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MistBuster® Training Video

The following video goes over the ins and outs of a MistBuster®, maintenance, and general troubleshooting.

Video Transcript

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Coolant Selector Switches
Lights out/flashing
Continuity check
Lights on, w/ bypass (blow-by) – change to oil mode
Excessive zapping
Handling of cell
Contact boards
Power supplies
Interlock switch
Speed controller
Charring on contact board
Shorting test (2 screwdrivers)
HV probe

Hello this is Paul Stanton with Air Quality Engineering. I’m going to be going over the ins and outs of a MistBuster and basic troubleshooting. So first off let’s kind of go through the anatomy of MistBuster 850. You’ve got the front access panel, you have indicator lights here to show you the status of the power supplies when they’re on. That means the cells are fully energized. When they’re off it means that the cell most likely has a short in it. Then you get your speed controller. All the way counterclockwise is off. All the way clockwise is low when you first click it on it is at the highest fan setting.Looking at the front of the door you’ll see three buttons that are test buttons. What these are used for is to test to make sure the cells are energizing properly. When you push and hold these and get both lights to go out while you’re collecting you should see some bypass out of the top. Then when you let them go the light should come back on and then you don’t see any bypass coming out of the top.

Going inside the MistBuster you’ll see two filters on the bottom. These two filters are impingements before the cells. It keeps large particulate and droplets away from the cells to protect them. Then you got your first cell, so an optional third cell that can be easily added either in the future or when you order the unit. Then on one side of impingement is the contact board for each cell. When you install your cell in your MistBuster what you want to make sure to do is to have the handle facing towards you, the airflow arrow pointing towards the fan, the contacts on the cell should be on the right side. Below you’ll see the ionizing grid with the fine wires, the collection side will be on the top. The reason to make sure that your cell is installed correctly is if it’s installed upside down or backwards the cell will not energize and it will not collect.

So with the door open you can see there is a label inside that has your serial number, model of MistBuster, it’s marked what voltage of MistBuster you have and the schematic of the wiring inside the unit. Then you can also see the inside mechanism of the test buttons. All these do is when you push the button is they go in and they touch the cell and short it out. When you look at any of these test buttons, the mechanism, make sure it’s, when it’s not engaged or pushed in that it’s fully retracted against the door. If any of these are sticking too far out that can also cause a short in your unit.

So the nice thing about the MistBuster it’s easy to enter into the electrical cabinet or electrical part of the cabinet to service the power supplies or any internal components. The Phillips heads are pretty much a quick snap faster, that is a quarter turn, to open up the door. Once you’ve undone all snap on fasteners what you’ll see is two power supplies in 850, 500 you’ll see one power supply and in the 2,000 without the cell upgrade you’ll just see two power supplies. With the third cell upgrade you’ll see three power supplies. Each power supply can supply power to two cells, and in this unit one power supply supplies power to the two cells on the top and the bottom power supplies power to the cell on the bottom.

Starting from the bottom the speed controller is located on the very bottom towards the front. Then there’s a capacitor for the motor of the impeller. There’s the interlock switch so when you open up the door the unit disconnects the power and you get no power and it’s turned off for safety. Then on top of that there’s the two power supplies. And then each power supply has its own indicator light showing you the status of the power supply. So how the power comes into the unit. On non-CE versions you typically will have a cord. CE units you will have a power entry module that has a removable cord with two fuses inside of it and an on/off switch. When you go in from the cord or the power entry module the power then goes to the interlocks switch. It then splits from there where the common is then supplying power to the fan and the power supplies and then the hot is going through the speed control. So the speed controller acts as an on/off switch for the power supplies and a variable output for the motor on the impeller.

