If you were Registered and logged in, you could reply and use other advanced thread options
|
Posted by Don Ocean on November 16, 2008, 10:31 pm
Jeff Wisnia wrote:
> kool wrote:
>>> One of the GE Weathertron Model 3AAT80B1A1 thermostats in our home is
>>> doing its thing and when the temperature setting is increased a few
>>> degrees above ambient the auxillary heaters come on OK to supplement
>>> the heat pump's output.
>>> The blue "Aux Heat" indicator recently stopped lighting in that mode.
>>> I could live with it that way, but being an engineer I'm sort of anal
>>> about having everything working the way it was designed to.
>>> I suspect it's just a "burned out bulb". The thermostat is old enough
>>> so I'd doubt that the indicators use LEDs.
>>> Before I approach it, can someone tell me if replacement lamps are
>>> available and easily screwed or snapped in place or will I have to
>>> figure out what tiny bulb to buy and use my past years of electronic
>>> repair experience to solder it in.
>>> It would be annoying to toss out an otherwise working thermostat just
>>> for the want of a bulb.
>>> Thanks guys,
>>> Jeff
>>> --
>>> Jeffry Wisnia
>>> (W1BSV + Brass Rat '57 EE)
>>> The speed of light is 1.8*10^12 furlongs per fortnight.
>> It's a tiny incandescent bulb about the size a Motrin gel-cap , with
>> two little wires protruding from the bottom G.E.# 35E. It just sits in
>> the hole over a blue plastic lens.(the bulb is clear.) Mounts only by
>> the wires soldered onto the wires in the stat.
>
>
> I soldered in a new bulb yesterday. Tracing the circuit showed that
> here's a single diode in the common return lead of both bulbs so the
> bulbs effectively see only half of the nominal 24 volt AC supply.
>
> I used a 12-14 volt "grain of wheat" bulb and it works fine now.
>
> Jeff
Now that would be RMS voltage and that diode would indicate the bulb is
DC rather then AC. basically that bulb has a half cycle to cool and a
half cycle the heat and produce light. If all of that is not needed,
redesign and install a lifetime LED.
>
|
|
Posted by Fartikus on November 17, 2008, 6:23 am
> Jeff Wisnia wrote:
>> kool wrote:
>>>> One of the GE Weathertron Model 3AAT80B1A1 thermostats in our home is
>>>> doing its thing and when the temperature setting is increased a few
>>>> degrees above ambient the auxillary heaters come on OK to supplement
>>>> the heat pump's output.
>>>> The blue "Aux Heat" indicator recently stopped lighting in that mode. I
>>>> could live with it that way, but being an engineer I'm sort of anal
>>>> about having everything working the way it was designed to.
>>>> I suspect it's just a "burned out bulb". The thermostat is old enough
>>>> so I'd doubt that the indicators use LEDs.
>>>> Before I approach it, can someone tell me if replacement lamps are
>>>> available and easily screwed or snapped in place or will I have to
>>>> figure out what tiny bulb to buy and use my past years of electronic
>>>> repair experience to solder it in.
>>>> It would be annoying to toss out an otherwise working thermostat just
>>>> for the want of a bulb.
>>>> Thanks guys,
>>>> Jeff
>>>> --
>>>> Jeffry Wisnia
>>>> (W1BSV + Brass Rat '57 EE)
>>>> The speed of light is 1.8*10^12 furlongs per fortnight.
>>> It's a tiny incandescent bulb about the size a Motrin gel-cap , with two
>>> little wires protruding from the bottom G.E.# 35E. It just sits in the
>>> hole over a blue plastic lens.(the bulb is clear.) Mounts only by the
>>> wires soldered onto the wires in the stat.
>> I soldered in a new bulb yesterday. Tracing the circuit showed that
>> here's a single diode in the common return lead of both bulbs so the
>> bulbs effectively see only half of the nominal 24 volt AC supply.
>> I used a 12-14 volt "grain of wheat" bulb and it works fine now.
>> Jeff
> Now that would be RMS voltage and that diode would indicate the bulb is DC
> rather then AC. basically that bulb has a half cycle to cool and a half
> cycle the heat and produce light. If all of that is not needed, redesign
> and install a lifetime LED.
Here is an explanation how it works.
The bulb would get approx 12 VDC pulses and the 0.7v junction voltage of a
(silicon) diode would reduce the actual by 0.7V
http://www.wisc-online.com/objects/index_tj.asp?objID=SSE402
By the way, a grain of wheat bulb is incandescant, so it does not matter
whether you feed it AC or DC. If an LED wre used (with a current limiting
resistor to reduce the voltage to the LED to its rating, feeding it the
pulsating approx 12VDC would be fine as long as it was wired for the correct
polarity.
|
|
Posted by Mark on November 17, 2008, 1:47 pm
> Here is an explanation how it works.
> The bulb would get approx 12 VDC pulses and the 0.7v junction voltage of a
> (silicon) diode would reduce the actual by 0.7V
that is wrong..... it is NOT 12 Volt pulses...
24VAC RMS means is +34 Volts and - 34 Volts peak. Through a 1/2
wave rectifier, the bulb will see 1/2 sinewaves of 34-0.7 = about 33
Volts peak.
