Dual heater program issue
I have two 200w heaters. I had been running them individually with each one programmed to alternate every 4 hours. This worked great until we left for a couple days and the house was left unheated for a couple days and the heaters running individually could not keep up with the demand. I'm now trying to have them both turn on when 0.2 degrees below RT then have one turn off at 0.0 and the ther turn off at 0.2 degrees above RT. Heres my programming:
Heater 1
Fallback OFF
Set OFF
If Tmp < RT+-0.2 Then ON
If Tmp > RT+0.2 Then OFF
Min Time 002:00 Then OFF
Heater 2
Fallback OFF
Set OFF
If Tmp < RT+-0.2 Then ON
If Tmp > RT+0.0 Then OFF
Min Time 002:00 Then OFF
My problem is that both are turning on and off together.
Also, are there any safeguards that I should be thinking about incorporating?
Dual heater program issue
Quote:
Originally Posted by
nicholb
I have made a few changes since originally posting my dual heater program. First off I went ahead an edited the seasonal table so it ranges from 76-80.5. That is much easier than trying to add values to the RT statements and set cut offs. The way I was doing it before lead to some rapid heater cycling. So here's my current. The program is designed to use each heater for 12 hours and have the unused heater act as backup. I also have a virtual outlet to watch for an error condition of both heaters on for too long (indicating a bad heater). Comments in [] are not actually in the program.
Heater 1
Fallback OFF
If Temp < RT+-0.1 Then ON [turn on the heat if more than 0.1 below RT]
If Temp > RT+0.1 Then OFF [turn off the heat if more than 0.1 above RT]
If Time 00:00 to 11:59 Then OFF [turn off the heat if it is not your turn to be running]
If Temp < RT+-0.3 Then ON [turn on the heat anyway if it is more than 0.3 below RT as the other heater is not keeping up]
If Temp > 81.0 Then OFF [fail safe shut off heat if temp is above 81]
If Temp < 70.0 Then OFF [fail safe, if the temp ever reads this low, the temp probe must be bad]
Heater 2
Fallback OFF
If Temp < RT+-0.1 Then ON
If Temp > RT+0.1 Then OFF
If Time 12:00 to 23:59 Then OFF
If Temp < RT+-0.3 Then ON
If Temp > 81.0 Then OFF
If Temp < 70.0 Then OFF
Heat-Err [this will only read as on if both heaters are set to on]
Set OFF
If Output Heat1 = ON Then ON [turn on the error if heater 1 is running]
If Output Heat2 = OFF Then OFF [turn back off if heat 2 is not running]
Defer 010:00 Then ON [wait 10 minutes before alerting so i don't get an alarm for occasional times when backup heat is needed]
And finally in my alarm programming I have these heat related statements.
If Temp > 82.0 Then ON
If Temp < 75.0 Then ON
If Output Heat-Err = ON Then ON
Very interesting read! I do remember back in the winter my heaters were cycling about every 20-30 minutes. Occasionally both were need. I keep my house at 72 degrees year round (geo thermal). My tank is 250 gallon. I am running two finnex 500 watt titanium heaters. What might be a safe cycle of these heaters?
Over the last 24 hours, I also have noticed that since this programming change as Russ suggested, both heaters are coming on at the same times (together).
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