The recent Boiler Talk episode.

Harvey Ramer

I the most recent Boiler Talk event, Mr. John Barba made the claim that a DT circ will prevent boiler short cycling in conventional boilers. I had a little bit of a problem with this, as a low flow with a higher DT or a higher flow with a low DT might very well be transporting the same amount of BTU's, according to the Universal Hydroninc Formula. This should have no effect on the cycle rate of the boiler, however he did provide some convincing case studies to support his argument.

I lay awake till midnight last night pondering this and I believe I might have the answer. I wonder if that low flow is allowing stratification to occur in the boiler. If that is the case, and the aquastat is close to the top of the hx, that could increase cycle time.

Interesting stuff!!

Harvey

icesailor

You can design a heating system so that it whispers sweet nothings in your ear.

Start putting tapped ports on your boilers, or get some flanges with 1/8" FPT tappings. Put some tridicator gauges. After you have designed that perfect Delta T into the system, see how close you came to the numbers. If you get that 20 degree #, it was an accident usually. The "experts" that think you can run 900' loops of 1/2" PEX under a slab will be so far off,,,,

Delta "T" and ECM's can do it with ease. Its easy to figure out head pressure and Delta T. A lot harder to achieve it.

hot_rod

look at the heat output from a typical fin tube baseboard emitter. They usually show the output at two different flow rates. Doubling the flow rate does not double the output.

If you change the flow rate thru the emitter, which is what I think the ∆T circ is doing as the speed varies, then the output changes.

At design conditions with a perfectly designed and installed system, the boiler matching the heat emitter you would get a 24 hr non stop cycle.

Change any factor, like lower the load, and the boiler will cycle more.

Unless the boiler output modulates it's output, as the load changes.

This article helps explain the heat output changes.


http://www.pmmag.com/articles/96339-how-flow-rate-affects-heat-output

Rich_49

Harvey , While it may seem that way , the mere fact is that a low Delta t would show that less BTUs were delivered where a higher Delta T would inversely show that more BTUs were delivered . Delta T is the product of how many BTUs left and returned . Kind of like having a bad rash you want to get rid of it , not have it hangin around . Why would we want to spend dollars pumping fluid that is giving us no benefit ? That's not efficient . It's just responsive to actual energy being transferred to the space in real time , much better than what we've had . I have been there to see a chronically short cycling boiler steady right out when BTUs that before the pump change were returning to the boiler were then being delivered , you just have a much better chance of the boiler operating as intended with the Delta T being monitored and controlled in this fashion .
Anthony Reikow put in a 008 VDT and set his boiler diff to 25* and saw a 15% gain in efficiency or as it were a 15% decline in his gas or oil bill , don't remember which fuel . I personally ripped out 4 B&G 100s on an oil system and replaced them with 1 0013VDT and 4 zone valves in a rather large rooming house and witnessed a 33% drop in fuel usage the first month which by the way was colder than the previous month . Why , because more BTUs were delivered to the space when the Delta increased and since it was colder the system required more flow and the boiler fired at a designed for rate and since more BTUs were delivered people throughout the building were warmer , the system was quieter . Improvement all around . Let's face it , there are a lot of hack systems out there and it is not magic but it will improve even the worst systems . Seen systems with too high a Delta (series loop ) that were returning too cold and rotting boilers while leaving the rooms at the far end cold , this can eliminate that . Seen systems where Delta was to narrow , not leaving enough energy out there because flow was excessive , this can eliminate that . And on some jobs it can lessen or eliminate short cycling through thermal purge if all is set up right . It's just a tool that improves efficiency system wide . I gotta be honest , I think cast iron boilers should have a bit of mass added also just so they can NEVER short cycle when capably arranged and programmed .

