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Posted by Ed Sievers on October 15, 2009, 10:44 pm
My daughter's furnace (and her little Boze radio) received a bit of a jolt
from a secondary leg of a lightning strike which hit (and penetrated) the
roof across the street this past summer. I had to replace the furnace
control board ($132 wholesale from an AC parts house) and then the AC worked
just fine the rest of the summer. I didn't c/o the heater at the time, but
she tried it the other day and it doesn't work. I was very careful ground
myself while installing the replacement controller last summer so as to
avoid static discharge and of course labeled all the wiring to ensure I
connected it up right. Now, on startup, the induced draft fan starts a
couple of times and on the 3rd try or so, gets up enuff speed to trip the
draft sensor switch and keep running. The hot-surface ignitor never heats
up though nor does the gas valve open. Without a normal startup, eventually
everything shuts down...as it should. I thought maybe another lightning
strike near the house had "zapped" another controller, so I bought a
replacement + a spare. I have tried both the new ones......same result.
All the flame roll-out sensors, hi-temp sensors, etc are "made" and the gas
valve reads about 150 ohms, so I believe it to be OK. As a last resort, I
disconnected all the T'stat wiring (as per directions) and ran a "self
check" on the currently installed controller. After an intitial delay, it
is supposed to turn on the draft blower and leave it on, then the ignitor
(for 15 seconds .... but not the gas valve) , then turn on the big blower at
low speed (heat) for abt 30 sec and then high speed (cool). Instead, I just
get a flashing red status indicator light on the control board......and the
literature says this can either be: (1.) a problem with the 120 v. power
polarity (reversed) or (2.) a twining problem. Well, the power is hooked
blk to blk and white to white (as it has been for 6 years now) so that isn't
the problem but what the heck is a "twining problem? Also, since the first
event is supposed to be the induced draft fan coming on.......I'm wondering
if it may have some lightning-caused shorted turns or something. I would
think that the control board only provides power to that little motor via a
relay, but maybe the board gets feedback info and is "smart" enough to know
that the current draw to that little motor ain't right? (That's a stretch,
but I am about at my wits end......and I intend to call out a tech who is
more up-to-date than I am on HVAC) Any thoughts from any AC wizards out
there? TIA.....ed s (long,long ago retired A/C dude) in TX.
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Posted by Tony Hwang on October 15, 2009, 11:54 pm
Ed Sievers wrote:
> My daughter's furnace (and her little Boze radio) received a bit of a
> jolt from a secondary leg of a lightning strike which hit (and
> penetrated) the roof across the street this past summer. I had to
> replace the furnace control board ($132 wholesale from an AC parts
> house) and then the AC worked just fine the rest of the summer. I
> didn't c/o the heater at the time, but she tried it the other day and it
> doesn't work. I was very careful ground myself while installing the
> replacement controller last summer so as to avoid static discharge and
> of course labeled all the wiring to ensure I connected it up right.
> Now, on startup, the induced draft fan starts a couple of times and on
> the 3rd try or so, gets up enuff speed to trip the draft sensor switch
> and keep running. The hot-surface ignitor never heats up though nor
> does the gas valve open. Without a normal startup, eventually
> everything shuts down...as it should. I thought maybe another lightning
> strike near the house had "zapped" another controller, so I bought a
> replacement + a spare. I have tried both the new ones......same result.
> All the flame roll-out sensors, hi-temp sensors, etc are "made" and the
> gas valve reads about 150 ohms, so I believe it to be OK. As a last
> resort, I disconnected all the T'stat wiring (as per directions) and ran
> a "self check" on the currently installed controller. After an intitial
> delay, it is supposed to turn on the draft blower and leave it on, then
> the ignitor (for 15 seconds .... but not the gas valve) , then turn on
> the big blower at low speed (heat) for abt 30 sec and then high speed
> (cool). Instead, I just get a flashing red status indicator light on
> the control board......and the literature says this can either be: (1.)
> a problem with the 120 v. power polarity (reversed) or (2.) a twining
> problem. Well, the power is hooked blk to blk and white to white (as it
> has been for 6 years now) so that isn't the problem but what the heck is
> a "twining problem? Also, since the first event is supposed to be the
> induced draft fan coming on.......I'm wondering if it may have some
> lightning-caused shorted turns or something. I would think that the
> control board only provides power to that little motor via a relay, but
> maybe the board gets feedback info and is "smart" enough to know that
> the current draw to that little motor ain't right? (That's a stretch,
> but I am about at my wits end......and I intend to call out a tech who
> is more up-to-date than I am on HVAC) Any thoughts from any AC wizards
> out there? TIA.....ed s (long,long ago retired A/C dude) in TX.
