Buffer Tank - How To?

Ron Schroeder

Hi Brad,

I really haven't sat down and looked at all of the possabilities with a condensing boiler but with loads like typical over-sized baseboards that don't really need 170 degree water and house loads that are smaller than the typical oversized boiler (or a system where the DHW is a bigger load than the space heat) it seems to make more sense to design around the buffer first and the boiler second. Larger delta T in the buffer will of course allow greater storage in a smaller tank but with a condensing boiler, the highest temperature should be as low as possable while still keeping the lowest temperature still high enough to work with the radiant that you have which would limit the delta T.

With the Primary/Secondary method, you could have the buffer helping the lower temperature loads while still having the ability to isolate the buffer when there is a call for higher temperatures. .......just a thought, you could have a low temperature and a high temperature buffer??? More thinking while typing, ...if the buffers were reverse indirects, the low temperature indirect/buffer could be a DHW preheater for the high temperature indirect/buffer. ........dang, there goes KISS ;-)

van_6

Buffer Tank - How To?

I've got a traditional primary/secondary piping system with my Buderus G124. I am considering adding a buffer tank to help with short cycles when just radiant zones are calling (radiant is injection and there are 3 radiant zones). What is the best way of adding the buffer tank? Is it as simple as a super insulated tank (indirect tank for instance) piped in series with the primary loop?

Brad White_25

Personally I piped my

buffer tank on the return side. If you install it in the supply side, you have to wait to charge the tank before you get the water temperature you need at the radiation.

Mine is piped in parallel, sort of a side-car to the main. When the return water comes back too warm, a circulator starts and charges the tank. This forces the tank contents (cool to start) back to the boiler to prolong condensation while banking the hotter return water to carry over between (and to postpone) burner cycles. Once the tank is at temperature and the return water drops in temperature (below 120 F or so), the circulator stops and return continues to the boiler bypassing the tank. Simple.

You can pipe it in series (all return water passing through the tank) but the mass is not always needed yet you wind up heating it. No way to save it for low-load days. This is why I did mine in parallel.

You could also couple it in to the return of the radiant loops (assuming the other parts of the house are more conventional panels or baseboard), thus saving the less-warm water for where it can be put to use. This gets into some control strategies, not as simple as my "whole system" return strategy.

Lots of ways to do this.

For a tank, I use a Super-Stor 30 gallon. Thought it was a 40-45 gallon, wish it were. Solid well insulated tanks.

hr

With that type of boiler

piping it in series could keep the boiler in extended condensing mode. As on a cold start the boiler has the building load and the buffer to get up to temperature.

I like the PS piping best. It allows the buffer to come on and go off line as needed.

Before you start run some numbers to see how much capacity is needed to accomplish your goal. If this is to handle micro loading, know and calculate that small load against the proposed buffer tank.

Siggy's HDS program has an excellent module to play what if games with buffer tanks, www.hydronicpros.com for a test drive.

Simply adding a 20 or 30 gallon tank may not "buy" enough benefit to offset the cost and trouble involved.

Base your decision on some BTU calcs for best results and performance.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Paul Rohrs

Buffer tank

Brad,
Are you using a simple aquastat to cycle the pump on and off only when there is a call for heat?

With low temp radiant floor heat and high temp DHW on priority, I like to pipe the buffer tank in series.

Lots of ways to do it, look at all of the variables for the specific job and determine the best control strategy, then pipe accordingly.

My .02 cents

Regards,

PR

Biggerstaffradiantsolutions.com

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Brad White_25

Hey, Paul

Thanks for checking in.

My buffer tank circulator runs in parallel off of a reverse aquastat set at 120F. (It has nothing to do with the call for heating by the house thermostat.)

The tank is charged off of the return (closely spaced tees in the return line). The boiler always sees the coldest water. When the HWR temp is still low, it goes straight to the boiler. In effect it is "in series" when the charging circulator is in operation and is in effect bypassed when the HWR is low in temperature anyway.

The main heating circulator runs based on OA temperature below 65F adjustable. I use a Ranco controller for that.

As an added twist (not added in discussion to keep things clearer), on the return from the tank to the HWR main, I again split off to heat my basement (manually switched). Just a touch of heat, I admit jury-rigged, but keeps the HWR colder longer and my MZ condensing longer too.

This heating return is separate from the DHW of course.