Harvey Ramer

Rich said:

Harvey , While it may seem that way , the mere fact is that a low Delta t would show that less BTUs were delivered where a higher Delta T would inversely show that more BTUs were delivered . Delta T is the product of how many BTUs left and returned . Kind of like having a bad rash you want to get rid of it , not have it hangin around . Why would we want to spend dollars pumping fluid that is giving us no benefit ? That's not efficient . It's just responsive to actual energy being transferred to the space in real time , much better than what we've had . I have been there to see a chronically short cycling boiler steady right out when BTUs that before the pump change were returning to the boiler were then being delivered , you just have a much better chance of the boiler operating as intended with the Delta T being monitored and controlled in this fashion .
Anthony Reikow put in a 008 VDT and set his boiler diff to 25* and saw a 15% gain in efficiency or as it were a 15% decline in his gas or oil bill , don't remember which fuel . I personally ripped out 4 B&G 100s on an oil system and replaced them with 1 0013VDT and 4 zone valves in a rather large rooming house and witnessed a 33% drop in fuel usage the first month which by the way was colder than the previous month . Why , because more BTUs were delivered to the space when the Delta increased and since it was colder the system required more flow and the boiler fired at a designed for rate and since more BTUs were delivered people throughout the building were warmer , the system was quieter . Improvement all around . Let's face it , there are a lot of hack systems out there and it is not magic but it will improve even the worst systems . Seen systems with too high a Delta (series loop ) that were returning too cold and rotting boilers while leaving the rooms at the far end cold , this can eliminate that . Seen systems where Delta was to narrow , not leaving enough energy out there because flow was excessive , this can eliminate that . And on some jobs it can lessen or eliminate short cycling through thermal purge if all is set up right . It's just a tool that improves efficiency system wide . I gotta be honest , I think cast iron boilers should have a bit of mass added also just so they can NEVER short cycle when capably arranged and programmed .

This would seem to coincide with Ray Wolforth's observations. He noted, that he has seen the BTU output of heat emitters increase when he throttled down the flow. This would seem contrary to the manufacturers ratings, but it's very hard to argue with observations in the field.

Harvey

Rich_49

Ray's a smart guy . All baseboard is rated for a 65* entering air temp . How often is that the actual temp entering the convector ? Less often than everyone thinks is my guess . Baseboards are usually at the corner of an exterior wall / floor intersection . What are the odds the air infiltrating at that point are always 65* ? Very slim chance that entering air form outside when it's 20* there is gonna be 65* . In fact that target temp is always moving as the indoor and outdoor temps . We all admit that mod con boilers were tested in lab conditions to achieve the high AFUEs and we do our best to get as close to those conditions with our jobs to get as close to rated efficiencies . Why do we believe that Panel Rads w / TRVs are so much more comfortable than many other types of visible heat emitters ? Because they are , I think it's solely because of where the thermostat (TRV) is located and the fact that it is able to vary flow through the emitter based on temp at the device . I have seen people set up baseboard with panel TRVs , Big old CI Rads with TRVs . What do all these devices do with this addition ? They vary flow rates at the device and they vary Delta T back at the boiler would be my guess .
We have (few) designed around an AWT which made Out door reset sound great , as it is . We design systems to overcome adverse outdoor conditions to keep the occupants of a particular building comfortable .
When exactly was it that we as industry professionals decided that Delta T was of little to no importance ? Building heating systems should be designed to be responsive and able to adapt to the real time conditions in which they are operating , people should not have to make allowances at any time . Everyone needs to make a decision , are we gonna design systems that make people comfortable , be as efficient as possible at all conditions and provide the same level of comfort throughout the range of outdoor temps , wind speed , differing infiltration . Fact is that baseboard or any BTU delivery device should operate at or close to the designed for building requirements at ALL TIMES . ODR , what good is it if we are not delivering those BTUs at the rate we designed for ? It's this simple guys , as the conditions change so must the flow rate . Delta T shows this in real time , if you design a system around a 10. 20 , 30 , 40 * Delta T if that is not what is happening in the system , you have failed . Why not use a tool that allows you the opportunity to be successful more of the time and that keeps your customers comfortable more of the time . I cannot believe the discussions that have taken place over the past couple years over this technology . All the manufacturers base equipment performance , whether it be heating or cooling on how much energy is lost or gained by the delivery .
During the boiler room episode that prompted this discussion someone brought up Reynolds numbers , i am glad they did . How do you think a GSHP would work if the ground loop did not shed or gain enough BTUs while traveling through the source side ? Don't hurt yourself , I'll tell you the answer , It wouldn't perform as designed and that would be a big deal and the manufacturer would tell you so when you called them and asked why it was not reaching a COP of 4 .
Delta T is the DIRECT RESULT of HEAT DELIVERED . Will anyone out there tell me that this is not accurate ? I'll be waiting .

icesailor

Back To Basics:

It's the puddle draining into the stream. There is little flow out of the puddle and the sun heats up the water in the puddle. The puddle slowly drains into the stream. It adds heated water to the stream but not enough to notice.

