After receiving my new Globe Enersaver thermostat last weekend, I was anxious to get it installed and ener-saving.  I already described why I needed a new way of controlling my heat pump, but the installation didn’t go as smoothly as I had hoped.

Luckily, in the battle of man versus machine, I had the help of a few electronic allies.  Let the battle begin!

As I mentioned in my previous post, the wiring diagram provided in the thermostat guide book was not entirely comprehensive.  I had an X2 wire in the original stat that controls the auxiliary heat, but the diagram suggested I connect it to the neutral common pole.  Not a good idea.

Luckily, I recognized the oversight and got everything wired up properly.  There are quite a few wires to connect, and on my unit (every unit is different, so don’t follow this for your house!), they have the following functions:

Blue (B) – The common wire, connected to “C” on the stat.

Red (R) – The “hot” wire that provides the power, connected to “R” and, by internal circuitry, to “RC”.

Green (G) – Controls the fan

Yellow (Y) – Controls the heat pump compressor

Orange (O) – Controls the reversing valve that switches the pump from heating to cooling and connects to the “OB” terminal on the stat.

White (X2/E/Aux) – Controls the auxiliary and/or emergency heat, connected to W1.

I removed the old stat, replaced the back panel, and got the new one wired up in no time.  Then I spent some time programming everything, including a 5 degree deadband and 20 minute lag, and went to bed convinced I’d be saving energy.

The next morning, I awoke and saw the Globe displaying an “Aux Heat” icon and glowing red.  I checked out TED 5000, and saw this:

Take a look at the morning of the 21st.  You can see the hot water heater cycle on around 5:30, then a slight increase at 6:00 AM when the thermostat is programmed to warm the house up.  There’s a 20 minute lag, an then the strip heaters come on with a 10 kW spike!  Well, there goes fifty cents!  Another cycle starts at 8:15 with the same profile, and wasting another forty cents.  I was livid!

That night, I took the faceplate off the thermostat, checked the wires, and replaced everything.  I then programmed the stat to wait an hour before switching to auxiliary heat, thinking that I just didn’t give the heat pump enough time to do its job.

The next morning (22nd) I get the same small power draw at 6:00 AM which lasts for an hour before the STRIP HEATERS COME ON AGAIN!  Now it’s getting personal.  That money is starting to add up to dollars throughout the course of the day, and it wasn’t even that cold out.

That’s when I broke out my second electronic ally – a meat thermometer with a temperature probe.  I had read that heat pumps put out cooler air than a gas or oil furnace, but it should be in the 80-100 degree range.  The next time the thermostat cycled, I was right there with my thermometer in the register.

Reading: 66 degrees, the same temp that the house had dropped to while we were away.  Air was blowing, but the heat pump was not pumping heat.  That small power increase at 6 AM had been the fan turning on for an hour with no compressor (a 2 kW load) behind it.  That’s why the strips were turning on!

I checked the yellow wire, and indeed it was a little loose. I clamped it down with a screwdriver (and screwed in all the un-wired terminals just in case) and voila – on the 23rd I had liftoff.  The heat pump kicked in at 2 kW, ran for 20 minutes to warm the house up to 70 degrees, and cost me seven whole cents.  A thermometer in the duct read in the 85-95 degree range.

I can now keep an eye on everything in Google PowerMeter.  Take a look at the morning peaks before (left) and after (right).

And the winner of the battle between man and machine: Man (with a little help from machines…)