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Home > Archive > Home Repair forum > July 2005 > Yet another A/C question...............
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Yet another A/C question...............
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Problem (I think)
I have a 3000 S/F ranch with central A/C. The A/C is controlled by the same thermostat as my heat.
It's the standard issue Honeywell t-stat, round with A/C and Fan switches at the 11:00 and 2:00
positions. Heres the thing thats strange. When I set the temp to say 80, the A/C comes on but
doesn't shut off until the temps down around 70 - 72. This is according to the thermometer on the
t-stat, as well as a digital thermometer I have on the other side of the room. This same t-stat is
spot on in the winter months when used for heat. Why is there such a wide swing in tempurature on
A/C but not with heat ???? When I pop the cover off the t-stat there looks to be an adjustment
pointer on the bottom. what does this adjustment do ???? I'm stumped here..... Thanks for the
help....
Brian
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Brian wrote:
> Problem (I think)
>
> I have a 3000 S/F ranch with central A/C. The A/C is controlled by the same thermostat as my heat.
> It's the standard issue Honeywell t-stat, round with A/C and Fan switches at the 11:00 and 2:00
> positions. Heres the thing thats strange. When I set the temp to say 80, the A/C comes on but
> doesn't shut off until the temps down around 70 - 72. This is according to the thermometer on the
> t-stat, as well as a digital thermometer I have on the other side of the room. This same t-stat is
> spot on in the winter months when used for heat. Why is there such a wide swing in tempurature on
> A/C but not with heat ???? When I pop the cover off the t-stat there looks to be an adjustment
> pointer on the bottom. what does this adjustment do ???? I'm stumped here..... Thanks for the
> help....
Possibilities:
1) The t-stat is out of calibration. What does the temperature rise back
up to before it calls again for cooling?
2) The t-stat may have a worn-out bimetal (that's the ribbon spring
looking thing behind the bulb assembly). No problem in heat mode
because it wasn't bad during winter.
3) Short, causing current to flow through the heat anticipator or
cooling compensator during call for cool. This will fool the t-stat into
thinking its warmer inside than it is.
This is a typical problem in older Honeywell rounds when they pass about
20 years in age. How old is this stat?
In any case the t-stat seems to be the defective component. There are
other possibilities, but most would cause erratic cycling which you
didn't report. Given that this is a common fault for this t-stat odds
are its due for replacement. HTH.
hvacrmedic
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| TURTLE 2005-07-24, 9:06 pm |
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"Brian" <unisaw@hotmail.com> wrote in message
news:fsgrd196jlmfd78tnjpihs6gisjivsnvba@4ax.com...
>
> Problem (I think)
>
> I have a 3000 S/F ranch with central A/C. The A/C is controlled by the same
> thermostat as my heat.
> It's the standard issue Honeywell t-stat, round with A/C and Fan switches at
> the 11:00 and 2:00
> positions. Heres the thing thats strange. When I set the temp to say 80, the
> A/C comes on but
> doesn't shut off until the temps down around 70 - 72. This is according to
> the thermometer on the
> t-stat, as well as a digital thermometer I have on the other side of the room.
> This same t-stat is
> spot on in the winter months when used for heat. Why is there such a wide
> swing in tempurature on
> A/C but not with heat ???? When I pop the cover off the t-stat there looks to
> be an adjustment
> pointer on the bottom. what does this adjustment do ???? I'm stumped
> here..... Thanks for the
> help....
>
> Brian
This is Turtle.
Pull the ring cover and see if any wires are hanging up on the mercury bulb
going to the subbase. If not change the thermostat for you got a bad cooling
antipistator in the sub base and getting a long range on cooling.
TURTLE
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"Brian" <unisaw@hotmail.com> wrote in message
news:fsgrd196jlmfd78tnjpihs6gisjivsnvba@4ax.com...
>
> Problem (I think)
>
> I have a 3000 S/F ranch with central A/C. The A/C is controlled by
the same thermostat as my heat.
> It's the standard issue Honeywell t-stat, round with A/C and Fan
switches at the 11:00 and 2:00
> positions. Heres the thing thats strange. When I set the temp to
say 80, the A/C comes on but
> doesn't shut off until the temps down around 70 - 72. This is
according to the thermometer on the
> t-stat, as well as a digital thermometer I have on the other side of
the room. This same t-stat is
> spot on in the winter months when used for heat. Why is there such
a wide swing in tempurature on
> A/C but not with heat ???? When I pop the cover off the t-stat
there looks to be an adjustment
> pointer on the bottom. what does this adjustment do ???? I'm
stumped here..... Thanks for the
> help....
>
> Brian
If it's a mercury switch based stat (not electronic), make sure it's
level. There will be some pegs on the base that you put a level on.
As Turtle pointed out, that "pointer" is the anticipator...
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| On Tue, 19 Jul 2005 22:52:59 -0500, RP <no_mail_no_spam@yahoo.com> wrote:
>
>
>Brian wrote:
>
>
>Possibilities:
>1) The t-stat is out of calibration. What does the temperature rise back
>up to before it calls again for cooling?