Coolant Selector Switches

Spinning the unit around. So on the back side of the unit you have three selector switches. These are what are known as coolant selector switches. Whether you using water soluble coolant or an oil. With oil you want all the knobs pulled out so the contacts come in contact with the collector side of the cell. In water some of you want to actually push these in which then will disconnect the collector contacts from the cell. So going to the side of the unit with the contact boards you’ll see that there’s three contact boards. Each contact board is labeled with an I and a C. The contact towards the door is the ionizer one label with I. The one further back is the collector contact and when you operate the coolant selector switch as you pull it out you see that the contact goes in to connect to the cell and when you push it all the way in you’ll see it pulls it away. So here’s a closer view of the contact board. The front contact is ionizer and the back contact is the collector. And when I operate the selector switch you’ll notice that the collector contact pulls away. The reason for doing this is that in oil mode we fully energized the cell with the power supply. Then in water mode we’re getting an induced charge from the ionizing section. The unit itself has an impeller that moves the air that’s a one piece impeller and motor that’s located on the top of the unit. The intake is just above the cells located right here.


Now let’s go into the troubleshooting a MistBuster. One thing that you might run into is the whole unit appears to be completely dead. One thing to make sure is that the door is fully seated and actually pushing the interlock switch. If it’s not fully closed and it’s not pushing the interlock switch you’ll turn it on and nothing will happen on the unit. Easy thing to do is continue to turn the knob till you hear click and the unit comes on, you hear the fan spin up and the lights come on. Normal operation you’ll hear the fan running and the two lights will turn on. Then when you open up the door if the units on everything should turn off. That is normal operation of a MistBuster. Also, when you adjust the fan speed and when you go down low you should hear and see that the fan is slowing down, and as you increase the speed the fan itself will spin faster.

Lights Out/Flashing

Okay now let’s go through a common issue that you’ll probably run into. The common issue that you’ll probably run into is that one of these indicator lights will be out, both of them might be out and the fan’s still running, or one of the lights may be flashing or you hear constant ticking noises. So what you do is you go shut the unit off. Go up to the unit and open it. One thing to make sure to do with a well-insulated screwdriver. What I mean by a well-insulated screwdriver is one that has a nice plastic handle that’s over the shaft that does not have any metal sticking out the rear of it or out the sides that could transfer a little bit of a shock to you. This is high voltage but it is low amperage.

First thing you want to do before you touch any of the cell is to short the cells out. To do that is pretty simple. You’ll see these holes in the side of the cell. You rest the screwdriver on the edge of the hole and touch the plate inside. Sometimes you might see a little bit of residual spark, sometimes you won’t. The cells will hold a residual charge. So let’s say that the bottom light’s out or it’s flashing. Typically you’ll run into kind of the same issue if the bottom one is out. What you want to do is take the cell out for that area. If it’s part of the unit that’s powering two cells what you want to do is take both cells out. You can either close the door and see if the light comes on, or with the same screwdriver push it into the inner lock switch and see if the light comes on. If the light does come on then your cell probably will need to be washed. So if you determine that the cell is the culprit of why the light’s not coming on, it’s most likely that there is either buildup in the cell, it could be that one of the wires may have broken and is sitting inside the cell and shorting it out. So the best thing to do when you find out that you have a cell that’s an issue is if you see excessive buildup first thing you really want to do is go through and wash the cell. If the cell is fairly clean then the thing you want to do is inspect that you have all nine wires.

The other thing you also want to do is really look through and make sure that there is nothing bridging any of the plates inside of it. Yes there are two contacts that go to the cell. It is not a complete circuit. What we’re doing is energizing the collector and the ionizer with two different voltages positive DC. There is no completed circuit anywhere in this cell and there’s insulators on the side of the cell to keep the collector side insulated and there’s also insulators for the ionizing section. So once you have cleaned this cell the way to deal with any residual debris inside of it is you could use compressed air to try to blow it out or a long screwdriver, thin screwdriver, to get in there and brush it out or a long bristled paintbrush to kind of brush between the fins to knock anything out. What you do not want to use on these cells is anything that may introduce very fine metal particulate such as steel wool. If you do that then it’ll be hard to clean that out and it’ll short the cell out.

Continuity Check

So if you’re dealing with a cell that you’re still having problems with it functioning and you still can’t see anything inside the cell, what you can do is a continuity check. So you take a standard multimeter set it in continuity mode to see if there’s any continuity from the ground side of the cell to any of the contacts. So the simple thing to do is take one of the leads and touch the frame and touch the collector. As you can see there was no beeping noise. There’s no short on the cell. If I literally take the screwdriver stick it between the plates, you hear that there’s continuity. This is kind of acting like a major short in the cell. That can be anything from a little burr of metal to a buildup in the cell that’s causing it to short out. If you do find that you are missing some wires, you can run the cell with one or two wires missing. If there is all the wires missing there’s no point running the cell because you’re not ionizing the particulate to collect it inside the cell. Each wire you lose you will reduce its efficiency.

