Why Can’t We Crank the Heat AND the AC?

We’re entering the awful, awful season where mother nature will swing between very warm and very cold. Just last week we had a good four inches of snow, a high of forty degrees, and a low below freezing, only for a high of over fifty the very next day. This weather calls for both heating and cooling in some circumstances, but we can’t always give you both.   Fond, Freezing Memories The schools I went to growing up had a very annoying problem: they could heat or they could cool, but they could not do both. This was always problematic and stupid to kid-me sitting at his desk contemplating a textbook bonfire for warmth. Of course, it’s wasteful to run the heating and cooling at the same time, but surely we can just turn off the furnace and crank up the AC? We’ve done it in the car all the time, you just twist a knob and you go from freezing to roasting and vice versa. At small scales, climate control is pretty easy to accomodate. You use air ducts and mix hot and cold air to get the net desired temperature. Facilities with forced air heating and cooling can pretty readily fling themselves from one temperature to another like your car. Other facilities have completely separate systems for heating and cooling. There might be a little split AC unit in every room and a master hot water heating system. […]

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Fire Safety in Live Systems

Industrial and residential settings increasingly have one big thing in common: you can’t eliminate all the hazards. When a fire breaks out, we want our buildings and our equipment to default to a “safe” state. We want to shut off gas valves, kill electrical breakers, and get anything explosive like propane bottles and gas cans as far from the fire as possible. Unfortunately, some situations are not this simple.   Standard Residential Procedure When a house fire breaks out, the fire alarm goes off, you evacuate, and at some point the local emergency dispatch center hears about it and dispatches fire fighters, police, and EMS. Their first priority is to get everyone out alive. Along with that they need to prevent the fire from spreading to nearby fields and buildings. Lastly they’ll try to save as much of the structure as possible, but sometimes all they can do is watch it crumble. The process of actually handling a fire is a multi-stage exercise in chaos. On scene, fire fighters need to run hose line to spray water, teams have to enter the building to locate trapped victims. Part of the crew has to set up a constant water supply, either from a hydrant or a relay team of tankers that will drive a circuit between their fill station and the fire. Along the way, the fire fighters need to ID and remove as many hazards as possible. They’ll go right […]

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Electrical Fire Safety

There are a ton of safety devices that are preventing you from being shocked, from starting fires, and from destroying expensive equipment. The problem is, no matter how many safety devices we put in the building, something is always going to go wrong. When things go wrong, it’s essential to be prepared for the absolute worst.   Causes of Electrical Fires The absolute root cause of electrical fires always comes down to energy. The copper wiring carries electricity, electricity is energy. The movement of electricity always creates heat. More electricity means more heat. When things go wrong, there’s too much electricity or not enough insulation to contain the electricity, or some other fault that allows heat to build up or electrical arcs to occur and start a fire. This can happen any number of ways. There can be an electrical short, perhaps water getting into a non-GFCI bathroom or kitchen outlet. There could be something shoved into a socket that really doesn’t belong there, thanks to an overly curious toddler. There can be corrosion, causing an electrical short. It could even be down to a cheaply made product skipping out on essential internal safeties (this happens more often than most people realize). In all of these cases, there’s going to be a battle on two fronts.   Stopping the Power and the Fire If you’re not quite thinking straight, you might try to extinguish an electrical fire with water. The […]

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Oil Burner Ignition

Gas systems need either a hot surface or a pilot light to get started, but not oil systems. Why the difference? It boils down to the fuel being fundementally different. Fuels like propane and natural gas enter the combustion chamber in a gaseous state. Once part of that material is lit on fire, it will conduct the heat and light the entire fuel stream. This doesn’t work for oil.   The Major Difference Oil enters the combustion chamber as a liquid and it requires extreme heat to light. This makes a pilot light nearly pointless, as it would be just as easy to light the main burner as the pilot. A hot surface igniter would be a viable option except it needs to be in the path of the fuel stream, where it would endure the direct-heat of the flame throughout operation. Oil as a fuel source is a completely different beast, unrelated to gas heating. These problems all stem from heating oil’s chemical make up. It’s a cousin of diesel fuel used in over the road trucking, but thicker. It shares some of diesel’s inherent safety. Heating oil and diesel require either extreme heat or extreme pressure. This is why diesel trucks don’t have sparkplugs. At least for an engine’s needs, a spark wouldn’t work well in the long run. They generally remain in a liquid state as well, rather than readily becoming gasses.   A Really Big Spark […]

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Gas Furnace Ignition

We’ve talked a lot about the safety systems keeping your furnace from burning down the building or blowing up your building. This all begs the question: how do we get the flame started in the first place? It’s actually not a fully straight forward answer, and it varies by fuel source and furnace design.   The Old Fashioned Pilot Light In days long-gone, a furnace needed a constant flame to light it’s burner. This was called a Pilot Light. It was just a tiny, constant little flame like a lit candle. When the burner started, it simply had to turn the gas on and the pilot would ensure that the whole burner lit afterwards. The solution worked well enough, but by modern standards is an incredibly wasteful way to run a furnace. In systems with an always-on pilot light, fuel would always be getting burned, even if there wasn’t heating anything. Overtime, this adds up to hundreds and thousands of gallons of wasted fuel. It certainly worked for a time when we had no better alternatives but it’s a relic in today’s high-efficiency world.   Intermittent Pilots One of the major hurdles of moving on from a pilot was creating enough energy to light the fuel. It takes more than just a spark for ignition, it can take significant voltage. Between the fuel mixture, spark size, spark temperature, and everything else, it’s a difficult ballet to directly, electrically light a […]

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What if the Furnace Runs Dry?