Anyone ever had a "Lack of heat" call and found a main partially hot but cold after some point because the impellor was bad and the flow was so slow that the heat emitters sucked all the heat out of the water? Mostly found with copper baseboard? The flow is so slow that the heat is transferred out of the water and in to the room through the emitter.

The only thing about Delta T's is that it is a goal to design for. It isn't constant, its just there. Its not a perfect world. Progress, not perfection.

Turbulence? Stratification? You get them both in baseboard loops. The horizontal runs are laminar and stratify. The runs turn to the vertical and develop turbulence that breaks up the stratification by mixing. The same turbulence that us used when mixing adult beverages with ice. If you want to see and understand Delta T better, get a couple of Tridicator gauges by the same manufacturer and put them on the supply and the return. You will see what goes on. Not only will you see and understand what Delta T is all about, you will also see and throw thermal lag running the burner. I think what The Flo Pro Team is trying to show is that you don't need hydraulic mining pumps to push water around in a heating system. Why else would they be pushing "Delta T" or ECM pumps that only slow the water down?

Some of you need to look at the most important pump in all of our lives. Our HEARTS. It pumps faithfully for decades and doesn't usually complain. It pumps very low pressures. If certain exact controls say that it needs more fluid, it pumps faster. It can increase pressures. If the pressures get too high, it can break old pipes. If you slice open someone's Carotid Artery, the pressure will pump the fluid great distances, and less and less as fluid loss occurs. Just like a Delta T or ECM pump. Until they run out of fluid to pump.

hot_rod

Or the sales and marketing team is over pumping the engineering team

hot_rod

If btus are returning to the boiler and there is still a call for heat, sounds like you don't have enough heat emitter connectrd

Rich_49

Maybe we should just radiate the entire outside wall in case it gets 100* below Rod .
* Maybe you forgot the term " designed for Delta T ?
* Maybe you forgot about the existence of Gils system sizer wheel , what was the constant in that ?
* Maybe you're lobbying for a new job with one of the P pump manufacturers . But forget about Wilo because they have that dreaded IR upgrade that makes the pump respond to temp differences , by the way they call it a 650.00 upgrade , and it's purpose some may ask , well boys and girls it's purpose serves to further the efficiency of operation of both standard and modulating condensing equipment through temperature control logic .
* Maybe BTUs are returning because you thought the Delta should not remain constant or as close as possible .
* Maybe you think the Reynolds number does not change at varying conditions .
* Maybe you believe that flow should always be turbulent as opposed to being what it needs to be at any given time . i have looked at my system requirements and found that the flows change , the temps change , and the one thing that remains constant is Delta T or at least it is supposed to since we designed for it .
* Maybe you don't design for it in which case you're all good .
* Maybe the increases in efficiency , decreases in boiler on time , decreases in peoples fuel bills , fuel and electric , people stating that areas that used to not heat are now comfortable are all just a figment of my imagination . Maybe I should stop coming within 2 degrees of my designed for AWTs and let the ends closest to return get cold and rot boilers with low RWTs .
* I guess the thousands of these new fangled Delta T pumps must not be working like we think they are , we should stop guys , right away , a couple of relics said so .
* Last but not least , how the hell did Pressure become a design concern other than for setting a pressure regulator and properly charging an expansion tank ?
* Maybe the Europeans are NPSH .

4Johnpipe

An attempt at explaining Delta T pumps. National studies have determined the fuel efficient range for "most" cars is between 40 & 60 MPH...some say 45 to 55. If I leave my driveway to head to NY it takes just about an hour exactly. Lets say the national speed vs. efficiency study is our heat emitter best design for heat emission and lets use the 40-60 MPH (happens to a 20 MPH difference). If I drive to NY and maintain 55 MPH I will get there in about an hour and twenty minutes. Round trip 2 hours 40 minutes. When I get home I will have used less gas. If I boogie up the Parkway at 75 MPH I get there in just under an hour but used up a lot more gas but I make the trip quicker. So I arrive sooner with nothing to do or plan for the trip and arrive "on time". If I use a set speed pump in a fin tube system and send the water through quicker it comes back home hotter(with nothing to do) which shuts down the boiler. If I use a VDT circulator (and plan for the trip) the water comes back right "on time" and uses less gas. The VDT pump isn't going to design your system. We have to do that. What the VDT pumps do is keep the speed limit (Delta T) within the efficiency range. This allows the heat emitters, whatever they are, to use the water moving through them to their maximum potential. Cold room greater heat emition from fin tube...warmer room less heat emition from fin tube. The VDT just keeps the water moving to satisfy the supply and return temperature sensors. It is hoping that the heat emitters have been sized for the room heat loss so this can be achieved.

