piping two boilers in tandem

hydronicsmike

...and where would the supply sensor be located if boilers operated by a staging control?

Mike

waldo

boiler piping

I am going to pipe two boilers together for a new house. all the zones are hydro air, 8 total. The boilers are oil fired, cast iron block.
My question is this? would it be more efficient to pipe them primary secondary or just the standard piping arangement, twining the feed and return together on each boiler and piping out to manifolds? I am looking for the most efficient way to pipe these boilers while trying to keep it simple

hr

Whatever you do

don't pipe them so flow from the system, or the other boiler, runs through an unfired boiler Otherwise you have just built a cooling tower!

P/S really is the best option. Pair this with a tekmar two stage boiler control for some nice control and efficiency options.

hot rod

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Ron Schroeder_3

two boilers

can also be piped reverse return for best flow through both boilers. Isolation valves prevent water flowing trhough the unfired boiler and allow maximal boiler rotation capability. As stated a two stage control will stretch your fuel as far as it can possibly go, particularly if an outdoor reset strategy is incorporated. Don't overlook the possibility of using mixing valve strategy for ultimate occupant comfort.

waldo

reverse return?

> can also be piped reverse return for best flow

> through both boilers. Isolation valves prevent

> water flowing trhough the unfired boiler and

> allow maximal boiler rotation capability. As

> stated a two stage control will stretch your fuel

> as far as it can possibly go, particularly if an

> outdoor reset strategy is incorporated. Don't

> overlook the possibility of using mixing valve

> strategy for ultimate occupant comfort.

waldo

reverse return?

what do you mean by reverse return?

hr

Two piping

Here is a simple dual boiler piping. Stage 'em rotate 'em, fire them together, pull mixed temperature zones, very simple. Checks on, or in the circs, of course.

hot rod


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Ron Schroeder_3

reverse return piping

has the water flowing first in, last out through the boilers. Call me 604-533-9445 or send me an email address and I will email you a schematic.

Unknown

Fred

What exactly are you talking about? How are isolation valves going to be operated in that kind of configuration? manually or motorized?

The preferred method these days is Primary-Secondary with both boiler supplis and both boiler returns piped in parallel first. Two tees at the boiler connection no more than (5) five pipe diameters apart. Control can be accomplished with a 262 Tekmar control or equal. Better control can be accomplished with a Tekmar 264 which can stage each boiler burner and injection pump individually for 4 stages of operation at shutdown. By that I mean that as each boiler shuts down, its burner will shut off first and its pump will post purge to reduce the internal water temperature to reduce standby losses. Here is a graphic depicting piping arrangement. Hope this helps.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Mike T., Swampeast MO

Noticed your "hot" link attempt Hotrod.

1) Precede the A HREF= with an "less than" symbol (shift + comma)

2) After "HREF=" DO NOT enclose the web address in quotes.

3) After the web address use the "greater than" symbol (as you did) and then type in a "human understandable" name for the link.

4) After the "human understandable" use a "less than" symbol, then a regular slash (lower case of question mark) then A then a "greater than" symbol.

Have attached the hotlink instructions as an image. Can't do in text as it "does its' thing".

Ron Schroeder_3

A simplified piping arrangement would have only one primary circulator with boiler circulation being caused by the natural pressure drop that occurs across the boilers in this kind of plumbing arrangement, water being lazy and all.

When isolation valves are specified they are always motorized. Some installations call for power open spring shut, others are specified to power open and power shut. I have had the greatest exposure to Belimo valves.

I have no quarrel with your proposed control strategy though I would take issue with your statement that "The preferred method these days is Primary-Secondary". This generation of crimpers may prefer primary/secondary piping. This generation of mechanics also leave the boiler circulators where the packaging department puts them. The Dead Men understood reverse return piping. They also understood gravity and convective flows. They would certainly have frowned on primary secondary piping and all of the additional circulators (read wasteful electrical consumption, service intensity, expense of purchase) that this strategy engenders. But then again, they understood water. (IMHO)

Ron Schroeder_3

A simplified piping arrangement would have only one primary circulator with boiler circulation being caused by the natural pressure drop that occurs across the boilers in this kind of plumbing arrangement, water being lazy and all.

For an excellent article and depiction of this piping arrangement see figure three in Mark Eatherton's excellent article in PM magazine. His words and drawings are much more powerful than my ramblings:

http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,4298,00.html

While his article specifically deals with DHW tanks, please do not miss the point of his discussion which primarily deals with water flow or hydraulics. When you substitute boilers where Mark drew tanks and a tank/heating system where he drew the heat source you will get the idea.

