Hold-Fire (repeat cycle) timer wiring question

This started as an inquiry which I made within another thread, but I thought it warranted a thread of its own.

Is there any means whereby to have a Tork or Intermatic (or other) repeat cycle timer reset itself (such as at least the Tork does automatically in the event of a power outage) and begin counting time all over again each time the boiler fires on its own due to a standard heat call? The goal here would be to eliminate most (to all) of the unnecessary timer generated "hold fire" fan cycles that would occur following standard T-Stat or Aquastat driven heat call fan cycles, as such unnecessary timer generated firings would merely in such instances be wasting coal.

The mechanical timers are fairly simple. They run on their own via a simple clock motor. No power they stop, apply power they run. To way to reset them except physical intervention.

There are electronic repeat cycle timers on the market that will reset from zero when power is removed but then you have to have a much more complex wiring system to accomplish this on thermostat call.

I set my repeat cycle time for 1 minute of run for every 30 minutes. This just fans the fire enough to keep it alive without overheating. I haven't seen much coal usage in the mild weather while on idle. I plan to measure it someday in a couple of weeks of so.

My Keystoker Timer (30min repeat cycle) keeps a very small fire when no heat is being called. Just enough to keep it going. I think I have 4 pins (1 pin = 15 sec) every 10 mins.

If you have more than a certain amount of power outages, you should put a fire out temp switch so it shuts everything down and as to waste coal either.

I found 2 intermatic timers on ebay, used, and if they fail, their are replacement motors for them. Simple rotating clock face dial with clip trippers on the round dial. I have a 4 hour timer that starts a 5 minute timer. The 4 hour each trip runs 2 1/2 minutes that starts the 5 minute timer, I can run a couple seconds for each tripper added, I do anywhere from 45 seconds to 1 minute 20 seconds once an hour. The 5 minute timer only runs when the 4 hour one is triggered. An hour timer would be good to go for one minute. I would not worry about a timer that resets from power failures .

For those of you with Coal Gun manuals handy, is this where I would install the timer (see pencilled in and yellow highlighted in the attached PDF)? I apologize in advance for the lousy snapshot of the relevant wiring schematic from the manual. The logic here is to leave the LWCO active and also leave the L4081B and the hopper temperature sensor active, but circumvent (bypass) the actions of the L4006A with the repeat cycle timer. The blower motor is in the upper right hand corner of this image.

Or would something like the incorporation of this relay circuit work (see attached PDF, relay has a 120VAC coil energized by pins 2 and 7). The object here would be that a Tork 60 minute repeat cycle timer which resets itself and starts its timing cycle all over again from zero if the source of power feeding it is broken would be utilized, and the intent is that any time the boilers original hot line to the fan motor (the blue line, receiving its signals from the current boiler circuitry which is regulated by the boilers internal temperature via the L4006A aquastat, with line breaks coming from the L4081B and the hopper temperature sensor) is hot the relay circuit attached here breaks the current to the timer, thus taking it off line (de-energizing it) and resetting it again when the L4006A breaks on high temp (at 180 degrees). Thus whenever there is a normal heat call from the existing boiler circuitry the timer is reset and it begins its 60 minute countdown all over again. If there is no standard heat call to fire the boiler fan within a period of one hour, then the timer fires the fan for two minutes.

I'm not much of an electrician, so a good look at this relay circuit logic (the attached PDF) by someone who deals in this sort of thing would be well appreciated. I used this relay as an example, primarily because I happen to already have this octal relay sitting around. I would be utilizing only one of its two independent sides in this application.

I just realized that in my above PDF drawing the line marked "Blue line from fan motor" should have more properly been labeled as "Existing blue (hot) line to fan motor". It would be jumper connected to pin #2 of the relay as the hot line to activate (pull in) the relays coil.

lsayre wrote:This started as an inquiry which I made within another thread, but I thought it warranted a thread of its own.

Is there any means whereby to have a Tork or Intermatic (or other) repeat cycle timer reset itself (such as at least the Tork does automatically in the event of a power outage) and begin counting time all over again each time the boiler fires on its own due to a standard heat call? The goal here would be to eliminate most (to all) of the unnecessary timer generated "hold fire" fan cycles that would occur following standard T-Stat or Aquastat driven heat call fan cycles, as such unnecessary timer generated firings would merely in such instances be wasting coal.

I don't understand what you are trying to do. A standard AHS coal gun boiler doesn't have a "hold fire" timer. Doesn't need one, it will hold fire for 1-2, maybe 3 days when the power fails. For aquastat initiated combustion blower operation, then are necessary to maintain the water temperature in the boiler. What am I missing?

A more important consideration is when the power outage is so long that the fire does go out. Then when power is restored it will just run continuously until it empties all the coal in the hopper. You end up with rice coal in your ash bucket. Don't ask how I know this.

