AA-130 and AHS S130 : Time From Idle to Full Heat Output?

McGiever wrote:Did I see correctly...a AA260 can burn 19.2 lbs/ hr.?...where does that put the AA130?

I calculated it this way:

The 1949 Bureau Of Mines report stated that the AA-130 actually has on the order of (from memory) 116,000 BTUH input.

I then assumed the typical anthracite pea to have 12,300 BTU's per pound.

116,000 / 12,300 = 9.43 lbs./hour max feed (and also burn) rate. (which is how I came up with 0.157 lbs./min of burn rate at maximum rated output)

***Not relevant here, but at max fire the same report stated that the efficiency of the AA-130 is (coal dependent) 80% to 81% (call it 80.5%).
At idle I presume the efficiency falls off noticeably from 80.5%. By my calculations overall efficiency (idle fire and max fire and everything inbetween) is about 70%.

My fire (fan on) cycles to satisfy one heat-calling zone tend to average about 17 minutes in duration. I assume my boiler is eating about 2.3 lbs. per average firing cycle. Thats about 0.135 lbs. burned per minute.

If at idle before firing it is sipping 0.007 lbs./minute, and at max fire it is eating 0.157 lbs./min., and the ramp-up time is assumed to be 5 minutes, then:

1) Assume that during the 5 minutes of "ramp up" the average burn rate is (0.007 + 0.157)/2 = 0.82 lbs./min burned

2) Assume 5 minutes of ramp up time.

3) 17 minutes - 5 minutes = 12 minutes at max fire

4) (5 x 0.082) + (12 x 0.157) = 2.294 lbs coal burned per firing cycle (close enough for government work to my 2.3 lbs. estimate)

5) 2.294/17 = 0.135 lbs./minute (average fuel consumption rate per 17 minute firing cycle)

Thus, if ramp-up is linear (where in reality it is quite likely exponential), then by this simple and quasi-empirical method (educated guess) ramp up from deep idle to full burn calculates to about 5 minutes.

Mine is a 260 so I'm not sure how it relates but it never runs 5 minutes at one time once up to temp no matter how many zones are calling. 3-4 minutes tops. Member Townsend has a 260 on steam in a big old house with high ceilings, its run time is in seconds, not minutes, to satisfy the thermostat.

coaledsweat wrote:Mine is a 260 so I'm not sure how it relates but it never runs 5 minutes at one time once up to temp no matter how many zones are calling. 3-4 minutes tops. Member Townsend has a 260 on steam in a big old house with high ceilings, its run time is in seconds, not minutes, to satisfy the thermostat.

I have right close to 42 ft. of HWB (3/4" fintube hot water baseboards (no idea which brand or model, but 52 years old) on each zone loop, and my circulation ranges from roughly 2 to 3 GPM per zone (~3 GPM for only 1 zone calling, and on down to ~2 GPM per zone by the time all are calling). Would that matter any?

I would rate the insulation and the infiltration rate of our 1964 built home to be moderate and high respectively.

So for the 260 are you saying 2-3 minutes to ramp up, then 3-4 additional minutes to fan off? Total of about 5 to 7 minutes of the fan running per heat call?

lsayre wrote:

coaledsweat wrote:Mine is a 260 so I'm not sure how it relates but it never runs 5 minutes at one time once up to temp no matter how many zones are calling. 3-4 minutes tops. Member Townsend has a 260 on steam in a big old house with high ceilings, its run time is in seconds, not minutes, to satisfy the thermostat.

I have close to 42 ft. of HWB (3/4" fintube hot water baseboards (no idea which brand or model, but 52 years old) on each zone loop, and my circulation ranges from roughly 2 to 3 GPM per zone (~3 GPM for only 1 zone calling, and on down to ~2 GPM per zone by the time all are calling). Would that matter any?

I would rate the insulation and the infiltration rate of our 1964 built home to be moderate and high respectively.

I probably have twice the radiation with leaky windows and bad insulation (the house is 2200'). My answer is, I have no idea! Keep in mind though, I have twice the coal you have on tap lit up in the firetube. I think that gives me a significant edge in the race to peak output. Not sure, just a guess.

