Aux1 waste not thought

[SolarMusher]

Hi all,
I was looking at the classic this morning when it just began the Absorb with full amps and Aux1 waste not that couldn't really divert because there was not enough power at this time and I was wondering if it could be possible to make V high relative to the amps as seen from the shunt (real amps to batteries). This way, Aux1 wastenot would become more useful and accurate for water heating. Just to set this amps value where the user wants it to be and aux1 would only start to divert when the PV array wil produce sufficient power.
No more wastenot On/Off problems on cloudly days.
I believe that Float only is not the best Aux1 setting for heating in winter days with only 3 hours of float when there is 4/5 hours of heating time available on Abs/Float.
Just a thought from here,
Erik

[Westbranch]

Erik, makes good sense from out here...   

[SolarMusher]

Hi Wb,
For those who could be interested in 60VDC water heating. My set up is running as expected with these 2x 650W simutaneous elements (2x 3000W/120V), with a small 5 hours of good sun this 40Gl tank was hot enough to keep the propane WH from starting for all the evening. Of course, if aux1 really began to divert when power is available, it would be almost perfect for this time of year. Actually by full sun, it took almost 3/4hr for Aux1 to stop blinking (Vhigh -0.2/delay 0.1sd) and for the 3.2 kw array to really supply enough power to hold Abs and elements. March should be better and will provide the 6hrs it needs to get water to 120°F. SSRs x2 are warm but never hot, I think it would be even better/safer to mount theses heatsinks on a good 1/4 thick aluminium plate.
Maybe I'm asking too much from my system but I would like to try it with real 2x1260 Watts/48Vdc elements (simultaneous) to get the 120°F in less than 3hrs, then I'd have no other choice than to go with aux2 pwm and forget the whizbang/end amp or to buy another classic with a few panels. Not simple.
Erik

[kitestrings]

Maybe I'm asking too much from my system but I would like to try it with real 2x1260 Watts/48Vdc elements (simultaneous)

Erik, We've been doing this with our MX60 and a nearly identical (3.2 kW) PV array for several years now.  It works very well in the summer period especially for us.  One suggestion you might consider is to raise the temp settings on the tank.  We're using a 40 gal Marathon tank, with 1,200w 48VDC elements.  The allowable upper limit temp for this tank is 170F.  If you put a mixing valve on the outlet it allows you to effectively store more BTUs when available.  This goes against conventional thinking - to avoid mixing cold, and unnecessary heat losses we normally set lower ~120F) - but with PV/diversion the energy source is free, and otherwise untapped.  Ours goes to a LPG instantaneous water heater and we set the outlet temp from the Marathon to meet the max inlet to the LPG unit.

Best, ~ks

[Westbranch]

Just thinking this through a bit.. 

What happens if you wanted to do some opportunity loads ( laundry?) and the diversion is heating water?  Is there some way of priorizing the flow of electrons or do you think the 'load' will cause the Classic to shut off the aux diversion and charge the battery again?

[SolarMusher]

Just thinking this through a bit.. 

What happens if you wanted to do some opportunity loads ( laundry?) and the diversion is heating water?  Is there some way of priorizing the flow of electrons or do you think the 'load' will cause the Classic to shut off the aux diversion and charge the battery again?

Nothing really bad, heating is then stopped when a laudry starts because voltage is under abs voltage if there's not enough PV power to hold abs + loads + diversion. A little more power and you will have abs + loads, and full power will give you abs + loads + diversion. The problem is when there's power for abs and loads but not enough for diversion, this makes aux1 blinking continuously (keeping the abs voltage) without sending any power to diversion even if there's some extra power available.
But is that really a problem? I don't know.
Erik

[SolarMusher]

Maybe I'm asking too much from my system but I would like to try it with real 2x1260 Watts/48Vdc elements (simultaneous)

Erik, We've been doing this with our MX60 and a nearly identical (3.2 kW) PV array for several years now.  It works very well in the summer period especially for us.  One suggestion you might consider is to raise the temp settings on the tank.  We're using a 40 gal Marathon tank, with 1,200w 48VDC elements.  The allowable upper limit temp for this tank is 170F.  If you put a mixing valve on the outlet it allows you to effectively store more BTUs when available.  This goes against conventional thinking - to avoid mixing cold, and unnecessary heat losses we normally set lower ~120F) - but with PV/diversion the energy source is free, and otherwise untapped.  Ours goes to a LPG instantaneous water heater and we set the outlet temp from the Marathon to meet the max inlet to the LPG unit.

Best, ~ks

Hi Kit,
Could you suggest a mixing valve (maybe a pic), I have asked to my plumber and he didn't know what I was talking about...
I have kept the original upper AC thermostat so I could safely raise temp to 140°F safely (I hope  ) and changed the lower one for a second Eco thermostat with 150°F security (simultaneous/ but independently controlled).
Erik

[Westbranch]

Not a problem, as you put it, the (Classic's) system program is dynamically managing all available power, through cloud edge events , no sun, full sun, etc... Just another day in paradise!

[SolarMusher]

Not a problem, as you put it, the (Classic's) system program is dynamically managing all available power, through cloud edge events , no sun, full sun, etc... Just another day in paradise!

I agree for the Classic but PV could become a problem if VOC is changing suddenly and constantly until there's enough power, that's not the way they are supposed to work.

[Westbranch]

Won't those fluctuations, be so fast, thinking of E-o-C events, that that spike is not noticed unless you re looking at the readout at the time?  And the Hyper Voc capability of the Classics will kick in?

