Sunday, November 18, 2018

Fixing the Honeywell 4000 Programmable Thermostat (It's Not as Smart as it Thinks!)

This post is offered to alert you to two features built into the Honeywell 4000 series thermostat that you might not realize are affecting your life and comfort.  The device is very intelligent - but the manufacturer and installers assume that you are not!

We participated in a "*free energy audit" this summer.  It took about a year for the busy auditors to get around to us.  The (apparently) high demand for this audit service is fueled by the promise of *free replacement light bulbs and a *free programmable thermostat.

Such a deal!

Now that the heating season has arrived, we find that the furnace comes on at an unpredictable time each morning and the humidifier doesn't work.  So much for the world of "intelligent devices."

The free thermostat is a modern Honeywell 4000 series which is replacing a much older Honeywell device.

We programmed the new thermostat to set the temperature way back (I am too embarrassed to divulge Linda's idea of an ideal sleeping temp - we once froze the pipes overnight in a previous home) for sleeping and bring it back on a half hour before I get up.

This seemed to be working as the heating season began, but then the heat began coming on earlier and earlier than the prescribed "wake" time.  The installer had taken us through the programming cycle - we checked the "setting" instructions - we even checked a couple of YouTube videos.

If that wasn't bad enough, the furnace was cycling on and off much more frequently than before.  These short cycles bothered me for two reasons - first, you only get so many "starts" before maintenance is required and second, our humidifier on the furnace does not start until well into the "on" cycle of the furnace - we were suffering from dry air.

I quickly diagnosed the frequent cycling - the heat anticipator was set wrong.  What's a "heat anticipator?"  In the old days, it was a small heating coil mounted below the bimetal strip in the thermostat.  It had a rheostat wired in series to control how much juice got to it.  The purpose is to warm the sensor a bit faster than the room to prevent the device from overshooting the setting.  Follow this link for example to read about the one shown below on the familiar old "clock face" Honeywell unit.

Now then - where is the heat anticipator located on the new Honeywell 4000?

You have to open up the Installation Instructions and probe deeply to find the intelligent electronic replacement:

Instead of a "Heat Anticipator," you get a "Heating Cycle Rate" - the default setting is 5.  I set it back to 3 for an opening bid.  Perhaps 1 will be better.

As for the the heat coming on at a much earlier time than actually programmed - that is due to the "Adaptive Intelligent Recovery!"   This feature is easily disabled once you find out about it.  The feature tries to figure out how much before your "Wake" time it should start the furnace.  It is easily confused by people who sometimes open windows at night!

I was planning to go back to the old thermostat this weekend - but maybe I have outsmarted the intelligence in this device sufficiently that we will be able to live with this genius in the house.

*TANSTAFL Warning!  Of course, the new light bulbs and thermostat are not really free.  They are built into the price of our utilities - so naturally, you will want to maximize your share too.  You might have to sell the thermostat on eBay and go back to the old one - so save the box and instructions.