3 Ways to Keep Your Pellet Heater Glass Clean

Cleaning the glass door on a pellet heater is easy, it’s keeping it clean that can be difficult. Below I’ve listed 3 ways to keep your pellet heater glass clean. As I’ve mentioned elsewhere, pellet heaters need regular maintenance and I clean my glass door about once a week. However, the glass door on a pellet heater can turn black or get dirty due to many reasons. So what makes the glass on a pellet heater change colour and eventually get dirty or black? It has to do with pellet quality and airflow. While there’s no way you can prevent the glass from getting dirty, if you follow the tips below you’ll minimize the amount of cleaning required.

  • Pellet heater glass gets dirty due to poor quality pellets, improper airflow, or lack of regular cleaning. Use good quality pellets and clean the glass weekly.
  • Have your pellet heater professionally installed and tuned for optimal airflow. This ensures an efficient, clean burn and minimizes glass soot buildup.
  • Perform regular maintenance like emptying the burn pot and deep cleaning the heater yearly. This prevents ash buildup which restricts airflow.
  • If the glass turns black very quickly, do a deep clean and check pellet quality. It likely indicates an airflow issue that needs addressing.

Pellet Quality

One of the biggest reasons glass doors on pellet heaters turn black is due to poor quality pellets. Were the wood pellets stored properly or are they just cheap pellets? Wood pellets that aren’t stored properly, meaning off the ground and in a dry area out of the rain, will contain more moisture and won’t burn as easily or as clean. Cheap pellets usually produce more ash and may leave clinkers in the burn pot. They burn dirty because of the impurities they contain. If old pallets are broken down and turned into wood pellets, then it’s possible they’ll contain chemicals and other materials that will not burn properly or cleaning.

Expensive wood pellets often come from high quality raw material, which is cleaner and it’s why the burn cleaner. Usually it is sawdust or waste wood material that is left over from processing timber. This kind of waste wood material is usually very clean and very high quality. Because it’s so clean, it burns extremely well but it’s not cheap and wood pellets made from this kind of material usually cost more. If the glass door gets dirty quickly, it could be your pellets. More expensive pellets burn cleaner but some people would prefer to have a dirty glass door and keep the money in their wallet than burn it in the heater.

Exhaust Fan Speed

Another reason the glass door gets dirty is because the pellet heater isn’t tuned properly. Tuning here refers to the exhaust fan speed, the feed rate which determines how often pellets are fed into the burn pot and how well the fire in the burn pot is burning. Exhaust fans need to be tuned just right so that the fire in the burn pot is burning correctly. If a flame is burning slowly, it’s called a lazy flame. A “lazy” flame will not burn as hot and as efficient and will result in more ash and a dirtier glass door. A flame is “lazy” because there isn’t enough air flowing through the heater creating an efficient fire.

Likewise, if the exhaust fan speed is too high, the fire will be burning too fast. This means pellets will be burnt too quick and you’ll go through a bag of pellets much faster than you should, costing you money. This kind of flame won’t turn the glass door on your pellet heater black, but it will mean you are wasting money. You can easily adjust the exhaust fan speed but the tricky part is getting it right so the flame is burning correctly. This is why it is important to have your pellet heater properly installed. Changing the exhaust fan speed without knowing what you are doing will result in a less efficient and dirtier burn.

Ash Buildup

Pellet heaters need to be regularly cleaned. As I’ve mentioned elsewhere on this website, you should be emptying the burn pot once every few days, cleaning the burn chamber once a week and at the very least doing a deep clean and service once a year where you vacuum out exhaust ports in the pellet heater and clean the flue. It doesn’t matter if you burn expensive or cheap pellets, there will always be ash left over and some of this ash builds up within your pellet heater. Not cleaning this ash out restricts the airflow and this will cause the fire in the burn pot to burn not as efficiently.

Much like an incorrectly tuned exhaust fan, restricted airflow due to ash buildup will result in a poor and dirty burn in a pellet heater. Poor airflow will result in more ash, turn the glass door dirty very quickly and possibly have more clinkers than you normally would. Just cleaning out the burn chamber once a week isn’t enough. No matter how expensive or how clean pellets burn, there will be ash slowly building up inside the pellet heater and flue. Just because you can’t see the ash doesn’t mean it’s not there. Pellet heaters should be deep cleaned once a year to ensure airflow is not restricted and the fire can burn efficiently.

How to Keep Pellet Heater Glass Clean

So, what can you do to stop the glass getting dirty so quickly? While there’s no way to prevent the glass from getting dirty because wood pellets are made from wood and wood produces ash, after all pellet heaters burn wood and wood produces ash, there are a few things you can do to ensure the glass stays clean as long as possible.

Perform Regular Cleaning

As I mentioned above, I clean the glass door on my pellet heater once a week. The longer you don’t clean the glass door on a pellet heater the dirtier and blacker it will get. This makes it harder to clean due to the buildup of soot. Some people will clean the glass daily and others once a month. How often should you clean your glass door? This is a personal choice but I think cleaning once a week is a nice middle ground. The glass doesn’t get too dirty, so it’s still easy to clean and you can still see the fire. However, if you enjoy seeing the fire, then you may want to clean more often.

Burn Quality Pellets

Next, if you enjoy a super clean glass door on your pellet heater because you like looking at the fire, then I recommend burning medium to high quality pellets. The downside here is you could pay up to 50% more for higher quality wood pellets to get a cleaner burn. Is it worth it? If you are only using your pellet heater a month or so a year, then you probably won’t spend much more money. However, if you run your pellet heater 9 months of the year for heating, then obviously this could turn out to be very expensive. How much money are you prepared to pay to keep the glass door clean by burning more expensive pellets?

Use Professional Installation

I am all for people doing DIY cleaning on their heater (one reason I created this website), provided they are doing it properly, but I think a pellet heater is best installed by a professional. The main reason being pellet heater installers know how to tune the exhaust fans to get an optimal burn. I see all too often people online posting about how their pellet heater is burning dirty. The majority of them have installed the pellet heater themselves and didn’t adjust the exhaust fan to get an optimal burn. Pellet heater manufacturers have guidelines on what levels of airflow are needed to ensure a clean burn and usually only professionals have the tools to measure this correctly.

Warning: Extremely Black Glass

Is your glass door on your pellet heater turning black quickly? While it is normal for glass doors on pellet heaters to get dirty and eventually turn black if you don’t clean them, it is NOT normal for a glass to turn black after one day. If you clean the glass door and after just 8 hours of burning the glass has turned jet black, then this is a good indication there is a problem with your heater, usually airflow. If this happens I’d strongly recommend doing a full deep clean and check the quality of your pellets or book your pellet heater in for a service. If you don’t you’ll also probably start getting an E5 error code.

Dirty Glass Door Summary

It’s normal for the glass door on a pellet heater to get dirty and eventually turn black. It’s caused by poor quality pellets or restricted airflow due to needing an exhaust fan tune or a deep clean. If a dirty glass door worries you, clean the door frequently and burn good quality pellets. If you notice the glass getting very black very quickly then deep clean or book your pellet heater in for a service.

Pellet Stove Glass Gets Black – What to Do?