How long does it take to get your tank up to temp.

[machinistbcb]

How long does it take to get your tank up to temp from initial start-up of 60 degrees to 180 degrees?? I finaly got my tank insulated with 12" to 20" on blown in celluose and I fired the boiler up last night. The top of the tank went to about 135 degrees with 4 hours or so then the bottom caught up with the top temp. After about 12 hours the whole 1500 gallon tank was around 145 degrees. Does this seem to be tanking longer than is shoud to get up to temp ? I think a 3 way valve would help a lot when starting from the cold temp below 120 degrees, also I wish I had a little more BTU My tarm is rated at 105,000.

 

[Nofossil]

How long does it take to get your tank up to temp from initial start-up of 60 degrees to 180 degrees?? I finaly got my tank insulated with 12" to 20" on blown in celluose and I fired the boiler up last night. The top of the tank went to about 135 degrees with 4 hours or so then the bottom caught up with the top temp. After about 12 hours the whole 1500 gallon tank was around 145 degrees. Does this seem to be tanking longer than is shoud to get up to temp ? I think a 3 way valve would help a lot when starting from the cold temp below 120 degrees, also I wish I had a little more BTU My tarm is rated at 105,000.

Don't know how you have things plumbed, but the numbers work out reasonably well. 1500 gallons is about 12,000 pounds, so every degree is 12,000 BTU.

60 degrees to 145 degrees is just over a million BTU. Over a 12 hour period, that's about 85,000 BTU/hr delivered into storage. 85.000 BTU/hr is just about what I'd expect from a unit with a maximum output of 105.000 BTU/hr.


I'm curious about why you have so little apparent stratification. You'll find that as your tank temp gets closer to 180, it will be harder to heat it - less temperature difference to work with.

 

[Bad Wolf]

Somebody check my math:

1,500 gallons is 12,500 pounds of water. (8.328lbs/gallon) Thats 12,500 BTU's per degree of temp rise. 60 to 135 is 75 degrees. 12,500 x 75 = 937,500 BTU's. The TARM 2000 is rated at 102,500 BTU/hr. With no heat loss that should have taken over 9 hours.

I'm interested in the answer. I'm also installing a TARM 2000 and 1200 gallons of umpressurized storage.

Greg H

 

[in hot water]

How long does it take to get your tank up to temp from initial start-up of 60 degrees to 180 degrees?? I finaly got my tank insulated with 12" to 20" on blown in celluose and I fired the boiler up last night. The top of the tank went to about 135 degrees with 4 hours or so then the bottom caught up with the top temp. After about 12 hours the whole 1500 gallon tank was around 145 degrees. Does this seem to be tanking longer than is shoud to get up to temp ? I think a 3 way valve would help a lot when starting from the cold temp below 120 degrees, also I wish I had a little more BTU My tarm is rated at 105,000.

BTU required = 8.33 (weight of 1 gallon) (V 1500 gallons) (180-60)

So 8.33 X 1500 X 120 or 1, 499,400
Call it 1.5 million BTU

If the boiler is actually putting out 100,000 BTU/ hr then 15 hours. But there will be some losses and the closer the delta t the slower the exchange. Pretty tough to have the boiler cranking full output, unless you standby to stoke.

hr

 

[WoodNotOil]

Mine moves pretty quick up to 150*. It takes a really long time above that to see much difference and I too notice that the bottom temp is rising significantly during the the slow upper temp charge. I think there is a point at which the thermocline is disrupted somehow. Maybe it is that the coldest bottom layer below it is pumped completely out, charged and returned to the top. Then the thermocline becomes the bottom layer and a new thermocline must take its place. In some instances the temp differential may not be significant enough for one to remain or even form. This my be one of the ongoing problems yet to be solved with heat storage systems where the water comes in and out of the tank. See http://books.google.com/books?id=Es...&hl=en&sa=X&oi=book_result&resnum=4&ct=result (scroll down to page 295 "6.7 Conclusion")

 

[Nofossil]

my math was based on approximating the weight of water at 8 lbs/gal, and an 85 degree temperature rise from 60 to 145 in 12 hours.

 

[in hot water]

Mine moves pretty quick up to 150*. It takes a really long time above that to see much difference and I too notice that the bottom temp is rising significantly during the the slow upper temp charge. I think there is a point at which the thermocline is disrupted somehow. Maybe it is that the coldest bottom layer below it is pumped completely out, charged and returned to the top. Then the thermocline becomes the bottom layer and a new thermocline must take its place. In some instances the temp differential may not be significant enough for one to remain or even form. This my be one of the ongoing problems yet to be solved with heat storage systems where the water comes in and out of the tank. See http://books.google.com/books?id=Es...&hl=en&sa=X&oi=book_result&resnum=4&ct=result (scroll down to page 295 "6.7 Conclusion")

The shape of the tank matters also. tall skinny tanks as opposed to horizontal type LP tanks, when talking stratification.

Another spin on that heat formula

To determine the rate of heat transfer into the water add time into the formula Q= 500 X Flow X delta T 500 being 8.33 (weight of water) X 60 (minutes per hour)

So 500 X 10 gpm X (180-60) = 600,000

With a warmer tank 500 x 10 X( 180- 145) = 175,000 There is a density number to consider as warmer water transports heat at a reduced rate, not enough to change the answer here by much.

hr

 

[WoodNotOil]

Good point about the shape of the tank. Mine is 4x4x12 concrete lined with EPDM unpressurized and flat plate hx. The shape probably acts a lot like a pressurized horizontal LP tank would.

Machinistbcb - What are the dimensions of your tank? Is it an LP tank and if so, what is the orientation?