On Thursday, October 8, 2015 at 2:44:06 PM UTC-4, mj wrote:
replying to Ed Pawlowski , mj wrote:
esp wrote:

On Sat, 31 Mar 2012 11:06:48 -0400, "Stormin Mormon"
It has been on the market for years. It is cheaper to build, more
difficult to field repair.
All aluminum coils were starting to come into play in the late 1960's.
I worked for a company that made HVAC units until 1970 and we made our
own copper tubed coils and they started to buy aluminum coils.


I have a 3 year old Trane 4 ton unit. It has aluminum coil. It has been
serviced 9 times for slime on the coils. I have been told that if it had
some copper, like my two 1 1/2 ton units, I would not have this problem.
My repair company is trying something new-laying pieces of copper tubing
in the pan to try to stop the slime build up.

--

Interesting. I know copper is used in boat bottom paint because it's
toxic to barnacles. Which leave one wondering how it's OK in copper
water pipe? I guess very little leaches out? But if that's the case,
how would having copper tubing in the coils kill slime? Zinc is used on
roofs with problems to keep algae from growing. If you drive around here,
you can see roofs where there is no algae on the roofs below flashings,
vents, etc that are made of zinc.