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To Troubleshoot a Goodman Gas Pack one should understand sequence of operation for gas packs
Gas Furnaces Sequence of Operation – Why is furnace sequence of operation important? If a technician is to properly troubleshoot a gas furnace he needs to know the proper sequence of operation for the particular furnace he is troubleshooting.
Gas Furnaces Sequence of Operation - Troubleshooting
In gas furnace troubleshooting I believe the most common furnace to fail is the furnace that never gets regular furnace preventative maintenance performed. In most cases, you will not need to troubleshoot a furnace if regular maintenance is performed. An annual check of the furnace by a professional HVAC technician will help you avoid many problems that arise in furnaces during the heating season when you really want to rely on your furnace.
Additionally, the best advice is to get your gas furnace a maintenance check and tune-up at least yearly so you will not have to worry about spending any time during the colder months in a cold house. Additionally, worrying if your pipes are going to break and so and so forth. Furthermore, it is truly hazardous to your health and your dwelling not to have a reliable furnace so make sure you get regular furnace maintenance.
The Basics
Additionally, you need to understand the basics of furnaces. If there is any doubt whatsoever, it is best to call a professional and let them troubleshoot the furnace. After all, we are talking about fire and gas that can explode. When in doubt, leave it to the professionals to troubleshoot your furnace. A professional understands basic electricity and electrical components and controls, different types of gas systems, and these system’s functions. They also understand all the necessary things to be wary about with safety. Additionally, and things to look for to stay safe whenever they are troubleshooting furnace systems.
Gas Furnaces Sequence of Operation - Type of Furnace
First, you need to know what kind of furnace it is that is having issues. Then you need to know the sequence of operation for the furnace if you are to troubleshoot the furnace properly. Knowing the sequence of operation will help in troubleshooting a gas furnace. Most HVAC technicians know in any troubleshooting scenario the furnace sequence of operation is important when troubleshooting gas furnaces.
Below, I will run through a few different scenarios for the gas furnace sequence of operation. Additionally, this will help you understand the importance of knowing the gas furnace sequence of operation when troubleshooting a gas furnace.
Gas Furnaces Sequence of Operation - The Standing Pilot Gas Furnace
The standing pilot gas furnace is the most basic of all modern gas furnaces. They are being replaced with newer electronic ignition gas furnaces. The standing pilot gas furnace remains in use. So it is necessary to troubleshoot a standing pilot gas furnace from time to time. With most standing pilot gas furnaces, you will have two major components in the gas furnace that will need to be checked for problems.
Furthermore, the air side of the standing pilot gas furnace consists of a blower motor, a few safety controls, and the blower motor control. The gas side of the standing pilot gas furnace consists of a gas valve, a pilot assembly, the pilot and main burners, and the flue which exhausts the gases after the combustion process is complete. Finally, the sequence of operation for the typical standing pilot gas furnace goes like this:
1. A call for heat from the thermostat
2. The main valve in the gas valve energizes provided none of the safeties are tripped
3. Provided the pilot light is lit the main burners fire and begin heating the combustion chamber
4. As the combustion chamber heats up the fan limit control slowly heats up. As it heats up it reaches a cut-in in temperature for the blower
5. The blower kicks on and runs continuously
6. When the thermostat is satisfied the main burners turn off
7. The blower continues to run to dissipate extra heat out of the heat exchanger. When the temperature reaches the cut-out setting on the fan limit control, the fan stops. Finally, the heating sequence of operation is complete
Standing Pilot
In the standing pilot gas furnace sequence of operation, there are many things going on. A good technician will follow the sequence through to determine where the furnace has a fault and make the repair.
Gas Furnaces Sequence of Operation - There are many different types of electronic ignition high-efficiency gas furnaces in use today. There some that are proprietary to various manufacturers. Then there are some manufacturers that use another manufacturer’s controls for the electronic ignition part of the gas furnace. Additionally, Trane gas furnaces are an example of a company that makes their own electronic ignition gas controls for their furnaces.