For those who want only a picture to look at see: http://www.hotwater.com/PDFSpecSheets/E1102.pdf

I have successfully utilized this piping arrangement for the past seventeen years. It has yet to fail my clients.

When isolation valves are specified they are always motorized. Some installations call for power open spring shut, others are specified to power open and power shut. I have had the greatest exposure to Belimo valves.

I have no quarrel with your proposed control strategy though I would take issue with your statement that "The preferred method these days is Primary-Secondary". This generation of tube crimpers may prefer primary/secondary piping. It works and it certainly is a simpler arrangement for those who are not comfortable with hydraulic concepts. But this generation of mechanics also leave the boiler circulators where the packaging department puts them, Hmmm The Dead Men understood reverse return piping, heck, they probably invented it. They might have frowned on our reliance on circulators instead of sound hydraulic design and the expense that this strategy engenders (read wasteful electrical consumption, service intensity, expense of purchase). But then again, they understood water. (IMHO)

hydronicsmike

Glenn - Fred

Glenn,

as always, you said it nice and clear and I couldn't have said it any better. I agree.

Fred - I think why "Parallel Primary / Secondary" is the "preferred" piping method today, is because it is the most efficient piping method.

Parallel Primary/Secondary (not to be confuseed with 'just' Primary/Secondary - 2 different piping options) results in the lowest stand by losses and greatest effieciency, as the water only has to flow through a boiler that is active (firing) resulting in the lower stand-by losses. Also, both boilers see the same return water temperature.

Reverse Return means the water has to circulate even through an offline boiler, resulting in added and unneccessary losses through the (offline) boilers chimney or even jackets. Although most jackets are very well insulated, there are still losses.

Again, I know where you are coming from and why you like to keep the amount of pumps to a minimum. Its the European Way and Electricity is expensive there. That is the only reason, in my opinion. If electricity cost the same over in Europe as it costs here, would they have gone to single pump systems? I think not, but could be wrong.

Neither piping method is wrong. Instead, I would like to say that each have their applications. I, for one, like reverse return for DHW applications with Copper Fin-Tube boilers, where the parallel primary/secondary I prefer for any boiler used for heating systems. I am sure there are many other applications each piping szenario would suit...

Again, its a matter of preference and thank goodness, not all of us have the same opinions all the time or else none of us could continue to learn anything.

You guys Rock!!

Mike

Ron Schroeder_3

Thanks Mike

As usual your perspective cast a different and soothing light on the discussion.

In my defence, I erroneously assumed that designing a 'green' system is always in the customers' best interest. When providing counsel I consider not only the ease of installation but the total cost of materials involved. These costs include the raw material and the energy required to manufacture all of the components. Additionally I consider the cost of installation, operation, service, repair or replacement, and ultimately disposal. No, I do not have all of my own ducks in a row but that does not discourage me from designing to the gold standard. My no compromise, no hold barred has served me well in private practice as well as in the Technical Service here.

Call me a dreamer, forvie me my enthusiasm though. Regards.

Ron Schroeder

How I piped my last 2 boiler system

> I have no quarrel with your proposed

> control strategy though I would take issue with

> your statement that "The preferred method these

> days is Primary-Secondary". This generation of

> tube crimpers may prefer primary/secondary

> piping. It works and it certainly is a simpler

> arrangement for those who are not comfortable

> with hydraulic concepts. But this generation of

> mechanics also leave the boiler circulators where

> the packaging department puts them, Hmmm The

> Dead Men understood reverse return piping, heck,

> they probably invented it. They might have

> frowned on our reliance on circulators instead of

> sound hydraulic design and the expense that this

> strategy engenders (read wasteful electrical

> consumption, service intensity, expense of

> purchase). But then again, they understood water.

> (IMHO)




Hi Fred,

Primary/Secondary is only a wasteful electrical consumption if the typical oversized circs are used. In most cases, much smaller circs can be used in a P/S system than in other piping methods. In fact some of the P/S systems that I have designed could use a circ in the primary loop about 1/2 the capacity of the smallest TACO or Grundfos.

...........but then again most regular piping systems have over sized circs too.

By the way, the last 2 boiler system that I did was P/S but the takeoff for the boilers was slightly different from usual to balance the return temperature to both boilers if they were both running at the same time. I interleaved the two boilers. I had 4 closely spaced "T"s. The first "T" was boiler #1 return, the second "T" was Boiler #2 return, the third "T" was boiler #1 supply and the fourth "T" was Boiler #2 supply. This way, the first boiler didn't heat the return water to the second boiler. Also, the two boilers were not even close to being identical in any way, not even in fuel type but especially in internal head loss so this worked better than just manifolding them togeather.

Ron

hydronicsmike

Fred...

...you're a fine gentleman with great values.

