hot water dump load again

[NUMNUM]

i have read the post over and over and still do not understand how to wire a dump load to my classic 150.i have a 600 watt dc element 24 volts with thermostat.it sounds like i need a 40 amp relay and a diode.like many before me i don't understand how to wire it up.also can the 150 be programed to turn the element on at night.for a short time if needed.i have the heater hooked up to the batterys as of now with a little gray box ( timer) set for 2 hrs when the sun is up and thats fine unless its cloudy and i forget to turn it off.so as always hope someone can help and thanks if they do.hope someone will post a wiring diagram.

  num

[zoneblue]

Well im no expert but youd need to take into account at least:

-if you use a relay for switching dc , itll need to be a very heavy duty one, to last long. The constant arcing will kill automotive type relays eventually. solid state will definately be better for dc heaters.
-for a relay youll need aux1, non pulsed. use waste not hi and a hold time, maybe something llike 20seconds. So every 20secs it will turn off, retest if theres still spare power then turn on again if so. repeat til dusk. for solid state you can use aux 2 PWM.

-there are two aux ports and each can only do one thing. ie day/nite OR wastenot. You could theoretically use both contacts, using a dry contact OR arrangment i suppose.  But running the heater at night makes little sence unless you have another power source other than solar.

- the aux ports are minimally documented in the manual. keep rereading til it makes sense. then ask about any gaps. firmware adds new features every month.

-aux port can be either contact or powered output. Only use the latter if you are sure that your relay wont draw more than the aux port is capable of driving. Otherwise use dry contact to power your relay. Add something to supress the arc on the dry contact from your big realy coil (reverse diode). Also solid state is a better option.

-if powering the element by dc youll need to consider the thermostat. You cant put dc through it, it will die from arcing. for that you could try to use low voltage low current sense circuit, something  like 5VDC and a transister to turn on your relay.  So if both thermostat transister and aux port are on turn the main relay on. If powering the heater with ac this isnt required, its designed to swtich ac.

- personally id go a step further, and add a small interface baord, with an opto isolator to protect the classic. Some people have reported odd behaviors when the aux port is overloaded.

i will try to draw a schmatic at some point, wont be this week.

[NUMNUM]

im thinking of a crydom 24 vdc 40 amp solid state relay with input voltage less than 12 vdc.i have a dc thermostat .all this has been working fine on the battery .i dont no how to wire the relay ...

NUM

[Halfcrazy]

Here is a wiring diagram take a look and see if it helps: http://www.midnitesolar.com/pdfs/CLASSIC_DIVERSION_CONTROL_2_RELAYS.pdf

You would want the example on the right.

Ryan

[NUMNUM]

thanks ryan that should do it.what about the diode i have been reading about.should i put one in,and if so dose it go between the cc and the relay positive side.thanks again .

num

[TomW]

thanks ryan that should do it.what about the diode i have been reading about.should i put one in,and if so dose it go between the cc and the relay positive side.thanks again .

num

Pretty sure he means across the coil so it shunts the back EMF when the coil field collapses. A "flyback" diode. Here is some info on those:

http://en.wikipedia.org/wiki/Flyback_diode

[NUMNUM]

i dont think i have a coil tom ? ssr .?

[TomW]

i dont think i have a coil tom ? ssr .?

Maybe I should read closer? I am old school and we didn't have SSR back then. SSR might need it on the controlled side for same reason?

I will poke Ryan & boB on this.

Tom

[boB]

i dont think i have a coil tom ? ssr .?

Maybe I should read closer? I am old school and we didn't have SSR back then. SSR might need it on the controlled side for same reason?

I will poke Ryan & boB on this.

Tom

No, the SSR should not need a diode.

If using Aux 1 and a semi-slow switching frequency, a diode should also not be necessary across the load
to prevent flyback voltages.  Sometimes, especially at high PWM frequencies like you might get from
the Aux 2 output, you may encounter high inductance in your loads when turning off and have
to snub them.

If this is just on and off once in a while, you probably don't need to worry about that.

boB

[NUMNUM]

 hi bob ryan is saying use the drawing on the right ,it says to use aux 2.will aux 1 or 2 work for this, the heater comes on 2 times a day. is a diode a save way to go.