Electronic Ignition
For this reason, when you troubleshoot an electronic ignition gas furnace you need to understand the sequence of operation. Especially for various types of electronic ignition systems. You also must understand how the controls work. A good technician can walk up to an electronic ignition gas furnace and figure out basic problems in a few minutes. Furthermore, for the sequence of operation for an electronic ignition gas furnace see this article.
Of the different types of electronic ignition gas furnaces, there are direct-fired gas furnaces and indirect-fired gas furnaces. The indirect-fired gas furnace uses a pilot light. The direct-fired gas furnace lights the main burner ignition without a pilot light. The key in both systems is that each electronic ignition system has it’s very own method of proving the flame or proving the fire exists. Lastly, if no fire exists then the system shuts down to prevent gas from being spewed into a where it can become very hazardous.
Gas Furnaces Sequence of Operation
I have a high efficiency trane gas furnace that when the thermostat is turned up a couple degrees the burner come on and before the temperature is met it shuts down and cycles several times before the temperature is met. Is this normal?
The unit is not quite two years old. Last winter during the cold spell the condensation drain line froze and backed up shutting the unit down until I got it thawed out with a hair drier. The installer has now insulated the drain line and no problems this winter.
No, it does not sound normal. I’m thinking its something electronic. You need to call the HVAC contractor to look at the problem for a repair. Not really enough information here to make a solid determination of what is going on.
I have a Coleman furnace. The thermostat calls for heat, The furnace begins to cycle, the furnace cycles, blows warm air. The hi-limit trips,(4 flashes) turning off the burners. After warm air leaves the plentum, the hi-limit resets itself, and the furnace continues till the thermostat is satisfied. Does this sound right?
If you have good airflow then it sounds like you either have a bad limit switch or it could have something wrong with the heat exchanger. It will require you to make a call to an HVAC contractor to inspect it, troubleshooting, and make a solid diagnosis.
Before you call a technician, take the indoor temperature and the temperature of the hot air coming from the furnace, if it is more than 60 or 70 degrees difference make sure the filter is clean, the vents are all open try leaving doors open to where vents are located, if the temperature does not change much call the technician for the low air flow. Loose belts, a motor trying to fail, or a motor not wired for the
proper rpm,loose insulation causing restriction, a duct system improperly designed are the most common problems. It could be a poorly functioning limit switch or limit switch set to high. It could be too much fuel input. When the furnace is operating properly it will extend the life of the furnace.
Thank you so much sir…it helps me a lot.
My furnace is running and hot air is coming out of the fresh air make up pipes. Prior to the make up air being installed, the furnace would shut off. I had to take the panel off to get enough make up air. Then the outside make up air (two 3″ PVC pipes) were installed.
The furnace is running this morning and steam is coming out of these pipes. Is this normal? It seems that they are acting as an exhaust system instead of a make up air system.
Comments?
I’m thinking what you are describing here is a condensing furnace where you have an intake (one of the 3″ PVC pipes) that pulls combustion air from the outside as designed. This is good especially for tight houses. Older furnaces do not have this and derive the combustion air from inside the home. This air is in no way used inside your home as it is strictly used for combustion air so the furnace has enough air to safely burn the gas. The 3″ PVC pipe is the exhaust pipe where the products of combustion are exhausted outside the home. Unless you live in the far North then it is unlikely you have any sort of make-up air system. Make-up air systems are used in commercial buildings to bring fresh air in from the outside because some of the old stale air is being exhausted for various reasons. It is in the code for commercial buildings that they have so many changes of air per hour depending on the purpose and use of the building. This reduces the CO2 level inside the building and increases the fresh air into the spaces inside the building. For example, a movie theater requires more changes of air per hour than an office would. As far as I am aware, there is no code for this in residential systems except some places up in the Northern reaches of the country and only in new construction where the homes are designed and built to be super tight. So you likely only have an intake for combustion air only and an exhaust to exhaust the combustion fumes. And it is normal for steam to come from the exhaust pipe. The intake pipe I would say no as it should be sucking air into it and not exhausting anything out of it.
Nicely done. Clear,precise & accurate information.