need help setting the Vf3000 to Idle

I have been adjusting this boiler for 2 weeks and ended up with no fire in the boiler 3 times.

Right now I have the restrictor plate off.
the stoker shaft set 4.5 turns out.
time on= 4
time off=15
aquastat=170*

It has been 72* here during the day and 65* at night... so not much call for heat.

The Vf3000 is reading abou 190* all the time.... a few times I have seen it go to 195-200*


when I used the restrictor plate set at 50% The temp was lower but the ash didn't look completely burned.
with no restictor plate the coal ash looks more completely burned.

Thanks for your input



the manual says don't go less than 4 in the on mode, if i set it to 3 the fire goes out.

Is this as good as it gets?
do I need to add a low speed blower when in off mode?

I have no experience with the VF boiler only the VF stoker stove using the same grate and timer. I would say unplug the combustion fan from the control and run it 24/7. Also set up the restriction plate using a manometer to achieve -.02" to -.04" WC over fire negative pressure. If you have a fire which is above the set point and approaching 200* I would think that is an indication that you need to reduce the on-time and set it up to allow the aquastat a chance at controlling things and a true idle fire when not calling for heat.

Just my two cents, I'm sure those with VF boilers will chime in soon.

Sync
How much of a fire do you have at idle? 190 degrees at idle sounds like a very high pilot flame. 4 minutes on out of 19 minutes total is about 21%, a very high rate for pilot mode. I run about 6% at idle, my boiler water runs at about 140 to 145 when there is no call for heat. The fire at this setting is pretty small, maybe about an inch or so wide and all the way towards the back of the grate.

I'm not sure why you experience outfires as you pilot flame is fairly large. Do you have the high temp control wired to cut power to the stoker or blower, or does it just turn on a dump valve for the excess heat.

You can try using a shorter on time and dialing back the off time, say 2 min on, and 8 min off, this will have the stoker running more often, but for shorter times, it might help somewhat.

The stroker length should be set for the maximum amount of red coal on the grate without pushing burning coal into the ash pan. After this is adjusted, you then set the on / off times for the desired pilot flame.

Member Coalmeister has built the variable speed control for the combustion blower using the Harman stoker control, hopefully he will chime in here with his thoughts about combustion air.

Bill A.

Chiming in here, but not much help as I have not run mine yet. Had to insulate my piping and finish some outdoor projects like fixing tractor equipment for winter, scraping & painting the house blah blah

Will fire her up next week, it's supposed to be cold! I think 65-70 degrees outside makes the learning curve a lot tougher, those temps are definitely on the very high end of its operational envelope, another reason I waited til it gets cold. I need all the help I can get

with a draft inducer running and pulling .04 on the manometer. I have my on time set at 5 minutes and off set at 9 minutes to get a near complete burn of coal that drops in the ash pan.I have about 1.5 to 2 inches of fire with the restrictor plate 1/2 way open.My A350 control set point is 170 water temp in boiler is 160 degrees.I have been running those settings for three weeks now.I set mine by watching the ashes to get the least amount of wasted coal.

When I first started this boiler I used the restrictor plate set at 50% restriction.
is seemed to idle better and was easier to get it to idle at the right temp.
but the coal ash didn't look completely burned.
here is a picture of the coal ash not completely burned

when I removed the restrictor plate the ash now looks completely burned but the boiler is hotter and harder to control.
here is a picture of ash more completely burned.

here is a close-up

I am thinking that if I install another blower to run slow speed when in off mode it will just blow the extra heat up the chimney which will solve the problem but waste BTU's

so I will try playing with the on off times to see if I can get better control of this boiler.
rigth now I am running 3 on and 12 off and the temp is about 175* which is close enough.
I'll have to keep an eye on it

** update *

I got through the night and still have a fire so I guess this setting is good.
The temp is between 175-180* (with the aquastat set to 170*

here are the settings I ended up with:
stoker shaft 4.5 turns out
on time= 3
off time= 14

here are some shots of the fire.:

at the beginning of the on cycle:




at the end of the on cycle:


is this as good as it gets for idle mode ?

Don,
I have my stoker control set at 2 on - 15 off. I have the feed rate adjusted to just under 1/2 the complete travel of the pusher block.
It finally started to get cold here, but last week when temps were in the 60's and 70's I had over firing problems.

I made marks on the stoker where the dots are to mark the complete travel of the pusher block, then I adjusted from there. The dots are for reference.
The Harman manual recommends 1/3 travel for a small fire, 2/3 for a medium fire and FULL for a high fire.

My coal ash looked allot like your first picture while it was warm out last week. But now it seems to be burning more completely, like your second picture.
I wanted to look into running the combustion fan all the time, but I am afraid of over firing. I am guessing it would take a completely different set up on the control box to achieve this.