[BC] Northeast scorcher

[RichardBJohnson at comcast.net]

If you have been hearing or watching the weather reports, you probably know by now that the Northeast has some hot weather and, in fact, there were record temperatures reported at Boston's Logan International Airport today. I was stuck in I-495 traffic for two hours on my trip home from work. Fortunately, my air-conditioner in my truck works.

However, when I entered my house, I discovered something horrible! The inside temperature was so high that all my digital thermometers were flashing and I do not have any analog (read mercury) ones. They were all out of range, plus my ten-year-old Honeywell programmable digital thermostat was demanding heat, and my high-efficiency gas furnace was dutifully providing it!

Normally, I turn off my furnace power when the heating season is over. I forgot to do it this year and I found that there is likely a bug in the 8-bit Honeywell software, probably having to do with sign extension where a number over 127 suddenly becomes negative!

It was so hot in my house that many of my framed digital photographs developed runs! I have never seen anything like that before.

After I turned off my furnace and opened all the windows, I un-plugged the thermostat and brought it outside. It started to register temperatures at about 140 degrees as it cooled down. However, the "heat on" icon did not turn off until the indicated temperature was below 135! Apparently, the scaling for temperature is such that 135 or thereabouts represents 127 in some register somewhere.

Heads up if you have a similar Honeywell thermostat! It doesn't have a model or part number and I have seen them still being sold at Home Despot (sic).

Cheers,
Richard B. Johnson
Book: http://www.AbominableFirebug.com/