Mark Eatherton

Easy Rich. Hot Rod meant no harm. I, like Harvey, am having trouble wrapping my arms around this because as I stated during the talk Show, I was taught that to size the circulator, you needed to know the required flow (based on the easy math number of 20 degree delta T), and worst case pressure drop scenario, which ALL pump manufacturers (including Taco) have been preaching since forever. Now, we are told that we have been over flowing these systems since forever (understandable and believable) and that we can turn the flow rate WAY down and achieve greater system efficiencies.

Again, as I stated, in my experience, with a bang bang boiler OR a modcon boiler, when I choke the flow down to achieve a 40 degree delta T, the discharge temperature of the boiler rises quickly, and the boiler starts bouncing off its high limits. Short cycle city for sure. Now, we are being told that it won't cause the boiler to short cycle, and again, in my minds eye, it doesn't make sense, and until it does, I can't get behind the initiative. Remember, I am old school, but also maintain an open mind to anecdotal experiences as provided to me by people like yourself and Dave Yates. Thank you for sharing this information BTW.

The other thing that causes me consternation is the reduced flow and its effects on the Reynolds numbers. To my knowledge, no one has performed tests on different emitters (BBR, cast rads, panel rads, RFH, RCH, RWH, etc) and its (significantly lower flow rates) effects on heat transfer. I know its going to degrade, but how much, I don't know, but need to know before I am comfortable significantly reducing the flow.

And all of this is so new, that I am not sure ANYONE knows the answers. But again, you, and Dave Yates have both made statements that got my attention, but I am still searching for answers to how it is that it works so I can justify it in my mind.

Now, as I also stated, in my many years (over half my life, and I am now 61) experience, even on those jobs that I know for a fact were properly sized, when I show up and see the boiler doing a 50% duty cycle at "design" condition, it tells me that everything (emitters, boilers, pipes, pumps, EVERYTHING) is probably oversized by a factor of two. So even though I am still confused, I will keep an open mind, and keep moving forward. I think my biggest fear stems from having seen systems with undersized circulators whereby the flow was VERY low, and the emitters at the beginning of the circuit were extracting the majority of the heat, leaving the balance of the emitters less hot than they needed to be to accomplish the goal of even warmth.

And to your point, yes they (Taco) do have a LOT of the BumbleBee circulators out there, and I can't honestly say that I've seen anyone with any issues related to poor heat delivery on these forums. I've heard noise issues, but then again, all the pumps I've dealt with over the years have had noise issues of one type or another.

They are obviously on to something. What, I am not 100% sure, but I do have one, and when I get it installed, will be able to document the operating characteristics and compare them against what is there now (DP circ) and report back later.

In all honesty, I am not certain that all that we've been taught over the years as it pertains to sizing of all components isn't extreme overkill, but there's not a hydronics contractor in their right mind that would say "Oh, the load says 100,000 btuH. I think I will set a 50,000 btuH boiler and also cut the flow in half"… I did it in my own home (boiler size wise) but kept the circulator properly sized based on standard engineering values. My home stays snug as a bug in a rug, even below design conditions (0 degrees F for Denver).

Just when you think you know everything you need to know, you find out you don't know squat… or the rules have been changed. This is the case with the DT pumps. They pretty much go against everything we've been taught (and are still teaching) making it hard to easily swallow the pill. It just doesn't make sense, other than seeing the information coming out of the field from people like yourself.

Thanks for sharing.

ME

4Johnpipe

Mark you said~~I think my biggest fear stems from having seen systems with undersized circulators whereby the flow was VERY low, and the emitters at the beginning of the circuit were extracting the majority of the heat, leaving the balance of the emitters less hot than they needed to be to accomplish the goal of even warmth.~~
The coolest thing with VDT is that this will be corrected with them. We can control the range of DT via a setting on the circulator. When this condition wants to occur. The return water would be cooler than the setting on the circulator and will speed up to reach the desired setting. What I have found on existing systems in a boiler swap situation is we close off some of the louvers on the fin tube or remove some of the fin tube inside the enclosures.
The VDT all but ensures one section can not rob "all" of the heat.

