No filter?

[David Meiland]

American Standard 90% propane furnace, and from what I can see there is no paper filter, just this electronic air cleaner that's (a) not turned on and (b) connected to a clock timer for some reason. I'm confused. What gets the big stuff if there's no paper filter? And, why put the electro on a timer?

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[Bill Kibbel]

There's no need for a "paper" filter. There's a pair of screens called prefilters preceding the pair of cells of the air cleaner.

The air cleaner should be energized when the blower starts. Timer be stupid.

[Mike Lamb]

https://customer.honeywell.com/resource ... 9-0756.pdf

Those Honeywells have a test button you press when the furnace is running to see if its working. It makes a tick tick sound.

There are 2 large cells and 2 skinny pre-filters. I turn off the power button and pull out the first cell to see if it looks dirty.

I once put a cell back in backward and broke it. I bought a replacement at an HVAC dealer. One cell costs $240.

[Neal Lewis]

Great idea. Combine a paper filter with an electrostatic air cleaner. Until it catches on fire...

[StevenT]

There's no need for a "paper" filter. There's a pair of screens called prefilters preceding the pair of cells of the air cleaner.

The air cleaner should be energized when the blower starts. Timer be stupid.

Do the pre-filters have to be maintained? By owner or technician?

[Bill Kibbel]

Do the pre-filters have to be maintained? By owner or technician?

The screens (pre-filters) get vacuumed. The cells get run through the dishwasher.

These electronic air cleaners are very common here. Is that not the case elsewhere?

[kurt]

I thought the pre filters also could go in the dishwasher. Pretty common filter here, although they are being supplanted by pleated media types.

[StevenT]

Are the screens made of paper? Are they a fire hazard as noted above?

[Mike Lamb]

The filters are metal like at a kitchen exhaust hood.

[David Meiland]

OK, mystery solved. I went back and looked at this again, and realized that there are slots for thin metal filters in frames, and that they were not installed. They are a sort of coarse, swirly mesh that you can see through, and would only get the big stuff. That being the case, do these things work well if turned on, and why might a clock timer be connected? I rarely see these, most folks here use the 3-for-$10 pleated paper filters from Ace.

[randynavarro]

I see the electronic cleaners frequently. Yes, they just catch the big stuff. The large energized cells do the rest.

Timer is unusual if it's tied to the filter; however its a very common piece of hardware for controlling the whole-house ventilation feature of the air handler. IOW, it's supposed to set to run the blower intermittently. It may also be linked in with a bathroom fan and/or isolated intake duct with a motorized damper pulling fresh air in to the system from outside.

[David Meiland]

There is an intake duct from outdoors, piped to a return, with a motorized damper. The lo-vo wire exiting the bottom of the timer goes into the furnace cabinet, the wire from the damper is not the same one. The electronic air cleaner is plugged into the outlet that is just above and in contact with the clock. I assume the flex going into the clock is its power.

I often see timers for running the air handler, and most have the outside air duct also. Many do not have a damper on the outside air. Maybe the air cleaner is "slaved" to the air handler somehow, except that it's power switch is off.

[Richard Moore]

Maybe the air cleaner is "slaved" to the air handler somehow, except that it's power switch is off.

David, the normal (never seen one different) set-up is for the air-cleaner to only have AC power when the blower is working, whether that's during normal heating/cooling or when the fresh air ventilation timer starts up the circulation. Of course it does need to have the switch on, but even then you will only see the filter power light come on when the blower is running.

I have always assumed the filter electrical power is just connected to the same leads or terminals as the blower motor.

On a side note, there are slots for the pre-filters above and below the large electrostatic ones. Make sure the pre-filters are up-stream, or first, in the air-flow. I usually include this link in the report for my clients...

https://customer.honeywell.com/resource ... 9-0756.pdf

[Scottpat]

I seldom see electronic filters, maybe 1 out of 100 homes. When I do find them they are often no longer working or have enough dirt on the pre-filters that you could plant corn on them!

[randynavarro]

There is an intake duct from outdoors, piped to a return, with a motorized damper. The lo-vo wire exiting the bottom of the timer goes into the furnace cabinet, the wire from the damper is not the same one. The electronic air cleaner is plugged into the outlet that is just above and in contact with the clock. I assume the flex going into the clock is its power.

I often see timers for running the air handler, and most have the outside air duct also. Many do not have a damper on the outside air. Maybe the air cleaner is "slaved" to the air handler somehow, except that it's power switch is off.

Unless it's an issue of semantics or I'm mis-understanding, what you've described is the setup I mentioned in my previous post.