I have seen situations where the air flow was more than the old unit and the
duct work was not modified - caused problems. If same BTU, same air flow,
then this will reduce a lot of potential problems.

Then could be problems with a newer high efficiency unit. Old venting for
exhaust gases might not be right. Also venting for fresh air might need to
be modified.

Then new code regulations may apply and modifications may need to be made to
bring everything up to code.

Old thermostat may have problems with new unit.

And of course do they know what they are doing? Know codes, wiring, etc...


"Harry Muscle" wrote in message
However, since this is a remove and replace situation, will any of the
points you mention really apply? The house is prefectly comfortable as
is right now, it's just that the existing furnace is 35 years old.

The reason why I posted this question is that the comments I've read
about the installation being most important are usually part of answers
to persons just like me ... replacing a furnace, not a brand new
installation. I can understand a brand new installation where all the
duct work needs to be run, etc. That's a lot more planning and more
chance of things going wrong like you mention. But what can go wrong
when you're basically swapping in a newer furnace.

Thanks,
Harry