Ultralow NOx furnaces, what are they and should I replace my furnace with one, or should I switch to an electric heat pump? Hi, I’m’ Mitch Bailey, and I am going to help you answer these questions.

Unless you have been living under a rock, you have heard about the push to get rid of everything that uses fossil fuels in California. This is the push to electrification for the state. The goal is to reduce and eventually eliminate the pollution and carbon output from fossil fuel appliances and vehicles in the state. California’s lofty, however in my opinion misplaced goal, is to completely ban gas furnaces, water heaters and gas stoves by 2030, in addition to appliances they plan on banning gas cars sold in California by 2035.

However, you might not know that for many in California a change has already taken place. Depending on where you live in the state of California, you have no choice but to replace your furnace with an Ultralow NOx or ULN furnace. Let me explain what a ULN furnace is, the reasoning that brought us Ultralow NOx furnaces, the science behind the regulations, where this science is misleading, where it all goes wrong, and despite all this, the actual reason that I actually recommend that you not purchase a ULN furnace, and instead make the switch to a heat pump.

Prior to 2018 there was no such thing as an Ultralow NOx furnace, they didn’t exist. So, why do we need them and how did they come about. For this we have to go back to 1978 when the California South Coast Air Quality Management District (SCA) adopted rule 1111. Almost three decades later in 2005 the San Joaquin Valley Air Pollution Control District (SJV) adopted their own rule 4905. Both of these rules established a mandate to reduce the quantity of nitrogen oxides emitted by gas furnaces, from 40 nano grams per joule to 14 nano grams per joule, a 65% reduction of NOx.

You see, nitrogen oxides or NOx is produced when we burn fossil fuels. Cars, furnaces, water heaters, and gas stoves all create NOx as a byproduct of combustion. This NOx that we put in the air combines with volatile organic compounds (VOC’s) to become smog. In turn, the UV light from sunlight reacts with the smog to create ground level ozone. The higher the concentration of NOx, and VOC’s, combined with higher summer temperatures and extended daylight hours facilitate the creation of greater and greater concentrations of ground level ozone. Ground level ozone is a carcinogen, so the EPA set a maximum level of 70 parts per billion to eliminate the adverse health effects.

However, each year the level of ozone in areas served by SCA and SJV exceeds the 70 parts per billion. These areas in the Central valley and LA basin have a recurring weather phenomenon that develops on a regular basis. Topography plays an important role along with the moderate weather that California is blessed with. This weather phenomenon is called an inversion layer. In the summer months the Central Valley and the LA Basin, which are surrounded by mountains, develop an inversion layer with warmer air at higher altitudes and cooler air at ground level. This inversion layer holds in all the pollutants in the air like the lid on a pot. This does not change unless a low front moves through with winds to mix the upper layer with the lower layer and thus blowing out all the smog. When high pressure sits over California the inversion layer forms and holds this smog mixture at ground level and concentrates it, thus occasionally exceeding the 70 parts per billion several days a year. In the linked video I show demonstrate this for you. This demonstration is a good representation of an inversion layer that accurately simulates what occurs over the Valley and the LA Basin with cold air at ground level and warmer air aloft. Now, if a low-pressure system comes through, it will stir the air causing the cooler air below to mix with the warmer air aloft and the two layers will combine. This in turn clears out all the smog. California exceeds the 70 parts per billion set by the EPA only when inversion layers develop. The science is very sound on this. However, as I will explain at the end SCA and SJV are using this to mislead you and in my opinion lie to you, more on this later.

So, in 2015 both SCA and the SJV mandated that manufacturers build a furnace that reduced the current allowable levels of NOx by 65%, this is how the ULN furnace came about, because no such furnace currently existed. They gave manufacturers four years to build such a furnace. In the interim, heating and air contractors were allowed to continue installing standard furnaces and pay a mitigation fee for homes in SCA or SJV territories. However, these air districts put a hard date that completely banned standard furnaces, October 2019 for SCA, and April 2020 for SJV, after which they would no longer allow a standard furnace to be set and pay a mitigation fee, they required all furnaces that are replaced be ULN in these districts.

