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Home > Archive > Home Repair forum > February 2006 > HVAC Fan Runs 24/7, Please Add Opinions. Thanks
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HVAC Fan Runs 24/7, Please Add Opinions. Thanks
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| Glen Cooper 2006-02-26, 12:21 am |
| Hi gang,
A friend called. The HVAC fan runs all the time in her 1 story home built
in 1979. She has a digital stat above her return duct in the hall, the only
return, 1700 square feet or so.
The problen started when she used the heater for the first time last season
a few weeks ago, Houston, Texas is hot most of the time. :-)
I have no specifics: model, make, electric or gas, original unit...
She has a digital stat. It is set to Auto..
I am not a pro HVAC man, I am a locksmith, I make lost car keys. That said:
I think the possible cause IS NOT the thermostat (she wants to buy this
first), but a relay AND/OR a thermal limit switch located by the heater
output on a PCB or on the side of the attic unit some place, (max limit
switch with a double pole [winter/summer push/pull switch depending on the
year of production and ajustable temp settings?). I think the heater
switch is effecting the AC too because the heater around here isn't used
much and once it shorts it shorts and you know.., (now she says the AC fan
stays on too), it shorted last year. (Would this be correct?).
She can cut the AC or heat off or on at the stat, the fan stays on hi BTW,
not low which I understand happens up north on purpose to allow the basement
air to go upstairs and vise/versa to lower the bill, not that complicated
here. We don't have basements being Houston.
That said, Possible causes;
(1) Bad limit switch?
(2) Bad fuse or relay on PCB controlling limit switch?
(3) Bad relay from thromastat controling fan? (Note: style of heater
unknown)
(4)Rat bit the stat wires shorting the green control wire to the feed wire?
Naww...)
Am I missing something, Thanks. Tomorrow is Sunday. Thought I could help
her out while not doing nothing else.
Ed
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| m Ransley 2006-02-26, 1:21 am |
| put the thermostat to Auto not On
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"Glen Cooper" <lockserviceTAKETHISOFF@copper.net> wrote in message
news:4401236b_5@newsfeed.slurp.net...
> Hi gang,
>
> A friend called. The HVAC fan runs all the time in her 1 story home built
> in 1979. She has a digital stat above her return duct in the hall, the
only
> return, 1700 square feet or so.
>
> The problen started when she used the heater for the first time last
season
> a few weeks ago, Houston, Texas is hot most of the time. :-)
>
> I have no specifics: model, make, electric or gas, original unit...
>
> She has a digital stat. It is set to Auto..
>
> I am not a pro HVAC man, I am a locksmith, I make lost car keys. That
said:
>
> I think the possible cause IS NOT the thermostat (she wants to buy this
> first), but a relay AND/OR a thermal limit switch located by the heater
> output on a PCB or on the side of the attic unit some place, (max limit
> switch with a double pole [winter/summer push/pull switch depending on the
> year of production and ajustable temp settings?). I think the heater
> switch is effecting the AC too because the heater around here isn't used
> much and once it shorts it shorts and you know.., (now she says the AC fan
> stays on too), it shorted last year. (Would this be correct?).
>
> She can cut the AC or heat off or on at the stat, the fan stays on hi BTW,
> not low which I understand happens up north on purpose to allow the
basement
> air to go upstairs and vise/versa to lower the bill, not that complicated
> here. We don't have basements being Houston.
>
> That said, Possible causes;
>
> (1) Bad limit switch?
> (2) Bad fuse or relay on PCB controlling limit switch?
> (3) Bad relay from thromastat controling fan? (Note: style of heater
> unknown)
> (4)Rat bit the stat wires shorting the green control wire to the feed
wire?
> Naww...)
>
> Am I missing something, Thanks. Tomorrow is Sunday. Thought I could help
> her out while not doing nothing else.
>
> Ed
We could guess for hours, the only real way of correcting the problem is to
go there check the settings. I remember when I moved into my last house with
a digital stat, took me a couple of weeks with the manual to get it working
the way I wanted.