Lights on, with Bypass (Blow-by) – Change to Oil Mode

So let’s go into another thing that you may run into with the unit. You might see that the lights are on solid but you see bypass and pushing any of the test buttons and getting the lights to go out or whether they go out or not you don’t see any change in the bypass. And you’re running in the water-soluble mode. When you’re not collecting anything one thing to do is put the unit into oil mode so if it fully energizes the cell. And if the lights go out then what I would do is go back to the testing that I talked about earlier. Take the cell out, see if the light comes on solid. Put it back in, see if the light goes out. Do that for each cell then you isolate which cells are actually causing the short. The reason for doing this is when the cells are getting a reduced charge if there is a short on the collector side you may not see that on the indicator light. So when you short the unit out and everything and it’s not changing how much mist or smoke is coming out the top and it seems like it’s a 100% bypassing the best thing to do is put it in an oil mode when you’re not collecting and see if the light stays on. If it doesn’t stay on that means you have a short in the cell, it needs cleaning and inspection. You can straighten out fins from accidentally being bent or mishandling where you’re grabbing the cell and pulling the fins over. You want these fins as straight as you can get them. Big thing is that they aren’t touching each other. To straighten them out the easiest thing to use is a flat nose pliers to go in there and kind of straighten the cells out. Make sure that all the plates are in the combs on the top and the bottom. And you can also go in there with a screwdriver and if there’s a slight kink and kind of straighten it out. The main thing is get it as straight as possible. If a plate is fairly close to each other that will actually cause nuisance arcing.

Excessive Zapping

A common thing that you’ll run into when there is buildup on the cell is that you’ll hear constant clicking but it isn’t completely shorting it out. The unit majority of time should stay fairly quiet with an occasional snap or pop here or there. Excessive snapping that’s constantly happening – that means the cell either needs to be cleaned or inspected and also possibly straighten out any of the plates that could have been bent.

Handling of Cell

When handling the cell the majority of time you want to handle it by the handle or the outside frame. And you can hold it from the ends. It’s not advised to pull on any of the ionizing grid, on any of the contacts, when lifting the cell because you could pull these off and damaged insulators or any of the contacts. And you definitely do not want to grab on the collection grid. If you grab on the collection grid too hard you will bend plates and short the unit out, short the cell out. At the same time when you’re going in and servicing the unit and cleaning, either replacing or cleaning the cells, you also want to get in there and wipe down your contact boards because there can be build up on those and those can also be a culprit of shorting the unit out. When you’re cleaning your cells in the MistBuster and servicing the unit, an important thing to make sure is that this bare area of metal is clean and if it’s not make sure to clean it off. It’s important that the outside of the cell gets a good ground. And on either side you’ll see an area where there is no paint and this should be nice and clean to ensure the cell gets a good ground. When you’re washing your cells in your MistBuster you can wash the pre-filters in the same solution that’s used to wash the cells. These are heavy duty impingers that can take multiple washes before they need to be replaced.

Contact Boards

When the light’s not coming on or is still constantly flashing without the cell, the big thing to do is to take a look at your contact boards inside of it and make sure they’re clean and wiped down, And you may not actually see it on the side when you open up the unit. The best thing to do also is to open up the side panel and see if you have any buildup on the side of the unit. On this side of the contact board. Go through and give a good wipe down and clean up this side of the contact board. And while you’re at it the other thing to look at is that all your wires are in good condition, intact, you don’t see anything broken or any wires sitting loose shorting out on the outside of the cabinet. If that’s happening that will also cause light to go out.