Everything eventually fails. In the name of safety, we try to account for as many failures as we can, because things end in tears when we don’t. One of the scarier scenarios to consider is when a furnace loses it’s water supply. You might think that the furnace would never run without water, but that’s often not the case. You might also thing “how could it possibly run dry? It’s got an automatic feeder and a pressurized water supply.” And we’ll have to answer, “everything fails eventually.”   Cutting Out the Supply As we’ve brainstormed around the office, there’s at least half a dozen ways that a furnace’s water supply could be cut off, that might not prevent the system from operating. It is terrifying how many of these failures can happen in common, every day circumstances. Pump Failure The well pump to the facility shorts out or has it’s power supply cut off. Water Main Failure The city water supply is cut off due to construction, age, you name it. Facility Pipe Failure A technician closes a valve they shouldn’t, a main supply pipe rusts, hard water clogs a pipe. Internal Leak/Failure A leak inside the furnace prevents water from remaining in the boiler. Shorted Pressure Sensor A short causes a sensor to read incorrectly, signalling the automatic feeder to not-run Failed Water Feeder The feeder has seized up or otherwise just doesn’t feed. Internal Blockage Hard water builds […]

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Carbon Monoxide Detectors

Last week we covered how a draft inducer and it’s attached pressure sensor can help prevent Carbon Monoxide from leaking out of a furnace. This week we’re moving up to the next line of defense: a dedicated Carbon Monoxide Detector. These are often installed in new homes and offices as required by local building codes in most of the United States. Where they’re not installed by construction, they’re usually installed by the facility’s owner as a precaution.   What’s the Big Deal? Carbon Monoxide is one of the deadliest, common compounds in the world. It’s is a colorless, odorless gas that will kill you at the right concentrations. There’s only two ways for someone to know they’ve been exposed to a harmful dose: Use a detector or Recognise the Symptoms before it’s too late. The initial symptoms include headache, dizziness, weakness, vomitting, chest pain, and confusion. In large part, these common symptoms can be attributed to hundreds of other ailments, including the common flu. Greater exposure can lead to passing out, arrhythmia, seizures, and death. Even then, there will be longterm complications, including memory problems, movement disabilities, and fatigue. Most people are not able to detect and react to these symptoms as Carbon Monoxide poisoning before it’s too late. They’re often waived off as a flue or some other lesser problem until it’s too late.   How Do We Detect An Invisible, Colorless, Odorless Gas? While Carbon Monoxide itself is […]

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What is a Flame Sensor?

If a roll out switch is a master “things have gone horribly wrong, stop the show” switch and thermisters are basically limited to measuring temperature, how do we know the burner is actually making a flame? Sure, the thermister will read heat, but that takes time. Imagine the igniter has failed, it takes maybe 10-40 seconds to register enough heat to confirm a flame. The combustion chamber is now pumped full of a potentially explosive fuel mixture and nothing is happening. We need something much, much faster, we need a flame sensor.   How Not to Detect a Flame The way a person knows something is on fire is usually the bright flames and the fact that sticking their hand near it becomes really painful. This approach doesn’t quite work for a furnace. We could measure the light output, that requires more processing power to interpret the data, some incredibly sensitive hardware to detect the tiniest start of a flame, and it doesn’t work on every fuel type. There are systems that work this way, but it’s a little more expensive. We could measure the temperature, but we run into challenges with making a sensor you can shove in the heart of a flame for years on end without failure. It has been done, but it’s expensive. There are however, laws of physics we can exploit to detect a flame without anywhere near so many challenges. We can detect a […]

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What is a Rollout Switch?

Your furnace is full of sensors, regulators, switches, and detectors of near everything. There are flame sensors, temperature sensors, pressure switches. That’s a lot of stuff that mostly feed into a controller that operates the furnace as long as it sees all the right readings. That one device is an almost single failure point. The only good way to stay safe is with redundancy. In most cases, these are physical, mechanical safeties which will over-ride every other part of a system and force it to stop cold. Cutting Power on Failure The Roll Out Switch is in simplest terms, a very fancy fuse. Most furnaces will have several of them spread throughout, each tuned to a particularly temperature. One near the burner or heat exchanger may be designed to trip if the furnace exceeds it’s maximum rated operating temperature. Another near the controller board may be set much lower, perhaps around 90 degrees celsius, just shy of when most silicon chips start to fail. Some may rest near the fuel line and manifold, set to extremely low temperatures, in case a leak and fire occurs away from the burner. In the event that any of these switches trip, all power to the furnace is cut. There’s no shutdown process, it just loses all electrical power. If things were going wrong or at risk of going wrong, this usually stops the problem dead in its tracks. A shut down furnace cannot […]

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