Subsequently, the manufacturers dutifully complied and designed ULN furnaces, or at least a few did, many brands instead of developing their own, bought the design from other manufacturers. In 2018 the first few pilot furnaces were being installed in homes and being tested. That’s when I began to hear stories from the contractors installing them. These contractors were saying that the new units were having multiple problems. About the same time as I was hearing these stories I attended training on the upcoming release of these new furnaces, and after that training I could easily see problems with them myself. At the trainings I learned that these ULN furnaces had a narrow band that the gas pressure had to be set to, while standard furnaces have a much wider band of pressure. What makes this bad is the fact that if the gas line going to the furnace is not sized adequately, problems will arise when the furnace is running and the water heater or gas stove is running at the same time. The gas pressure could drop as these other appliances come on and drop the gas pressure out of that narrow band or range it needs to be operated in. In addition, the design requires a burner chamber that is sealed with the flames from the burners not visible to the technician. This removes one the greatest indicator used to determine when a furnace might have a cracked heat exchanger. Not having this ability to visually monitor the flame, in my opinion, can be potentially dangerous for the customer. And finally, since this was first generation and not a tried-and-true technology, combined with all the stories I heard about them, I made the decision not set ULN furnaces. We advise our customers to install a heat pump and avoid ULN furnaces when it is time to replace their system.

Unfortunately, I am talking from experience about the problems with Ultra Low NOx. Even though we advise our customers to stay away from Ultralow NOx does not mean that all the customers took my advice. Being in business means that we would do what the customer desires, and in some cases, this meant installing a ULN furnace. Every ULN furnace we installed has had some problems. The biggest problem is how low we have to dial down the gas pressure to mitigate a harmonic sound that these furnaces would make when operating. The attached video has one of the ULN furnaces acting up and I having to adjust it to get rid of the sound, which is deafening and sounds like a smoke alarm going off. But that is not all, after adjusting the pressure to eliminate the sound we have been finding that the efficiency of these furnaces are no longer within specification. The efficiency drops from 80% down to around 66%. That means that the customer is now wasting 34 cents on every dollar. This loss in efficiency alone should keep you from setting an ultralow NOx furnace, and switch to a heat pump.  

Speaking of efficiency, furnaces come in several efficiencies, 80% being standard and 90+ the high efficiency version with the higher efficiencies between 92% and as much as 98% depending on the model and brand. However, the majority of standard and ULN furnaces that are installed are 80%, I would estimate better than three quarters of the units today are 80 percenters. This percentage, 80 or 90+, is based on the AFUE rating or annual fuel utilization efficiency. Basically, it is just as it is stated, with an 80% furnace every dollar you spend on heat 80 cents of that dollar is delivered into the home while the other 20 cents of heat is exhausted out through the flue. While a 95% furnace only wastes 5 cents through the flue. Because some furnaces are only a couple of percentages off from 100 percent you might think that they can be very economical to run. However, a heat pump is actually cheaper to run at today’s prices for natural gas compared to a heat pump at today’s electric rates.

Before I go any further allow me to explain what a heat pump is and how it works. Simply stated, a heat pump is your air conditioner working in reverse. Air conditioners absorb heat from the air inside of the home and rejects that heat outside. We call this the refrigeration cycle. The refrigeration cycle uses a refrigerant to absorb the heat from the air inside the home as it passes through the indoor coil, the refrigerant evaporates in this coil and during this evaporation it absorbs heat. The vapor refrigerant is then pumped to the outside coil where it is condensed back down into a liquid, as the refrigerant changes from a gas to a liquid in the outside coil it rejects the heat that was absorbed from the air inside home into the outside air. The prime difference between an air conditioner and a heat pump is that a heat pump has a reversing valve. The reversing valve changes the direction that the refrigerant flows so that heat is absorbed from the outside air as it evaporates inside the outside coil and then is pumped back to the inside coil where the refrigerant condenses back into a liquid and rejects the heat it just absorbed from the outside air into the air inside the home. There are a few other parts thrown in to make this process as efficient as possible.

Furnaces use AFUE, while Heat pumps use HSPF or Heating Seasonal Performance Factor to rate their efficiency. However, a better matrix that we can compare operating costs between a furnace and heat pump is the COP or Coefficient of Performance. The COP is the amount of BTU’s that a heat pump will produce divided by the power consumed or wattage. Since we know how many BTU’s to Watts we can determine how much it costs to produce a million BTU’s at a given COP. As for natural gas, it is sold by the therm, whereas a therm is equal to 1050 BTU’s we can use this to calculate the cost for a furnace to produce a million BTU’s and compare that to the heat pump. A few years back I created a spread sheet and chart in order to compare the cost to produce a million BTU’s using LPG, natural gas, and a heat pump, and it shows that it costs less to produce a million BTU’s with a heat pump than a 95% gas furnace. In addition, several utilities like SMUD, MID and TID reduce their electric rates in the winter which equates to even more savings if these utilities provide electricity to your home.

