Ever find yourself troubleshooting a faulty coffee roaster burner? If so, you’ve come to the right place. We’ve put together a guide to diagnosing your burner issue and resolving its root cause. Before we begin, we should note that many of the images come from components on the P Series Probat Roasters but the diagnostic paths below pertain to most all industrial coffee roasters including our both our B270R and B540R. Let’s get started.
If you start your roaster and it won’t light, you’ll need to follow one of two diagnostic paths in order to remedy the situation…
The Burner does not try to light
In general, the burners on all industrial coffee roasters are going to need air, fuel, and spark to light.
The air is provided by the combustion fan. Check to make sure that the fan is running. There is a pressure switch associated with keeping the fan running. Ensure that input is on. (Inputs vary by roaster)
There are also pressure switches on the exhaust air side. Those need to be checked too. (Again, inputs will vary by roaster)
Next we can take a look at the gas. Check to ensure that the gas is turned on and that there is sufficient pressure. There are high and low pressure switches associated with the gas pressure. Ensure they are in the appropriate state. Low should be on and High should be off. (Inputs will vary by roaster, so be sure to check the manual)
There is a gas valve positioner that controls how much gas is allowed into the burner during any given phase of roasting. This could be out of adjustment or inoperable. If you suspect this to be the problem item, the gas valve positioner will need to be assessed by a Probat service technician.
If you have air and fuel, then the last item to take a look at is the ignitor.
The ignitor is a sort of specialized spark plug. This is the most complicated item to check but can be done if you’re comfortable around live electrical items and confident in your abilities. Do keep in mind, however, that when you attempt to complete electrical type repairs on your own you put your own health, the health of others, and your property at risk. Please only proceed if you are experienced in this area.*
To check the ignitor, remove it from the threaded hole. There are two types. One looks like a conventional spark plug. The other looks like a ceramic rod with a metal tip. Pictured below are images of both the component itself and also how it would appear via looking into the top of a variety of industrial coffee roasters.
To test the conventional spark plug looking ignitor, grab the body of the ignitor with insulated pliers, and hold the ignitor body against an uninsulated part of the roaster. (an exposed bolt thread for example)
When you try to start the roaster, you should see a spark jump the gap from the center electrode to the metal tab.
To test the other style ignitor, again hold the body of the ignitor with insulated pliers, and place the metal tip close to an uninsulated part of the roaster.
Again in this instance, when you try to start the roaster, you should see a spark jump the gap from the center electrode to the uninsulated part of the roaster.
The burner tries to light but fails.
Path 2 indicates something more subtle, but still on the order of some condition not being met.
If the burner tries to light but then stops or goes out, then the possible culprits are;
- Marginal air, water or gas pressure, or the flame sensor. The pressure is just enough to get the process started, but then fluctuates causing the process to abort. This could be due to actual pressure fluctuations or faulty sensors giving fluctuating readings. This is especially true when dealing with gas pressure. If the supply volume is insufficient to support the burner needs, which are generally higher at startup, then these demands of startup can cause the pressure to drop.
- If the burner lights but the flame then goes out within a few seconds, it could be the flame sensor. When working with a flame rod type, the flame sensor can be checked by using a torch to apply heat to it (a lighter isn’t sufficiently hot.) Alternately, if you are working with the UV type, you can check the flame sensor by simply holding a flame (a lighter works well here) a few inches in front of the sensor.
- If you do this when the burner lights and it then stays lit, then the flame rod/sensor is defective.
The UV type sensor has a glass window on the front of it. The flame rod just looks like a ceramic rod. Refer to the images above for a visual on both the placement of the sensor within an open roaster, as well as the component itself where the ceramic rod is exposed.
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*The information contained herein is not mean to be comprehensive and is for informational purposes only. You should not undertake to perform anything described herein without adequate training and/or supervision. The Author disclaims any responsibility for any injury, damage, or loss as a result of reliance upon the information found on this site/blog.