Kevin O. Pulver

I like it

I just piped one identical to Paul's diagram... except I didn't use red and blue pipe like his, just copper. ;-)
If anyone sees anything wrong with it, I got the idea from him! One GREAT thing about this is you need only two tappings. That old water heater should last a few more years as a buffer since it has no fresh water shouldn't it?Kevin

Paul Rohrs_4

Brad,

I have Siggy's "Modern Hydronic Heating" and have taken his (RPA)"Radiant Precision" course. Your drawing reflects what he proposes also. (In terms of piping buffer tanks as a parallel circuit)

A couple of questions: In this setup for high-temp rads, lets say that your boiler is purring along at setpoint and you have a 20° Delta T. The reverse acting stat senses the warming return temp and engages the secondary buffer tank loop and sends the colder water back to the boiler, this sustains and enhances the condensing mode with the cooler return water. Is the boiler not going to recognize this and try to compensate by adjusting to a higher firing rate? In essence, any fuel savings with the enhanced and prolonged condensing mode might be offset by the higher firing rate?

I am not suggesting piping a buffer tank in series will ignore the same scenario. I think piping the buffer tank in series will "charge" the tank initially to the reset temperature, then the system can enjoy the correct reset and the lowest return. (?)

Regards,

PR

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Brad White_9

Funny thing

Paul. I piped this up a couple of years ago, then bought Siggy's book to find other ways. The validation felt good, I have to tell you.

By the way, to anyone reading this, it is an EXCELLENT book. Best technical book I own, bar none.

I am not worried about a higher firing rate because my boiler is a Monitor MZ (on-off). In fact, this is the very reason I conceived this arrangement. The short cycling was driving me nuts. By piping in parallel I could remove it as a variable when not needed. I agree it could be larger, I did not have the advantage of Siggy's book nor software, but did have the tank already. If I get serious, I could manifold another one or two as a battery. Not this year..

The MZ works off of a space thermostat so once satisfied and burner off, (or off on limit) it coasts for about five minutes before again firing. Made a big difference in short cycling. I have been begging Pete at MPI to offer a modulating MZ and he tells me one is in the works.

If the boiler WERE modulating, I agree with you 100%, the firing rate would increase to "defeat the tank" and negate the savings.

The reason I would not pipe the tank into the supply is that it would be a "mass to be heated" and would take precedence over my radiator. IOW: Have to wait for my hot water to arrive.

In your case, with HWR reset (Munchkin) and if the tank is the primary controlled variable, then the supply-side tank makes sense to me.

Good question! Thanks for keeping me on my toes and for making me smarter by reading your posts.

Brad

Paul Rohrs_4

Brad

I re-read my Modern Hydronic Heat book once a year. Seems like I always pick up a variable and apply it somewhere else on the hydronic food chain.

I am "tainted-goods" hydronically speaking. If I could choose any other profession, I wouldn't. I approached Siggy at Wetstock III in Denver a few years back and asked him to autograph my book. He did so without hesitation.
It's worth more than gold to me.

It reminds me of the guy who found an old Guttenburg bible but then threw it away because some guy named Martin Luther had scribbled notes all over it.


Regards,

PR

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Brad White_9

Well Said, Paul!

(LOL)

Siggy is one of the icons in this business. Your practice of reading The Book once a year should be taken to heart. I will. I tend to use it as a reference upon need, but at leisure one may absorb better and prevent rather than react to a situation. After 28 years on the design side of this business, books like that and the great minds of The Wall keep one fresh and humble.

Best,

Brad

Brian_18

Smart(er) Buffer Tank for Mod-Con Applications

I've been thinking about this topic a lot, for future inclusion into my own system. I too think introducing too much cold return water to a modulating boiler will cause it to react by ramping up, and thus negating some of the benefits. Why not use a Tekmar VS injection controller in reverse? If I'm not mistaken, the temp sensor Tekmar uses is a NTC design thermistor (negative temperature coefficient). Meaning as the temperature rises, the resistance falls, and tells the Tekmar to slow down. Why not substiture a PTC thermistor? By using it, the resistance would climb as the temperature rises, and thus drive the Tekmar to speed up. (reverse acting VS injection). This would "smarten up" the buffer tank to only grab BTU's when they're available, and not dump too much cold water by running the buffer pump at full speed. Maybe the Tekmar guys would like to comment on this modified application.

Paul Rohrs_4

Experience (?)

Brad,

28 years designing? Wow, who did you design for? Wholesale side of the house? Are you a contractor now?

