I am trying to hook up honeywell rth7500 to singlestage hestpump
I have 5 wires g y w r b
I hooked the green to g the yellow to y the w to o/b
Red to R BLUE TO C
The unit works great that way the heat comes on goes off as it should however the cooling comes on runs good but when it goes off there is something still on and a soft humm or running noise comes through the ventilation system (won`t stop keeps going)
Honeywell tech says that is normal for this thermostat it is annoying and I believe something is running that shouldn`t and will eventuall burn out if always on please help
I am new to this if I am doing anything wrong iN asking this question olease let me know thanks

If you talked to Honeywell and they say it is normal then it must be normal. You can ttrace down the noise by going to your indoor unit and finding the problem. Post back with your results.

Yes trace down the noise. Tangentially, I am interested to know what Honeywell thinks is normal about this - that is, keeping something energized.

You connected "W" to "O/B"? The hum is probably the electric auxiliary heater. That is NOT normal. Correct this ASAP or problems with the auxiliary will surface - and soon. "W" circuit should be connected to "W" terminal on t-stat.

It is probably the transformer.