Hurry up and get that VDT installed and start your documentation...You will be pleasantly surprised!

4Johnpipe

Another thought I had talking about slow flow...How did good old gravity systems ever work? They may have had 1/2 GPM on a good day...just a consideration...

bob_46

Ice said
Some of you need to look at the most important pump in all of our lives. Our HEARTS. It pumps faithfully for decades and doesn't usually complain. It pumps very low pressures. If certain exact controls say that it needs more fluid, it pumps faster. It can increase pressures. If the pressures get too high, it can break old pipes. If you slice open someone's Carotid Artery, the pressure will pump the fluid great distances, and less and less as fluid loss occurs. Just like a Delta T or ECM pump. Until they run out of fluid to pump.

To expound ,the heart pumps 2000 gallons per day almost 1.5 gpm . The adult body has over 50,000 miles of blood vessels . The head pressure leaving is 5.2' w.c.

hot_rod

Mark Eatherton said:

Easy Rich. Hot Rod meant no harm. I, like Harvey, am having trouble wrapping my arms around this because as I stated during the talk Show, I was taught that to size the circulator, you needed to know the required flow (based on the easy math number of 20 degree delta T), and worst case pressure drop scenario, which ALL pump manufacturers (including Taco) have been preaching since forever. Now, we are told that we have been over flowing these systems since forever (understandable and believable) and that we can turn the flow rate WAY down and achieve greater system efficiencies.

Again, as I stated, in my experience, with a bang bang boiler OR a modcon boiler, when I choke the flow down to achieve a 40 degree delta T, the discharge temperature of the boiler rises quickly, and the boiler starts bouncing off its high limits. Short cycle city for sure. Now, we are being told that it won't cause the boiler to short cycle, and again, in my minds eye, it doesn't make sense, and until it does, I can't get behind the initiative. Remember, I am old school, but also maintain an open mind to anecdotal experiences as provided to me by people like yourself and Dave Yates. Thank you for sharing this information BTW.

The other thing that causes me consternation is the reduced flow and its effects on the Reynolds numbers. To my knowledge, no one has performed tests on different emitters (BBR, cast rads, panel rads, RFH, RCH, RWH, etc) and its (significantly lower flow rates) effects on heat transfer. I know its going to degrade, but how much, I don't know, but need to know before I am comfortable significantly reducing the flow.

And all of this is so new, that I am not sure ANYONE knows the answers. But again, you, and Dave Yates have both made statements that got my attention, but I am still searching for answers to how it is that it works so I can justify it in my mind.

Now, as I also stated, in my many years (over half my life, and I am now 61) experience, even on those jobs that I know for a fact were properly sized, when I show up and see the boiler doing a 50% duty cycle at "design" condition, it tells me that everything (emitters, boilers, pipes, pumps, EVERYTHING) is probably oversized by a factor of two. So even though I am still confused, I will keep an open mind, and keep moving forward. I think my biggest fear stems from having seen systems with undersized circulators whereby the flow was VERY low, and the emitters at the beginning of the circuit were extracting the majority of the heat, leaving the balance of the emitters less hot than they needed to be to accomplish the goal of even warmth.

And to your point, yes they (Taco) do have a LOT of the BumbleBee circulators out there, and I can't honestly say that I've seen anyone with any issues related to poor heat delivery on these forums. I've heard noise issues, but then again, all the pumps I've dealt with over the years have had noise issues of one type or another.

They are obviously on to something. What, I am not 100% sure, but I do have one, and when I get it installed, will be able to document the operating characteristics and compare them against what is there now (DP circ) and report back later.

In all honesty, I am not certain that all that we've been taught over the years as it pertains to sizing of all components isn't extreme overkill, but there's not a hydronics contractor in their right mind that would say "Oh, the load says 100,000 btuH. I think I will set a 50,000 btuH boiler and also cut the flow in half"… I did it in my own home (boiler size wise) but kept the circulator properly sized based on standard engineering values. My home stays snug as a bug in a rug, even below design conditions (0 degrees F for Denver).

Just when you think you know everything you need to know, you find out you don't know squat… or the rules have been changed. This is the case with the DT pumps. They pretty much go against everything we've been taught (and are still teaching) making it hard to easily swallow the pill. It just doesn't make sense, other than seeing the information coming out of the field from people like yourself.

Thanks for sharing.

ME

Proud to have you as a "relic" friend:). Pretty sure all those years of teaching hydronics at Red Rocks were not in vain. Regardless of some that would change the laws of thermodynamics to suit a new product. Keep it turbulent ME.

Rich_49

A heating system is an engine gentlemen . Follow the yellow brick road . My theory is the more we can maintain any of the state functions and / or variables the closer we are to achieving our goal , Could someone define our goal ?
http://en.wikipedia.org/wiki/Thermodynamic_state
My understanding that as a system tries to reach thermal equilibrium there are ever changing rates of energy transfer between the system and the environment in which it is operating . The more variables we can closely control the better we will perform .
For those who may have taken the wrong direction .
http://en.wikipedia.org/wiki/Thermodynamic_process . Please read thermodynamic potential

http://en.wikipedia.org/wiki/Differential_(infinitesimal)

hot_rod

As I under

Rich said:

A heating system is an engine gentlemen . Follow the yellow brick road . My theory is the more we can maintain any of the state functions and / or variables the closer we are to achieving our goal , Could someone define our goal ?
http://en.wikipedia.org/wiki/Thermodynamic_state
My understanding that as a system tries to reach thermal equilibrium there are ever changing rates of energy transfer between the system and the environment in which it is operating . The more variables we can closely control the better we will perform .
For those who may have taken the wrong direction .
http://en.wikipedia.org/wiki/Thermodynamic_process . Please read thermodynamic potential

http://en.wikipedia.org/wiki/Differential_(infinitesimal)

as I understand it

Hot goes to cold, always
The rate of heat transfer is based on delta T, wider delta, more energy transferred
Turbulent flow promotes the best energy transfer

In a modern engine we can adjust rpm, fuel mixture, valve timing to get optimum performance

We don't force the engine to work in a small rpm range even though best hp and torque is defined at certain rpm

As the load on the car changes the engine adjusts. You would not lock the engine at 3000 rpm to travel 30 mph

So why lock a boiler distribution to one temperature condition. On cold start a wide delta t moves the most energy. As the system warms the delta t lessens.

Just this AM I got notice of a new Taco "self sensing series". Pump that modulates based on pressure changes in the system, without the need for external pressure sensors

Sounds an awful lot like a delta P pump

4Johnpipe

Rod said~~
As the load on the car changes the engine adjusts. You would not lock the engine at 3000 rpm to travel 30 mph~~

I wouldn't lock the engine at 3000 rpm's however if I did and at that rpm my car was doing 55 I would benefit from the highest available gas mileage (I've got places to be...LOL). The gas peddle determines the load on the engine. Much like a thermostat determines the load on a boiler.

~~So why lock a boiler distribution to one temperature condition. On cold start a wide delta t moves the most energy. As the system warms the delta t lessens.~~

VDT circulators have nothing to do with locking the boiler temperature. The boilers limit controls along with more modern ODR controls do that. Cold starts allow more energy to be extracted from the emitter due to colder air entering the fin tube convector (as an example). As the room that the emitter warms the entering air (to the convector) warms and less convective action takes place. When we have a slower flow of constantly heated water as with a VDT we get convection that more accurately correlates with the convective properties of the emitter. It is especially at these conditions that a boiler will short cycle with a fixed speed pump. The convector by design is no longer able to extract the renewed heat from the hot water and returns it to the boiler hot. This causes the boiler to heat up quicker...its not cooling down and the circulators run longer. I would use an example of power braking here. One foot on the brake and one on the gas...tires spinning and going no where...

Rich_49

Rod said
"as I understand it

Hot goes to cold, always . CORRECT. Less and less hot transfers as the cold gets warmer .

The rate of heat transfer is based on delta T, wider delta, more energy transferred .

ALMOST RIGHT . The driving Delta in this instance is the differential between the system and atmosphere . As that Delta narrows between these less heat will be transferred . Again Delta T at the circulator is the product of how much heat was transferred .

Turbulent flow promotes the best energy transfer .

CORRECT MAYBE .
Except I would replace the word best with most . More aptly I would believe that the best energy transfer would be the one where it takes place at the rate where the system and the atmosphere allowed such using the least amount of energy .


In a modern engine we can adjust rpm, fuel mixture, valve timing to get optimum performance .

PRETTY GOOD ANALOGY . We adjust these things based on needs and the needs of our systems change from moent to moment . Would you tune your car for the quarter mile to drive in NYC ? In our modern heat engine similarly to the internal combustion engine you mention we want certain things to happen . the one that comes to mind for me is the fact that we don't want fuel (water) that is not being burned (transferring heat) to be introduced into the engine . Narrower Delta T is the same as smelling fuel at your exhaust . Something is wrong.

We don't force the engine to work in a small rpm range even though best hp and torque is defined at certain rpm

THE BEST horse power and torque happens to be ever changing depending on the conditions you are driving under . We don't wanna change the result . Rod , Delta T is a result

As the load on the car changes the engine adjusts. You would not lock the engine at 3000 rpm to travel 30 mph .

PERFECT . So why in the world would you move enough water through the system to deliver 3000 BTU when you only need 1100 BTU . By the way emitters are rated at a specific EAT , I contend that after about 1 minute of on time that condition changes and heat transfer between atmosphere and system becomes lesser also . As this happens the delta T in the fluid narrows which says to me that the BTUs are not being transferred and we should slow down .

So why lock a boiler distribution to one temperature condition. On cold start a wide delta t moves the most energy. As the system warms the delta t lessens.

IF THE DELTA T narrows we used too much energy to not deliver the BTUs . Again Delta T is the product of what was delivered , it is the answer to our math equation . Maybe nobody explained the name of the game to many we move energy around and for the past many years it has been our job to move that energy while using less energy . So please explain to me how getting BTUs back to the point of origin that should have been delivered is efficient .

Just this AM I got notice of a new Taco "self sensing series". Pump that modulates based on pressure changes in the system, without the need for external pressure sensors .

THAT is amazing , Taco makes pumps for all kinds of parameters . This surprises you why .

Sounds an awful lot like a delta P pump

Rod , maybe you should click on some of the stuff I attached unless of course you know everything in which case , don't bother . Narrow Delta T in a system in which the pump was sized using a calculation which includes Delta T in the equation has been a phenomenon which we had to accept up until recently . Fact is that the conditions within our systems are changing in a way that we cannot see or that has ever been modeled . It is based on what's going on in the system and what is happening in the atmosphere around our emitters . Maybe nobody told you this but as we near thermal equilibrium heat transfer lessens , that's why it's called equilibrium . It cannot be achieved inside the system because if it could we would not need a system . here's one for you , If we want to widen the Delta T between the outdoors and the indoors the most efficient way there is to keep the BTUs we have produced transferring the most energy they can with the atmosphere . That is our business and I hope you and those teaching the next generation would embrace that fact .
I still love you Rod .

hot_rod

You said "fact is that the conditions within our systems are changing in a way we cannot see or that has ever been modeled"

Really! Inside that copper tube?

Stop drinking the koolaid

Harvey Ramer

Obviously there are a lot of differing opinions

Rather than generalize, lets pick a scenario and roll with it. Lets look at a conventional boiler with a single speed circ and zone valves or single speed circ for each zone. No difference for this scenario. Lets put 3 or 4 zones on the system and take a medium load condition, which is the majority of the heating season. We have, at most 2 zones operating simultaneously.

Now lets look at the differences in the above scenario between the Bumblebee and the single speed.

Heat emitters:
Single speed; Over pumped, Higher average surface temp, Faster heat transfer, low DT.

Bumblebee; Lower average surface temp, Slower heat transfer, Nominal DT.

Return Pipes Uninsulated:
Single speed; Higher average surface temp, Faster heat transfer
Bumblebee; Lower average surface temp, Slower heat transfer
Heat lost here is wasted.

Boiler Start on call for heat:
With the bumblebee the boiler will reach high limit more quickly but spend less time in a condensing state. A conventional boiler can gobble some BTUs while condensing. All the water that forms on the heat exchanger has to be either evaporated or turned to steam. Takes some energy for a phase change.

Boiler in operation between high limit and differential cut in:
Single speed; The amount of till the boiler hits the cut in will be less. We know this because the return piping and emitters are losing heat faster. The amount of time till the boiler hits the high limit is more.

Bumblebee:
The amount of till the boiler hits the cut in will be more. We know this because the return piping and emitters are losing heat slower. The amount of time till the boiler hits the high limit is less.

Duration of call for heat:
This is a tricky one. On one hand we have a difference in AWT of the emitters (favors single speed). On the other hand we have a boiler that is condensing a little longer (favors bumblebee).


That was a fun exercise. Still some unknowns but I think, all things considered, I tend to favor the Bee in regards to total fuel consumed.

Don't tell me to insulate the pipes! This is just a scenario. One that I see all the time.

And I'm only concerned with the fuel consumed by the boiler, not electricity usage.


Harvey

Rich_49

Delta T of fluids has been telling us for years that LESS WORK was achieved than we intended by design . The guys at Taco recognized this obviously and moved us closer to EXERGY . I for one am damn glad to have a tool that is allowing my systems to do the most WORK possible using the least amount of energy . You my friends are not listening to the systems . I now have a stethoscope and a tool that makes hearing much easier .

As far as keeping it turbulent , be my guest but remember that it was Planck that said " Frictional pressure never does positive work "

Harvey Ramer

You misunderstood me. I said I tend to favor the Bee in regards to total fuel consumed. That means I think the Bee might take a little less. I should have been more clear.

If you have a fixed water temp, the average surface temp will be lower with a 20 deg dt than with an 8 deg dt. Lower surface temp, slower heat transfer. End of story.

I was looking at the entire system operation from a call for heat till the thermostat is satisfied. And what I wrote is not conclusive or a law. It is merely the musings of a wet head.

Disagree if you will, but I believe I am correct in everything I wrote.

Harvey Ramer

You are only thinking of boiler on time. Think of boiler off time. When the the boiler is off it is not using any fuel. And remember to consider the entire duration of a heat call. Not just what is going on in the midst of a call.

Rich_49

Everyone is focused on a mechanical equation and mechanical work and keeps forgetting or disregarding the natural processes that are going on simultaneously .
First thing I would like to address is the forever mention of Reynolds numbers . Osborne Reynolds only studied heat transfer between fluids and solids boys and girls . I might add that he also depicted 3 types of flows , we seem to forget the third which are Transitional flows occurring between 2,000 and 4,000 . I believe these flows are what is taking place a lot of the time . So fluids to solids heat transfer is all the Reynolds numbers dealt with and that is mechanical work but what about the heat transfer that must take place between the solid wall of the pipe and the reservoir ( room air ) ? That is a process in which we have no control , in fact the only way to influence it would be to widen the Delta T . So make the fluid hotter or open a window . Neither is what we are attempting to achieve .
The Reynolds numbers are very predominant in geo exchange and heat exchangers sizing. Rightly so as both these processes are dependent upon fluid to solid to fluid and fluid to solid to solid or fluid as we are learning from thermal batteries . Neither of these technologies deals with the rate of transfer between a solid and AIR . GET IT ? Enough about Reynolds numbers because they have little to contribute to our conversation .
I believe I have figured out how to explain the lessening of the short cycle to an extent .
A 50,000 BTU boiler will heat 5 GPM . We can keep that boiler running forever if we take 50,000 out every hour . At a 20 degree Delta T the average temp in a boiler with a high limit of 180* and an AWT in the emitter of 170* we can achieve thermal equilibrium within the system . The hotter return water cannot lower the AWT of the boiler thus reaching high limit faster . Besides that why in the hell would one want to move 171.4 GPH instead of 120 GPH . Congratulations you have now managed to hurt your combustion and wire to water efficincy , good job . Thermal equilibrium is not a foreign idea now is it ? To learn about this phenomenon read Siggy's latest edition of Modern hydronics .
We can never forget that there are forces beyond our control that influence the rate at which we can transfer energy . I keep hearing about a pump that slows down in this discussion , Shh it speeds up also . Program your desired , designed for Delta T on the dial and start installing more efficient systems for your customers and our industry fore Christ's sake . We might want to also think about how our industry got to it's pathetic state , I have thought about this long and hard and can only come to following ; some think they know it all and have not been teaching theory but instead spouted off about products and 1/4 of the knowledge that went into developing that tech and compartmentalization or not teaching the laws and all that they encompass and address .
If one truly believes in the laws and studies them he will be taken to things like this

http://en.wikipedia.org/wiki/Parabolic_partial_differential_equation

http://en.wikipedia.org/wiki/Stochastic_process

http://en.wikipedia.org/wiki/Partial_differential_equation

And never forget about EXERGY . That is our job .