Regards,

PR

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Brad White_9

Engineering, Paul

I work in Boston for a company called TMP Consulting Engineers, founded by my mentors from when I started in 1977. I have worked in this area since then, Companies like Scorziello Associates, Francis Associates/SCI, Shooshanian Engineering, my last job, BR+A, I was there for over 20 years. Been here for five years. We do a lot of schools, commercial projects, high rises, university work.

I also have taught at the Boston Architectural Center, a night school for architects. Incredible experience, teaching is. Keeps hubris in check

Mostly designed university projects, hospitals, specialty medical (Proton Therapy Centers, MRI's) laboratories, libraries, historical, performing arts centers, light industrial. Everything sub-nuclear. Project management, design, construction, commissioning, the works.

My hands-on experience is as a homeowner and property owner. (No longer a landlord, no regrets). I have installed the hydronic side of several houses, small stuff but fun.

But as far as the professional side, the basics are so easily forgotten and the priciples espoused here on The Wall are universal. I tend to be the maverick, exploring newer technologies to the consulting engineering side, not relying on "more is better" but "intelligently less is more efficient". God, I love this field.

Showing my age? I am 48 and feel 20 years younger, like a kid in fact.

Et tu? Contractor I gather, and educator too?

Brad

Paul Rohrs_4

Recently

left the wholesale/design side (after 17 years)of the counter to be a radiant contractor. My target market is new residential/commercial radiant. Our market is ready for it, I just need to keep greasing the wheels of sales and land the HO's who can see and justify the value. I went to the University of Nebraska in the teachers college. That is the extent of my teaching credentials, other than "splaining" radiant to potential customers.

I love learning and exploring on the CAD side of the house. I document every job with a mechanical and electrical drawing. Luckily, my weapon of choice, the crayon has been banned from engineered drawings, and Visio is where I spend quite a bit of time. I am a visual person so it helps for me to put ideas on paper.

Nice meeting a kindred spirit. Glad to know you.

Regards,

PR

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Brad White_9

Kindred Spirits Indeed

Likewise, Paul. Something about a well documented design (Visio too) has a great feeling associated with it. I too am visual (both right and left brain in balance actually) so the creative side and technical side each play against each other.

I would be pleased if you would add my address

bewhite (at) rcn.com

to your address book should we want to exchange ideas off-line. Much as I enjoy this, the threads go astray with informative results!

The pleasure is mine.

Brad

Weezbo

A?

May i chirp up Tacos Load match for some lively and entertaining supplemental investment ? *~/:)

Brad White_9

You mean the diagramming software?

If it is the one based on HVAC Solution, I own a copy of that also. Much more robust and "thinking"/interactive between components. I downloaded a copy from the Taco website (Freeware apparently, but limited to the hydronic aspects) and already had the full version. If you try the Taco branded version, I think you will like it.

Good call Weeze, I mean, Uponorius

Alex Giacomuzzi

Buffer Tank Piping...

I Have a question for both Brad & Paul...

Given that Paul's design is in series with the Munchkin on the supply side with a separate DHW and Brad's is piped primary / secondary .... on the return side, is there possibly some useful middle ground between these two designs?

I believe I understand what each of you have written even including the small basement loop off the buffer for Brad. What I was thinking is with the buffer on the return loop piped primary / secondary it appears (mainly) to assist in the cold water return portion --- as stated to help the condensing mode and the cycle time, but not really controled to draw hot water from the buffer to circulate within the system without firing the boiler. Is this correct? Once the buffer comes up to temp, how does it unload its energy?

The series connection that Paul shows would allow for reducing boiler cycling also, increased colder water to the return of the boiler (and to the loops) along with being a hot water source buffer (supply) before the boiler comes back on... I do not know if it is set up this way, but it certainly could be. This makes sense.

Now for the question to integrate a bit.....

Given Pauls piping diagram, could the buffer shown actually be the DHW tank and a buffer(rather than only a buffer) which would normally has a aquastat on it (which has a differential temp. assoc. with it)? This buffer -- DHW tank could be sized accordingly for possibly both purposes. If increased boiler water storage was required it could be a reverse indirect like an ErgoMax for example. This could eliminate a pump and a separate tank (again if the sizing criteria works out correctly).

The piping would have to be primary / secondary coming off the boiler loop, not in series with it.

What are your thoughts...... Just thought I would ask..
Interesting thread..... Regards Alex

Brad White_26

I'll take my piece of this, Alex

Excellent thoughtful questions.