I too, try to design my systems to be most cost effective while providing the most energy efficient system possible. You have been in the business obviously for a long time and you've been a true professional. I simply wanted to point out the differences from my perspective, as it may not be clear to everybody what the available options and differences of each could be. I am sure you know and many others may, but the ones who don't may appreciate the differences pointed out.

Another piping option not often mentioned, but shown by some of the condensing modulating and wall hung boiler manufacturers, is what I assume to be called "reverse return parallel primary secondary". Had a good discussion with a gentleman Dan knows in Denver, Colorado this past fall. In fact, Dan knows this guy so well, he once wrote an article about him. And no, it wasn't Mr. Eatherton...:)

Fred, while I have your attention...are there any plans on making a more cost effective alternative to a Vitocom equivalent? I am not saying that the Vitocom isnt cost effective for what it does, but will there be something similar to allow Energy Management Systems to interface to Viessmann Controls?

Please say a warm 'hello' to Andrew for me when you see him.

Thanks,

Mike

Boilerpro_3

One very important item has been forgotten

In any boiler piping arrangement for multiple boilers, protection for Hot shock of a cold boiler must be provided when using conventional boiler designs. This occurs when the system is already hot from another boiler firing and then a cold boiler is turned on. The boiler is shocked by the hot water entering the cold heat exchanger. I see alot of multiples/ modulars failing in a short period of time (under 10 to 15 years) where this problem is not addressed.

In my installations, I use natural gas standing pilots to keep the heat exchanger typicaly at 100 to 140F when in standby, or install check valves on the boiler outlets and drill an 1/8 inch hole in the flapper to allow some hot boiler water to backflow into the off boiler. Standby losses will be higher, but at least the boilers will last.
Another alternative is to install a low limit control on the boiler pump (assuming each boiler has its own pump), so the pump will not pull hot system water into the cold boiler until it warms up on its own.

Seperate thermostatic mixing valves on each boilers return also work, as would many other such mixing dvices, such as Burnham's control which you can ask Glenn about. These mixing devices will also protect the boiler from cold return water and cold Thermal load shock that has been discussed much more widely than the hot shock problem found only with multiple/ modular installations.
Otherwise you need to go to a more shockproof Boiler design, which I don't think is that common in oil, except for some German designs.

Boilerpro

Ron Schroeder_3

Vitocom

If I told you I'd have to kill you (spoken with a German accent).

The Vitocom is presently available in a 0-10V version and there are tests to see if a LON version is viable.

Viessmann controls are intended to operate optimally without outside interference. We provide variously, external calls for heat, external changes to programming, fault outputs and if needed other outputs can be ordered. Once building management systems seek to assert control the intention of the Dekamatik controls becomes redundant.

In the past primitive outside dependent controls have been available where we relinquish every function to the control of the BMS with the exception of the burner modulation control. These have had to be specified at the time of order.

Cost effective means that the product performs as advertized and the customer gets what he paid for. More cost effective would mean that the product performs better than advertized and that the client gets more than they paid for. Corporately we do not presently offer drive up service until 3 am but I might be convinved to think outside the bun. Speaking of which, that is what I already do. Are you coming?

Ron Schroeder_3

re: the forgotten important thing

Sorry to have overlooked the points you so accurately raise.

I guess I am just spoiled to be able to work exclusively with equipment that is relatively immune to these concerns and bcause of that didn't include boiler protection information in my post. Apologies all around.

hydronicsmike

Vitocom

""I'll be baa'aack!!"" (the governator)


I understand and respect what the Viessmann Controls are designed for and have worked with them for a couple of years before coming to Canada.

The reason I am asking, is because I know there are guys who like to have their building oparated by a Energy Management System (maybe tN4, Delta, Siemens, Reliable, Caleffi or whoever) and if such an interface exists, they would possibly love to keep the Viessmann Boiler operated by the Viessmann Control. I hate to see boilers that are modulating by nature, simply turned on and off and its efficiency drop off unneccessarily because an option simply wasn't available because of limitations. I am thinking Vitodens applications. I understand that the Vitodens Control or Boiler Sequencer has an optional Vitocom interface to deal with this, but I am told it has a nice price tag attached to it. Again, I am sure it is worth what it costs, just looking to see if I can help make happy customers.

Interface = variable Boiler target Signal based on 0-10Vdc Signal

Only happy customers are good customers, you well know.

I am planning on being at the fishing trip, but will know for sure by tomorrow. I'll drop you an email and let you know then for sure.

Mike

Unknown

Fred

The problem that I have with your method of Reverse-Return piping in a modular application utilizing just the system pump is this. Depending on how the modules are sized (50% of load, 60% of load...whatever) the system pump is sized for the gpm flow of the whole system. With just one boiler getting the flow of that system pump you are not providing the proper gpm flow through that module to maintain the desired temperature rise through the boiler. This is of course unless your pipe sizes are dead on or you utilize a circuit setter or some similar device to control that flow.