Power Supplies

If the light’s still not coming on, what you want to do is then look at the side with the power supplies. When you inspect the power supplies all the way or should be nice and secured to the power supply. The power supply physically should look in good condition. Another thing you can also do is disconnect all high-voltage leads. Turn the unit on and see if the light comes on. What that does is eliminates any issue that could be happening with the high-voltage leads going between the power supply and the contact board. If the light comes on then you may have to replace the high voltage wires leading to the contact boards. If the light still doesn’t come on, the rest of the unit’s energized and the other power play is illuminating the light, what I would do is go through and replace the power supply. If you’re still not getting both lights illuminating but the fan is turning on, with the unit on I would take your multimeter and the best way to check to make sure that you’re actually getting power to the power supplies is to check on both sides of where the leads come in. It’s better to do that than to read it to ground because if you have a 208 to 240 volt unit or even a 120 volt unit, it’ll look like you have power but you may have dropped either your neutral or you may have dropped one of your legs, especially if you have a machine tool where you have separate breakers or fuses, that one side can drop off. If you’re still getting power on one leg and you’re reading it to ground, you’ll actually see power on both sides of the power supply where the power is going into it. The reason for that is a little bit of power actually bleeds through the power supply and you can actually read the 120 of the 208 on either side. But when you try to actually power the unit because the other leg isn’t there it won’t power on.

Interlock Switch

If you’re still having issues with your MistBuster turning on where the power supplies and the impeller are not energizing, and you have tested that your interlock switch is properly engaging with the tab from the door, the thing to do is to check the interlock itself for proper operation. So the interlock switch is actually switching two halves of the circuit. The top part of the half is one side of the circuit, the bottom half of the interlock switch is the other half of the circuit. What you’ll notice is three contacts on each side. The power comes in on the outer two contacts and then the power should be coming out at the inner two contacts. The contact that is not used is the one that’s in between the three on either side. That’s because the inner two is normally open so when the door is open the circuit is open. When the door is closed these contacts will energize. To test the interlock what you want to do is take your multimeter and read the continuity from the outer contact to one of the inner contacts. When the door is open there should be no connection. When the door is closed there should be a connection. That goes for the top and the bottom. Sometimes what you might see is that one half of the switch may not be switching properly.


Now you have the speed controller. What you can look at is the output voltage that varies for the impeller and the output for the power supplies. So if the fan isn’t working but the lights are coming on. First thing I’d actually do is go inside and spin the fan by hand. So a good operating impeller on a MistBuster should spin freely and easily when you spin it and it should spin for a period of time. If you spin it and then it stops quickly or you feel roughness when you’re turning a little bit, most likely there might be a bearing issue and I’d replaced the fan. The other thing to check is to pull up and down and see if the impeller stays in place or if it actually moves. If there’s decent play up and down then it’s probably time to replace the impeller. The impeller on this is what’s known as a backward curve fan. So for some people who don’t understand what that means is when you see it spinning it looks like it’s spinning backwards compared to a common squirrel cage fan that you see in HVAC equipment.

Speed Controller

Going back to the speed controller one thing that you’ll see when you try reading the output that is actually for the fan is you may not see it actually vary. That is actually normal. The big thing is when you’re actually running it you turn the fan up and down the speed changes. If the speed doesn’t change you replace the speed controller. If your fans not working after you’ve checked physically the fan that it’s spinning just fine, there’s no issues, you don’t feel any major play in the fan itself, what you want to do is go back to the speed controller, especially if the lights are coming on for the power supplies, is you take off the blue connection going to the capacitor. Then attach the red where the blue wire went to the capacitor. Then supply power to the unit and see if the fan comes on. If the fan comes on replace the speed controller. So another thing to look out for with the speed controller is that when you turn it on you get no power out of it, but you’re getting power into the interlock switch and coming out of the interlock switch. If you’re running into that scenario what I would do is also replace the speed controller.


If you’re still having issues with the fan running and you found that the fan’s spinning easily, the speed controller appears to be operating fine, the interlock is operating fine, the power supplies are turning on and off, what you can do is check the capacitance of your capacitor with a multimeter. First thing you want to do is disconnect the power to the unit. Then you remove the black boot for covering on the contacts. Then just to make sure that there is no charge in the capacitor you take a well-insulated screwdriver and then touch the two contacts together. Once that is done take your multimeter and set it to read capacitance. You put both probes on either side and read it. What you’re looking for is a capacitance that is close to what is marked on the capacitor. This is what’s printed on the capacitor. If it doesn’t match I would replace the capacitor. If you’ve gone through and checked your speed controller interlock switch, your capacitor, your power supplies are turning on and off, and everything else looks good, what I would do is go through and replace you your impeller.

