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Van Wert Coal Stoker Technology

Or, at least, that pertaining to the Economy Anthratherm, model VA13 A12.

Van Wert was one of the local anthracite coal burner companies based in Peckville, PA. , and happened to manufacture the stoker I'm using for home space and hot water heating.

It uses a 2-1/2" feed auger to move buck-sized Anthracite coal from a 55 gallon holding barrel into the stoker.

The main feed auger is mounted into a cast gearhead assembly where a second, shorter auger is positioned at a right angle, and redirects coal flow into the bottom of the burner pot.

A single 1725 RPM motor is used for auger feed, combustion blower, and ash knock-off. A 3-1/2" OD pulley sheave is mounted to the motor shaft, and is coupled to the worm gear box via an AP35 belt, and 3" OD pulley sheave on the gearbox side. This gives a gearbox input shaft speed of approximately 2000 RPM.

The worm gearbox features a straight-thru input shaft that drives the combustion air blower wheel, and a 600:1 ratio output shaft for coal feed and ash knock-off. This reduction yields 3.35 RPM, and is further reduced using a #41 chain transmission system consisting of a 10 tooth sprocket on the gearbox side, and a 21 tooth sprocket on the Van Wert gearhead side (0.476 reduction) to yield a final speed of 1.60 RPM into a main gear in the Van Wert assembly.

This main gear is directly coupled onto the right angle coal auger into the burner pot, and drives a right angle gear set for the main feed auger. The main coal auger side of the right angle gear pair has an offset bolt positioned where the ash knockoff tie rod is mounted. Thus, the main and 90° coal auger, and ash knock-off all operate at the same 1.60 RPM speed.

The blower housing is fitted with a variable opening for air flow adjustment. Combustion air is routed into a plenum which exits into the bottom of the burner pot along with fuel from the 90° coal infeed auger.

Through experimentation I've learned it burns approximately 11.4 pounds of coal per run hour, although the 'VA13' in the model number suggests 13 pounds/hour. This means that, at approx. 8650 BTU/pound (figuring for burner efficiency loss), it produces heat on the order of 100,000 BTU, (or about 29.3 kilowatts) per run hour.

I use 6 tons or less (through the 2005-2006 season it looks like it'll be about 4-1/2 tons) per year, so, figuring for coal at $160/ton, electricity at $0.08/kWH, and considering that power is power (a thermal BTU isn't any different than the equivalent heat developed by passing electricity through a resistance immersion heater) I heat my home, and make hot water for $960 a year using coal, and it would cost about $2400 a year using electricity.

This makes sense, because there is an approximately 3:1 ratio between using a primary fuel directly, and using that same fuel to generate electrical energy and deliver it to the point of use.

There is a rough 1:8 weight ratio between coal, and the ash it produces, so I generate about 3/4 a ton of ash per year. This is used for fill building up the south side of the property so there isn't any disposal problem.

This year started having problems with clinker formation, and partially burned coal after having never had this sort of problem. The clinker build-up looked as though it was sticking to the side of the fire pot as it was assuming it's interior shape. I left the coal receiver go empty, and let the fire go out  during the April Fool's weekend, and found out why - the fire pot is coming apart. Guess this isn't too bad a run, insofar as the stoker was built in the mid-1950's, but that is of little comfort as Van Wert has been out of business for a number of years.

With any luck I'll be able to find a used one, but might end up needing to fabricate a replacement, and that replacement won't be more than a stop-gap measure. The original firepot appears to be cast iron or cast steel (based on the grain) and I'll need to make a replacement out of concentric rings cut out of steel plate - no way it'll hold up.

Stoker coal usage tracking is done in a spreadsheet (OpenOffice Calc), but I don't have it in a format that is clear enough to simply upload a copy to share with the user community. Until I bite the bullet and clean it up suffice it to say usage tracking has advantages. One feature that comes in handy is I record when a coal delivery is made, then use each month's run hours (and estimates for future months) subtracted against it to determine when I'm going to run out of coal.

I don't know how accurate it is because the 2006-2007 season started with maybe 1/2 ton (eyeball estimate) remaining in the bin, I didn't start tracking until March, and summer usage is low so any error makes a big difference - my original estimate was the last week of August, and I made it to November (and still had about 200# remaining).  Its a lot easier to estimate 200# (about what it takes to fill the feeder barrel) than a half ton so this year's estimate will tell the tale. As it stands, based on tracked usage to date, and using last years usage to estimate upcoming months I should run out of coal  in mid-April.

While setting up an HMI computer for a project at work used a Fuji PXR temperature controller to comminicate with (via Modbus RTU) for testing, and to get a better handle on how do scaling in Lookout, and captured several days worth of room temperature data.

Temperature Trend

Data ends on January 13th at 8:58 AM. The 'spike' at a little after 3 AM on the 13th was when I temporarily entered a bad scaling value. On the 11th I dropped the thermostat by a degree at 3:49 PM, and the resulting drop (from 73.4 degrees, right after the stoker had shut off) to 71.1 degrees, a change of 2.3°, took 4 hours, and 15 minutes. This is a rate of about 0.54° per hour at whatever outside temperatures obtained at the time.

