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I would like to disable second-stage heat completely on my Carrier furnace. How can I do that?

Why? => My Carrier furnace often goes into "limit switch fault" and then "limit switch lockout" (more info below). I'm pretty sure this only happens when switching into the second stage and I want to confirm this by disabling the second stage for a while to see if the problem stops. (Also, my house is small and the furnace is *way* over-rated, it doesn't take long to come up to temperature even without the high-heat stage.)

I believe my thermostat is not controlling the second stage, it's done by the furnace itself if it's still on after a certain period of time. The wires being used by my thermostat are Y1, W1, Rc, and G.

Is there a jumper that I can set, or some other way to disable it?

Thanks!

Info from the manual on the two error codes:

Fault Code 33
LIMIT SWITCH FAULT—This fault indicates the limit switch, rollout switch, or auxiliary limit switch is open or unit is operating in high-heat-only mode due to 2 successive low-heat limit trips.

Fault Code 13
LIMIT SWITCH LOCKOUT—This fault indicates the limit switch has tripped 10 times in a row in high fire or 3 times in a row in low fire during a call for heat. Control will auto-reset in 3 hr.
 

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Carrier 2-stage controls typically have a dipswitch labeled "LHT" (low heat only). If this is put in the ON position, the board will NOT use it's internal auto-staging algorithm...it will respond to the inputs from the thermostat only. So if you only have a 1-stage heat input to the control on the W/W1 terminal you will only get first stage operation.
 

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Yep. it is tricky to do.

If you are familiar with moving DIP switches on circuit boards you can move switch SW1-2 to ON and it will stay on low. There are 3 sets of switches so you must get the right one. SW1/SW2/SW3. SW1 package has 8 switches.

There is a wiring diagram on the back of one of the doors and it shows where they are. Or P. 24 in this manual. Do it with the power turned OFF and the thermostat set to OFF and not demanding heat. The turn the power on and the board re-configures itself. Then turn the heat up.

Make sure you touch bare metal on the furnace B4 touching the board so you do not give it a static spark/shock and damage it.

https://www.manualslib.com/manual/747665/Carrier-58mvp.html?page=24#manual
 

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Like yuri said it can be done with dip switches, that being said without knowing whether it is actually happening on 2nd stage or what limit is actually tripping you should probably get that solved first.

Fix it right, not the right now fix


Sent from my iPhone using Tapatalk
 

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this furnace has a variable speed blower so it should be compensating for ductwork to an extent.

it's very possible that it's over-fired on second stage or the ducts are severely undersized.

I suggest trying to figure out why it's tripping high limit on high fire.

Clock the gas meter (http://hvactechhangout.com/home/system-measurements/how-to-clock-a-gas-meter/) and check the temperature rise on both stages. (http://structuretech1.com/diy-furnace-test/)

If it's burning too much gas you have to call a tech for adjustments.

If it's burning the correct amount of gas you have an airflow problem. Check your filter, make sure all vents are open.

Fan speed is factory set and it automatically compensates for ductwork; still may be able to tweak it up a little bit. there may be an adjustment, like plus 10%.
 

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SW 1-4, turn it to off position to raise heating airflow. this may help with the limit tripping. factory setting is on.

page 37 of manual posted in this thread.

granted if the furnace is grossly oversized you may just want to keep high fire off. 80 000 is a lot.
 
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