Does anyone have good information on the actual output of a 7260?
I'll try to keep the reason for this question short but here are a few details.........
In 2005, back when fuel oil was $1 something per gallon and the raw milk price was crowding $20/cwt we put a heating system in a brand new 1,100 cow dairy facility. The owner wanted everything in-floor radiant including about 4,000 sq ft outside holding area plus 150' of outdoor gutter for the free stall barn.
Lot's of load! We installed a Viessmann Rondomat with a 2 stage Weishaupt burner firing at about 325K/625Kbtu. (That thing will make some serious heat.......) Problem is now that oil is nudging $3.00/gl around here and milk price is poor, the massive load is busting his budget. So he hired the local CB guy to install a 7260 for him to heat his barn. The CB guy told the owner it would heat everything (NOT) and actually hired a decent mechanical contractor to install the thing for him. He did a nice install on it. 1-1/2" pex, an adequate circ and a correctly sized HX and 2" copper tied into our piping. The installer had contacted me and sought my opinion on where exactly to tap into the piping. Being that the Viessmann runs up to the 220* range for domestic hot water production through the indirect, I told him to tap into the return from the low temp circuit after the mixing valve and just let it dump as much heat as it could into the return before the boiler. Which he did in good fashion.
The dairy guy had asked me for a quote on wood heat and I gave him an option for an Econoburn 500K with 1000gl storage or a pair of Garn1500's. But the CB was way less shekels so he went that way. What can I say.......
Anyhow the farmer called me and said he had no heat in a couple areas after the CB was installed and would I take a look at it. Turned out that there was some air in the system that had things constipated so nothing serious there. After taking care of that I was looking things over and decided to see how the wood side performed. I checked the wood load in the CB (fully loaded, probably 300#s of wood in it) and the water temp (189*) and then went back in the mechanical room and kicked on the holding area floor. I watched the 4-way valve and it held steady for about 10 minutes indicating that the wood side was dumping enough heat into the return to keep the Viessmann above 140* which is the minimum temp I have programmed into the boiler control. So far so good. Walked out to the CB and watched the temp (draft blower had already kicked on) which was already down to 171*. Within another 10 the CB had dropped to 150* and I heard the Viessmann start up in the barn. I opened the door on the CB to see if the fire was going good and was greeted by an inferno of flame and smoke so there was no question whether the wood was doing its job. The smoke coming from the stack looked like a house fire but had lightened up from what it was at the beginning.
I went back in the mechanical room to check temps and found the Viessmann at full trot, chugging 4 gallons/hour with the Termovar type valve diverting heat back to the CB to keep it above 150. Actual water temp going to the HX from the CB was 138 with return to the CB at only 113. I watched the temps for a few minutes and observed the return to the CB climb to about 140 as the mix valve on the Viessmann side of things picked up the load and then drop back as it cycled closed again. I scratched my head for a minute or two and figured out that the Viessmann was picking up not only the floor but also the CB until the mix valve let it catch up. This is not what the guy bought the CB for.
The specs on the CB website denote a water content of 764 gallon in the 7260. Dropping the temp from 190-150 in 20 minutes figures out to a load of around 750,000 btu's per hour and it was obvious this was waaaaay more than it wanted to handle. Now, as I stood there and watched for another 1/2 hour, the slab began to stabilize and the temps came back a little. The Viessmann went to low fire but stayed on and the CB climbed back to the 165* range. It would go no further than that.
My seat of the pants calculations lead me to believe that the CB was able carry about 275-300K of the load from the floor. That's making a lot of assumptions about flow rates actually making past the Termovar and to the HX. I'm just curious if anyone else here has ever played with this model CB and gotten a feel for actual ouput. Looking at the amount of wood the thing burned in the hour or so that I watched the system I would have expected more oomph from the CB.
Any input?
I'll try to keep the reason for this question short but here are a few details.........
In 2005, back when fuel oil was $1 something per gallon and the raw milk price was crowding $20/cwt we put a heating system in a brand new 1,100 cow dairy facility. The owner wanted everything in-floor radiant including about 4,000 sq ft outside holding area plus 150' of outdoor gutter for the free stall barn.
Lot's of load! We installed a Viessmann Rondomat with a 2 stage Weishaupt burner firing at about 325K/625Kbtu. (That thing will make some serious heat.......) Problem is now that oil is nudging $3.00/gl around here and milk price is poor, the massive load is busting his budget. So he hired the local CB guy to install a 7260 for him to heat his barn. The CB guy told the owner it would heat everything (NOT) and actually hired a decent mechanical contractor to install the thing for him. He did a nice install on it. 1-1/2" pex, an adequate circ and a correctly sized HX and 2" copper tied into our piping. The installer had contacted me and sought my opinion on where exactly to tap into the piping. Being that the Viessmann runs up to the 220* range for domestic hot water production through the indirect, I told him to tap into the return from the low temp circuit after the mixing valve and just let it dump as much heat as it could into the return before the boiler. Which he did in good fashion.
The dairy guy had asked me for a quote on wood heat and I gave him an option for an Econoburn 500K with 1000gl storage or a pair of Garn1500's. But the CB was way less shekels so he went that way. What can I say.......
Anyhow the farmer called me and said he had no heat in a couple areas after the CB was installed and would I take a look at it. Turned out that there was some air in the system that had things constipated so nothing serious there. After taking care of that I was looking things over and decided to see how the wood side performed. I checked the wood load in the CB (fully loaded, probably 300#s of wood in it) and the water temp (189*) and then went back in the mechanical room and kicked on the holding area floor. I watched the 4-way valve and it held steady for about 10 minutes indicating that the wood side was dumping enough heat into the return to keep the Viessmann above 140* which is the minimum temp I have programmed into the boiler control. So far so good. Walked out to the CB and watched the temp (draft blower had already kicked on) which was already down to 171*. Within another 10 the CB had dropped to 150* and I heard the Viessmann start up in the barn. I opened the door on the CB to see if the fire was going good and was greeted by an inferno of flame and smoke so there was no question whether the wood was doing its job. The smoke coming from the stack looked like a house fire but had lightened up from what it was at the beginning.
I went back in the mechanical room to check temps and found the Viessmann at full trot, chugging 4 gallons/hour with the Termovar type valve diverting heat back to the CB to keep it above 150. Actual water temp going to the HX from the CB was 138 with return to the CB at only 113. I watched the temps for a few minutes and observed the return to the CB climb to about 140 as the mix valve on the Viessmann side of things picked up the load and then drop back as it cycled closed again. I scratched my head for a minute or two and figured out that the Viessmann was picking up not only the floor but also the CB until the mix valve let it catch up. This is not what the guy bought the CB for.
The specs on the CB website denote a water content of 764 gallon in the 7260. Dropping the temp from 190-150 in 20 minutes figures out to a load of around 750,000 btu's per hour and it was obvious this was waaaaay more than it wanted to handle. Now, as I stood there and watched for another 1/2 hour, the slab began to stabilize and the temps came back a little. The Viessmann went to low fire but stayed on and the CB climbed back to the 165* range. It would go no further than that.
My seat of the pants calculations lead me to believe that the CB was able carry about 275-300K of the load from the floor. That's making a lot of assumptions about flow rates actually making past the Termovar and to the HX. I'm just curious if anyone else here has ever played with this model CB and gotten a feel for actual ouput. Looking at the amount of wood the thing burned in the hour or so that I watched the system I would have expected more oomph from the CB.
Any input?