You are correct in that my buffer tank addresses only prolonging condensing mode and to lessen short-cycling. As I mentioned in a reply to Paul, my boiler is on-off, not modulating so has it's own challenges.

How does it unload it's energy? The buffer circulator operates by a two-stage relay. Well, not really two stage but two relays wired in parallel such that the pump continues to run whenever the HWR pipe temperature is too high OR when the tank temperature is above setpoint. I think of this as a "pole-vaulter" set-up. The buffer charging pump grabs water from one side and discharges to the other.

When the buffer comes up to temperature the charging pump continues to run until the in-tank circulator sees the temperature drop below setpoint.

What is key in this is that the buffer charging circulator flow rate is about 75 percent of the main flow rate. The mains flow about 8 gpm and the charging tank has a rate of about 6 gpm. The 30-gallon tank is depleted in about five minutes. There is always a T-Mix in the rejoining at the return. But the buffer tank forms a time delay and allows the boiler to rest a bit between cycles. I admit the tank volume could be larger.

If this were better thought out (and I admit I did it on the fly), I would use a 3-way diverting valve in the main and base tank charging on boiler inlet temperature and spare the buffer tank circulator.

Paul Rohrs

Alex

I think I would need more information. High temp secondary loops? Condensing Boiler? Zoning by circulator? DHW with priority?

I threw this pic together thinking this is what you are talking about. I will think about controlling this and let you respond if there are changes to be made before I go further.

Regards,

PR

Biggerstaffradiantsolutions.com

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Brad White_26

That is what I pictured, Paul

An inverted indirect as buffer. If for direct heating of the domestic it could be unpredictable but has pre-heat value prior to going to the finishing heater.

Paul Rohrs

I agree

Ideally, I am thinking I would rather put all of the secondary zone pumps off of a variable-speed injection-mixing loop for reset, and run the DHW buffer on closely spaced tee's prior to that. A simple NO/NC relay I think would allow DHW on priority, then as that satisfies, the relay can then fire as needed for buffering with an additional set-point controller (Tekmar 150) with an adjustable differential. I think there are a few more variables to hammer out before control logic can be applied.

(Alex, the new Tekmar TN4 equipment is a thing of beauty. Find your heat-loss and zoning needs, adopt the control strategy, then pipe accordingly.)

PR

Biggerstaffradiantsolutions.com

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Alex Giacomuzzi

I Understand......

Hi Brad....
Thanks for the reply..

Based on what you have described, I am assuming your circulator to the buffer tank can or does run on past when the boiler burner has stopped. At least that is what I am reading into this. I understand the first contact and am reading into the second.....

I presume your boiler circulator is also running while the burner is off in the above circumstances.. Do you run constant circulation?

A thought regarding the referenced 3 way valve and no circulator. This would also work as you are thinking. Another possibility, although not "perfectly clean" but I think usable would be to have a 2 way full port ball valve between the 2 closely connected T's. I am assuming your connection piping size to the buffer supports 10 gpm. The 2 way would either force the flow thru the buffer when it is closed, or allow it to short circuit around the buffer when it is open. Just a thought.. You might not need a full blown 3 way here to accomplish what you want.

I will reply further below..

Thanks Alex

Alex Giacomuzzi

I Stand Corrected.....

Brad & Paul.......
I may have been mixing some thoughts between non condensing and condensing boilers... Sorry.

For noncondensing boilers, at least those that are operating above the 130--140 return temp range, the idea of combining a buffer along with the DHW into a singe vessel piped in series with the boiler and the remaining secondary heating loops piped in parallel (several---- closely spaced T's prior to the buffer in a descending order of temperature requirements will work fine.

BUT ---- with condensing technology and lower temperature operation of the system at times for outdoor reset and lower design emitter temp requirements, the above may not be the best design. In fact it is not the best design.

Paul....
Your "More Desireable Layout" (above) which has the buffer and a DWH separate appears to be a better design than the combo especially given how and when DHW calls and needs may come into the system. I really do not want to sacrifice a good hot shower.... Now the only question is the exact location for the buffer. Given that condensing boilers will service a variety of emitters ranging from fan coils and fin tube on the high temp end to basement radiant on the low temp end, there maybe good design reasons to have high temp emitters before the buffer yet have low temp radiant after the buffer. Each design could vary. Each can work.

