Blower Time-Delay After Cooling
Alorac Jones
running. Why aren't cooling systems designed so that the blower motor
stays on for some short period of time after the compressor cycles
off, so that air is blown across a coil which is still cold (and
wet!)?
I could easily design and install a device to keep the blower motor on
for a period of time, such as two minutes, after the compressor cycles
off. Would it be a good idea to do so? Why or why not?
I'd appreciate any thoughts or ideas.
Big "G"
Gavin
Alorac Jones wrote in message <35b9fbbf...@newshost.cyberramp.net>...
Robert Gracie
Many systems DO have that feature, as a matter of fact many high Eff.
systems will even ramp the blower speed (ECM Motors, etc..), both on the
call for cooling and after... Go find a good thermostat, and if will have
this feature..
--
Robert Gracie
Gracie Appliance, Heating & Air Conditioning, Inc.
http://home1.gte.net/rgracie/
T.Bush
relay.
>Go find a good thermostat, and it will have
>this feature..
paul milligan
>The thermostat has nothing to do with it. This is a function of the blower
>relay.
Which is controlled by the thermostat.
Paul
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Jabarco
>systems will even ramp the blower speed (ECM Motors, etc..), both on >the call
for cooling and after...
Dear Alorac,
The manufacturer's installed this feature to increase the SEER rating of the
their systems. Without it, the SEER ratings are lower. However, I would not
recommend setting my thermostat to cycle the fan off (AUTO position) while in
the cooling mode. Leaving the fan in the (ON position) allows the indoor
blower to continue to run after the compressor has cycled off allowing the
indoor fan to create a draft and create a cooling effect. Cycling the fan off
(AUTO position) stops the indoor fan and stops the draft that creates a cooling
effect. Therefore, this condition (no air moment) can cause the occupant to
feel uncomfortable and cause the occupant to lower the temperature setting at
the thermostat, starting the compressor and consuming more energy than would
have been required by just allowing the fan (ON position) to continue to
operate after the compressor has cycled off. I would only recommend using the
Auto position for the fan in the heating mode (winter months) when I'm heating
my house because I would not want a draft in the winter for the opposite
reason. I would feel a draft after the heating cycles off. Therefore, the
AUTO position can be more comfortable in the heating mode and the ON position
is a cheaper comfort in the cooling mode.
Enthusiastically,
Jabarco, HVACR/PTST
Robert Gracie
sequencer fan delay, or a logic system to delay the blower. Many electronic
thermostat's come with adjustable fan delay's to improve a systems SEER.
This is nothing new...
--
Robert Gracie
Gracie Appliance, Heating & Air Conditioning, Inc.
http://home1.gte.net/rgracie/
T.Bush wrote in message <6pd8u1$jn2$1...@news-1.news.gte.net>...
>The thermostat has nothing to do with it. This is a function of the blower
>relay.
>
John Mills
>
> The thermostat has nothing to do with it. This is a function of the blower
> relay.
>
> >Go find a good thermostat, and it will have
> >this feature..
As Sherman T would say, HORSEHOCKEY! Many good electronic thermostats
will
leave the G energized for 90 seconds or so after the call for cooling
ends.
The White-Rodgers 1F90 series has done this for years!
--
HVAC Advice, Pictures, Links
http://www.geocities.com/~johnmills
http://www.appelheat.com
catfish
it with solid state circuitry in their low voltage control boards.
Janitrol/Goodman does it by using a sequencer to bring on the fan.
--
catfish aka Bill
http://catfish.home.ml.org
*** Since light travels faster than sound,
*** isn't that why some people appear bright
*** until you hear them speak?
Alorac Jones <alo...@cyberramp.net> wrote in message
35b9fbbf...@newshost.cyberramp.net...
Panmetron
>However, I would not
>recommend setting my thermostat to cycle the fan off (AUTO position) while in
>the cooling mode. Leaving the fan in the (ON position) allows the indoor
>blower to continue to run after the compressor has cycled off allowing the
>indoor fan to create a draft and create a cooling effect...
Sorry Jabarco but
I strongly disagree !
Running the fan continuously will decrease comfort by increasing humidity
especially in high humidity climates such as here in Florida
Two reasons account for this increase in humidity:
1) If any duct leaks are present. Most systems have some leakage and running
the blower while not cooling will cause outside air to migrate into home
increasing humidity and lowering efficiency.
2) If the blower runs beyond a minute or two from compressor it will begin to
evaporate moisture from the Evap coil and pan and may even pull in outside air
from the drain (especially if it has no trap which many I found don't). This
moisture is put back into the house by the fan increasing humidity.
The thermostat will cycle to keep the house cool but the humidity will
increase.
I have tested this with my own home and found that the Humidity went up to
about 70% with the fan running all the time vs 55% with it cycling with the
system.
You are right about the increased SEER due to the fan off delay which is about
2mins for many systems. This gets the residual cooling of the coil but running
it too long will begin to evaporate moisture from the coil.
Also, your draft effect can be obtained through the use of ceiling fans that
will create a draft making occupants feel more comfortable and maybe allowing
them to increase temperature to reduce energy consumption.
Greg
Panm...@aol.com
Jabarco
>
>I strongly disagree !
>
>
Apology accepted.
>I have tested this with my own home and found that the Humidity went up to
>about 70% with the fan running all the time vs 55% with it cycling with the
>system.
Have you tried sealing the duct leaks in your home or trapping your drain?
Enthusiastically,
Jabarco, HVACR/PTST