Restoring A Rollaway Industrial Electronic Air Cleaner

[EddyCurr]

A 1982 Tepco Model 21 "Rollaway Industrial Electronic Air Cleaner" followed
me home. Similar to the PAC III built by Tepco later after it became a division
of Trion, these units were sold for use as portable welding fume extractors
(amongst other applications).

My unit is complete and in reasonably good physical condition, but it has a
few deficiencies that prevent it from operating as intended.

Three of nine wire elements on the ionizer chassis are missing. The wire
measures 0.0055", I understand that tungsten is used for ionizer elements.

I find I can get pure and thoriated tungsten wire on eBay in 0.005" and
0.006". Is pure tungsten suitable, or is thoriated required. Will the difference
in resistance matter significantly?





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[rockrat]

While I have no clue to your answer, I am interested in the project. Please keep us informed of your progress and how it all turns out in the end, yes? Photos are always welcome.

Cheers
rock~

[EddyCurr]

Thanks.

An OEM manual for the Model 21 is available from OnTimeMall. In
addition to instructions, it includes specifications, exploded views,
parts listings and wiring diagrams. A search of OTM brings up many of the
parts but they do not appear to be available.

Trion has a manual for the PAC III which appears to have superceded
the Model 21. The illustration looks like the PAC III has two ionizer and
cell modules but I believe that this is an image of the larger capacity
PAC III DP unit (previously known as the Model 25).

The Cell Assembly is shown below. For perspective, notice it is on a piece
of 3/4" plywood resting on top of a B&D Workmate table. It is made of Al
and weighs 36 lbs.



There are smaller plates in between those that are visible. Particles pick up
a charge as they pass the energized ionizer upstream from the cell. As the
charged particles pass through the cell, they are attracted to the plates of
the cell. (The cell needs to be cleaned periodically - the manual recommends
a weekly schedule for an industrial welding application.)

Mfr's lable.



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[Duffy]

For what it is worth, I dismantlled a couple of residential electronic air cleaners. I think that they were both Honeywell units. In any case, the wires are terminated by nothing more than tiny brass shoe eyelets. I have a bunch of the wires; they are 0.006x about 18". would they be any help?

[macona]

I cant imagine they would use tungsten. You can tell if it is by how brittle the wire is. I think I would just use some stainless wire. Its not like they get hot or anything.

[EddyCurr]

Thanks for the offer, Duffy. May I take a rain check on that?

The wire on this ionizer has no lugs attached to the wire ends. There
are holes in the nine legs on each of two stretcher brackets (anode ?).
The wire passes through a hole in a leg and is tied back along itself, then
a piece of shrinkwrap is used to cover the joint.

The legs are designed to apply tension to the wire when the two brackets
are fixed in place on the ceramic stand-offs that isolate the stretcher
brackets & wire from the perimeter frame.

There is a short section of tube on each ionizer wire. I don't know whether
these are to weight the wire for stabilization or whether they contribute
somehow to ionization.

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[EddyCurr]

I cant imagine they would use tungsten.

Research on several sites offering parts confirms that tungsten is commonly
used for ionizer elements.

I've handled remains of one of the broken wires. I haven't tried bending it
to failure, but it feels delicate. Of course, it is just 0055" dia and old with
dirt or oxidation on it, so no surprise that it might seem brittle. I'll look at
it again, thanks.

With 12,000 VDC/5 ma Max passing through the ionizer, one would think
it might get a little warm, no ?

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[Weston Bye]

With 12,000 VDC/5 ma Max passing through the ionizer, one would think
it might get a little warm, no ?

Uh, no. 12,000V X .005A = 60 Watts. If you packed all the tungsten wires in the space of the filament of a 60 watt light bulb, then it would get as hot as a 60 watt lightbulb. The heat dissipation will be distributed over the area of the tungsten wires - pretty spread out. You probably wouldn't notice a temperature rise anywhere along the length of wire. (after shutting it off and letting it discharge, of course )

[Black_Moons]

12,000v at 5mA = no matter how thin those wires are, there resistance won't generate any noticable heat.

Most of that power is being used to ionized air, the power lost in the wires (And hence heat generated by thier resistance) would be P=I^2*R

At 5mA, thats basicly nothing. Of that 12,000 volts maybe only a volt or two are being lost in the wire, hence basicly nothing of that 60W total power is being turned into heat (By the wires anyway, Usally all energy eventualy turns to heat somewhere..)

And no, it would'nt matter if you used thicker or thinner wires, except maybe a slight change in how efficent it is at ionizing air.

[EddyCurr]

Thanks for the reality check, Weston Bye & Black Moons.

Since there doesn't appear to be appreciable heat involved in this app,
do you have any thoughts as to why tungsten is offered rather than
SS for replacement elements by mfrs of ionizers?

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