If you were Registered and logged in, you could reply and use other advanced thread options
|
Posted by RichK on July 20, 2005, 9:04 am
Hi,
I have an old Lennox furnace (circa late 60's) with an A/C added on. The
schematic has not been marked up after an addition of the A/C. Had an air
blower relay failure recently and noticed that A/C compressor still switched
on, even without the blower running. That can't be right. When heat is
used, the blower does not come on unitl the air is hot.
Can someone point me to a "typical" schematic for a Furnace-A/C system.
Rich
|
|
Posted by Mikepier on July 20, 2005, 11:01 am
You're right, the blower does not come on until the air is hot. But in
A/C mode, the fan should come on rightaway along with the compressor.
What happens when you turn the fan switch to "ON" on the T-Stat?
|
|
Posted by RichK on July 20, 2005, 2:49 pm
----- Original Message -----
> You're right, the blower does not come on until the air is hot. But in
> A/C mode, the fan should come on rightaway along with the compressor.
> What happens when you turn the fan switch to "ON" on the T-Stat?
When I trurn T-Stat to ON, the fan does go ON. As it does in Auto. But the
fan running is not a permissive, either via a relay or flow switch, for the
compressor, at the present. I want to correct this and could devise my own
way, but am looking for a standard schematic, if there's such a thing :-)
Would be easier for someone else to recognize it in a future. I also want
to either draw a schematic, or print one out, if I find one, to which I will
rewire it.
Rich
|
|
Posted by Matt on July 20, 2005, 11:36 am
For the furnace wiring:
http://www.secretlifeofmachines.com/secret_life_of_central_heating.shtml
For the AC wiring (Actually it's a fridge, but its close enough):
http://www.secretlifeofmachines.com/secret_life_of_the_refrigerator.shtml
|
|
Posted by udarrell on July 20, 2005, 11:39 am
RichK wrote:
>Hi,
>
>I have an old Lennox furnace (circa late 60's) with an A/C added on. The
>schematic has not been marked up after an addition of the A/C. Had an air
>blower relay failure recently and noticed that A/C compressor still switched
>on, even without the blower running. That can't be right. When heat is
>used, the blower does not come on unitl the air is hot.
>
>Can someone point me to a "typical" schematic for a Furnace-A/C system. Rich
>
>
Hi RichK,
Well, they should have installed what is known as a "Sail Switch" that
will only close the 24-volt control circuit when adequate airflow turns
the sail and closes the switch.
The "Sail Switch" will work if the evaporator gets ice over, or return
filter gets overloaded/clogged.
There should always be a sensor that performs that duty to protect
equipment.
Other sensors can be used too "that require an adequate amount of
airflow/or pressure." An air pressure switch needs to be down-stream of
the evaporator to leave the switch open if there is not adequate
pressure to close it. This protects against a lot of things and indicate
to a knowledgeable tech a lot of things.
They should be illustrated in the schematic and included in a trouble
shooting owner's manual guide. indicating the various causes for the
switch to not close!
- udarrell
--
Optimizing Air-Conditioner Efficiency
http://www.udarrell.com/air-conditioning-efficiency-btuhr-evaporator-coil.html
|
| Similar Threads | Posted | | Need wiring diagram/schematic for NuTone IM-303 Intercom Master Unit | July 5, 2007, 9:44 am |
| Need wiring diagram for electric drill | December 1, 2006, 5:04 pm |
| Req: Need schematic or source to get a schematic for a Bryant 588 gaspack | October 16, 2006, 8:16 pm |
| Hobart Toaster Wiring Diagram Needed | November 29, 2007, 2:14 pm |
| where to get a schematic for a ge refigerator | December 13, 2005, 11:01 pm |
| typical cost of garage fumigation? | September 12, 2007, 12:56 pm |
| Typical heat pump cost ? | June 11, 2008, 11:50 pm |
| Ryobi Gas Trimmer - Need Schematic | May 8, 2006, 3:12 pm |
| What was the typical furniture finish in the 1930's, 40's? | January 9, 2007, 11:11 pm |
| not your typical paint stripper question... please read | April 20, 2008, 12:59 am |
|
|
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap