External Control of Max-E-Therm, relay - 2 or 3 wire, how does it work?

[ideal2545]

Hi All,

I'm currently building a custom pool controller using some relays, and I'm trying to figure out the best approach to the Max-E-Therm 400 that I have. I'm reading the documentation and I can do either a 2 wire or 3 wire install. The 2 wire requires the use of the firemans switch (from which two wires then go to the external control interface) and this part gets confusing to me, the 3 wire does not? If it does not then can I just apply 24v AC to the spa side or pool side? If thats the case then would the heater then just use whatever the max is set to for that type or would I just need to just turn off the heater when the pool or spa temp hits a certain temp?

If anyone has any idea its greatly appreciated.

Jon

 

[JamesW]

You never apply voltage to the remote terminals.

The heater has 24 VAC at one terminal and it looks for 24 VAC to return on the other terminal to indicate that the remote switch is closed.

So, a remote is simply an on/off switch.

For a two wire, you connect to the fireman's switch and then turn the heater on (Pool On or Spa On) and set it to about three degrees higher than the maximum temperature setting that you will need.

When the remote switch is closed, the heater will run until the switch is open again or the water reaches the set temperature.

With a two wire remote, the remote controls the temperature set point by opening the switch.

For a three wire remote, the heater sends 24 VAC out on the common wire and looks for it to return on the Pool terminal or the Spa terminal.

If it returns on the Pool terminal, that's the same as pressing the "Pool On" button.

If it returns on the Spa terminal, that's the same as pressing the "Spa On" button.

So, the heater is controlling the temperature based on whether the Pool On or the Spa On is selected.

When using a 3 wire setup, you move a jumper on the board to disable the "Pool On" and "Spa On" buttons on the heater membrane pad.

For a 3 wire setup, you have two remote switches. One for Pool On and one for Spa On. You can only close one at a time to select Pool or Spa.

 

[ideal2545]

Thanks a lot, this is extremely extremely helpful

 

[keene3b07]

You never apply voltage to the remote terminals.

The heater has 24 VAC at one terminal and it looks for 24 VAC to return on the other terminal to indicate that the remote switch is closed.

So, a remote is simply an on/off switch.

For a two wire, you connect to the fireman's switch and then turn the heater on (Pool On or Spa On) and set it to about three degrees higher than the maximum temperature setting that you will need.

When the remote switch is closed, the heater will run until the switch is open again or the water reaches the set temperature.

With a two wire remote, the remote controls the temperature set point by opening the switch.

For a three wire remote, the heater sends 24 VAC out on the common wire and looks for it to return on the Pool terminal or the Spa terminal.

If it returns on the Pool terminal, that's the same as pressing the "Pool On" button.

If it returns on the Spa terminal, that's the same as pressing the "Spa On" button.

So, the heater is controlling the temperature based on whether the Pool On or the Spa On is selected.

When using a 3 wire setup, you move a jumper on the board to disable the "Pool On" and "Spa On" buttons on the heater membrane pad.

For a 3 wire setup, you have two remote switches. One for Pool On and one for Spa On. You can only close one at a time to select Pool or Spa.

Where is that jumper? I am installing an intellicenter and the existing compool system used a 3 wire setup. Now nothing works