I'm trying to convert to a programmable Honeywell Thermostat. BAYSTAT240 uses:

Red R 24vac
Brown T Thermister
Orange O Reversing valve for cooling
Green G Fan
Yellow Y Compressor
Black X2 Heat Strip = E
Blue B Common = C
White W (jumped to U) Heat Strip Aux

Honeywell TH5220D has

Y2
W2
G
W
C
Y
R
Rc

Honeywell refuses to assist on this model. Can anyone help?

Hre you go. All the information you need is contained in this doc. READ and follow directions. If you cannot follow these directions please call a professional before you cause some damage.

NOTE You will not have a brown T wire connected to your new thermostat. It is for a thermister in the outside unit

http://customer.honeywell.com/techlit/pdf/69-0000s/69-1783.pdf

Here is the honeywell list and it has a crossover for your stat.

http://customer.honeywell.com/NR/rdonlyres/5583F336-15A7-4301-BDC0-AD22653CDA20/581/706627.pdf