Constant circulation ---- which I am a huge proponent of is another design and piping decision. Being able to move energy even in small quantities is a lovely thing in a radiant system especially when the burner is not on and the system is just equilibrating. The only cost for comfort is 35W--- 80Watts.

Sorry for the bit of a boon-doggle.

Regards Alex

Brad White_26

Good points all around, Alex!

Yes you are right in reading what I have left out for brevity. You have an excellent mind.

I do run constant circulation on my secondary loop (and primary for that matter, it is internal to my MZ condensing boiler). The buffer tank indeed does run past the burner time, exactly what I want it to do.

I also have the MPI reset control (A Tekmar OEM product) and TRV's on my radiators. By default, even without the OD Reset, constant circulation gives a form of "poor man's reset" because the burner fires off of room temperature. With the OD Reset, it is more fine-tuned. I keep the supply temperature as low as will do the job and run about a 25 degree delta-T. 140 F max. water at zero ODT it returns 115 degrees on average. (Warm-up periods it comes back at room temperature and condenses like crazy. I live for that!

I have contemplated the "ball valve between tees" and agree it is a simpler (and more commonly available) way to achieve the same things. Excellent reminder of the KISS principle, thank you.

As for the temperature decay you cited in your reply to Paul, that is not a concern of mine. My system has a 3-way diverting valve that takes all boiler capacity to DHW production so it does not affect the heating side temperature. Takes about 10 minutes from a cold tank, 5 minutes to top it off. Even without the buffer tank and especially with it, this drop-out from heating mode is undetectable in the heated space.


Best Regards,

Brad

Ron Schroeder

In general, I like to pipe a buffer tank so all of the loads pull from the buffer and the boiler just recharges the buffer. Just like the buffer tank was a big low loss header. That way many small calls can pull from the buffer without the boiler turning on at all and when the buffer needs recharged, the boiler can run for a long time.

If the buffer is just piped in series with the boiler, any time there is flow, the boiler acts as a heat sink that doesn't help heat the load.

The only other way that I have tried that I like is to have both the boiler and the buffer on seperate secondary loops off of the primary with all of the loads on secondary loops too. It's a little harder to control but the loads can then pull from either the boiler, the buffer or both and the buffer can be recharged without any loads being on too.

Brad White_9

I tend to agree

Ron, and from your perch at the BNL, I appreciate your perspective all the more. When the buffer tank is in parallel on the return (on demand, see my postings above) and in a non-modulating plant, is the merit there? It was a seat of the pants plunge to do that, to stop short-cycling.

Your concept makes sense from my perspective when there are many smaller zones that call intermittently, such that one does not overtax the others. This to allow coasting and down-time between boiler firings, yet something to allow a long burn time to charge it, if I understand it correctly.

Do you find that temperature swings in the buffer tank become an issue if the differential is at a certain range? Interested to read your thoughts.

Brad

hr

I've done buffers a number of ways

Alex hits the nail on the head, it depends on the requirements of the application.

I have installed and modified my MZ several times to lessen the cycling. I hung it on the side of a 120 gallon insulated tank in series. Stepping back it looked a lot like a two piece Polaris or Voyager.

I built custom adapters (ala Munchkin) to increase to 1-1/4 right at the boiler connections. I doubled up on circs, with the onboard and an additional one.

It's a hard beast to tame. Maybe I'm too picky. The modulating feature will make this a preimer boiler. It struggles with out it.


I've also built the buffer as the primary loop. Connect top and bottom with a circ. Then closely spaced tee for input and take offs.

Currently my wood fired boiler pipes to a primary and buffer via a VS pump. Siggy's thermal clutch method where the sensor at the boiler return controls the return temperature by changing RPMs at the circ. Fairly simple and cleaner than a 3 way thermostatic.

I'm still waiting and watching for that super insulated 50 gallon modulating condensing heater. Would a 100K with a 10-1 turndown be too much to ask I long for the day when buffering is a thing of the past. It's always a "fix"

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Ron Schroeder

I'm still waiting and watching for that super insulated 50 gallon modulating condensing heater. Would a 100K with a 10-1 turndown be too much to ask I long for the day when buffering is a thing of the past. It's always a "fix"

hot rod

Hi Hot Rod,

Until they can get that big uninsulated hole out of the middle of a heater, I think low mass boiler/high mass buffer is the way to go.

Ron

hr

They all have a hole, somewhere!

regardless of the capacity. The Polaris and Voyagers had the vent connections at the bottom, really not much standby loss with that arrangement.

