Extra part for vf3000

How much did the contoller SA-12 cost ?

The controller , the SA-12 is a micro PLC, made by Crouzet, an older model, the newer model retails for about $150 or so. I run a program that I wrote, which controls my stoker in a manner similar to the way the Coal Trol does for coal stoves. The grey box on top of the boiler converts the water temp to an analog voltage which the PLC reads.

Can you still keep your -.05 draft with the blower running full speed?

Changing the blower speed doesn't have much affect on draft when its read at the breech of the boiler, it has more of an effect when you monitor the overfire draft, buts its still not that great a change, maybe .01" or so. The combustion blower on the Harman just isn't that big, i suspect its somewhere in the 75 to 100 cfm range.
When the boiler is cooking, the draft is around .05" or so, in idle its more like .01 to .02", especially in the summer with the warm weather.

What I have noticed with the restrictor plate, which I did have installed for a while is that it tends to limit how much heat you can get out of the boiler when its firing close to capacity. Harman's method to check the draft is detailed in the Magnum stoker stove manual, your supposed to monitor the draft at the breech, and then monitror it over the fire, by removing the small 1/4" plug and inserting the probe there. There is a plug in the door of the boiler also for this purpose. They don't mention at what firing rate your suupposed to do this.

Harman also assumes that the combustion blower only runs during the actual stoking, not continuously as many people on this forum do. Without the blower my boiler will go out within 15 minutes or so in the warm weather, there just isn't enough draft to keep it going especially with the low idle fire I run. With the blower, I have never experienced an outfire. By running the blower at a lower rate, I can keep more of the heat in the boiler, and I think I get a better burn with less unburned coal in the ash.

Keystoker has added a small blower to help with outfires in the warm weather, and If I remember correctly, they claim it saves coal also.

Thats very interesting info highlander, Coalkirk is saying that without the restricter plate on he got CO2 in his basement.
so from this should we assume either you have a very good chimney draft, so good a draft that it can take the blower max output .
And coalkirk needs the restrictor because he has a poor draft in his chimney so he has to choke back the blower with the restrictor plate?

Highlander, do you have a 2 story house where the chimney is really tall?

Sync,

My chimney is fairly tall, its about 20' of vertical pipe, it drafts fairly well. With the Combustion blower running continuously, I haven't had CO problems, and there is a detector close to the boiler so I would know.

Highlander wrote:
It can be easily installed with the standard controls, by using the distribution blower socket which isn't used with the boiler setup. You set the time for the distribution blower to the maximum and run this power from the distribution blower socket through a small paddle fan control to the combustion air blower. The power from the combustion air socket goes directly to the blower. When the unit stokes, the bower runs full speed, when it doesn't, it idles at what ever speed you set the control to.

Highlander,

Thanks for taking the time to write this up. Sounds like you have your's tweeked to the max, I think you should sell an aftermarket kit.
I am setting up my VF3000 now and I like your idea of the paddle fan rheostat. Is the blower then tied into (or powered by) both power sockets?

Coalmeister wrote:
Thanks for taking the time to write this up. Sounds like you have your's tweeked to the max, I think you should sell an aftermarket kit.
I am setting up my VF3000 now and I like your idea of the paddle fan rheostat. Is the blower then tied into (or powered by) both power sockets?

Coalmeister, its powered by both sockets, the combustion blower socket powers it directly, and the distribution blower powers it through the speed control. It will run full speed during the stoke, and then revert back to the slower speed with power from the distribution socket.

Hey Highlander, I tried the method you discribe but it backfeeds and makes my stoker run at a slower speed at the same time. Did I miss something and this is going to be a moment?

Kevin

Hi Kevin

Coalmeister had experienced the same thing, here is what I wrote him:

You probably wired it as described, I had opened up a Harman control box a while back and thought I saw 3 relays, one for each socket, I may have been mistaken, or they may have changed the design, don't know, doesn't really matter.

From what you are describing, you are seeing a back feed of power from the fan control to the stoker motor, if the two receptacles share a common relay, then this would happen.

There are two ways to fix this, the simplest is to plug the combustion blower plug, the direct connect one, into the distribution blower socket and set the extend time to something small say a minute or so. The other plug, the one going to the speed control would then get plugged into the SAME receptacle as the Harman stoker control box is plugged into. It is important that you plug it into the same receptacle on the wall so that there is no possibility of being on two different legs of your 240V service which is possible. Turn the speed control off, when plugging the circuit in, since there is a possibility of having 120V on the pins of the other plug.