I want to make it clear; we decided not to use ULN furnaces and switch to heat pumps not only because we were trying to avoid potential problems that ULN furnaces may have, but we also made this decision because it makes economic sense to use a heat pump as they are cheaper to run, in addition heat pumps use tried and true technology.

Earlier I had said we were being misled. I saw this happening back in 2015, when the air quality districts enacted their rules and started charging a mitigation fee, I tried in vain back then to get the supply houses, other contractors, and manufacturers to join forces to put together a war chest and hire attorneys to fight this mandate of ULN furnaces and the interim mitigation fee. Remember how I said that these air pollution districts were misleading you and lying to you? Well they are, and here is where they have misled you. Back in 2015, when all this began for me, I took a look at the data they were using to justify these mandates, and I saw a glaring lie that they used to justify these changes. You can see this data yourself by going to this link http://www.valleyair.org/waaqs/naqiapp.aspx?a=Merced,%20CA,%20USA See this chart, look closely and you will see that we do exceed the 70 parts per billion of ground level ozone during the year. Furthermore, these charts also show when this actually occurs. Notice the time of year that the levels are exceeded? Yep, they are all in the summer months, none in the winter months. I don’t know about you, but I don’t run my furnace in July. This was confirmed by an individual high up that worked for SJV, he told me that they considered furnaces “low hanging fruit”, that they could mandate something, and the manufacturers would just do it. They did this even though they knew that it would have no effect at all on the actual days that we exceeded the 70 parts per billion. Those days that it does exceed the 70 parts per billion is actually from vehicle emissions, long summer days, high summer temperatures and the inversion layer that plagues us during the summer.

What is even worse is the amount of money that has been wasted on these regulations from the millions in mitigation fees to the millions the manufacturers spent producing an expensive and finicky furnace that is only made for certain parts of California. When you consider that all this was completely unnecessary and would have no effect at all on the goals they were trying to meet. Then you can see where regulators with the stroke of a pen can wield unbridled power to bully the private sector and waste millions in precious resources and dollars. Even worse, because I am not the only contractor that chose not to install ULN furnaces, many of the suppliers now find themselves in a predicament because of their non-action to nip this in the bud before it became the problem as it now exists. Now many of the suppliers and manufactures have inventory of thousands of ULN furnaces they are having trouble getting rid of. Again, this costs the industry and the public resources and money needlessly.

Finally, there was nothing wrong with standard furnaces and the central valley and LA basin has paid the price. The bureaucracy and elected officials that run the state have already decided not to keep fossil fuel appliances and switch everything over to electric, heck they are even banning gas cars which is the most boneheaded move anyone could make. Think about it, banning something before the infrastructure is in place, this could literally be the definition of stupidity. And now for the 900-pound gorilla in the room, another thing that is not being considered is that solar and wind are too unreliable to provide consistent power that is needed for our 39 million residents. So, we must build more gas fired power plants to provide all the electricity we need when the sun does not shine, or the wind does not blow. Last year the Governor of California had to sign an emergency order authorizing gas power plants to keep California from having rolling blackouts as detailed in these articles. Think about it this way, you are replacing your gas appliance or vehicle with an electric appliance or vehicle to get rid of fossil fuels, yet I will now be getting my electricity generated from a gas powerplant, so you are actually achieving nothing by trading my fossil fuel vehicle or appliance to get electricity generated by a gas powerplant, this is yet another definition of stupidity.

Now that I have gotten that off my chest, I still feel the heat pump is the best choice. However, I think you should also consider dual fuel. In some cases I recommend that you keep your existing furnace and replace only the coil and the outdoor unit with a heat pump. This is the best of both worlds. You use the heat pump most of the time to heat the home, and on the coldest nights you can use the furnace as backup. This minimizes the use of gas to heat your home, satisfying the reduction in NOx and carbon pollution, in addition to costing less to run. The only drawback to this is that they are not a matched system that will get you energy rebates or tax credits, as this combination will only be standard efficiency and not high efficiency. However, if the existing furnace is old, it would be better to switch out the complete system from natural gas to heat pump. In short, heat pumps have been around for decades and are quite efficient. They are definitely a better choice over Ultralow NOx furnaces.

I hope you found this informative, and you learned enough to make a proper decision on replacing your system with a heat pump that will help make you comfortable while saving you money.