It rises back up to the set temp before it comes back on.
Whats that slide adjustment thing on the bottom of the t-stat ????
>2) The t-stat may have a worn-out bimetal (that's the ribbon spring
>looking thing behind the bulb assembly). No problem in heat mode
>because it wasn't bad during winter.
Actually, this problem started at the end of last summer but I had forgotten about it. The heat was
ok this winter though.
>3) Short, causing current to flow through the heat anticipator or
>cooling compensator during call for cool. This will fool the t-stat into
>thinking its warmer inside than it is.
>
>This is a typical problem in older Honeywell rounds when they pass about
>20 years in age. How old is this stat?
Just about 20 years old............. Now i'm noticing it's 12 degrees colder than it's set for
and the A/C is still running........ Maybe it's time for a digital t-stat............. Are they
any good ????
>
>In any case the t-stat seems to be the defective component. There are
>other possibilities, but most would cause erratic cycling which you
>didn't report. Given that this is a common fault for this t-stat odds
>are its due for replacement. HTH.
>
>hvacrmedic
>
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| On Wed, 20 Jul 2005 04:00:20 GMT, "Rick" <notta@goodone.com> wrote:
>
>"Brian" <unisaw@hotmail.com> wrote in message
>news:fsgrd196jlmfd78tnjpihs6gisjivsnvba@4ax.com...
>the same thermostat as my heat.
>switches at the 11:00 and 2:00
>say 80, the A/C comes on but
>according to the thermometer on the
>the room. This same t-stat is
>a wide swing in tempurature on
>there looks to be an adjustment
>stumped here..... Thanks for the
>
>If it's a mercury switch based stat (not electronic), make sure it's
>level. There will be some pegs on the base that you put a level on.
>
>As Turtle pointed out, that "pointer" is the anticipator...
>
That pointer is all the way to the left......... Is that where it's suppose to be ????
Thanks..................
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"Brian" <unisaw@hotmail.com> wrote in message
news:7rird1tqoso2qo0bld0qdkkmnhj0b25gfc@4ax.com...
> On Tue, 19 Jul 2005 22:52:59 -0500, RP <no_mail_no_spam@yahoo.com>
wrote:
> Just about 20 years old............. Now i'm noticing it's 12
degrees colder than it's set for
> and the A/C is still running........ Maybe it's time for a digital
t-stat............. Are they
> any good ????
Yes, they are. Honeywell also makes a digital Round, but I wasn't that
thrilled by it. Very hard to read...
Electronic stats are pretty cheap these days..
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Brian wrote:
> On Wed, 20 Jul 2005 04:00:20 GMT, "Rick" <notta@goodone.com> wrote:
>
>
>
>
>
> That pointer is all the way to the left......... Is that where it's suppose to be ????
That has no effect on cooling whatsoever. That's a heating element
that's inline with the heating circuit only.
It's has little numbers on it. 0.2, 0.4 etc. These are the current draw
of the 24volt heating circuit, and it should be set to match that
current. Anyway, not your present problem.
hvacrmedic
>
> Thanks..................
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"Brian" <unisaw@hotmail.com> wrote in message
news:q5jrd158o3lpp251aam4qkkuatbaph1m23@4ax.com...
> That pointer is all the way to the left......... Is that where it's
suppose to be ????
>
> Thanks..................
That's the heat anticipator-from what I recall it's supposed to be set
to match the current draw of the gas valve in the furnace
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| On Wed, 20 Jul 2005 04:13:36 GMT, "Rick" <notta@goodone.com> wrote:
>
>"Brian" <unisaw@hotmail.com> wrote in message
>news:q5jrd158o3lpp251aam4qkkuatbaph1m23@4ax.com...
>suppose to be ????
>
>That's the heat anticipator-from what I recall it's supposed to be set
>to match the current draw of the gas valve in the furnace
>
I have an oil fired furnace........ Does it do anything for that ????
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"Brian" <unisaw@hotmail.com> wrote in message
news:fsgrd196jlmfd78tnjpihs6gisjivsnvba@4ax.com...
>
> Problem (I think)
>
> I have a 3000 S/F ranch with central A/C. The A/C is controlled by the
same thermostat as my heat.
> It's the standard issue Honeywell t-stat, round with A/C and Fan switches
at the 11:00 and 2:00
> positions. Heres the thing thats strange. When I set the temp to say 80,
the A/C comes on but
> doesn't shut off until the temps down around 70 - 72. This is according
to the thermometer on the
> t-stat, as well as a digital thermometer I have on the other side of the
room. This same t-stat is
> spot on in the winter months when used for heat. Why is there such a wide
swing in tempurature on
> A/C but not with heat ???? When I pop the cover off the t-stat there
looks to be an adjustment
> pointer on the bottom. what does this adjustment do ???? I'm stumped
here..... Thanks for the
> help....
>
> Brian
Is the digital t-stat under a duct or in the cold air stream? If so move it
to another location and see if the same situation happens.
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