Actual BTU Out-put????

[fuelfarmer]

How many of you have measured the actual BTU out-put of your boiler? How did it compare the the rating of the unit?

If you did measure, were the numbers just estimates from charts and graphs, black art, or some other means?

 

[goosegunner]

I do weighed burns and I usually end up with 4000-4500 btus per lb of wood to storage.

That being said I run my loads at the same time. So it is difficult to determine what I have going to loads in pstead of storage.

I do a guesstimate of load btus vs outside conditions.

The average is considerably less than 200k btus per hour for boiler output.

gg

 

[JP11]

I think that I for sure can get well over rated BTUs. in a sustained snapshot (like a couple hours out of the 4 hour burn) My wood has been quite wet.. but I've seen thru numbers on the boiler of in excess of 20 degrees with 21 or so GPM. I think that over a full 4 hour burn I would hit the manufacturers 205k btu pretty close.

 

[hobbyheater]

How many of you have measured the actual BTU out-put of your boiler? How did it compare the the rating of the unit?

If you did measure, were the numbers just estimates from charts and graphs, black art, or some other means?

I measure more what I'm getting in BTUs per lb of wood. 144 lbs of dry hemlock gives between 750,000 to 850,000 BTUs into storage.
The Jetstream is rated at 120,000 BTUs per hr. and is very consistent at putting 105,000 BTUs per hr. to storage.

 

[BoilerMan]

but I've seen thru numbers on the boiler of in excess of 20 degrees with 21 or so GPM.

Thats the info you need to find the answer to this question.

GPM and T (temp rise through the boiler)

A flow meter, and two direct contact thermometers is the most accurate way to know BTU output.
Those with storage can do the same calcs, T x gallons heated = BTU

 

[jebatty]

I've measured btuH output and efficiency numerous times. I think this is my most recent post to the Forum. Storage Charging / Stratification / Efficiency Although it deals with efficiency, the data easily is converted to output. With 137 lbs of wood, 89% efficiency, and 6.5 hours of burn time, output is: 137 x 6050 x 0.89 / 6.5 = 113,489 btuH. Rated capacity of the Tarm is 140,000 btuH, so this is average output of 81% of rated output. Other test burns clearly show that during high burn periods output is somewhat greater than the rated 140,000 btuH. For me average output over a burn period is a more realistic measure of boiler performance than is peak output. In other posts I have stated as a rule of thumb that for most gasification boilers 75-80% of rated output is a good estimate of average output over a burn period. The higher number would more accurately reflect usable output if the boiler is in the heated space, and the lower number if not.

 

[Bob Rohr]

a BTU meter would be the most accurate measurement of what is actually going to the load. Measuring the flow rate and the delta T as mentioned above. This is a hot subject in the solar thermal industry right now as metering and incentives for solar should be based on the system output, not the cost or number of collectors. California has taken the lead onn this and they want to offer incentives based on production, as the do with the PV (electric) side of solar.

By years end there should be a standard in place to regulate BTU metering. It will look a lot like the current European standard. The company I work for has several folks on that committee.

Another inexpensive and simple method is with the new solar controllers. The setting is called OHQM option-heat quantity metering. You install a sensor on supply and return, and enter the fluid type, and flow rate from a flow meter installed inline. The control will correct for variations if the pump is operated in a variable speed position.

We have compared these OHQM readings to a certified and sealed BTU meter and found them to be very accurate. So the solar controller can be a multiple delta T function for your system and a heat metering all for one price in one control.

On our control it reads out in KWh as most homeowners do not know BTU/hr. Reading in KWh allows you to compare to energy prices easily.

For best accuracy and a certified meter, you can also connect a rotary pulse meter as an option.

hr

 

[Trex83]

Same idea here, we are trying to fit a SR pulse meter an two thermometers with a datalogger on a BioMass 60. My father is afraid the SR meter and the Danfoss VTC mixing valve will create too much of a pressure drop and reduce the flow to the boiler. Just have to find a scale to measure the wood going in the load.
We also expect to be a difference when starting the boiler with a coal bed or a cold start. I will post a pic when its all setup.
trex

 

[BoilerMan]

This sounds like fun! What type of Cv rating if any does the SR meter have, you could crunch the numbers to calculate if it'll slow flow too much.

 

[Trex83]

This sounds like fun! What type of Cv rating if any does the SR meter have, you could crunch the numbers to calculate if it'll slow flow too much.

The only indication I have is the new generation SR II meters from Sensus and to compare it with other water meter standards. I have an older model of SR on 5/8. Not sure how long its going to take the heat either.
About 4 ft of head loss at 12 GPM.
My mixing valve is CV of 10 and looking at the curve about 1.5 psi at 12 GPM (3.5 ft head loss). Three or four 90 deg bends (if I make room for the SR meter). Then looking at 8 or 9 ft of loss... oups! Now only at about 6 GPM for the small pump. I think my dad was right in the first place...

 

[BoilerMan]

After reading about the Sensus meter I think your right, too much restriction for what your trying to do.
Taylor

 

[Trex83]

After reading about the Sensus meter I think your right, too much restriction for what your trying to do.
Taylor

Already got another pump. We should have about 20 GPM for a BioMass 60. The model we had wasn't enough even without the flow meter installed...
Thanks for the help.