Charring on Contact Board

When you’re servicing your unit when you’re looking at the contact boards and your cleaning goes off if you see any char marks and burn marks on it that’s typically the result of buildup on the contact board. That’s highly conductive. That’s causing very light amount of arcing over a period of time. If left that way long enough it can actually short out the high voltage. In that scenario what you want to do is actually replace the contact board.

Shorting Test

One thing that you might run into is that it appears like everything’s functioning just fine for the MistBuster. It just seems like you’re getting too much bypass and it’s just not collecting at all. You put it in and out of oil mode and the lights just stay on. It looks like everything’s functioning just fine. A test that I like to do to make sure that the cell is actually fully getting energized and that there isn’t some disconnect from the contact board or any issues like that is what I like to call a shorting test. With the MistBuster in the oil mode what you do is you take two screwdrivers that are well insulated, with the MistBuster turned on, use one to push the interlock switch, the other one you rest it on the outside in the hole and then bring it into the plate. You should get a nice snap from the screwdriver when you ground it out. Then you do the same thing with the ionizing side. You rest it against the outside of the frame. You go in and then you get close to the wire. You should either get a nice snap or an arc from the ionizing wire. The reason for doing the short test is to see if there’s some break in the connection between the high voltage power supply and the cell. If there’s a break either on the ionizer or the collector you may not be getting any collection. The one thing to look at why that might be happening is you do is you take the cell out and you look at both the contacts inside and the contact on the cell and make sure that there’s no buildup that’s keeping anything from connecting to each other. If you see any build-up on either side, clean it up and try again and see if that improves. If it significantly improves it was the build-up that was keeping himself from getting fully energized. The other thing to also look at is that the contacts inside the cabinet are fully extended and touching the cell. And that the contacts aren’t damaged. If the contacts are not fully reaching out and touching the cell, what you want to do is just lightly bend them further into the cabinet to make sure that you get good contact. If you see that the contact is really damaged or it’s not repairable, what you do is you replace the whole contact board.

HV Probe

A good investment to get is a high voltage to ground probe. They’re fairly inexpensive and they connect to most basic multimeters. So with the high voltage probe, you connect it into your multimeter. You take the ground connection, you connect it to an unpainted ground part of the unit and basically you start touching any of the high voltage connections. Do not use your multimeter directly onto the high voltage; one, you could possibly shock yourself, two, you can actually short out your multimeter. So what you want to do with the cabinet open is with the screwdriver push the interlock switch and then you touch the probe to the high voltage energized parts of the cell. On the collector side of cell you should be reading around 3,000 to 4,500 volts. On the ionizing side you can test it directly on the ionizing wires. And you should be reading anywhere from about 7,200 volts to about 9,000 volts. Typically you’ll see around 8,000 for the ionizer and around 4,000 for the collector. The other thing that’s nice about that high voltage probe you can also use it to read it directly from any point to the high voltage in the unit itself. So you can read it right at the power supply, you can read it right at the contacts, and the nice thing about being able to read the high voltage everywhere from the power supply to the contact board to the cell is you can make sure that there’s no broken wires, anything disconnected between the high voltage power supply and the cell. If anything becomes disconnected such as ionizer or collector, that can cause issues.


When you’re washing the cells in your MistBuster what you want to use is either the detergent from Air Quality Engineering, or aluminum safe, alkaline based detergent. After you’ve soaked the cells what you want to do is take them out then rinse them in hot water. We don’t recommend using a high-pressure pressure washer because it can actually bend the fins in the cell. If you bend the fins in the cell back and short the cell out. Thank you for taking the time to watch this video on the ins and outs of a MistBuster and the basic troubleshooting MistBuster. If you have any further questions feel free to give us a call or send us an email.

Air Quality Engineering

Air Quality Engineering