge.
When I did a power budget I allowed for 250Ah/day but at anchor Im just using 100, mostlly the fridge. I had in mind the power to run the watermaker and the water pump and allowed enough for nav gear when on passage, so I have a large excess.
Maybe the simplest is to replace the element with 12v and wire it directly to the batteries and us the switch on the power board to heat when I feel its necessary/available power?

I think with the amount of solar and wind, and your low power consumption heating water is a practical option for you.
If it was me I would keep it simple using the KISS principle.
The extra efficiency of a 12v element will only be slight and you can stay with an AC element. Simply turn the inverter and Element on when you have excess power and be careful you don't drain the batteries too much.
A simple kitchen timer would be a sensible precaution.

The next level up would be an electronic timer that would turn the inverter ( or it's output off). A simple domestic AC timer switch could do the latter cheaply and easily.

The next stage is a semi, or fully automatic system. This will difficult and complex to do switching such high loads. I think you need to go to one of the advanced / integrated solar controler battery monitor and possibly inverter set ups.
Outback make these for example but they are expensive.

[monte]

So is it possible to use this unit wired to the solar charger with a dump load wired to one of the elements and wire the other element to my batteries via a switch.
Water Heating Element for 12V or 24V DC
The output would be 29.2 A 400w per element. So I guess it would take 3 times longer per element to heat the HWS.
A sunny day with 30A excess on the solar would heat it in about 1.5 hrs
If I want to heat from my batteries the second element would do the same.
And if I plug in at the dock it would do the same and the shorepower will keep the batteries topped?

[monte]

I just checked and it seems the tristar controller cant work in dump load at the same time as regulating mode so the dump option may be out.
So Im thinking just change the element to 12V so the battery discharge rate is reduced and manually switch the HWS on/off as required.
Even if I use a timer to just turn the hot water on for 30 mins..discharging at a rate of 130A is bad for my batteries isnt it?

[noelex 77]

Originally Posted by monte

I just checked and it seems the tristar controller cant work in dump load at the same time as regulating mode so the dump option may be out.
So Im thinking just change the element to 12V so the battery discharge rate is reduced and manually switch the HWS on/off as required.
Even if I use a timer to just turn the hot water on for 30 mins..discharging at a rate of 130A is bad for my batteries isnt it?

Make sure the wattage of the 12v element is less otherwise the current drain from the batteries will be the same. A 1000w 12v element and a 1000w 110 AC element run from an inverter will have a very similar current draw from the battery.
The inverter has some losses, but the 12v wiring will as well so the net result is the 12v element will be more efficient, but only a few percent.

The 130A discharge is within the capability of your 700AHr battery bank. Every discharge shortens the life of the batteries and high current discharges are a little more punishing, but the depth of discharge and the number of cycles are the big factors in battery life.
With high discharges like 130A the amount of energy taken out of the battery is higher than you would expect due to the Purket formula.
Without looking up tables I would guess an extra 30%. So 130A for 1 hour is drawing not 130AHrs but 170AHrs ( note this is not technically quite correct, but it will give you the right idea)
Some battery monitors allow for this effect and will display the correct SOC even for high discharges.

[Lagoon4us]

Ok forgive me for any ignorance shown but when those panels are at their peak isn't this the best time for the load levels you are talking about because it will reduce the outgoing by the high charge rate?

[noelex 77]

Originally Posted by Lagoon4us

Ok forgive me for any ignorance shown but when those panels are at their peak isn't this the best time for the load levels you are talking about because it will reduce the outgoing by the high charge rate?

Yes.
The most effecient time will be when the controler would normally be regulating. The excess power that the batteries will not accept can then be used by the heating element.
However most hot water units start cooling down resonably rapidly so there will be some loss of energy if the hot water generated in the afternoon but is used in the evening.

[Lagoon4us]

We find our Quick Boiler holds the heat fairly well.

My whole point of this thread was to answer as to whether the excess could be automatically channeled to the HWS and/or a Circuit that activates a seperate inverter to run our De-sal.

You have come close to my idea probably because i was a bit unclear, it's fine to manually switch over BUT the timing of the state of charge hence availibility of excess would never be accurately controlled by a person. I never saw the answer as being over automated as some suggest, the answer that i was looking for was, i think, just a matter of using the correct controller with dump provisions ie a windgen one? Or one used on outback australian/isolated solar chargers that do just this.
I'm seeing a control panel that has a simple switch HWS~DeSal and i set that switch so if and when excess is generated it goes to the pre-selected choice for that day.....

My Desal will simply go into filter flush mode should the regulator shunt the charge back to re-charging the batteries...

My HWS would simply absorb the offered excess or switch off if the regulator shunt the charge back to re-charging the batteries....

Does that make sense?

Cheers

[noelex 77]

Originally Posted by Lagoon4us

Does that make sense?

Cheers

Yes it does and that is what I was meaning by an automated system. In the sense that that the controler automatically diverts the power.
For a 12v heating element it could be done reasonably easily with say an Outback 60 controler. Using the auxiliary function in diversion relay mode. Their is a diagram of how to do this in the Outback fx 60 handbook.

I really cannot see a way to do this in an automated way to the Watermaker. The controler can divert power to the Watermaker which would start, but when the conditions were not met power would be cut to the Watermaker without a rinse cycle. The plasmatronics pl40 regulator has a very sofisticated options of programming and can be set to run for a number of hours. So it could be programmed to start the Watermaker say when the batteries had reached float then maintain power to the Watermaker for many hours so it could run through its cycle, but the solar panels could have reduced their output by the time the Watermaker finishes.

[Lagoon4us]

Ahh i believe the rinse cycle is 12 volt....When i cut 240 to it then it automatically goes to a dc rinse cycle....

[noelex 77]

Originally Posted by Lagoon4us

Ahh i believe the rinse cycle is 12 volt....When i cut 240 to it then it automatically goes to a dc rinse cycle....

That is a help, it gives a means of inititiating a rinse Cycle. I think it could be done with a complex controler like the outback 60 using the aux function in diversion relay or low battery disconect ( which will connect and disconect at different voltage points).

[monte]

the tristar also has an optional relay switch that will turn on/off a generator or WM, I think up to 6 devices can be set to turn on and off at various charge levels.
Morningstar Corporation » Relay Driver

[hummingway]

Originally Posted by monte

the tristar also has an optional relay switch that will turn on/off a generator or WM, I think up to 6 devices can be set to turn on and off at various charge levels.
Morningstar Corporation » Relay Driver

That looks like the answer.

I think I have a Seaward 6 gallon, 1500w 120v on my boat. It has a temperature pressure release valve but I don't think it has a thermostat. As far as I can determine most of them don't. Do you have to be concerned with the water overheating and venting into the bilge on a regular basis?

[monte]

Mine does have a thermostat. I think they all would have or they would heat continually?