Summer Stoker Tooth/Air/Timer Settings?

Hello,

Does anyone have a recommendation for correct settings to run the DF-520 during the summer? I started with 4 teeth, 4 air and timer set to run twice an hour for 2.5 minutes per recommendation, and this was way too hot since the temperature of the boiler was raising 10 degree every half hour. Once I hit 200 I lowered to 3 teeth then after couple hourse to 2 teeth, 2 1/2 air with same timer setting and continued to dumped some heat, but this still was increasing at 5 deg per half hour. I lowered to 1 tooth and 1 3/4 air to stabilize the temperature at 185-190 degrees. I check it at 3am and it was at 185 with slightly red bed of coal so figured it was good, but the fire was out when I checked it at 8am.

The best lowest settings seemed to be 2 teeth with 2 1/2 air so should I reduce the timer to run only once an hour rather than the twice an hour to keep the boiler temperature constant? Should I have left it at a setting of 2, and let the boiler temperature settle at a high temp? What is the highest temp recommended? Its amazing how much heat is generated burning coal. I assume the temperature was high initially since there was a lot of coal when it was started. How hot will it go if I let it run with setting of 2? Is there a way to prevent the stoker from running when the boiler exceeds a certain temperature or do I not have to worry about it with it only running twice an hour for 2 minutes on the timer?

Thanks,

Dave

I would first read this thread: Pictures of a burned pipe and worm due to improper feed/air

The Installation and Operating Manual clearly states:

Due to different hardness and quality of coal, the rate of feed may have to be kept at 4 teeth or higher, in order to prevent the fire from migrating down into the coal feed tube during long periods of standby due to warm weather or low demand.

The following, in bold print:

If excessive heat is detected on the aluminum coal pipe outside of the boiler jacket, the rate of feed should be increased immediately to keep from damaging this pipe or other components of the pot assembly. Also, check rate of air for possible problems.

I'd start over and set it back at what they recommend, I'm sure stoker-man will have some specific advice. We run the aquastat at a low of 140 and a high of 160 in the summer. Adjust that instead. Knock it up to 160-180 in the winter. Note i have a Van-Wert but its nearly identical.

I had the same problem and what Richard says is true. Lower the temps. Scott

Mine is at 4/4 and the timer is set so it runs 2 minutes ONCE per hour. Aquastat is set at 140/190. Fire hasn't gone out yet. The only problem is after someone takes an extra long shower - making the stoker really fill up the pot with hot coal - the temp might get up around 180-190, then if there is no further demand the excess heat just radiates into the basement which is kind of a waste. I tried setting it at 140/150 but it acted crazy.

I tried 4/4 2 minutes Twice per hour last night with Aquastat set to 140/160 and it went out last night.

I'll try 4/4 2 minutes ONCE per hour tonight with aquastat set to 140/190. I believe I had too much coal piled up the first time I started the unit.

Thanks for the replies,

Dave

Dave, Do 4/4 and 2 minutes per half hour at 140/200

Tried 4 teeth and 4 air with timer set to 2min twice an hour and aquastat set to 140 low and 200 high last night. It ran fine for hours, but it was out again in the morning. I'll try it again tonight, but any other recommendations? I have verified the timer is working correctly and running for at least 2 minutes every 30 minutes. Stoker seems to work fine, and there is coal in the bin. The temp runs around 150 to 180 for hours while checking it until I stop checking it around midnight. In the morning, the temp is still over 140 so the stoker wasn't running. Should I increase the "on" time on the timer by a 1/2, one or two minutes? Checked the draft and it was at -0.02 (with oil running after coal went out).

Thanks,

Dave

Is a timer available that will run the DF-520 3 times an hour rather than 2 times? Otherwise it looks like I am stuck with running oil until it gets colder.

Thanks,

Dave

Dave:

I am assuming that you had another outfire last night or early this morning. What were the settings you had for last night into this morning?

Manny

Dave, I'm going to have to check into this with other users because there is another person having trouble like you are. If you think the fire is going out because the boiler is staying over the high limit, maybe you can lower the low limit to 120 degrees. Some people use 2 minutes per hour. My friend runs on 1 tooth of feed and gets away with it. I'll try to gather some info about this, but in reality, most people run the stoker all year long without outfires.

One caller said his unit was increasingly getting hotter and hotter each hour because he wasn't using much hot water and the boiler wasn't dissipating heat fast enough. He's going to go to 3 teeth and 3 1/4 air and keep an eye on the pot to see that the fire isn't burning too deeply into the pot or pipe. He's also going to go to 2 minutes per hour. It's all experimental, but eventually you'll find the answer and just remember to record it somewhere.

Here is an experience of one user:


Low limit is 140 degrees
High setting is 205 degrees
The differential is 15 degrees.
My coal feed is set at 4 teeth.
The air is set at 5 1/2.
My timer runs twice an hour for about 80 seconds.

I've never seen the boiler temperature more than 170.

Do you feel the air is set too high? I see the manual reccomends an air setting of 4 with 4 teeth, and too much air can cause what I am experiencing (more clinkers, larger ash ring, and no "black spot" in the center).

I am not experiencing any out fires, and the coal feed pipe is cool to the touch.

Should I turn down the air?

Here is what I tried last night, and it almost stayed on since the boiler temp was over 150 at 7am (wife took a hot shower, then mine was cold indicating fire was out):

Feed: 4
Air: 4
Timer: 3 min twice an hour
Low: 150 (tried 140 past few nights)
High: 200
Diff: 10

The boiler temp normally was around 160 during the hours I monitored it. Next I have to debug the L6006A since its not shutting the stoker off when it goes below temp with the fire out. One step at a time.