The alternative method is to use a relay with a 120V coil plugged into the combustion blower socket, and then use the contacts of the relay to bypass the fan control when the unit is stoking.

Sorry for the confusion

Thank you for the clear up. I have it plugged into the distribution blower now and I will go ahead and try your solution. Thanks for the heads up on the hot plug, I figured that out but it is good that you thought to cover it. Just using the distribution blower has improved the burn.

Kevin

Thanks again Highlander, I have the reostat in working order now and I like how it is working.

Kevin

Good deal Kevin, glad its working for you.

Highlander wrote:

How much did the contoller SA-12 cost ?

The controller , the SA-12 is a micro PLC, made by Crouzet, an older model, the newer model retails for about $150 or so. I run a program that I wrote, which controls my stoker in a manner similar to the way the Coal Trol does for coal stoves. The grey box on top of the boiler converts the water temp to an analog voltage which the PLC reads.

Can you still keep your -.05 draft with the blower running full speed?

Changing the blower speed doesn't have much affect on draft when its read at the breech of the boiler, it has more of an effect when you monitor the overfire draft, buts its still not that great a change, maybe .01" or so. The combustion blower on the Harman just isn't that big, i suspect its somewhere in the 75 to 100 cfm range.
When the boiler is cooking, the draft is around .05" or so, in idle its more like .01 to .02", especially in the summer with the warm weather.

What I have noticed with the restrictor plate, which I did have installed for a while is that it tends to limit how much heat you can get out of the boiler when its firing close to capacity. Harman's method to check the draft is detailed in the Magnum stoker stove manual, your supposed to monitor the draft at the breech, and then monitror it over the fire, by removing the small 1/4" plug and inserting the probe there. There is a plug in the door of the boiler also for this purpose. They don't mention at what firing rate your suupposed to do this.

Harman also assumes that the combustion blower only runs during the actual stoking, not continuously as many people on this forum do. Without the blower my boiler will go out within 15 minutes or so in the warm weather, there just isn't enough draft to keep it going especially with the low idle fire I run. With the blower, I have never experienced an outfire. By running the blower at a lower rate, I can keep more of the heat in the boiler, and I think I get a better burn with less unburned coal in the ash.

Keystoker has added a small blower to help with outfires in the warm weather, and If I remember correctly, they claim it saves coal also.

My wife says I only half listen to her. She might be right because I obvously only half read Highlanders post in 2008. If you read my post yesterday "I need an Irish Coffee" in Freddys coffee house you know my boiler would not keep up with demand Tuesday night. So yesterday I was going over everything on the boiler to see if I had missed anything. Prior to last heating season, I installed the variable speed control for the combustion blower. Normally the VF3000 combustion blower does not run unless the stoker is running. This modification suggested by Highlander makes the fan run all the time but at a lower speed when not stoking. It made a very positive difference in the performance of the boiler. What I failed to notice is that he also said he completely removed the restrictor plate on the combustion fan.

Those of you that have been around here a long time may remember when I first fired my boiler, it pumped out flue gases through the coal hopper because the restrictor plate was not installed. That's a long story but basically the Harman manual at the time had no mention or even a picture of the restrictor plate. Unrestricted, the fan blew more air into the combustion chamber than my draft could handle so flue gases backed out of the hopper. Once the restrictor plate was installed and set everything was fine.

My chimney is an 8x8 terra cotta but it is only about 17' tall so the draft is not great. It's also on the outside of the house so its exposed on three sides. Running the combustion fan 24/7 has improved the draft by keep the chimney warmer. Fast forward to yesterday. I was fiddleing around with the setting on the restrictor plate to give the fire more air. I've been reluctant to do that since filling my basement with CO on startup 10 years ago. Anyway I opened it up completely to see what would happen. No flue gases back out through the hopper! The increased draft of my chimney is enough to deal with the unrestricted blower. And of course the fire is much more vigorous. Now it wasn't quite as cold last night as Tuesday night but the boiler was at 180 this morning. The real test will be Friday night/Saturday morning when it will be single digits again. Can't wait. I may have dissed my boiler when it was really my fault. We will see.