No, it only runs 2-3 minutes at most. It has to be below zero to run longer than that.

coaledsweat wrote:I probably have twice the radiation with leaky windows and bad insulation (the house is 2200'). My answer is, I have no idea! Keep in mind though, I have twice the coal you have on tap lit up in the firetube. I think that gives me a significant edge in the race to peak output. Not sure, just a guess.

Sounds like a mighty good guess. The 260 is a beast indeed!!! You may also have a fluff timer to periodically keep the idling fire hotter. I have no timer.

My routinely heated interior space is ~2,300 sq-ft (with 1/3 of that a walk out basement). Plus on rare occasion (say below 10 to15 degrees degrees F.) our garage loop (zone 4, about as big as the basement, and sitting directly below our bedrooms) periodically calls for heat.

I had the timer stick on, tried to repair it and it bit me again. I haven't run the timer in 4-5 years, it refuses to die. If off for two days it will roar back to full burn in 10-15 minutes.

coaledsweat wrote:Mine is a 260 so I'm not sure how it relates but it never runs 5 minutes at one time once up to temp no matter how many zones are calling. 3-4 minutes tops. Member Townsend has a 260 on steam in a big old house with high ceilings, its run time is in seconds, not minutes, to satisfy the thermostat.

If the 260 has twice the available BTUH input/output and burn rate, then by inference burn time to generate the exact same energy as the 130 should logically be half.

By this simple measure of comparison if I had a 260 instead of my 130, my typical overall ~17 minute firing cycles (with a zone heat calling) would be reduced to 8.5 minutes. all else being equal. And my 5 minute ramp up time would be reduced to 2.5 minutes.

That gets us much closer.

Then on top of this if you are moving more GPM's per minute through the baseboards than I am, that could potentially reduce your heat-call times as well. As would presumably the case for your HWB's being rated to deliver more BTU's per foot than my old HWB's.

And (all else being equal) twice the radiators in conjunction with twice the heat generating capability would also logically mean half the time to satisfy a zones heat call.

Lots of variables to consider here, with all of them summing up to your fan cycle time being much shorter than mine.

coaledsweat wrote:I had the timer stick on, tried to repair it and it bit me again. I haven't run the timer in 4-5 years, it refuses to die. If off for two days it will roar back to full burn in 10-15 minutes.

I tried to add a timer and I suffered the same fate. After it stuck on and bit me the second time I disconnected it.

Typically when my S130 is on idle, especially when it's been several hours, the boiler water temperature is very, very hot 220-240 deg F. This is a result of the idle fire continuing to increase the boiler water temperature above the aquastat set point (160-180) that turned off the combustion blower. When a call for heat comes, there are plenty of BTU's available. When the aquastat low set point (130-140) is reached the combustion blower starts. If demand continues it will be ten's of minutes before the high set point is reached to again turn the combustion blower off. If I'm in summer mode just using the boiler for domestic hot water via an indirect hot water heater sometimes the initial boiler water was so hot the combustion blower doesn't even turn on.

I can safely operate with temperatures above 212 because it's a pressurized system and I have abundant air expansion tanks. Designed so the pressure safety valve doesn't open. My boiler water doesn't boil. All my piping is copper, no PEX. I have the old interval timer for a control system. It takes some effort to dial in the proper interval so that the fire doesn't go off in summer use.

My boiler fires at 170 degrees, and when one of my cold zones room temp water thereby dumps into it, it consequently falls to about 157 degrees. Then about 16-17 minutes later it shuts off at 180 degrees. The zone is at the same time drawing heat from the boiler at the rate of about an estimated 18-20K BTUH.

The time for my steam boiler AA260 to get up to speed is different from your hot water systems. It often is quite variable as well. Length of idle time, quality of pot fire, and such. I also do not have a timer and have never had a fire go out. I would like to try one though to see if it helps with pick up times.

With the colder weather my boiler is firing more often, and I just timed it at 11 minutes to fire, satisfy a zones heat call, and shut down. And about 15 minutes after that, a second zone valve opened, and that one fired the boiler for 9 minutes. Times are coming down.