[SolarMusher]

Won't those fluctuations, be so fast, thinking of E-o-C events, that that spike is not noticed unless you re looking at the readout at the time?  And the Hyper Voc capability of the Classics will kick in?

No they are not spike (aux1 is not PWM but On-Off), it's not so fast, it's rather a continuous back and forth that can be read on the mngp, until there's enough excess power to hold a steady 58.8vabs voltage (Vhigh -0.2v/delay 0.1sd---VLow-0.4v/hold 1sd), that's what I don't like with it but that's the way it's working.
Erik

[kitestrings]

Could you suggest a mixing valve

Ours is a Honeywell AM-1.  Very simple - I put it in myself - hot, cold, adjustable mix.  They use the same type of device where they have a higher loop/boiler temp (in a school or commercial kitchen for example) and they want to drop to a hand-wash sink, or where scald protection is mandated.  I'm sure your plumber has seen it; maybe called something different.

Regarding control of the diversion, you can easily tweak settings to suit as I think you've suggested.  You can also just turn off the breaker, or turn off the aux function, during conditions when you don't want it.  Say your wanting to do a equalize, or you want to favor the batteries a bit more (longer absorb, etc.), or just based on the time of year and available resource.

I've messed about with ours a bit.  Currently we used the SS relays off the stock thermostats, which in turn control the SS relays (switching DC to the elements).  So they are interlocked; priority to top, and only one on at a time.  For our PV this works well.

I'm trying something new with our wind turbine, which is to power the aux control signal to hi-limit (as with the PV) but thru a small diode.  The same signal goes to the lower element terminal (the one the upper element switches to when it is satisfied).  The result is the PV diversion is unchanged, but we have both elements 'firing' off aux2 for the wind assuming they are calling for heat.  The wind has more variability, and there are times when the extra available load helps to keep the turbine voltage (PV input V) to the Classic better regulated.

Good luck with it.  ~ks

[dgd]

Could you suggest a mixing valve (maybe a pic), I have asked to my plumber and he didn't know what I was talking about...

I think it's known as a tempering valve, good wiki description...

I seem to remember boB saying some time ago that AUX1 could do slow pwm. Maybe it's not added yet to the firmware or it's there but just not documented.

Using up AUX2 with the WBjr certainly makes hot water control with waste not control more challenging. Perhaps we need a serial port to deal with the WBjr

Dgd

[SolarMusher]

Could you suggest a mixing valve (maybe a pic), I have asked to my plumber and he didn't know what I was talking about...

I think it's known as a tempering valve, good wiki description...

I seem to remember boB saying some time ago that AUX1 could do slow pwm. Maybe it's not added yet to the firmware or it's there but just not documented.

Using up AUX2 with the WBjr certainly makes hot water control with waste not control more challenging. Perhaps we need a serial port to deal with the WBjr

Dgd

David,
To clarify my first post about improving aux1 wastenot which was a bit confused, I was thinking about an Amps value (diversion) that would be relative (added) to the current needed as read from the shunt/whizbang to hold the Abs/Float voltage and that would then start Aux1 wastenot after a delay only when the array has enough power available.
That would improve aux1 wastenot with minimum diversion losses (vs aux1 float diversion)and let the users have the choice to keep the whizbang on aux2 and still use end amps to control the Absorb charge.
Erik
PS: Maybe that it could also solve the flickering issue with Aux2 wastenot pwm through an inverter? Or maybe that it doesn't worth it? I don't know.

[SolarMusher]

Could you suggest a mixing valve

Ours is a Honeywell AM-1.  Very simple - I put it in myself - hot, cold, adjustable mix.  They use the same type of device where they have a higher loop/boiler temp (in a school or commercial kitchen for example) and they want to drop to a hand-wash sink, or where scald protection is mandated.  I'm sure your plumber has seen it; maybe called something different.

Regarding control of the diversion, you can easily tweak settings to suit as I think you've suggested.  You can also just turn off the breaker, or turn off the aux function, during conditions when you don't want it.  Say your wanting to do a equalize, or you want to favor the batteries a bit more (longer absorb, etc.), or just based on the time of year and available resource.

I've messed about with ours a bit.  Currently we used the SS relays off the stock thermostats, which in turn control the SS relays (switching DC to the elements).  So they are interlocked; priority to top, and only one on at a time.  For our PV this works well.

I'm trying something new with our wind turbine, which is to power the aux control signal to hi-limit (as with the PV) but thru a small diode.  The same signal goes to the lower element terminal (the one the upper element switches to when it is satisfied).  The result is the PV diversion is unchanged, but we have both elements 'firing' off aux2 for the wind assuming they are calling for heat.  The wind has more variability, and there are times when the extra available load helps to keep the turbine voltage (PV input V) to the Classic better regulated.

Good luck with it.  ~ks

Kit, I did it about the same as yours, except that I've used these 2x AC 3000W/120V elements simultaneously to keep cost low. I'm now thinking that your setup is better and more efficient than mine because of the 1200W elements that you are using non simultaneously. That's the way it should work. In fact, I'd have prefered to make it Ac/aux2 pwm with 2x 2000w element through a second inverter but I'd have needed to add a second classic/aux2 and a few panels to make it perfect. Maybe an upgrade for next winter. Anyway, it's too late for now and too cold with our regular -20/-30°C temps to make any change. How did you deal with these 48V elements which seem to have longer connectors? Did the original covers/insulation still fit on connectors or did you have to build homemade deeper covers? A cheaper step for me would be to change these AC elements for 2x 48V non simultaneous elements to heat  faster.
Erik