margarita wrote:

also, the thinner line is supposed to be hot

Make that *warm*. The liquid line should never run over about 20ºF above
the outdoor ambient temp, or a max of 120ºF in areas that push the
century mark in mid-summer. This isn't even close to being hot enough to
melt the t-stat wire's sheathing. On a heat pump the suction line
(bigger line) can however get quite hot in heating mode, especially when
the indoor blower fails to run. Normal temps of the suction line
(bigger line) in heat pump mode run anywhere from about 120º-170ºF. This
is still not hot enough to melt the sheathing, but then the t-stat wire
shouldn't be in direct contact with the suction line, which is supposed
to be insulated. There is a possibility of the suction line melting the
wire insulation if the indoor airflow becomes reduced or non-existent
due to a system fault.



but not sure about the dufus that ran a low voltage line up against a hot
liquid line when the unit was installed

This is standard practice.

hvacrmedic