>
>
>
>
>
Hi,
Is the board grounded well? When draft motor runs, is the pressure
switch made to go to next sequence? The switch has small plastic tube
attached to it, maybe the hose is plugged up with dirt?(common issue)
Being differential type sensor blowing into the hose is not a good idea.
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Posted by Ed Sievers on October 16, 2009, 7:23 am
Thanks for the quick response, Tony. The delta P switch does, in fact,
close when the induced draft fan motor starts....it drops to "zero
ohms"......all the other safety switches/sensors read 0 ohms as well. Re
your other point, the board actually seems to "float" above physical ground;
i.e., it is a plastic board of course, and there is no grounding provision.
Now that you mentioned grounding, the furnace itself is not grounded that I
noticed. I'll check and see if the bare wire in the romex that connects to
the furnace is hooked up... + I will physically ground the whole furnace and
see what that does. I'll post back to the group when all is resolved. ...
probably not by me, but more likely by a pro from the local Carrier dealer
[who has a good reputation hereabouts.] :-) Regards, Ed S.
> Ed Sievers wrote:
>> My daughter's furnace (and her little Boze radio) received a bit of a
>> jolt from a secondary leg of a lightning strike which hit (and
>> penetrated) the roof across the street this past summer. I had to
>> replace the furnace control board ($132 wholesale from an AC parts house)
>> and then the AC worked just fine the rest of the summer. I didn't c/o
>> the heater at the time, but she tried it the other day and it doesn't
>> work. I was very careful ground myself while installing the replacement
>> controller last summer so as to avoid static discharge and of course
>> labeled all the wiring to ensure I connected it up right. Now, on
>> startup, the induced draft fan starts a couple of times and on the 3rd
>> try or so, gets up enuff speed to trip the draft sensor switch and keep
>> running. The hot-surface ignitor never heats up though nor does the gas
>> valve open. Without a normal startup, eventually everything shuts
>> down...as it should. I thought maybe another lightning strike near the
>> house had "zapped" another controller, so I bought a replacement + a
>> spare. I have tried both the new ones......same result. All the flame
>> roll-out sensors, hi-temp sensors, etc are "made" and the gas valve reads
>> about 150 ohms, so I believe it to be OK. As a last resort, I
>> disconnected all the T'stat wiring (as per directions) and ran a "self
>> check" on the currently installed controller. After an intitial delay,
>> it is supposed to turn on the draft blower and leave it on, then the
>> ignitor (for 15 seconds .... but not the gas valve) , then turn on the
>> big blower at low speed (heat) for abt 30 sec and then high speed (cool).
>> Instead, I just get a flashing red status indicator light on the control
>> board......and the literature says this can either be: (1.) a problem
>> with the 120 v. power polarity (reversed) or (2.) a twining problem.
>> Well, the power is hooked blk to blk and white to white (as it has been
>> for 6 years now) so that isn't the problem but what the heck is a
>> "twining problem? Also, since the first event is supposed to be the
>> induced draft fan coming on.......I'm wondering if it may have some
>> lightning-caused shorted turns or something. I would think that the
>> control board only provides power to that little motor via a relay, but
>> maybe the board gets feedback info and is "smart" enough to know that the
>> current draw to that little motor ain't right? (That's a stretch, but I
>> am about at my wits end......and I intend to call out a tech who is more
>> up-to-date than I am on HVAC) Any thoughts from any AC wizards out
>> there? TIA.....ed s (long,long ago retired A/C dude) in TX.
> Hi,
> Is the board grounded well? When draft motor runs, is the pressure switch
> made to go to next sequence? The switch has small plastic tube
> attached to it, maybe the hose is plugged up with dirt?(common issue)
> Being differential type sensor blowing into the hose is not a good idea.
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Posted by Joe on October 15, 2009, 11:57 pm
> My daughter's furnace (and her little Boze radio) received a bit of a jol=
t
> from a secondary leg of a lightning strike which hit (and penetrated) the
> roof across the street this past summer. =A0I had to replace the furnace
> control board ($132 wholesale from an AC parts house) and then the AC wor=
ked
> just fine the rest of the summer. =A0I didn't c/o the heater at the time,=
but
> she tried it the other day and it doesn't work. =A0I was very careful gro=
und
> myself while installing the replacement controller last summer so as to
> avoid static discharge and of course labeled all the wiring to ensure I
> connected it up right. =A0Now, on startup, the induced draft fan starts a
> couple of times and on the 3rd try or so, gets up enuff speed to trip the
> draft sensor switch and keep running. =A0The hot-surface ignitor never he=
ats
> up though nor does the gas valve open. =A0Without a normal startup, event=
ually
> everything shuts down...as it should. =A0I thought maybe another lightnin=
g
> strike near the house had "zapped" another controller, so I bought a
> replacement + a spare. =A0I have tried both the new ones......same result=
.
