Heater stages

[stre1026]

I just wanted to put this out there and see what everyone's ideas are...

I have a 180 gallon tank with a 40 gallon sump. I live in the Northeast so I have 2 x 500 watt heaters to keep the tank at temp. My electricity bill is through the roof so I wanted to see if there was a way to utilize the Apex to help me cut costs. I am already using the Apex to control the heaters. What I wanted to see is if I could save money by having the heaters turn on in stages much like the way some building HVAC systems work. Could I program the first heater to come on and if the tank is not at temp in a certain time, turn the second heater on? Would this help cut down on electricity use. I'm just thinking of times like this (I live in the Northeast) where we have great weather days and it's warm and some nasty cold days. 1 500 watt heater could probably heat the tank just fine...

Would this work? Ideas?

[nicholb]

Here's what I use for my dual heater program. It is set to use the seasonal temps but you could modify it to use a set temp.


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

[stre1026]

Thanks nicholb! This is exactly what I was looking for. I will try to get this setup.

[nicholb]

Glad to help.

I'm running this on a 110g in MN with a pair of 250w heaters. The second heater only comes on occasionally at night in the winter.

I originally had one heater as the primary and one as the backup. After a primary heater failure I got thinking about how I would know the backup heater was good. That's when I wrote this routine that has the heaters switch roles every 12 hours. That way I know both heaters are good.

[stre1026]

It's a great idea. You took it further than what I was thinking of doing. My only concern is I'm running one heater in my sump and the other in my overflow. I'm wondering if there would be an issue heating water primarily from my overflow.. I don't see why there would be, just a concern.. Any thoughts?

[nicholb]

In normal operations the water flow through the overflow and sump would be the same.

Do you have temp sensors in both places? If not, then I could see a situation where the main pump is off. If the heater without the temp sensor near it is primary it would continue to heat as the sensor would not shut it off. This could be mitigated if the heaters had their own temp control too. In that case you set the heater's temp just above where you normally have the tank.

[stre1026]

I do have temp sensors in both places. Though, the heater code is set to only use the sump's sensor. Maybe I should change that...

[nicholb]

You could keep the sump sensor as your primary control and just add a cut off line to the overflow heater's code so it shuts off if that sensor reads too high.

With the relatively small volume in the overflow you might have to play with that value as the heater may be able to quickly warm up the overflow to the cutoff point while the tank still needs heat.

[stre1026]

Thanks for the insight.

I'm going to leave it using the sump's sensor for now. It seems like it's going to work perfectly. Although, my heaters haven't been running for a while now as it's been warm in the Northeast. The chiller has been coming on instead!