My Carrier 58MCA furnace has a 66sec Blower On delay. The problem is
that I have to have the fan running constantly to assist the HRV
Ventilator feeding the return duct. When the Blower Fan stops for
"warm up", the ventilator is blowing out the unfiltered return ducts,
sending dust and crap into the air.
Can I switch off the Blower On Delay? What if the blower is running
off of a FanHandler (so it's quite slow during normal Fan On)? Would
disabling the Delay impede the warm-up of the heat exchanger enough to
cause a severe performance problem?
How can the Blower On Delay be modified? After studying the wiring
diagrams, it seems that the feature is not field adjustable.
Yes--but when the call comes for heat, the furnace automatically stops
the fan for 66sec while the burners light and the heat exchanger warms
up--then the fan comes back on. During this 66sec, my ventilator,
whose supply is connected to the furnace return, blows out the return
vents (since the furnace has temp. stopped pulling the return air).
Get it? Now, how do I disable this damn automatic "pause" in the
The HRV ventilator runs constantly and is not electrically connected to
the furnace or thermostat in any way. I just set it to run "normal"
(50cfm) or "Boost" (100cfm) or "recirculation".
No Carrier experts here? In the manual they mentioned a 5sec delay for
heat pumps (compared to the 66sec for NG)... what is the difference
between the two boards? Maybe I can reproduce that same
I have to say that Carrier themselves are perhaps the most unhelpful
company around... when I found a number (took quite some time), the
only respose I got was "call your local installer"... well, too bad
that guy doesn't have a clue either.. he doesn't make them; he just
installs them... duh..
Told you before....
1) Call a *competent* tech
2) If you just have to DIY, then talk to some controls folks (Honeywell)
3) You have to be smarter than the piece of equipment you are working with.
After you have re-designed your furnace, don't forget to have it
re-certified by UL, GAMA, and have it inspected by your local code
enforcement authority, then make sure that your insurance is paid current.
I don't care what kind of degree you have... or what kind of experience you
have... but fosile fuel burning appliances are not something that you really
need to be playing with *UNLESS* you have the training, education,
certifiications, licenses, and experience to do so.
That being said, its an easy fix, and no its not going to be free.
It's not my intention to play with any part of the appliance that
directly relates to the gas or some saftey features etc. But you don't
need a lisence to do some simple wiring to the motor (ie. Fanhandler)
or make a simple, mechanical adjustment to the board... if there is one
Not free as in "I won't tell you for free" or as in "you have to buy an
expensive part"? If it's #1, can I offer you some cash???? If it's
#2, then I'm going to look into James' advice above... thanks...
It's a timer circuit on the board and it's not adjustable. You could alter
it but it would be a pain. You won't find a schematic for it either. I'd
probably try to use the low voltage side of the fan relay to control a relay
at the ventilator so that it get's turned off when the furnace blower is
James, you sound like a superhero... willing to help the weak... do you
think shutting the ventilator each time would wear it out faster? When
you power it down, some flaps inside close and of course, the motor
doesn't sound like it likes to power up much when it does so(obviously
designed to run continuous). Any experience with these Venmar HRV 2500
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.