Any of the above are POSSIBLE, I would WAG doubtful. Go on line get the
manual for the stat, then set all of the variables for her. or call someone
on Monday. Personally I would never attempt working with locks.
| |
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| On Sat, 25 Feb 2006 21:44:45 -0600, "Glen Cooper"
<lockserviceTAKETHISOFF@copper.net> wrote:
>Hi gang,
>
>A friend called. The HVAC fan runs all the time in her 1 story home built
>in 1979. She has a digital stat above her return duct in the hall, the only
Same year as mine. I thought being above a duct was not the best
location, but that's not the problem now. I'm sure it works well
enough there.
>return, 1700 square feet or so.
>
>The problen started when she used the heater for the first time last season
>a few weeks ago, Houston, Texas is hot most of the time. :-)
>
>I have no specifics: model, make, electric or gas, original unit...
I have read your whole post, and I think the problem is that she has
keys in her vents. But don't tell her that. She'll expect you to be
able to fix that.
>She has a digital stat. It is set to Auto..
You don't say if it is putting out heat or not.
1) IF it is, is putting out too much heat, since it runs all the time.
2) Or are the ducts blowing room temperature air some of the time.
1) If the former, it might be the thermostat or it might be something
else.
2) If the latter, the only problem is that the fan is on all the
time. From what you say below, and from what you didn't say, I think
that this is the problem.
>I am not a pro HVAC man, I am a locksmith, I make lost car keys. That said:
Can you use a volt-ohm meter?
>I think the possible cause IS NOT the thermostat (she wants to buy this
>first), but a relay AND/OR a thermal limit switch located by the heater
>output on a PCB or on the side of the attic unit some place, (max limit
>switch with a double pole [winter/summer push/pull switch depending on the
>year of production and ajustable temp settings?). I think the heater
>switch is effecting the AC too because the heater around here isn't used
>much and once it shorts it shorts and you know.., (now she says the AC fan
>stays on too)
Do you mean even though it's cold, when she puts it on AC, the fan
blows, even though the compressor outside doesn't go on?
I suppose it could be the thermostat's fan auto/on swtich, although it
is usually a simple switch that is not likely to short. The manual or
prior posts will show what colors represent the fan/auto/on switch.
You can take the thermostat off the wall, put it on auto, disconnect
one of the two wires from the thermostat, and the meter should show
an open circuit at the two screws on the thermostat that connect to
those wires, the fan wires.. When you move the switch to ON, the
meter should show close to zero ohms. If it does both of those
things, especially the first, the thermostat is good, wrt this issue..
>, it shorted last year. (Would this be correct?).
Would what be correct? A few lines up you refer to "heater swtich".
Do you mean fan relay or fan swtich?
>
>She can cut the AC or heat off or on at the stat, the fan stays on hi BTW,
>not low which I understand happens up north on purpose to allow the basement
>air to go upstairs and vise/versa to lower the bill, not that complicated
>here. We don't have basements being Houston.
>
>That said, Possible causes;
>
>(1) Bad limit switch?
I suppose.
>(2) Bad fuse or relay on PCB controlling limit switch?
Doesn't the limit switich affect the relay, rather than the other way
around. A fuse doesn't sound likely.
>(3) Bad relay from thromastat controling fan? (Note: style of heater
>unknown)
Yes but what do you mean "from thermostat". YOu mean at the furnace,
right? If it's bad (always closed for example) the thermostat would
not make it open.
>(4)Rat bit the stat wires shorting the green control wire to the feed wire?
>Naww...)
I was going to suggest that you check the wires to the thermostat from
the furance when the therm is disconnected, but because of ignorance,
I don't know what would make those show that they are connected and
what wouldn't.
>Am I missing something, Thanks. Tomorrow is Sunday. Thought I could help
>her out while not doing nothing else.
>
>Ed
>
>
Remove NOPSAM to email me. Please let
me know if you have posted also.
| |
|
| You should listen to your friend (girl). She is right. It is the
thermostat. Its almost always the thermostat. If you suggest this and
you are right, you will most likely get laid as that is what you are
looking for................to be the hero to her.
