circuit boards

Can anyone tell me what year that gas furnaces began using solid circuit boards?
Also a lot of today's circuit boards will allow the blower motor run after the system shuts down. Can you tell me for how long it will allow the blower to run?
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Moe Jones
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25 years?

Depends on the board. Some you can adjust to various runs....

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Depends on the brand. 20 to 30 years I'd guess.
Generally somewhere between 30 seconds and a couple minutes. Some are adjustable. Before circuit boards some still did this but just with a delayed release relay. You can still buy them.

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1968...before that time all gas furnaces all used liquid circuit boards.
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Jeffry Lebowski wrote:

Not gas??
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Circa 1981.
-zero
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Moe Jones wrote:

Moe;
The very very first boards I saw were on 1974 Day & Night [Bryant] gas furnaces. They essentially were just so you could plug in the fan relay [R80128 Honeywell ?]. They had two relays [one for high speed fan - the other for the Electronic Air Cleaner]. Although there may have been some earlier.
The next circuit boards I saw came out in the condensing units by Carrier around 1974 - 1976 which at that time were called a CPCS [Compressor Protection Cycle System] which really was not much more than an over current protection monitor with anti short cycle. [7 minutes normal - 10 minutes on power failure.]
Then around 1979 or so, the intermittent pilot's starting showing up, and the boards started to provide timing for the indoor blower on heat. Today of course the boards are much much more computer oriented with WAN connection ability, HISTORY logging, and motor speed, gas valve timing control.
Was that helpful? I provide this only as a free service to other technicians in the HVAC/R trade.
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Zyp



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Zyp wrote:

Yes thank you. Another technician and I have questioned a control that is sold around here and I think it is not worth selling but to older furnaces.' The control allows the blower motor to run after the system shuts down for 3 minutes.The control is mounted under the thermostat and has a LED that tell the home owner that the control is working The other tech says that his customers like to see the LED glow and that the controls runs for the full 3 minutes. To me with furnaces around 10 years old can do the same but I am not too sure of a 3 minute run time for the circuit boards.
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Moe Jones
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Moe Jones wrote:

It has been my experience that "we all" like shinny things. Look at beer cans for example. Another good example is bass fishing boats. Put enough glitter on it, we'll buy it! ROFL
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Zyp



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