What Does it Mean to be UL Listed?
/BY MICHAEL TEAHAN
UL means two separate things
UL actually has two distinct functions: the first is that they are responsible for developing the safety requirements for equipment to be installed in homes and businesses, particularly if that equipment is somehow attached to a building by a water line or an electrical cable. The second is the actual testing of equipment to ensure it complies with the codes they created.
The first function is kind of a monopoly. They write the code, they own the code, and if you want a copy of the code to make sure your new invention is going to pass muster they make you pay for it. Cities, counties, and states then adopt those codes as their own and write them into law — which is easier than writing them on their own.
The second function has a bit of competition, though. While the equipment has to comply with the UL regulations, any certified testing lab can evaluate and approve a machine to be installed. There are dozens of approved labs who can certify equipment but the most common are UL and Intertek (ETL). These other labs exist because a government agency cannot require a specific company because it creates a monopolistic situation — which is illegal. But all of these other companies still have to pay UL to use the regulations they write — which is a pretty sweet racket.
Quick note on terminology: for the purposes of this article, UL and NSF refer to the codes and not the testing companies. This means that it is no way an endorsement of one company over another.
UL vs NSF
The best way to look at the difference between UL and NSF, I think, is that UL is concerned about whether the machine you install is going to catch fire, explode, or electrocute you when you are using it — or while its merely on and sitting on the counter. NSF on the other hand doesn’t care if it blows up. They are only concerned with whether something you make with that equipment and give to your customer is going to put them in the hospital with food or lead poisoning.
This first article is about UL.
What makes a machine UL?
With regard to espresso machines, a lot can go into making sure a machine complies with the code. It primarily revolves around protecting the operator of the machine from injuring themselves under normal use. This means things as simple as no sharp edges that aren’t protected, using safety devices to disable the machine if your hands get somewhere they shouldn’t or putting big red stickers on a brewing group so baristas don’t grab onto it as leverage to install a portafilter.
The thing is that although a lot of this is just basic common sense — don’t jam your finger into a running coffee grinder — common sense isn’t nearly as common as you might think.
Electrical Safety
Anything above 50 volts to ground in a machine has to be tested or carry a separate approved certification to be installed on a machine. The idea is that this is the threshold for posing a threat of injury to someone using the machine. A number of machine manufacturers have gone to lower voltage components, like 24-volt solenoids or gear motors, which don’t have to be certified and speeds the approval process.
Wires have to be approved to demonstrate they can handle the current and voltage needed to make things work — which is pretty straightforward, but they also may have to be jacketed if the wires have to move or be able to handle high temperatures in coffee brewers and espresso machines. Most wiring for espresso machines must be rated to 105°C. Because espresso machine boilers operate around 120°C, these wires must be secured a couple of inches from the boiler.
Contactors are also a concern. Not just because they need to be able to handle the current of what they are switching, but because every time they open they generate a spark. The materials used in the points must mitigate some of that and maintain integrity after repeated arcing. Whether or not a pressure stat is UL is largely a function of the coating on the points in the switch.
Venting
Espresso machines and grinders create heat and need to get rid of it, which means ventilation. UL wants to make sure that the vents are sufficient to keep temperatures under control but not so large they an operator can poke their finger into the machine or use a fork to fish out an espresso spoon. It should not be so large that it could swallow a spoon, either. While NSF is concerned about roaches getting in the equipment, UL is more concerned with fingers.
Access
Machines often have to come apart to clean and maintain and UL makes a distinction between things that a service technician is allowed to do and what an end user can handle. An end user will have to remove a drain tray to wash it, remove a grinder doser cover to clean the impellor or remove a hopper lid to clean coffee residue. None of these actions can expose high voltage wiring or potentially dangerous moving parts to a user.
This is why you will now find guards in front of the outlet port of a coffee grinder so no one will stick their fingers into the opening while its running — yes, people have done that. It is also why there is an obstruction at the base of the hopper so you can’t work your fingers around it and reach the burrs while they are spinning.
The distinction between what a technician is able to do and what an operator can do comes down to a tool. There has to be some positive, intermediate step to take before any potentially dangerous part of a machine can be accessed. In the case of the hopper, the obstruction at the base keeps out the fingers but to remove the hopper requires — in most cases — a screw be removed first to free the hopper. The side panel of an espresso machine that once removed exposes high voltage wires cannot simply be popped off, it must require that a tool be used to free the panel first.
Alternative solutions are micro switches and sensors that disable a machine when hoppers or panels are opened. The tricky part is that these devices should fail in the disabled position. Ideally. What this means is that if the switch fails the machine doesn’t work with or without the panel in place and not the other way around. In some cases, if this isn’t possible, there needs to be redundant failsafes in place.
While a screwdriver may not be an effective deterrent to keep a barista from trying to adjust a pressure stat, it’s what they have come up with.
Things that go boom
UL doesn’t require a vacuum breaker valve but it does require a pressure relief valve for any pressure vessel larger than 3” in diameter. The valve has to be certified and secured so that it cannot be adjusted. Tightening a leaking valve that has a bit of a leak kind of defeats the whole purpose of the valve. Should a PRV fail, it does so in an open position (they leak) and under no circumstances have I ever seen an unaltered PRV fail in a sealed position. When boilers go boom, it isn’t because the safety valve failed. Because boilers are tested to a specific pressure, the valve has to ensure that the relief pressure is safely below that rating.
This only applies to steam boilers, however. Steam is different from water in that when there is a breach, steam continues to expand and a lot of volume is needed to relieve the pressure, which is why they can explode. Water, on the other hand, can relieve all of its pressure with just a few drops. It is a powerful force when heated, but the expansion valve is all that’s necessary to protect the system and in either case it doesn’t create a dangerous condition. Just a costly one.
High limit switches are the other required line of defense. If the temperature in the boiler exceeds that which the pressure valve should have released, the limit switch removes power from the elements. The switch also cannot automatically reset itself, a technician is required to assess the cause and then reset the switch.
An important thing to understand about these critical safety features is that they must be completely independent of any of the normal controls for the machine. The high limit switch, for example, cannot simply disable the buttons or turn off the PID controller. It must operate without any input from any other device because it that other device fails in a closed position, the safety device wouldn’t work.
Conclusions
UL was set up to develop standards so that insurance companies could require that the equipment installed by companies didn’t burn the buildings to the ground. Or blow them up. They didn’t want to end up paying for some “Tesla wannabe’s” electrical science experiment. But at the same time, they didn’t care if the if the latte tasted nasty of made someone sick.
That was NSF’s job.