Bubba
On Sat, 25 Feb 2006 21:44:45 -0600, "Glen Cooper"
<lockserviceTAKETHISOFF@copper.net> wrote:
>Hi gang,
>
>A friend called. The HVAC fan runs all the time in her 1 story home built
>in 1979. She has a digital stat above her return duct in the hall, the only
>return, 1700 square feet or so.
>
>The problen started when she used the heater for the first time last season
>a few weeks ago, Houston, Texas is hot most of the time. :-)
>
>I have no specifics: model, make, electric or gas, original unit...
>
>She has a digital stat. It is set to Auto..
>
>I am not a pro HVAC man, I am a locksmith, I make lost car keys. That said:
>
>I think the possible cause IS NOT the thermostat (she wants to buy this
>first), but a relay AND/OR a thermal limit switch located by the heater
>output on a PCB or on the side of the attic unit some place, (max limit
>switch with a double pole [winter/summer push/pull switch depending on the
>year of production and ajustable temp settings?). I think the heater
>switch is effecting the AC too because the heater around here isn't used
>much and once it shorts it shorts and you know.., (now she says the AC fan
>stays on too), it shorted last year. (Would this be correct?).
>
>She can cut the AC or heat off or on at the stat, the fan stays on hi BTW,
>not low which I understand happens up north on purpose to allow the basement
>air to go upstairs and vise/versa to lower the bill, not that complicated
>here. We don't have basements being Houston.
>
>That said, Possible causes;
>
>(1) Bad limit switch?
>(2) Bad fuse or relay on PCB controlling limit switch?
>(3) Bad relay from thromastat controling fan? (Note: style of heater
>unknown)
>(4)Rat bit the stat wires shorting the green control wire to the feed wire?
>Naww...)
>
>Am I missing something, Thanks. Tomorrow is Sunday. Thought I could help
>her out while not doing nothing else.
>
>Ed
>
>
| |
| Glen Cooper 2006-02-26, 9:21 pm |
| Hello again gang. Great group I must say.
I disconnected the green fan wire at borh ends with the power off, checked
it for a short to the other wires. The fan cut off with the power on and
the safety switch jumped. I replaced the thremostat, and bingo!
Thanks again
Ed
| |
|
| On Sun, 26 Feb 2006 18:20:52 -0600, "Glen Cooper"
<lockserviceTAKETHISOFF@copper.net> wrote:
>Hello again gang. Great group I must say.
>
>I disconnected the green fan wire at borh ends with the power off, checked
>it for a short to the other wires. The fan cut off with the power on and
>the safety switch jumped. I replaced the thremostat, and bingo!
>
>Thanks again
>
>Ed
>
Great job. Make sure you leave all the safetys jumped and crack the
gas line a little to let it breathe. Make sure you replace the
thermostat again. It takes twice to get acclimated to your system.
Bubba
| |
| Glen Cooper 2006-02-27, 9:21 pm |
|
"Bubba >" <<ReMoVe likealake@iname.com> wrote in message
news:2cj402d18e9oocpqu38slo6lvpt8hnlep6@4ax.com...
> On Sun, 26 Feb 2006 18:20:52 -0600, "Glen Cooper"
> <lockserviceTAKETHISOFF@copper.net> wrote:
>
> Great job. Make sure you leave all the safetys jumped and crack the
> gas line a little to let it breathe. Make sure you replace the
> thermostat again. It takes twice to get acclimated to your system.
> Bubba
Thanks for the tips.
Ed
| |
| Glen Cooper 2006-02-27, 9:21 pm |
|
"Bubba >" <<ReMoVe likealake@iname.com> wrote in message
news:ioq302h5s08kopb2v75mk8kt26vh04m9g8@4ax.com...[color=darkred]
> You should listen to your friend (girl). She is right. It is the
> thermostat. Its almost always the thermostat. If you suggest this and
> you are right, you will most likely get laid as that is what you are
> looking for................to be the hero to her.
> Bubba
>
> On Sat, 25 Feb 2006 21:44:45 -0600, "Glen Cooper"
> <lockserviceTAKETHISOFF@copper.net> wrote:
>
Blonde hair, green eyes, about 5'8", about 37C/25/37, six figure income,
...., interesting night I must say. Thanks again Bubba for all your help!
:-)
Ed
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