Tonight I'm going to try increasing the time on the timer to 4 minutes on twice an hour, and might try running at a feed rate of 3 and air of 3 1/4 to allow it to cycle more with low temp set at 150.

BTW, what is the proper way to restart the fire? Do I remove all the ashes from the pot and manually turn the stoker to fill it again? Do I have to do anything else? I started the flame last night off center, and it stayed like that for a long time. Should push the red coals in the center next time or let it alone?

Thanks,

Dave

If you think the fire is going out because it's not running long enough, then increase the timer, but if it's going out because it's above high limit too long, then decrease the timer and possibly the low temp setting to 130.

From the new manual:

Starting the Fire

Note: If desired, the drive pawl can be flipped backward when starting a fire. In this position, the fan will supply combustion air, but no coal will be fed to the burner. Do not forget to return the drive pawl back to its operating position once the fire is established.

1. Fit the manual coal worm crank, furnished with the unit, over the end of the worm drive shaft. Turn the shaft counter clockwise until coal covers the bottom row of air holes at the bottom of the burner plates.

2. When starting the stoker for the first time, set the feed rate at 3 teeth and the air shutter at 3 ¼. If the stoker is being re-kindled, do not change the established settings, as they are adjusted already for the proper feed rate.

3. Wrap a handful of wood shavings, or a suitable substitute, in a sheet of newspaper and place it on top of the coal inside the burner pot. Ignite the paper and start the blower. This can be done by turning up the thermostat and using a switch nearby to shut down the blower quickly in the event of an emergency.

4. After the wood is ignited, place a small shovel of coal on the fire. When the coal is glowing red, add an additional layer of coal. Operation of the stoker should then be continued under control of the thermostat.

Outfires

1. A stoker-fired boiler is different from an oil, gas or electric unit in that the fire must be maintained by periodic running of the stoker, even though there is no call for heat by the thermostat or operating aquastat. This is accomplished by the timer. A normal setting on the timer is 2 ½ minutes of stoker operation per ½ hour. this is a suggested start and times may have to be varied to suit installation conditions, the quality of the coal being used, and the time of year.

2. An outfire in the stoker is a more prevalent condition during the summer months. It can happen even though you find nothing wrong with the stoker mechaninism. The following (A thru C) are some conditions which can cause an outfire. These are situations that start to develop where there is no apparent explanation. For other situations, refer to the service check list.

A. Feed rate too high for summer operation:

In this situation, where the stoker is maintaining boiler water temperature for domestic hot water and there is little domestic water draw, the boiler water temperature can reach the high limit setting. The high limit control overrides the timer, not allowing the stoker to run and results in an outfire. This occurs on a hot water system and can be corrected by dropping the feed rate, raising the high limit setting, lowering the operating setting on the aquastat to create more of a temperature spread between the operating and high limit setting on the aquastat, and decreasing the differential on the operating control.

The bypass piping, as shown in Fig. 7, is very important in helping to alleviate this condition by reducing stratification of the water in the boiler.
Removing insulation from the boiler will also help.

Note when adjusting the aquastat:

The L8124A or L7224A aquastat, furnished with this unit, has three settings.

1. The High Limit Setting: This shuts the stoker “off” when the water temperature reaches the temperature setting and overrides all other controls.

2. The Operating Setting (Low Limit): This setting maintains the boiler water temperature and shuts off the stoker when the water temperature reaches the setting, but not if there is a call for heat.

3. The Differential Setting: This setting determines when the stoker will be fired, as the boiler water temperature cools. For example: If the operating control is set at 160 degrees, with a 10 degree differential, the stoker will come on at 150 degrees (water temperature) and shut off at 160 degrees (water temperature). The thermostat or timer can override this setting, but cannot override the high limit setting.
B. Loss of draft:

This can occur during hot, humid summer weather, with low fire in the burner. Changing the number of minutes of operation per half-hour, increasing slightly the coal feed and air settings may help. Thoroughly cleaning the boiler, flue pipe and chimney, to remove fly ash buildup will also help. Be sure the fire and ash pit doors are closed tightly. Check that the clean-out lever is fully pushed back towards the boiler and that the clean-out cover plate openings are fully closed. Check that all openings, where outside air could infiltrate the boiler base, are sealed.


C. Too much draft:

This is most apt to occur during cold, windy weather where there is no barometric draft control in the stack. In this situation, the fire continues to burn, even though the stoker is not running. Addition of a barometric control, or proper adjustment of the barometric control, if present, will help. Exhaust fans can also cause this problem by drawing air down the chimney, through the burner and out of the fan housing inlet. This can be corrected by providing adequate outside air intake openings for both the stoker and the exhaust fan or discontinuing the use of the exhaust fan.

daluds wrote:BTW, what is the proper way to restart the fire? Do I remove all the ashes from the pot and manually turn the stoker to fill it again? Do I have to do anything else? I started the flame last night off center, and it stayed like that for a long time. Should push the red coals in the center next time or let it alone?

There's a post here I made on how I restart our van-wert, starting an emf coal furnace

One of the keys is to make sure you don't overfire once you get it lit, you can get a really big amount of fire going getting the water temp up. Instead light it and turn it off so the water can come up to temp slowly then turn it back on after about half an hour. You don't have to worry about this in the winter because the excessive heat generated will get used up quickly.