The down side of reverse indirects as buffers is they don't produce much DHW at radiant temperatures It gets too muddy keeping the buffer charged to 180 for good DHW production, then introducing a lower temperature mix down or loop.

I have found the tank in tank style of indirect able to produce fairly good DHW with low supply temperatures. As long as recovery time is not a big issue. It would be nice not to have to talk 180, even 160, anywhere in the system.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Maine Doug_16

I have found

that my E44 Ergo can produce lots of DHW between 140 and 150. It is in series with the primary loop with all zones and both boilers and VSI floor as secondaries. Since the VSI needs to be supplied with water all the time, the primary loop circ runs all the time and thus constantly stirs the tank. The floor is on outdoor reset, have the sensor for boiler outdoor reset for the panel rads but have not unleashed that yet.

Brad White_9

Ron,

were you involved with the BNL study (BNL-73314-2004-IR; Dr. Thomas A. Butcher) on Hydronic Baseboard and Condensing Boilers?

I passed that around our office where we design (among many other things) replacement boiler plants attached to fixed existing distribution.

The back-up data makes sense and is good to have. Tell the folks behind that report (including yourself) that it was one beneficial use of my tax dollars. (That is a compliment!)

Thanks

Brad

PJO_5

My thoughts...and a joke, too.

Gents,

Great thread! I did a system sort of like these, and will do another this summer...and am learning greatly from you guys.

I installed primary/secondary w/an E23 Ergomax in the primary loop three years ago to slow down the cycling of my 100k output oil-fired boiler. The other side of the Ergo is feeding non-barrier radiant (poor decision on my part) for the first floor. I also have baseboard upstairs (three zones).

I put the buffer right after the three high temp zones to help protect the boiler from condensing...I have a temp. gauge on the return and also see the temps throughout the system using two Azel Dual Digital Gauges. The boiler runs at 170F design, but this winter has stayed around 150/160 nearly all winter...and the return rarely falls below 135F. I reset the temps myself but that will change this year also...


I have learned two things from that work;

1) I tried to keep it simple, but went "too simple" because while the boiler is protected 100% of the time, it also still cycles too often IMHO. If I had done something like Brad's design with using the temp. switch on the Ergo at 130F and then kicking in the buffer as a side tank (instead of being in the primary loop) it would have been better.

2) I also should have put the boiler as a secondary loop due to it simply either heating the system or cooling it...that will be done this spring, but I was going to use the switch on the Ergo to run a boiler circ.

Based on these items, I propose the following for these improvements and also for work I will do on another system this summer.

First my house improvements;

1) Re-do the piping to match Brad's (Siggy's) design except have the temp set at 130/135F (vs. 120) to protect the boiler instead of condensing yet still get long cycles.

2) Run the primary circ. constant near design temps. While I hear everyone talk about how great this is to do all season, I don't get the same feeling in my own system...and I have five total pumps (six zones) so it's a pretty big difference in electrical use.


For my "other" system; Triplex with high DHW demand, which currently has a grossly oversized W/M CI 5 section dinosaur (oil-fired) that is about 30 years old...doesn't owe this place a dime. A 50 gallon gas HWH replaced the tankless coil, and was replaced with another unit about 8 years ago. Since I pay the fuel bill it's time to replace things.


I propose a Burnham LE-1 with a Phase III TR-80 for DHW. This indirect is oversized for the simple reason of the boiler being sized for the heating load (75k) and not the DHW. I will use the existing gas heater for a "pre-heater" to the indirect, and will take advantage of the 24 gallon (I think) buffer in the Phase III.

The Phase III will be in the primary loop with the three zones of baseboard (170, 165 and 155F design) in series as the temp. requirement falls. The boiler will be a secondary zone...this is similar to Siggy's "Signature System" from a few years ago.

Here's my quandry; because there is also gas there, I can also go with a mod/condensing boiler (140M or W/M Ultra 150 comes to mind) with the same set-up. While these zones are high temp. I am considering an addition to the place that would probably be radiant, and also there's a possibility for snowmelt in the future. These two items tell me I should steer towards the gas unit, but I also am a firm believer in using oil instead for the reasons many have posted here over the years (better btu value/more choices for competition, etc).

Regardless of the boiler choice, I am adding mass to the primary circuit while using a low-mass boiler...I'll just change the set-up depending on what type of boiler I have.