Yanche, during the roughly 2 straight weeks of excessively warm March temperatures here I did not lose my fire despite zero T-Stat calls for heat, so perhaps the "hold fire timer" idea is totally unnecessary, but during that warm span I noticed a fair percentage of partially burned to totally unburned coal in my ash pan. My primary thinking here is that a repeat cycle timer may even out the fire in the pot and yield properly burned coal (reduced to nothing but ashes) even under extended periods of little demand. My secondary thinking here is that during the summer we like to get away for vacations and during a vacation we would not even be taxing the boiler for DHW, so it would be most likely to burn out when we are not home for a few days to perhaps a week straight. That's when I would assume we would come home and find 300 lbs. or more of ground up rice coal piled up in the ash pan area (and this is something I'm trying to avoid also).

When its warm enough outside that there are no T-Stat driven heat calls and we are only using the Coal Gun for DHW for two, I'm only going through about 17-18 lbs. of coal per day.

I agree with Yanche that a cycle timer is not needed with the AHS and hopper feed. AA uses a cycle timer but I believe the reason AA uses one is because it is necessary to keep the coal topped off--not a need to run the combustion blower.

With the factory setup on the AHS and the thermo grate control the grate will cycle even without the combustion blower running if the ash temp drops below the SV less the set differential.

Yanche wrote:Doesn't need one, it will hold fire for 1-2, maybe 3 days when the power fails.

That assumes the chimney has sufficient draft. The gentleman that started the thread linked below had an outfire, and I am aware of a few others.

To Re-light or not to re-light that is the question

Bob wrote:I agree with Yanche that a cycle timer is not needed with the AHS and hopper feed. AA uses a cycle timer but I believe the reason AA uses one is because it is necessary to keep the coal topped off--not a need to run the combustion blower.

With the factory setup on the AHS and the thermo grate control the grate will cycle even without the combustion blower running if the ash temp drops below the SV less the set differential.

My S130 Coal Gun quite often sits and idles with the thermo grate controller temperature at below the SV. My grate motor only runs when the combustion blower is running.

Rob R. wrote:

Yanche wrote:Doesn't need one, it will hold fire for 1-2, maybe 3 days when the power fails.

That assumes the chimney has sufficient draft. The gentleman that started the thread linked below had an outfire, and I am aware of a few others.

To Re-light or not to re-light that is the question

I've seen my draft sitting at a dismal 0.01" when its been quite warm outside. Another good reason to periodically fire the boiler, as this increases the draft by heating up the chimney.

lsayre wrote:Another good reason to periodically fire the boiler, as this increases the draft by heating up the chimney.

Just a thought
With all this extra firing going on,will it over heat the boiler water and make it dump when there no call for heat.

ALSO-don't the coal guns boiler water temps. control the blowers to turn on when the water temps. drop. If so,the boiler temps. will decrease before the fire dies out and refire the coal.It seems the only way the fire could go out is if extended days of power loss or no coal in the hopper, or too low of boiler temp. settings. Or have I missed something.

Dennis wrote:

lsayre wrote:Another good reason to periodically fire the boiler, as this increases the draft by heating up the chimney.

Just a thought
With all this extra firing going on,will it over heat the boiler water and make it dump when there no call for heat.

ALSO-don't the coal guns boiler water temps. control the blowers to turn on when the water temps. drop. If so,the boiler temps. will decrease before the fire dies out and refire the coal.It seems the only way the fire could go out is if extended days of power loss or no coal in the hopper, or too low of boiler temp. settings. Or have I missed something.

I'm not sure that 2 minutes of firing (running the combustion fan) out of every hour is excessive. Also, the plan here is to have this 2 minute firing happen only when required, and not 2 minutes out of every 60 regardless of whether it is necessary or not. The Tork ACT120MFS 60 minute repeat cycle timer resets to zero minutes counted down each time that current to it is interrupted, and the relay is intended to interrupt the current to the timer whenever a standard (conventional) call for the combustion fan to cycle is achieved.

Whenever the boilers internal temperature drops to below 170 degrees (or 10 degrees below whatever temperature you have your aquastat set for, with mine being set for 180 degrees) the combustion fan motor will cycle on. If there has been an extended period of no combustion blower activity leading up to this point and the fire is thereby "sleepy" then at this juncture the fire can potentially go out. It actually happened to me the very first time I fired mine up. Hasn't happened since though. And yes, I did experience the nasty phenomenon of 300 lbs. of completely unburned coal sitting in my ash pan area....

I've noticed that recovery from a really sleepy fire can require the blower to run for as much as 45 minutes non-stop in order to recover from (and save) the barely hanging on fire, so asking the blower to run for 2 minutes out of 60 does not (to me at least) seem excessive.