Due to the time duration of the sine wave shape and the missing 1/2
cycle the RMS or heating value will be equivalent to about 16.5 volts
RMS. Connecting a 12 volt bulb to 24 VAC throgh a diode is like
connecting it to 16.5 Volts RMS. It will run bright and burn out in
a short time.
Mark
|
|
Posted by kool on November 17, 2008, 2:28 pm
>> Here is an explanation how it works.
>> The bulb would get approx 12 VDC pulses and the 0.7v junction voltage of
>> a
>> (silicon) diode would reduce the actual by 0.7V
> that is wrong..... it is NOT 12 Volt pulses...
> 24VAC RMS means is +34 Volts and - 34 Volts peak. Through a 1/2
> wave rectifier, the bulb will see 1/2 sinewaves of 34-0.7 = about 33
> Volts peak.
> Due to the time duration of the sine wave shape and the missing 1/2
> cycle the RMS or heating value will be equivalent to about 16.5 volts
> RMS. Connecting a 12 volt bulb to 24 VAC throgh a diode is like
> connecting it to 16.5 Volts RMS. It will run bright and burn out in
> a short time.
> Mark
Original bulb is GE 85E not 35E.
|
|
Posted by kool on November 17, 2008, 2:25 pm
>> Jeff Wisnia wrote:
>>> kool wrote:
>>>>> One of the GE Weathertron Model 3AAT80B1A1 thermostats in our home is
>>>>> doing its thing and when the temperature setting is increased a few
>>>>> degrees above ambient the auxillary heaters come on OK to supplement
>>>>> the heat pump's output.
>>>>> The blue "Aux Heat" indicator recently stopped lighting in that mode.
>>>>> I could live with it that way, but being an engineer I'm sort of anal
>>>>> about having everything working the way it was designed to.
>>>>> I suspect it's just a "burned out bulb". The thermostat is old enough
>>>>> so I'd doubt that the indicators use LEDs.
>>>>> Before I approach it, can someone tell me if replacement lamps are
>>>>> available and easily screwed or snapped in place or will I have to
>>>>> figure out what tiny bulb to buy and use my past years of electronic
>>>>> repair experience to solder it in.
>>>>> It would be annoying to toss out an otherwise working thermostat just
>>>>> for the want of a bulb.
>>>>> Thanks guys,
>>>>> Jeff
>>>>> --
>>>>> Jeffry Wisnia
>>>>> (W1BSV + Brass Rat '57 EE)
>>>>> The speed of light is 1.8*10^12 furlongs per fortnight.
>>>> It's a tiny incandescent bulb about the size a Motrin gel-cap , with
>>>> two little wires protruding from the bottom G.E.# 35E. It just sits in
>>>> the hole over a blue plastic lens.(the bulb is clear.) Mounts only by
>>>> the wires soldered onto the wires in the stat.
>>> I soldered in a new bulb yesterday. Tracing the circuit showed that
>>> here's a single diode in the common return lead of both bulbs so the
>>> bulbs effectively see only half of the nominal 24 volt AC supply.
>>> I used a 12-14 volt "grain of wheat" bulb and it works fine now.
>>> Jeff
>> Now that would be RMS voltage and that diode would indicate the bulb is
>> DC rather then AC. basically that bulb has a half cycle to cool and a
>> half cycle the heat and produce light. If all of that is not needed,
>> redesign and install a lifetime LED.
> Here is an explanation how it works.
> The bulb would get approx 12 VDC pulses and the 0.7v junction voltage of a
> (silicon) diode would reduce the actual by 0.7V
> http://www.wisc-online.com/objects/index_tj.asp?objID=SSE402
> By the way, a grain of wheat bulb is incandescant, so it does not matter
> whether you feed it AC or DC. If an LED wre used (with a current limiting
> resistor to reduce the voltage to the LED to its rating, feeding it the
> pulsating approx 12VDC would be fine as long as it was wired for the
> correct polarity.
On this application there is no DC involved. The power to the two bulbs
comes directly off of the "B" terminal on the stat through the diode to one
wire from each bulb. the other wire from the blue bulb (auxillary heat) goes
to the "U" terminal and the second wire from the red bulb (emergency heat)
goes to the "F" terminal. The F terminal is not fan as it also has a G
terminal as well as Y,X2,W, O,R and T. on the BAY subbase. 1981 vintage no
electronics other than 1 diode.
|
Page 4 of 6 < 1 2 3 > last >>
| Similar Threads | Posted | | thermostat calling for heat, not blowing then thermostat switches to heat 2 | October 24, 2008, 8:37 am |
| Looking for a new thermostat? | June 29, 2007, 1:41 pm |
| 2nd thermostat | May 3, 2007, 2:54 pm |
| Need thermostat | September 30, 2008, 11:02 pm |
| Digital Thermostat | July 9, 2006, 12:26 pm |
| replacement thermostat | March 19, 2007, 7:54 am |
| Thermostat recommendations | July 11, 2007, 8:23 am |
| window AC thermostat out of cal | June 4, 2007, 8:54 am |
| thermostat bypass | June 8, 2007, 8:32 am |
| overiding a thermostat | June 25, 2007, 2:00 pm |
|
|
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap