Now I see why the Grundfos person posted the video on You Tube.........

Mark Eatherton

I got my copy of Contractor Magazine, and the whole front cover (Advertisement) is ALL about Taco's variable speed controller based on delta T, and they are claiming that energy savings associated with ECM motors are garbage, and that their product holds a significant potential for electrical savings. Now, I know this is going to create some controversy, but being as familiar with the ECM circulators that are on the market, I'd like to take Taco to task, and have them prove to me, and the rest of the hydronic world how it is that they arrived at this conclusion.In my little minds eye, there is NO WAY that a conventional Taco 00 motor could possibly be more efficient than an ECM motor, regardless of the ECM manufacturer.They are claiming that Delta T is more efficient than Delta P, which is what most ECM circulators are programmed to run on.I'd love to see more of their assumptions...Anyone? Taco,WILO, Grundfos, Buehler??? Buehler???ME



PS, heres a link to their article



<a href="http://www.taco-hvac.com/images/vdt_resources/WhitePaper_00VDT_DT_DP.pdf">http://www.taco-hvac.com/images/vdt_resources/WhitePaper_00VDT_DT_DP.pdf</a>



ME

NRT_Rob

I could see the arguement

if you base on delta-T, your flow requirements range from 0 to full flow with the load.



if you base on pressure, it only varies with how many zones are calling. if you have a good reset curve, most zones should be calling most of the time all winter.



So if an ECM motor can do the same pumping power with 50% of the energy, just for round numbers, the question would be... how much are you at less than 50% load, where the delta-T method would have an advantage?

NRT_Rob

though the cost savings they report are pretty weak

they claim $3/heating season for ecm pump savings.



not sure how they get that. I could see that per MONTH, but not for a heating season.

Jean-David Beyer

Thinking about delta-T

It is not very cold here today, about 55F outside.



My upstairs baseboard system has lots of baseboard for the calculated heat loss.



So today, when it was running (mod|con boiler with outdoor reset), the hot water supplied was about 100F and the return between 98F and 99F. The circulator is just a Taco 007-IFC supplying 2.8 gallons/minute (calculated, not measured)..



But thinking about a delta-T circulator, what would happen? I assume it would slow down until the loss was 10F or whatever I set it for. Now the flow required for that must be pretty low. So would the delta-T slow down to about 0.56 gallons per minute? At some point does not the curve reverse? At the extreme of no flow at all, the two temperatures would be equal and it cannot slow down any more. At some point, slowing the circulator down will reduce the temperature difference. In other words, the circulator must go fast enough that the cooling in the supply and delivery pipes is negligable, but slow enough to get the set temperature drop. In my upstairs, where heat loss is quite small, these two may be contradictory.



Things will probably be all right when it gets really cold outside, but right now it cycles pretty fast because of the small heat load up there. The circs. run, but the boiler cannot modulate below 16K BTU/hr and the load up there, even on the design day, is only about 6500 BTU/hr, and it is a lot less than that right now. Downstairs, where the load is about 23K BTU/hr things appear just fine, even on a day like this. And if both zones were asking for heat at the same time (in cold weather), the boiler would have no trouble keeping up.

MarkPFalade

You're going to love this,,,

I just installed one on a hydro air circuit. I haven't started it yet. Thursday may be the day. Oil fired Crown CT-3 with an MS-40 and a Bryant Evolution HP setup. It's a variable speed air handler and I'm wondering how they're going to get along. My thought was I already need 180* for the indirect so instead of getting involved with reset I'd try the delta t pump on the coil instead and see what happens. If worse comes to worse I have the 007 that came with the boiler to swap out if it doesn't work. So I'm just fiddlin' again. It was a promo "sample" supply guy had sitting on his desk when I approached him about it. I tell him about it and he says, "You mean like this?"  It wasn't even in stock yet. lol...

I'll keep you posted. I wasn't thinking about electrical usage when I went for it. I understand that it uses the same amps regardless of speed whereas the others reduce amps as speed drops. Is this the issue?

Paul Pollets

A Matter of Opinion

Taco also bought the cover of PM mag and 2 pages in the back. I've never seen that before.



The Germans would argue Delta P, Taco argues Delta T. 



I've been logging the Grundfos Alpha in our shop this first week of heating season...the pump runs 2gpm 15w (AM) and levels off at 1 gpm at 12w late AM  I'll do the calcs when I return to the office tomorrow.



I wonder who wrote the "white paper" ?

Leo_G

Rob

if the old saw is true that running one of these small circs is the same as a 60 watt light bulb, then yes, I can imagine not a heck of a lot of over season savings on the electrical. But what I got from the article was not the electrical draw, but how the delta T circ, would insure that for a majority of the season, your boiler and system are working at the design parameters of 20* drop. This would insure that the boiler was right on its highest effeciency, therefore would be using markedly less fuel, which in most cases would save the consumer more money. We've all seen the dreaded waterout/waterin being very close in temp. and the boiler cycling like there is no tomorrow. Not only does this waste extravagent amounts of fuel, but also wears the controls out before thier time.



I for one am very interested in this technology and can barely wait to get my hands on it and give a go!



Leo G

Dave Yates (GrandPAH)

Zero: nose-diving to make a point!

Unless you're flying a plane with a big fat red red sun on its side, you'd have had to ignore the fact that Grundfos has had a delta-T circ for more than a decade. So why did they go to the delta-P and ECM motor technology?



Saw the Alpha years ago at ISH in Germany. It was a 7-watt deal back then and hits 5-watts at times now.



If the delta-P circs go ECM, then, and only then, will they be able to go head-to-head where energy conservation is concerned and even then, I can see lots of times where delta-T would cause (think hi-mass) circs to over-amp while climbing the energy ramp to meet a DT that doesn't need to be met in order to deliver comfort.



Stuppose you had a job with ten zone circs and a primary loop circ sucking down more than 1,200-watts 24/7 & that you swapped out those 10-circs for 10-zone valves that draw just 3-watts each along with two circs that ramp up/down from 5-watts to 28-watts to do the same work.



At 11-cents per kWh, you'd go from $450.00+ per year (using outdoor reset - therefore longer run hours) to just north of $26.00 per year. Then toss in utility deregulation that might double your rate in the next year.  



While we've been designing systems for specific delta-T's all these years, I have yet to see one that adheres to the numbers because virtually every single system zone is over-pumped by default.

Mark Eatherton

If 20 degrees is considered the "ideal" temperature differential...

then why even offer an adjustable DT of between 5 and 50? Why not make it a fixed 20 and be done with it?



I have been told by more than one knowledgeable senior engineer that the 20 degree delta T is an American invention, and it was done so to make the "math" easy. Each GPM delivers 10,000 btuH.



I also have it from knowledgeable European engineers that their Delta T is significantly larger than 20 degrees... more like 50?



Having been in the field a LOT during design conditions, I have seen ONE (count 'em) system achieve a 20 degree delta T, and that was a hot water BBR system being started on a new house, at design conditions. ONE....



And what about the hydraulics? If I place all my cards in the basket (heating system) in the fixed delta T arena, what is going to happen to that 1/2" zone serving the master bedroom on the far end of the system at mid design conditions if a closer zone is open? I'm thinking that the pump will not generate the proper head to give me the required flow to generate a reasonable flow to the far zone, and my delta T on THAT part of the system is going to be BIG, and the delivery of heat is going to be small, and I'm going to have a dis-satisfied, uncomfortable customer.



Now if the circulator is watching the delta T, regardless of how many zones are opened, I can be assured that the pump WILL maintain the pressure differential necessary to deliver comfort.



Delta T is a function of load being imparted, not choking flow...to simulate load.



The soap box is clear, for now.



ME

hot_rod

But

if and when Taco has a delta P, ECM circ this discussion becomes a mute point.



What if a delta T, ECM circ came onto the market? I'll bet they are not far away.



Doesn't the Grundfos Miximizer and Taco delta T circ both have tekmar "brains"?



And of course tekmar and others offer delta t controllers to fit just about any circ.



Many of the solar controllers have delta T functions, along with BTU metering and data logging, digital display, multiple outputs, etc, etc for about the same money as a delta T stand alone control.



Speaking just from electrical consumption, no question ECM saves big energy. This technology is and has been showing up on many electric motor applications. Fans, pumps, compressors, lots of potential energy savings.



I see a lot of applications for delta T circs, return boiler protection, especially for wood or biomass boilers could be a good market.



Delta T works nicely on solar collection circs also.



hr

Mark Eatherton

WILO has had DT for a long time...

It requires the use of a third party (Honeywell) controller to put out a 0 to 10 VDC signal, but none the less, it is here. It can't be used for cooling applications. can the Taco DT be used for cooling app's?



Lots of questions, but no official answers... yet.



ME



BTW, who DID write the "White Paper"? What are their qualifications?



ME

Unknown

Well, I have a Taco 008VDT on,

my Solo 60,,, the system is mono-flo (3 zones), and I have CIBB,,, not very knowledgeable on the voltage consumption side, but I have had to experiment on the Taco sensor placement side.



If I used ECM (depending on a smaller zone returning earlier),, would that not "relax" the pump into thinking no-flow is needed elsewhere?

The Steam Whisperer (Formerly Boilerpro)

Some other considerations......

If the pump is set at a fixed delta tee, what happens when loads are light on a system.  Take a loop baseboard system through several rooms designed for 20 DT at design load with 70 F interior temp on reset.   On a warmer day, the control will be calling for 90F supply and the return will be at 70F.  The first room on the loop will be too warm and the last too cold because there will be heat output at the beginning of the loop and none at the end.  This heating imbalance will diminish as water temps rise, but will always be there until design conditions.

Taking the same situation with radiant floor will be even worse, since supply temperatures typically do not get as hight.  A 10F delta tee in warmer weather will cause the beginning of the loop to heat while the ends leav the floor cold.  If you figure a floor with a design supply of lets say 110F (probably typical for many floor systems), on the typical day it would be running about 95 sup and 85 return.  The heat output would be about 60% higher at the beginning of the loop as opposed to the end.

The only place where delta tee would work well, I believe,  is in systems where every heating unit is supplied directly with boiler water.... no series loops or monoflows.

I think Taco has missed a fundamental of hydronic heating.  Most systems designed for X delta tee are designed for this delta tee only at design conditions, not thorughout the load profile.



Boilerpro

Paul Pollets

Testing

Mark, why don't you set up a bench test that would show flow rates and watts with the 3 pumps available? It would be relatively easy to log the differences, especially with a ZV or 2 on the piping array. It would be reasonable to compare the differences, so contractors really know what they're purchasing and the true advantages of smart pumps.

NRT_Rob

hi leo

at ten cents per kwh, a standard 15-58 circulator on high speed (90 watts) costs about $5/mo if it's on contuously.



an ECM pump can do the job at 45 watts, which is half the cost, or about $2.50/month.



even at 50% duty cycle, that's $3 every two months or so... not for the whole heating season.

NRT_Rob

that wouldn't answer the question

the question is how it would behave on a real multizone system, not what it is at given flow rates. that information is pretty easily extrapolatable from the power ratings of the pumps, I believe: figuring out how often you are at a given flow rate in the field is the real trick.



to address your other post, the euros do delta-P, but they are also doing mostly analog flow control valves too.. constant circ, where pressure resistance is actually related to your heat load (how closed a zone is).



for american systems where we are just ON or OFF, that's not the same think, and delta-P has very little to do with heat load. unless you're using Uniboxes or TRVs like a euro.



as much as I think the claims are overblown, I think there are significant number of systems where delta-T might have a real advantage. any constant circ system without TRVs/Uniboxes, or zone valved system.



but that's "might". I also suspect that the difference is not huge in terms of yearly energy savings.. cutting it in 50% with ECM tech vs more than that during the shoulder seasons and maybe not cutting at all on design day... you'd need some bin data and serious modeling to answer that. I imagine the difference would be $10/year at most for most residential systems between the two... kind of esoteric.



but i'm just making that up too.

NRT_Rob

this is an interesting point

for emitters with non-linear output compared to water temp (like baseboard) you make a really good point.... not that you should ever be installing series baseboard IMHO, but if you're stuck with it you're right, the relative temps between them stay the same but as water temps drop they drop faster for the lower temp emitters.



that's good thinking right there. but if it's not series emitters, you are just talking about the average temperature across the emitter when you are talking about delta-T, and backing down flow to keep the average a specified target compared to the supply temp isn't crazy. you could argue our regular way of doing it is just "CYA" for the shoulder seasons. on design day your average temp is supply minus half delta T, but on shoulder day it's supply minus much less.... kind of a "hedge" on the reset curve.

John Barba

Beware -- Marathon Post!

Boy, isn’t this fun…

First, some particulars:  I wrote the white paper, basically ‘cause I can do math.  Haven’t had anything I’ve written cause this much of a stir since the mid-80’s, but my name and address were withheld by request, anyway.

The particular white paper Mark references discusses the difference between Delta T variable speed circulators and Delta P variable speed circulators.  Both circulators try to get to similar places using different technology.  I read it again, as well as its companion piece on electrical efficiency, and I can’t find anyplace that says a 00 –series motor is more electrically efficient than an ECM motor.  It ain’t in there...

Of course ECM motors are more efficient, but the point to remember is that we’re dealing with a 1/25th HP motor.  Not a 1 HP motor.  Not a half HP motor.  1/25th!

We based electrical consumption on some assumptions.  First, we based it on the circulator running an average of 12 and half hours a day over 162.5 days – basically 6 months.  Of course, the circulator will run more in the colder times and less in milder conditions, but this was assumed as a heating season average.  We looked at an ECM circulator running between 5 and 60 watts during the heating season, with an average of around 30 watts; we looked at our 00-VDT circulator running between 25 and 80 watts, with an average of about 60 watts. 

We based the cost of electricity on a national average of .09 cents per kilowatt hour.  Your rates, of course, may differ.  We also accounted for standby electrical usage of ECM circulators, which need power for their electronics to remain in standby mode and to “learn.” This was determined as best we could by reading technical literature and instruction manuals.  Once everything was factored in, the ECM circulator saved an estimated $3.16 worth of electricity per year…based on these assumptions, your mileage may differ.  If your electrical rates are higher, the difference you see will be greater.  For instance, .18 cents per kilowatt hour would lead to a difference of $6.32 per year; .36 cents per kilowatt hour would be $12.64 cents per year, and so on. 

As far as the 00-VDT is concerned…this is not new technology for Taco.  We came out with the 00-VS variable speed circulator in early 2004.  This was, and still is, a multi-function circulator that can be used as a Delta T circulator (the 00-VDT), as well as for chilled water applications (yes, it can be used for cooling!), injection mixing (fixed temperature – etc.), fan coils, boiler protection, etc.  The 00-VS was not all that successful, however, due to the fact it simply had too many features (thank you for that lesson, Robert Bean!).  It’s still available, but we also have the 00-VDT now available. The Delta T is adjustable so the circulator can be used for a variety of applications.

As far as heat delivery is concerned, I think everyone here knows that GPM equals BTUH divided by Delta T times 500, and this IS a fundamental of hydronic heating.  As the heating load changes in a system, the required flow in a system changes, not the required Delta T.  For example, a properly designed and installed radiant loop may require 110 degree water and 1 GPM worth of flow at 0 degrees outside, but may only require 100 degree water and half a gallon worth of flow at 35 degrees outside at a 10 degree Delta T. 

With a fixed speed circulator, you’re kinda stuck on the pump curve, and the system has to adapt to what the circulator can do.  A system designed to a Delta T of 10, 20 or even (gasp) 50 would very likely NEVER see the designed for Delta T due to the fact that the system works where the system curve intersects the pump curve.  As Mark points out, you would be hard pressed to find a system with a fixed speed circulator actually working at the designed for Delta T – but that’s a function of a fixed speed circulator forcing the system to operate on its terms.  Does this mean those systems don’t work?  Hardly…but this is the reality we’ve been living and working in when using fixed speed circulators. 

With a Delta T variable speed circulator, the circulator adapts to what the system needs.  By monitoring the designed-for Delta T -- and 20 is what’s been generally used for baseboard applications, 10 for residential radiant, but you can dial in whatever the heck you want for whatever application you want – the circulator will speed up or slow down to maintain that Delta T, and provide the system with the flow necessary to do the job.

As for distant zones opening—as soon as that zone opens and receives flow, the return water temperature will drop, prompting the circulator to speed up, increasing both the flow and head pressure, and delivering comfort – again, reacting to the real world demands of the heating system.  Loads change, so should flow. 

Here’s a tit for your tat, Mark – what would happen if, say you had 4 zones of whatever you want, relatively equal in length and head loss, but two zones have lots of windows and a higher load, while the other two have fewer windows and a lower load.  How would a Delta P circulator know the difference if only the two higher load zones were calling?   I don’t know, either.

One thing you will always hear from Taco is nothing but the utmost respect for our competitors.  Grundfos and Wilo are both excellent companies – I have friends working for both outfits -- and both provide fine products.  We do, too, and that's what makes competition fun.  ECM circulators do use less electricity than a 00-series circulator, but when you’re talking about a 1/25HP circulator in a zone valve or multi-zone radiant application, it ain’t that much in terms of dollars and cents.  A Delta T circulator will help control return temperatures at the boiler, which will help the boiler run more efficiently…that energy savings typically more than offsets electrical savings.

 I’m glad Mark posted the questions…as usual, they’re really good ones….and I’m really glad people are interested enough to keep the discussion going. 

JMB

MarkPFalade

Questions for John

How do you think the 008VDT will play with a variable speed air handler? I'm thinking if they settle in together it's a beautiful thing but if they decide to hunt the party is over. Has anyone tried this at your end? I'm under the assumption, or was anyways, 20* DT was where I should be heading. Any input on that?

Thanks

Steven Gronski

My 2 cents

I just installed a Taco 008-VDTF6 on my heating system, replacing the 007. I have 4 zones,set up on constant circulation withwith out door reset on a Vitoden 200   6-24, and the thermostats are basically high limit switches at this point. I only have 1 zone that will usually shut down. My shortest zone is the zone with the most heat loss. This zone never seems to ever quite feel like a warm, evenly heated room . Last night it got below freezing and this was the first test on te VSD pump. The room felt warm and evenly heated like it was being heated with 180 degree water and my boiler was only making 119. The thermostat had actually shut down in this room, and it never does. I agree with JMB that a Delta P pump would not have known or sensed the rooms heat loss. I cant wait till its really cold and below freezing consistantly to see how this pump will really perform.I may have to start shifting the curve a little bit to not let the boiler catch up with the t stats. You can blow all the energy saved by a Delta P pump real easy, just leave a garage or basement light on. I bet its cheaper to zone with zone valves and a Delta T pump versus multiple Delta P pumps as well. As for myself, I have been installing  and promoting Delta T pumps on all my boiler replacements and new heating jobs. I just recently finished a heating system on a 130 victorian rehab. Its 15 zones. zoned with Taco ESP zone valves 0013 VSD pump with 28 cast iron radiators and 2 zones of radiant.All designed on 150 degree water on a zero day, with Tacos Flo Pro designer software. a perfect application for a Delta T pump. My competition bidding this heating job told the owner my proposed system would never work. The owners love it. Enough said.

Steve Gronski

Gronski Plumbing and Heating Inc.

Cranston RI

Steamhead

As I read all this

I am reminded that gravity-return steam requires no pump at all.



;-)



BTW- Steve, nice work.

Paul Pollets

TT not Vitodens

The boiler pictured in Steve's post above is a Triangle Tube, not a Vitodens...

John Barba

Clarifying...

Paul --  I think Steve was referring to his own home, which has a Vitodens, while the pictures are of a job he's been working on. 

Peace out...

JMB

MarkPFalade

I just did two gravity conversions

I used the Solo110 for one and the Excellence for the other. Both running on low speed. Warm and toasty is the report, which is a very good thing to hear. I like that I can put some gravity to work there as well. Kind of neat. Here's two shots of each and two shots of the Crown with the VDT. I did not do any of the iron work on either conversion. The had both been converted to oil in the 50's. Everything after the valves is me. Neutralizers ala Hot Rod ;-)

tim smith

Re: delta t vs delta p

One question I have is how will the delta t respond to zone closures and respond quick enough to keep velocity noise down??

NRT_Rob

now I see the disconnect

john was talking about savings compared to the variable speed pump, not a regular pump.

Dave Yates (GrandPAH)

JB - need clarification please

You wrote: We also accounted for standby electrical usage of ECM circulators, which need power for their electronics to remain in standby mode and to “learn.” 



Why would an ECM delta-P (or delta-T for that matter) circ be treated any differently electronically than the way we currently treat circs - by turning them on/off via a relay. Seems to me they'd be without any power when idle. 



Switching to the energy-production side for HVAC systems using ECM VS motors, the stand-by power consumption is being utilized to analyze indoor & outdoor conditions and how fast those conditions are changing in order to "know" how fast each of the ECM motors needs to run in order to meet comfort-demand. Indoor blower; compressor motor; and outdoor fan motor all must be coordinated by the brain. However, it looks to me like our hydronic systems brains are either mounted on the wall (Tekmar, Honeywell, etc) or housed inside the boiler & they draw a minimal amount of current in stand-by modes. The constant-draw wattages I've monitored (using a Kill-a-Watt meter) for my relay box and modcon during stand-by mode has been much less than I would have guessed.



What am I missing here? 

Mark Eatherton

Ferris Bueller to the principals office....Bueller....to the principals office now...:-)

John,



I respect you as a fellow plumber, former trades person and edutainer. Having been through your classes with your previous employer, I can vouch for your zest and zeal, and knew when you went to work for Taco, that you would take them to places they had never been. It is quite obvious that Taco has a dedicated group of contractors. More power to them. Somehow, I knew that your hand was attached to the pen that wrote the white papers.



I have to give you and your organization credit for having the moxie to change , or at least attempt to change the course of hydronic mankind as it pertains to fluid dynamics. I can only assume that Taco has done its' homework in the field prior to introducing the product. I have heard back from a few people who were not satisfied with the operation of the VS pump, but did not have enough experience or knowledge to help them out.



Oddly enough, I think I had something to do with their introduction. I mentioned it to Mr Sweet many years ago, and shortly thereafter, they came out with the product. Funny how that works, and even funnier how many times it has happened to me. If I had a dollar for every idea that I'd concived prior to it coming out, I could retire comfortably, and wouldn't be here in Clinton NJ teaching hydronic heating contractors :-)



But then again, if that were the case, I wouldn't have had the opportunity to go out for dinner with my good friend Gregg Jannone, so it all works out in the end.



I realize now that you probably have the pressure drop requirements covered due to your use of the steep curved pump. Funny that you should mention Mr Bean, because he is the one that taught me that the ideal pump had a perfectly flat curve, like the VS DP pumps have.



Regardless, it is you and Taco that will have to answer the question of time and exposure, and wether or not your mathematical formula is correct. I would only caution you that bending the average numbers to make your equation look good based on certain assumptions is not a good idea. Kind of reminds me of the use of averaging thermostats in warehouse conditions. 50 degrees F and 90 degrees F are an average of 70 degrees F, but neither are acceptable as it pertains to maintaining decent comfort.



I look at the boiler industry over the last 12 years, and more recently the last three, and I note that there a very few manufacturers who have not yet jumped onto the mod con band wagon. I look at the pump/circulator manufacturers, and I see the same situation happening as it pertains to DC-ECM motors, and it leads me to ask one last question. When is Taco going to be introducing a new line of DC-ECM circulators?



Thank you in advance for responding, and best of luck to you and yours.



ME

Unknown

Delta t vs Delta P

Here is a little food for thought

 

- Think overall system efficiency improvements as well as circ efficiency (collectively circ power consumption in the USA is huge – there are a lot of these little guys out there - over 3 billion watts annually)

- Operating circ efficiency is dependent on the system load profile (degree days).  Kind of like steady state vs AFUE with boilers

- Laws of thermal dynamics – changing heat output (or input) mainly requires changes in flow (at least that is what the BTU calculation shows us)

- Circs provide flow by overcoming piping friction.  Pipe friction varies with flow



Joe Gibbs wrote “Statistics can be manipulated to favor your own argument”

MarkPFalade

Guess I'll be finding out all by myself

about what happens when you hook a VDT to a variable speed fan coil. I'll know when I get home tonight. I can share if you'd like.

The Steam Whisperer (Formerly Boilerpro)

Using the Fundamental Formula to check system balance....

Let’s apply the heat transfer formula to look at system balance and I’ll ignore factors such as the reduced output from laminar flow in some heat emitters and the non linear output of most emitters.  For simplicity, let’s assume a 3 room baseboard loop, each room with the same heat loss, the thermostat is in the middle room, with a total loss of 20,000 BTU /hr and a delta tee of 20F at design conditions of 70F interior temp and 170F supply.  The loop is on full outdoor reset.  At design conditions with a 2 gpm flow based on 20F drop across the loop, the average temp in the first room’s baseboard is 166.6, the middle 160, the last 153.3.    The average output per foot of the last rooms baseboard is about 86% of the first rooms, so the number of feet of baseboard in the last room would need to be bumped up a little bit to keep the rooms heating evenly and the first reduced a little bit to balance against the middle room where the thermostat is at. 

 

Now, using a fixed flow of 2 gpm, taking that same loop, but in warmer weather at only 20% load, (170supply-70room temp)  x 20%, = 20F, giving us 90F supply water and a 4F delta tee,  the average temp in the first rooms baseboard is 89.35, the middle 88, and the third is at 86.66.  Once again the output of the last room’s baseboard is 86 percent of the first, so heat between the three rooms remains balanced.

 

Using a fixed delta tee if 20F in that same loop, also in warmer weather at 20% load, and running that same 90F supply, the average temp in the first rooms baseboard is 86.6, the second 80F, and the last 73.3F.   The average output per foot of the last room’s baseboard is only 20% of the first room’s baseboard and the all rooms would be running cold because the reset curve is too low.  Now let’s bump the reset curve up to compensate for the higher temp drop.  The middle room with the thermostat is satisfied with 88 degree supply water, so the new supply would be 98F and 78 return at 20% load at a fixed 20F delta tee.  The first room’s baseboard average temp would be 99.6, the middle 88 and the last 81.3.  The average output per foot of baseboard in the last room is still only 38.2 % of the first, so the system is still out of balance.  Remember that at design conditions at 20F temp drop the output the last rooms baseboard was 86% of the first and now it is only 38% of the first. 

 

With a fixed flow and variable delta tee  the relationship of the outputs of each room’s baseboard is linear, where at a fixed delta tee and variable flow it is not.  A fixed delta tee circulator cannot provide even heat distribution to a building with a series type of heating system, which includes series loop baseboard systems, monoflow systems, and radiant floor systems.   In radiant floor systems it is likely even room temps would be maintained, but the temperature across the floor from the beginning of the loop to the end would drop dramatically in warmer weather. 

 

Fixed delta tee flow would work fine with other systems where all units receive heater water directly from the source,  such as converted gravity systems and any other system that uses a ladder type piping layout with each heating unit on its own rung of the ladder.

 

Boilerpro

Mark Eatherton

What will i do with a non electric thermostated system?

I'm trying to work it out in my minds eye...



Normally, the valve works proportionally to the load. If it needs just a little heat, there is just a little flow. If it needs a lot of heat, it allows a lot of flow. What will the pump do when it is calling for just a little heat?



TIA



ME

[Deleted User]

when your say older or ladder are you referrring to mono-flows?

when your say older or ladder are you referrring to mono-flows?

Mark Eatherton

I think he's talking about parallel direct return...

Base board with mono flow tee's would be ideal for this VDT pump because it is a series parallel system.



BP, if I'm wrong, correct me.



ME

NRT_Rob

with TRVs, etc

that is when a delta-P pump is a good choice. the valves close down to slow down flow, flow slows down, they find a balance point.



with delta-T, I can see two possibilities:



1. you have a bypass. valves close down, more bypass occurs, delta-T shrinks and pump slows down.



2. You do NOT have a bypass: valves close down, slowing flow through the zones and raising delta T by some amount... speeding the pump up. Seems like this could quite a waste of energy.



I would use delta-P or a bypass on a TRV/non-electric flow control valve system.

Mark Eatherton

Egg Zachary my thoughts...

That is what I saw in my minds eye. Did you see it wink? :-)



ME

Brain Ross

I AGREE

JOHN,

I AGREE THAT WITH MOST RESIDENTIAL APPLICATIONS USING A 1/25TH HP CIRC. COMPARING BETWEEN DELTA P AND DELTA T YOUR TRIPPING OVER PENNIES WHEN COMPARING ENERGY SAVINGS.

HOWEVER I HEAR AND READ SO MANY COMPARISONS BETWEEN THE TWO AND IN FACT AT A LOCAL  SUPPLY HOUSE TRADE SHOW THE GRUNDFOS REP. REALLY COULDN'T ANSWER MY QUESTION OF HOW A DELTA P CIRC. KNOWS HOW TO ACHIVE THE PROPER DELTA T.

IF I UNDERSTAND THE TWO - A DELTA T WITH TRY TO MAINTAIN A PRESET DIFF. BASED UPON SUPPLY AND RETURN TEMPS. IT REALLY DOESN'T SENSE ZONE VALVES OPENING AND CLOSING. WHERE AS A DELTA P CIRC. WOULD.

AM I CORRECT?

MarkPFalade

I think

it it reduced usage along with flow it would be an excellent fit for variable speed air handlers. Question is, does it offer any advantages to that type of system otherwise? Like ME says, "I'm trying to wrap my mind around it" but I ain't makin' it. ;-) My thought so far is if you can keep the correct number of btus going to the coil at all times it must offer some type of advantage.



Another question I came up with is, in that application, if I widen the differential to say 30* or 40* wouldn't it serve in a similar capacity as outdoor reset? I believe you can further approach the optimum # of btuh required at any given time by doing so. Example being the smallest coil I could get was twice what the heat loss called for. Therefore at 20* delta tee I am still providing twice the btus necessary. Widening the differential should help alleviate that.

Anchorage

Noisy Taco 0013 VDT circulator....emit's loud modulating buzz while operating that wakes the house!

Noise from VDT variable speed circulatorsI have just installed a new 0013VDT and it appears to be functioning OK (from the hydronic heating perspective) with the TACO 702 reset controller master and ZVC 406 exp panel, a 175kbtu/hr boiler feeding 6 zones.



I have one big problem though....and that is with serious operating noise issues from the circulators electronics/motor windings! These electrical noises are loud enough to wake people sleeping in the house.. Flow noise is not a problem even at maximum throughput into one zone. Specifically the 0013VDT sets up a very audible "modulating buzz" when it is operating, particularly when it is changing the rpms. It's a little like sleeping next to an operating dish washer....even though it is one floor below and in the garage. The "electical" noise is propagated through the copper pipes direct to the convectors....not good!I have checked all the dip settings on the motor drive card, and even forced the controller with dip 2 to operate in the upper 60% RPM range where it is less noisy. I have tried using normal and log characteristics, fast and normal response curve. No major improvement. Left to it's on devices the motor will slow down and basically emit "tack-tack-tack-tack" cogging sound at very low speeds...Dip 2 off.Did TACO intend these devices for residential applications? I suspect the motor drive card needs some LC filtering to smooth or damp the triac switching/clipping, and I also think the windings need to be potted.Any ideas how I can get this $500+ investment in new hydronic heating technology to be silent like a fixed speed circ? I will contact TACO customer service this week and see what they advise...Thanks Ryan (in Anchorage , Alaska)

CMadatMe

Sounds Like

the pumps to big. Why the 13 and not the 8?

Anchorage

Choice between the 0008VDT and 0013VDT based on BTU throughput....not really head loss.

Hi Chris,

I mulled over the decision to install the 0008VDT or 0013VDT. The 0008 did not have the BTU throughput required for operations at -20DEGF, when all zones called for heat on a given setback thermostat program. It would certainly have been sufficient to hold a constant temp in all zones, but I suspect not for programable setbacks. If the pump curve were a little flatter it would do the trick...but the advice I got from TACO was that the 0013 would operate OK in the lower RPM range. They didn't mention the switching and winding noise though....