> All the flame roll-out sensors, hi-temp sensors, etc are "made" and the g=
as
> valve reads about 150 ohms, so I believe it to be OK. =A0As a last resort=
, I
> disconnected all the T'stat wiring (as per directions) and ran a "self
> check" on the currently installed controller. =A0After an intitial delay,=
it
> is supposed to turn on the draft blower and leave it on, then the ignitor
> (for 15 seconds .... but not the gas valve) , then turn on the big blower=
at
> low speed (heat) for abt 30 sec and then high speed (cool). =A0Instead, I=
just
> get a flashing red status indicator light on the control board......and t=
he
> literature says this can either be: (1.) a problem with the 120 v. power
> polarity (reversed) or (2.) a twining problem. =A0Well, the power is hook=
ed
> blk to blk and white to white (as it has been for 6 years now) so that is=
n't
> the problem but what the heck is a "twining problem? =A0Also, since the f=
irst
> event is supposed to be the induced draft fan coming on.......I'm wonderi=
ng
> if it may have some lightning-caused shorted turns or something. =A0I wou=
ld
> think that the control board only provides power to that little motor via=
=A0a
> relay, but maybe the board gets feedback info and is "smart" enough to kn=
ow
> that the current draw to that little motor ain't right? =A0(That's a stre=
tch,
> but I am about at my wits end......and I intend to call out a tech who is
> more up-to-date than I am on HVAC) =A0Any thoughts from any AC wizards ou=
t
> there? =A0TIA.....ed s (long,long ago retired A/C dude) in TX.
Lightning strikes are covered by your insurance and the furnace and
radio should have been repaired/replaced free of charge. Most policies
are pretty liberal in that respect, so a call to your agent might be a
good idea even at this late date.
If you're stuck with doing your own repair, then look for the power
relay on the board that handles the ignition/fans or such and see if
it can be checked without desoldering. I had a Modine heater that quit
last winter and traced it to some cold solder joints on the relay.
Nice 10 minute fix made me proud.
Joe
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Posted by Mikepier on October 16, 2009, 6:36 am
Check if you get 110v at the igniter at startup. If you don't, check
for continuity on the igniter. If its open, you have a bad igniter.
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> jolt from a secondary leg of a lightning strike which hit (and
> penetrated) the roof across the street this past summer. I had to
> replace the furnace control board ($132 wholesale from an AC parts
> house) and then the AC worked just fine the rest of the summer. I
> didn't c/o the heater at the time, but she tried it the other day and it
> doesn't work. I was very careful ground myself while installing the
> replacement controller last summer so as to avoid static discharge and
> of course labeled all the wiring to ensure I connected it up right.
> Now, on startup, the induced draft fan starts a couple of times and on
> the 3rd try or so, gets up enuff speed to trip the draft sensor switch
> and keep running. The hot-surface ignitor never heats up though nor
> does the gas valve open. Without a normal startup, eventually
> everything shuts down...as it should. I thought maybe another lightning
> strike near the house had "zapped" another controller, so I bought a
> replacement + a spare. I have tried both the new ones......same result.
> All the flame roll-out sensors, hi-temp sensors, etc are "made" and the
> gas valve reads about 150 ohms, so I believe it to be OK. As a last
> resort, I disconnected all the T'stat wiring (as per directions) and ran
> a "self check" on the currently installed controller. After an intitial
> delay, it is supposed to turn on the draft blower and leave it on, then
> the ignitor (for 15 seconds .... but not the gas valve) , then turn on
> the big blower at low speed (heat) for abt 30 sec and then high speed
> (cool). Instead, I just get a flashing red status indicator light on
> the control board......and the literature says this can either be: (1.)
> a problem with the 120 v. power polarity (reversed) or (2.) a twining
> problem. Well, the power is hooked blk to blk and white to white (as it
> has been for 6 years now) so that isn't the problem but what the heck is
> a "twining problem? Also, since the first event is supposed to be the
> induced draft fan coming on.......I'm wondering if it may have some
> lightning-caused shorted turns or something. I would think that the
> control board only provides power to that little motor via a relay, but
> maybe the board gets feedback info and is "smart" enough to know that
> the current draw to that little motor ain't right? (That's a stretch,
> but I am about at my wits end......and I intend to call out a tech who
> is more up-to-date than I am on HVAC) Any thoughts from any AC wizards
> out there? TIA.....ed s (long,long ago retired A/C dude) in TX.
>
>
>
>
>