If I ever get around to building and setting up a trending system for the stoker it would be interesting to get room temperatures from several sources (right at the thermostat, as well as from other locations) as well as the circulation water outlet and return pipes, flue temperature (before and after the damper), recirculation loop water temperature, stoker ambient temperature, and outside temperature. Another useful sensor that wouldn't be a big deal to devise is a CdS or solar cell based "light flux" detector so I can get a feel for how much solar energy is available (sunny winter days yield less power cost), and maybe even look for a cheap meterology setup that can report wind speed and direction.

Images

Components

Main radiator loop

An older pre-ITT B&G 'booster', model PAZ-3351 FX, part number 118844, 
225 PSI/250°F max. Pump motor is an equally old B&G 1/10th HP, 1725 RPM, 1 PH., 60 Hz., 115 VAC, 1.9 FLA, serial # MOT102-5-9-M, and 'protector' MB558JV (the 2nd and 3rd characters are partially missing, so may be incorrect). The FX is a date code (June 1980), and (if the JV is as well) indicates Sept 1978.

Second radiator loop

Taco cartridge circulator, model 007-F4, 1/25 HP, 0.70 FLA, 3250 RPM, 115 VAC, 1 Ph., 60 Hz., 125 PSI/240°F max.

Catalog section
Specifications

Main loop flow valve

Taco #221, Universal Flochek, 1-1/2” FNPT.

Catalog section
Specifications
Replacement parts

Second loop flow valve
ITT/B&G model SA-3/4 C19, Part# 107022, 125 PSI/250°F max. “C19” date code is March 1991.
Catalog section
Installation Manual
Parts Manual
Reducing valve

ITT/B&G model FB-38 J09, P/N 110192, Set at 12 PSI, 125 PSI/225°F max. “J09” date code is Sept 1990.

Catalog section
Installation Manual
Parts Manual

Pressure relief valve

ITT/B&G model A-8 J09, P/N 110005, Set at 30 PSI, 125 PSI/225°F max. “J09” date code is Sept 1990.

Catalog section
Installation Manual
Parts Manual
Expansion tank
I think this is the original which was in the house when purchased in the mid-60s. No nameplate is visible. The approximate effective dimensions are 11-1/2” inner diameter x 35” long, so (V = Bh = pi r^2 h) it has an approximately 3635 cubic inch (2.1 cubic foot) volume.
Main loop
Honeywell L8124A1007 triple 'Aqua-Stat' controller. 120V 60 Hz., 0.2A thermostat current. 
130-240F high limit.
Specifications (60-2061)
Installation Manuals (95-6571 and 60-0786)

Honeywell CT3400A1007 (mfg date code 9133) electronic thermostat. Obsolete.

Second loop
Honeywell RA89A1074 switching relay, single-pole, single throw, 120V, 50-60Hz transformer, 24V control circuit
Specifications (60-2481)
Installation Manual (69-0790)

Honeywell - similar to the CT3400, but part # must be on the back, and current generation units look nothing like it. I'm not bothering to pull it off the wall; its only a freaking thermostat.
Burner motor
GE 5KC35MN43H, 1725 RPM, 1/3 HP, 115/230V, 6.0/3.0A, SF 1.00, FR56 frame, Code L

Martin 41BS10-5/8 sprocket on gearbox output. 21 tooth sprocket on auger assembly side.
#41 chain.

3-1/2” OD pulley on motor; 3” OD pulley on gearbox. AP35 belt.

Motor and gearbox pulley sizes are the same as were on the unit when we obtained it. However, the motor is a slightly higher horsepower replacement (if memory serves, the original was 1/4 HP) obtained when the first motor quit, and it didn't have the same footprint, so needed to fabricate an adaptor plate, and increase belt length.

Calculations

8.48 Pounds per linear inch of feed barrel
11.48 Pounds/Hour
26.5 Effective barrel fill depth (inches)
1.35 Coal usage (linear inches)/hour
225 Barrel capacity – pounds
19.6 Barrel capacity – effective runtime hours
8650 Estimated Effective BTU/Pound
99,302 Estimated Effective BTU/Run Hour
$160.00 Coal Cost/Ton
$0.080 Coal Cost/Pound
29.1 Equivalent Kilowatts/Run Hour
$0.92 Coal Cost/Run Hour
$0.08 Typical Electrical Cost/kWH
$2.33 Equivalent Electrical Cost/Run Hour


6 Typical Coal Usage/Year (Tons)
1045 Typical Run Hours/Year
11.9% Utilization %
103,800,000 Typical BTU/Year
30,422 Typical kWH/Year
$960 Coal Cost/Year
$2,434 Equivalent Electrical Cost/Year

Parts/Info Sources

Taco Main Site                    http://www.taco-hvac.com/

B&G Main Website               http://www.bellgossett.com/

Keith Specialty Store            http://keithspecialty.com/hvac.parts.Honeywell.htm


An excellent general reference source is the HeatingHelp.com site in general, and their library in particular.

Part 4 of the "Beacon Boiler Reference Book - Boilers between 1959 and 1972" contains specification data for Van Wert boilers, although my specific model isn't on the list. My guess is the 'Economy Anthratherm' VA13 model number is suggestive of a 13 pound per hour maximum throughput.

Other interesting material includes the Ipex "Manual of Modern Hydronics", and the "How to Install Homart Hot-Water and Steam Heating Systems" manuals.

Created and maintained by Bob Welker for his own personal amusement. All trademarks, and so on that appear belong to their respective owners. None of the information contained within is guaranteed in any way.

Original work copyright 1999-2006 by Robert A. Welker.