help needed

[jeff5may]

Groovy. With your choice of power supply (wall wart, piggybacking off 24 VAC power, or my favorite, a USB power adapter), a 4 way relay module will do the job. For the control switching of 24 VAC power, you could use one based off ss relays. If you are planning to run some equipment directly, that's a different story. Your 4 relay outputs would be w, y, w2, and o.

[Acuario]

Hi,
ok here is a new version based on my understanding of your description.
It comprises of:

1. A relay module that switches either the combined Y+O (for cooling) or W for heating to a common source (from your description I'm not sure if the common is 0V or 24V but it should be irrelevant)
2. An SSR to turn on/off the heating element in the electric boiler
3. A DPDT relay to switch between HP or Electric boiler (I guess this runs the boiler pump). You'll need to build a bit of circuitry for it. You could also use the boiler contacts to feed power to the heater element (via the SSR) for security.
4. 3 temperature sensors, tank, inside, outside.
5. Display and keyboard for programming

The Arduino will work from a 12V supply so you'll have the 12V needed for the DPDT relay.

Have I mis-understood or missed anything?

[Mikesolar]

Originally Posted by Mikesolar

HPs in North america, like our forced air heating systems, have a W for heat, Y for the compressor, O/B for the the reversing valve (which is dependent on where the unit is destined to be placed. In the American south, the RV is usually set to cooling, power off as it is a cooling dominant climate and in the great white north, it is the other way around. Having both available means it can be tailored to specific needs). Where I am, O will power the RV to cool. So, on a cooling call, the stat will call for a fan, Y and O and in heating (in this case) it will only call for W. This is all outside of the control of the arduino which is just needed to switch over the HP from heat to cool at specific temps and turn on the electric boiler.

The HP does look after all it's own functions including switching the circ pump to the buffer tank.

The HP has 24Vac which runs to the stat so there is 24V at any switched pin.


No extra power is needed other than to provide power to the Arduino.

The reason for regular relays is that I do need some DPDT ones to switch off a heating circ pump on the buffer tank when the back up boiler is running (which has it's own pump). This is one of the outputs from the arduino which reads the outdoor temp at -15C and will shut off the HP in favor of the electric boiler.

The programming is quite house specific and I have determined that the HP will easily heat this house down to -15C but it is not great when colder than that.

At one time I did find some reed relays that would work directly with the max pin current of the arduino but they were not DPDT so i didn't buy them. It may be available.

Drawing will be coming soon of the wiring.

Darn, I forgot to do the diagram.......OK...... shortly

[Mikesolar]

Originally Posted by Acuario

Hi,
ok here is a new version based on my understanding of your description.
It comprises of:

1. A relay module that switches either the combined Y+O (for cooling) or W for heating to a common source (from your description I'm not sure if the common is 0V or 24V but it should be irrelevant)
2. An SSR to turn on/off the heating element in the electric boiler
3. A DPDT relay to switch between HP or Electric boiler (I guess this runs the boiler pump). You'll need to build a bit of circuitry for it. You could also use the boiler contacts to feed power to the heater element (via the SSR) for security.
4. 3 temperature sensors, tank, inside, outside.
5. Display and keyboard for programming

The Arduino will work from a 12V supply so you'll have the 12V needed for the DPDT relay.

Have I mis-understood or missed anything?

I think you are good. The only thing is that normally the trigger for the electric boiler is a dry contact such as a thermostat. 24V in in the boiler as is a relay for its pump. When the boiler is to be turned on, the signal goes through the NC contact for the HP load pump, which shuts it off (so as not to draw water through a buffer tank when not needed for heating).

I'll put my meager brainpower to this again shortly, haha

[Mikesolar]

OK, here is a simple relay drawing.

What is important is that the control need only turn on the heat pump through the pins on the left.

24vac comes from the HP, to the relays controlled by the arduino and the the arduino needs to determine which pin to apply power to and at what outdoor temp. As noted before, below 17C (for example) the system will be in heat mode and over 25C, it will be in cooling. I think temps need to be sustained for some period of time ( perhaps 12 hrs?) before a switchover to allow for hot days and cool nights.

I hope this helps. Acc on R1 is the arduino output that turns off the HP and turns on the electric boiler when outdoor temps are below -15C.

[jeff5may]

Originally Posted by Mikesolar

OK, here is a simple relay drawing.

What is important is that the control need only turn on the heat pump through the pins on the left.

24vac comes from the HP, to the relays controlled by the arduino and the the arduino needs to determine which pin to apply power to and at what outdoor temp. As noted before, below 17C (for example) the system will be in heat mode and over 25C, it will be in cooling. I think temps need to be sustained for some period of time ( perhaps 12 hrs?) before a switchover to allow for hot days and cool nights.

I hope this helps. Acc on R1 is the arduino output that turns off the HP and turns on the electric boiler when outdoor temps are below -15C.

ok, translating to standard wire colors, your acc output woulb be 2nd stage heat, w2. Heating call would be w, cooling call would be y. No problemo.

[Mikesolar]

That's the kind of thing I like to hear. wish I could be more positive about my own programming abilities. Oh well.