"D-" wrote in message
...
CBHvac wrote:
"Bob M." wrote in message
...
About 800 sq ft Cape Cod style house with forced warm air heat. Added
2-ton
York central A/C in 1989. Due to plenum shape, they put in a horizontal
coil
rather than an A-shaped coil. Worked well once I blew insulation into
the
house. Always felt very comfortable.
2 tons on 800SF...wow..
Replaced the furnace in 2000 with a Lennox gas unit, and they installed
a
new Lennox A-shaped coil in the output plenum. Same 2-ton capacity. Same
York compressor unit. The system will cool the house down quite nicely,
but
the humidity seems uncomfortably high at times, like over 50% even with
the
temp down to 74F. On days when it's in the mid 90s the system will bring
the
house down to the mid 70s and keep it there, cycling on and off as need
be. ("With proper sizing, probably should be running most of the time
when Out Door temp is in the mid 90's.")
The condensation pump runs, but not nearly as often as it did with the
old
setup. Cold air comes out of the ducts at about 58 degrees, so the
system
seems adequate for "cooling" purposes.
The fan speed was factory set to the highest speed.
Bingo.. Problem.
That 3 speed fan, isnt to go play with, its to allow for duct issues and
blower curves...
sniped the air moves slower across the coil, the moisture will
condense and drip
down and out. Never had this problem with the old horizontal coil.
Partially right..its not allowing the air enough time on the coil
Also, one of my upstairs rooms has its own 5000 BTU window A/C. When I
run
that unit to cool the room down to 74, then leave it to go back into the
main floor, there's a noticeable increase in humidity and the room feels
clammy and uncomfortable. It's this comparison that's got me thinking
the
central system isn't removing the humidity like it used to.
Any thoughts or suggestions? Is my analysis sound? I don't see any
moisture
around the furnace, so I'm fairly sure the condensed water is going
where
it's supposed to. When the thermostat shuts the system off, the
condensate
pump usually comes on a few seconds later to pump the water out. That's
why
I almost think it's saving it until the fan slows down or stops.
Slow the fan down, however when you do this, the current charge in the
unit
may not be enough...
I would type more on this, but my helper took my fingertip off in an
accident today, and typing is real fun right now..
Thanks.
Bob M.
If the latent load is high enough it may call for a 2 ton unit. Don't
know what his conditions are, but sounds like a 1.5 ton on that cooling
coil might do more of what he wants in respect to humidity, if there is
not sufficient continuous run time with the 2 ton unit. I know some in
S.W. WI that are cooling 2000 sq ft homes with 2 ton condensing units.
However, that's what the heat load is in those cases, so doesn't mean
anything for other conditions.
Well..there is part of the problem..we dont know where he is at...and that
is an issue..
"What is the Design Temp? With proper sizing, the unit probably should be
running most of the time when Out Door temp is in the mid 90's."
You got that right..
Slow the fan down, however when you do this, the current charge in the
unit
may not be enough...
I take it that the increased latent heat load on the evaporator will
vaporize the refrigerant faster requiring an increase demand for liquid
(R.) which will increase the heat load on the condenser increasing the
pressure which will increase the flow on an orifice or cap tube cooling
coil which might require a little more refrigerant. A TEV would open
more to keep the Super Heat in the correct zone.
Well..around here, with the high humidity, we go for the lower fan speeds,
and as we all know in the trade, that you design to med fan speed in most
cases, and use high or low depending on the situation, but here, we go for
the lowest possible..
When you do that, as long as the static is fine, you tend to find that the
superheat changes, and 9 out of ten times, you add a bit of refrigerant to
get things back in order, due to the lower fan speed, and slightly less
airflow over the coil..
Or, is your explanation different? Hope your finger heals like new! D-
Thanks...typing is bad enough...cant wait to go work in the rain
tomorrow..LOL
--
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