Here's a goofy thought I have in my head; when I put the boiler as a secondary circuit, can I use a zone valve between the tees of the primary loop that is controlled off the setpoint switch? This would be a normally open valve that closes on the call for the boiler to send the entire primary flow through the boiler. The primary pump would obviously go from about 8 gpm to 6 or so due to the added piping, but that works perfect for the boiler.

What say you, Wallies? TIA for any and all advice...

Here's my joke - from an "engineer" and with respect to John Runhke I went to school AFTER 15 years in the field and I don't have a PE...except for "Practical Experience".


AutoCAD Monkey

A tourist walked into a pet shop and was looking at the
animals on display. While he was there, another customer walked in and said
to the shopkeeper, "I'll have an AutoCAD monkey please." The shopkeeper
nodded, went over to a cage at the side of the shop and took out a monkey.
He fitted a collar and leash, handed it to the customer, saying, "That'll be
$5000." The customer paid and walked out with his monkey.



Startled, the tourist went over to the shopkeeper and said, "That was a very expensive
monkey. Most of them are only few hundred dollars. Why did that one cost so
much?"



The Shopkeeper answered, "Ah, that monkey can draw in AutoCAD -
very fast, clear layouts, no mistakes, well worth the money."



The tourist looked at a monkey in another cage. "That one's even more expensive!
$10,000! What does it do?



"Oh, that one's a Design monkey; it can
design systems, layout projects, mark-up drawings, write specifications,
some even calculate. All the really useful stuff," said the
shopkeeper.



The tourist looked around for a little longer and saw a
third monkey in its own cage. The price tag around its neck read $50,000. He
gasped to the shopkeeper, "That one costs more than all the others put
together! What on earth does it do?"



The shopkeeper replied, "Well, I haven't actually seen it do anything, but it says it's an Engineer."


Take Care, PJO


P.S. Dan, a belated Happy B-Day!!

Ron Schroeder

Hi Brad,

I was not involved in that study but Tom and I often discuss ideas of using exsisting heating equipment in more efficient manners with different piping and controls. I tend to specialize on controls but my basement piping still looks like a sci-fi movie.

BNL is now in the middle of a study that will be particularly interesting in quantifying short cycling, buffering and indirects among other things. I have been suggesting a few particular tests that will help model buffering.

Ron Schroeder

>Here's a goofy thought I have in my head; when I put the
> boiler as a secondary circuit, can I use a zone valve
> between the tees of the primary loop that is controlled
> off the setpoint switch? This would be a normally open
> valve that closes on the call for the boiler to send the
> entire primary flow through the boiler. The primary pump
> would obviously go from about 8 gpm to 6 or so due to the
> added piping, but that works perfect for the boiler.

Hi PJO,

I have often thought of the same thing but I haven't found a low enough restriction zone valve. I need something like a 1 1/4" full port version of a Taco ESP or a motorized version of the Webstone primary secondary purge T

http://store.webstonevalves.com/default.aspx?page=item detail&itemcode=58655

I am always looking for ways to save on the electricity used in the circs. I am now running 15 zones on a single 15 watt circ. for heat. The DHW/buffer is on it's own 007 but that usually runs for much less than an hour a day.

hr

Ron

if you need to move a lot of gpm through a ZV, consider the White Rogers 1361. You can drive a truck, or Ferrari through their passage ways! (Matchbox sized

They are a bit more prone to sticking, good water quality is important.

Used to be a favorite for indirect tanks.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Alex Giacomuzzi

Sorry No Joke..... Just some piping thoughts...

PJO ---

Your system and mine appear to be very similar in many ways. I have a traditional atmospheric CI boiler which I piped in a series loop with an ErgoMax E23 (which is used for my domestic hot water production) on the return leg to the boiler. I get good boiler protection in addition to good hot water production. I let the aquastat on the Ergomax be one of the inputs which start the boiler. I do use priority in the logic for the heating season.

My boiler is slightly larger than yours but I do not appear have a cycling problem... keep reading. I followed the same logic that you described above (hottest, hot, less hot) with my other loads ---- that is --I piped them all as secondaries off the primary loop. The first was to my fan coil which heats the existing portion of the house via a variable speed Carrier air handler. I just used the existing thermostat for the call into my pump and boiler logic control.

The second and third secondary loops are available as spares for some future baseboard or panel radiators in the basement or other locations and for a future separately attached garage floor.

The fourth secondary circuit is set up to feed my radiant system. I was lucky and was given an 80 gallon "Ford" Solar HX tank and I piped it in to be my radiant source heat tank which I also have integrated with a temperature outdoor resetting controller. The 80 gallon tank temp gets reset with the outdoor temp. Simple & neat.

Yes --- I have more than my fair share of surge or buffers.
When a boiler call comes in, normally one of the two buffer circuits will also call during the same period..... This does a real nice job on short cycling. Actually as any of the heating circuits calls, the water in the ErgoMax gets cooler. Typically at some point in the call, the priority will trigger on the DHW (because the other heating circuits are cooling it down) and the boiler does not know the difference, but the cycle has automatically been extended. Again...... on / off boiler --- no modulation.

There is another benefit with this extra separate buffer tank....... I am kind of decoupled so to speak from the primary boiler and the primary loop, so it is real easy to do a continuous circulation in just the radiant portion.

When I first started out, I wanted to incorporate continuous circulation, but I did not want to go thru the boiler loop for obvious reasons.... With this decouple, I can do it. In the radiant portion I have a single Grundfos on speed 2 pushing 9 radiant loops. Actually speed 1 can actually push it at about 1 gpm less in flow.

I treated my system as a bit of a design experiment and it sounds like many of us have done the same thing. I make the necessary changes as we move along. It has really been a wonderful learning experince and just great to talk to or email the great talent on this board... A Big Thankyou to all....

Regards Alex

Brad White_9

Well, dang, Ron....

Had I known that, I would have waited!

My basement piping has been termed "Dr. Frankenstein's Laboratory" by the folks at Monitor Products. Pete and former tech wiz Matt have seen it up close and personal. You and I both "get it".

Let me know if you need help or a sanity check. Forgive hubris.

Brad

hr

Got a drawing, Alex?

I like the idea of the high mass stone lined Ford tank as a radiant buffer. Is the coil piped to the primary loop and the tank volume for the radiant?

Also the Ergo in series? It provides return protection because it never runs below 140?

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Alex Giacomuzzi

No Dwg. HR ---- Just Sketches...

HR

Your Dwg is correct as you have it drawn. Thank you......

I will answer your specific questions & fill in some voids:

1. Regarding the (very heavy) stone lined Ford tank and the piping to it. The tank is no longer made, and with your help I contacted Siggy for any tank specific info he had in his files. I got some info, but did not feel comfortable (due to not quite knowing the exact heat transfer rate of just using the interior coil ---- I did not know how much flow I could actually pump thru it for example). Nor did I know the exact condition of the coil for long term use. I cleaned and pressure tested both the tank and the coil, but you still never know with used hardware.

So I piped the tank using the coil as you show in your diagram AND I made an additional parallel connection (able to be valved off) using flow check valves appropriately to the supply and return coming from and into the Ford tank from the radiant loop side. This piping connection was hot into the bottom of the tank and cold out of the top --- returning back to the boiler primary circuit. To reiterate..... secondary pump to a tee -- one leg to the coil the other leg to a valve and then the cold water inlet to the tank. In addition, I installed a simple B&G (rotometer style)flow meter (I really wanted to know the flow from the primary loop to the tank) and as it turned out, I am glad I piped it both ways. Just using the coil would have proved to not transfer the heat into the tank fast enough and probably caused the boiler to cycle on and off on its high temp...

2. The heating loop out of the Ford tank is the injection pump circuit for the radiant loop system. In the traditional radiant loop system I have a 15-58 main circulator running constantly pushing flow thru all 9 loops and just returning back to the pump. The injection attaches between two closely spaced "T's" (before the pump) that I have a full port ball valve installed between them. This gives me a fall back (or in car terminology --- a limp back mode if I need it) to be able to heat the space by putting the Ford Tank in series with the radiant loop by manually closing that valve (between the two tee's) if the injection circuitry were to have problems, or to open the valve and run with injection. I hope this makes sense..... The reality.... that little pump can pump the whole system ----- I was amazed!!!! I guess good things come in small packages..

3. The Ergo.... just like you have it shown is in series in the primary loop. It does provide return protection to the boiler provided you have it selected as PRIORITY and wired appropriately. If you do not select priority, or have it wired properly, you do not have protection. Normally I see my system cut back over around 135 deg F . This cut over point is adjustable via the aquastat on the Ergo. My boiler has a cold water return limit of 120 deg F. and I am staying above that value.

Again......... thanks for the nice dwg and thanks for asking some good questions.......

Regards Alex