Rachio + 220v pump

I just installed my 15th Rachio today. Every job is a little different! Most of my customers have old Intermatic 110v timers. So wiring the Rachio outdoor enclosure, controller and valves is a snap. But about 20% of my customers are on a lake and have a 220v irrigation pump + 220v timer.

Since the Rachio (at least as of now) only works on 110v I am faced with (2) choices. I have done both.

I can run a whole second circuit to the outside if the building, or somehow run 110v through a wall. This allows me to supply the Rachio at 110v while keeping the pump and pump relay both at 220v. But depending on the location of the breaker or adjacent outlets this could cost me $$$ in parts and 1hr++ in extra time on the install.

I can convert the 220v circuit to 110v. I.e. swap out the breaker, move the second phase (red) over to the (white) neutral bus. Change the internal motor switch to 110. I’m licenced so non of the electrical work if difficult for me.

But here’s the problem. An irrigation pump at 220v runs at LOWER AMPS and consumes LESS POWER. Should I spend the time and money to do whats best, running new 110v circuit Or should I save my time and money at the expense of a little extra on my customers bill. Keeping in mind that rarely could I pass the whole cost of either choice along to my customer.

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First, a quick disclaimer, attempt anything at your own risk.

In case you have access to a reliable ground (ideally from the main breaker panel), you can use it instead of neutral to provide 110V with one of the available phases. I’ve seen more than one AC install use this trick to provide a local 110V for transformers whereas only 220V is available otherwise. Do not use the local (concrete slab) grounding for the pump as there is no grantee that it is well grounded, this is more of the advice in case you have a copper ground line running as a third wire next to the two phases.

As far as 220 / 110 power consumption for the pump, differences should be pretty small. You will loose a bit more power due to generating more heat within the wiring (due to higher currents as you’ve pointed out), but as far as the actual pump power consumption goes, it should be roughly the same, this is due to power being based primarily on the load of the pump, not the input voltage.

Here is an example (link), note that at 115V, 1HP pump will consume 16.6 Amps, while at 230, it consumes 8.3.

115 VAC * 16.6 Amps = 1909 Watts
230 VAC * 8.3 Amps = 1910 Watts

If the wiring can afford the 110V Amp rating, your best bet may be to simply convert one of the existing lines to neutral.

P.S. For those wondering why 208V in the example uses less than 1900 watts, this is due to the pump being under-powered, this would be the same as running it on only 104 volts and expecting 100% of maximum performance.