Setting Gas Pressure on a Modulating Gas Furnace

[@ryanmurray3034]

feb 2023 and this still helps out a lot thank you!!

[@dominiquepierre916]

Hello I did modulating gas furnace valve setting like your video but still code 33 (over heat ) Filter clean ;all registers open . So frustrated of this furnace.

[@TECTubefilms]

Dirty filters and high gas pressure is two of many issues that can cause a limit trip. Start your troubleshooting by getting a supply temp reading, a temp reading from the limit switch location, and an external static pressure measurement. Then if you are a contractor, contact your local distributor's tech support with that information for next steps. If you are a homeowner, your HVAC dealer should be measuring this stuff for you.

[@davidlopan6649]

At around 11:56 you hit SW3-#2 on not SW1-#2

[@snaplash]

The manual for the 987M says to use the pressure tables, which have different rows for Avg, gas heat value at altitude, and 4 columns for Specific gravity of natural gas, Is it necessary to use these, and if so, how do you find the heat value and specific gravity numbers for your gas supply?

[@S0uthflorida]

19 minute video on how to set a gas valve lol ty btw

[@tomo9091]

Great help

[@dominiquepierre916]

Very great vidéo I have question; When we finish our setting on max fire and then we want to go for min fire ; Do we need to turn the furnace off while removing jumpers and stting the dip switches Or we have to do it while furnace is on ?

[@damon8201]

Shouldn't matter

[@EnjoyCalculus]

I'm not understanding how you kept the furnace in low fire mode. Surely different brand furnaces have different settings to keep the unit in low fire mode. I'm assuming this would be in the product manual

[@TECTubefilms]

We assume you are referring to getting it to low fire while you set gas pressure or other service needs. You can either use the jumpers like Dave described in the video or you can use the “check-out” screen of the communicating wall control. If you are talking about during normal operation, the wall control handles the staging as a function of its PID based on current deviation from setpoint and it’s rate of change. If you want to lock it in low fire permanently and never let it go to high fire again, we can sent you a separate video on that.

[@EnjoyCalculus]

@@TECTubefilms could i just jump R to W1 and leave W2 alone. Would that keep it in low fire mode so I can set the low fire gas pressure?

[@sunnytang3009]

@@EnjoyCalculuswhen SW1#2 IS OFF only R to W/W1 closed it has about 15 mins of Minimum Heat operation & then Maximum heat operation. so you need to turn on SW1#2. PS: He made a mistake, he thought SW3 was SW1, SW3 is for airflow & SW4-2 is for Intermediate Heat operation ( need to be OFF)

[@user-tq9cj2gs1g]

His drip leg is before his shut off valve

[@RalphsHeating]

I assume you are adjusting the gas pressure based on the temperature rise?

[@TECTubefilms]

You are adjusting it to make sure it is within the spec range. But then if you want to fine tune it within that range, you can look at temp rise.

[@JurassicJolts]

Can pulling the communicating plug like that damage the board? As opposed to turning the power off first

[@Balticblue93]

It really isn't the best practice, but it is pretty much the same thing as flipping the power switch. If you do it in one smooth motion, the system wouldn't know the difference as long as the connection is firm on placement and a quick removal to began with.

[@cliveramsbotty6077]

why are you going by burner pressure on a modulating burner instead of a flue gas analysis?

[@TECTubefilms]

We follow the manufacturer's installation manual which for this furnace (59MN7A) you can download at carrier.hvacpartners.com/products/detail/59MN7

[@TECTubefilms]

If after setting up the valve based on gas pressure, you then hook up your combustion analyzer to further check operation, we have no issue with that at all.

[@sunnytang3009]

@@TECTubefilms It still depends on Altitude

[@TECTubefilms]

We are a distributor that only services dealers in the Midwest… we don’t have “altitude.” LOL

[@darceltellis6881]

Training videos need accurate information. SW4 is to the right of SW1. The DIP switches below SW1 are SW2, SW3.

[@cynthiaroutin5644]

HELP - new install. Carrier infinity code 14 lock out fault - tech adjusted gas. Then got code 126 high heat fault - tech cut vent into trunk on top of furnace. Was told cutting a vent on top of the furnace would correct high hear fault. It did not correct the Fault 126. What should be done?

[@TECTubefilms]

If someone is recommending cutting an extra register into your supply or return duct to solve a high limit issue, it means that they either a) they grossly oversized the equipment that you need, b) the ductwork is very undersized relative to the furnace, or c) there is another issue that is misdiagnosed.

[@tylerhmmng]

I’m confused as to why you mentioned SW1 #2, when you make changes to SW3 #2. Or was that an error?

[@sunnytang3009]

He made a mistake, he thought SW3 was SW1, SW3 is for airflow. 1: Turn ON SW1-2 when using a two-stage thermostat to allow * Minimum Heat operation= when R to W/W1 closed Maximum heat operation= when R to W/W1 and R to W2 close 2: Turn ON SW4-2 when using a two-stage thermostat to allow * Intermediate Heat operation = when R to W/W1 closed Maximum heat operation = when R to W/W1 and R to W2 close When SW1-2 and SW4-2 are OFF allowed Modulating operation with a single-stage thermostat. (when R to W/W1 and R to W2 close it will have Maximum heat operation all the time) ( when only R to W/W1 closed it have about 15 mins of Minimum Heat operation) he got it right by luck.

[@johnd4348]

do we really need the music.

[@dominiquepierre916]

To be honest this brand is not good ; The gas valve fails a lot ;

[@TECTubefilms]

A lot? How many failed gas valves gave you seen on Carrier modulating gas furnaces?

[@dominiquepierre916]

@@TECTubefilms A lot Many times I have seen code 35 failed gas valve. The ignitor turns red but it does not shoot the gas .

[@TECTubefilms]

How many is a lot? 5 furnaces? 50 furnaces? We buy several hundred furnaces per year with these gas valves in Carrier, Bryant, Heil, and Day & Night units and have very low warranty claims on the gas valves over the past 9 years. At last check, it was less than 20 claims… out of almost 4,000 furnaces.

[@TECTubefilms]

We do have a 59MN7 in one of our training labs that we fully disassemble and reassemble every week. And we have the newbies adjust the gas pressure when re-installed. Sometimes some turns the screw too fast and/or too hard and it does damage the valve. Small adjustments are needed. Maybe that is contributing to what you are seeing in the field?