With pumped primary-secondary flow from the boilers to the system you are maintaining the desired flow rate through the boilers. As Boilerpro stated, variable amounts of flow and excessively cool return water for long periods of time can cause severe problems with commercial boilers that are intended to maintain a 40F degree temperature rise. Thus the RTC or Return Temperature Control system. This lets us take charge of the flow through the boiler and allows the Building Management System to reset the system water to very low temperatures instead of maintaining a minimum supply temperature such as 160F or so.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

[Deleted User]

Thanks Fred... That article got me more...

HATE mail then any article I've ever written. I had people calling me at all hours of the day AND night, yelling "YOU DON"T KNOW S#!t" and then hanging up. I showed them, I'd call them back using the immediate return redial (*69) feature on my phone and say "Yes I do, and I've got pumps that will pump it up any hill you got...". Then I'd hang up. It don't just run down hill any more...:-)

As for the piping of the boilers, with the newer high pressure drop "converters", like the Vitodens, Muncher, NYT etc, you'll need one pump per pressure drop. Even though the standby loss of these wonderful tea kettles are miniscule, why let it happen. Let the appliance go to room temperature.

Our current preferred method of piping the boilers is to pipe them in parallel with invidivual pumps with integral check valves. Then, when the appliance is off line, it is "OFF LINE". Dead in the water, cold, dead, until of course it's needed, and then in less than 30 seconds, it's back up and running producing useable BTU's. You can then take as manny secondaries as you need for whatever temperature and flow limitations you have. In whatever methods you want. 3 way, 4 way, VSI, reverse flow systems, so on and so forth.

One thing about hydronics is that regardless of what we think is the best, the best has yet to be discovered. But rest assured, when it does, the second place that will know about it are people that hang out here:-)

Here's a sample schemat of what I'm talkin' 'bout.

Thanks for reminding me of articles I forgot about:-) I spilled my guts in that one... (NOTE: Drawing edited 8/23/05)

ME

Ron Schroeder_3

I stand

corrected. Thank-you all.

Unknown

A question Mark


In the drawing you provided below, what is controlling the firing of the boilers? Do you set these up with different aquastat temperatures or are you using a stage controller? If you are using a stage control and both boilers are have satisfied, where is the system flow going to go? Just curious what control strategy you are using.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Unknown

Immune to problems?

Fred.....I haven't seen a commercial boiler yet that is "relatively immune" to circumstances that we sometimes see in the field. Situations such as schools where the boilers are maintaining temperature to be on standby for domestic water needs via a tube and bundle heat exchanger. Along comes a building maintainance individual who thinks he can save the school some money by shutting off the building heating circulators over the weekends during the intermediate temperature months such as October and April. Come Monday morning he comes back in and turns the pumps on again. No commercial boiler is going to like that kind of prolonged contact with cold return water, not even your brand!

Or how about the college dormitories with a building management system that is also maintaining 200°F water temperatures for domestic tanks while the computer system is trying to send 110°F water out for heating with 86°F return water on a 60°F March day. Once again, no commercial cast iron boiler is going to get along with that environment for long!

Or take for instance the commercial boiler installed in a Public Safety Building along with a chiller system. Boiler piping shared with the chiller system via 3-way mororized globe valves that failed to close tightly after 4 years. Boiler was maintaining temperature again for domestic hot water during the warmer weather. Its not the boiler that is at fault in these circumstances. It's not any one individual that is to blame either. It is a misunderstanding of the rigors that metals can endure when encountering things such as saturated water temperatures at varying system pressures.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

hr

The control, and sensor location

would depend on the rest of the distribution piping. In this case I built a bulge fitting for the two VS injection pumps to mix from. The sensor for the tekmar dual boiler control was straped on the feed to the bulge fitting, basically another primary loop, if you will.

The tekmar would watch and fire the boilers according to the imput from this section of the piping. I used a wirsbo DuoMix for two seperate VS controls and a mini tube to remote manifolds.

hot rod

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

[Deleted User]

Sorry....

I got wrapped up making Powerpoint presentations for my new class and neglected to respond to questions regarding my methodology for 2 boilers on a P/S loop. Ignore the first drawing if you will (already edited).

I should have explained the limitations of this system. The boilers are sealed combustion condensing boilers, and must be used with the manufacturers cascade boiler controls (Vision or Vitodens). The first pump is a continuous circ pump, and the point of reference for supply temperatures is on the supply branch serving that zone. Obviously, critical components are missing, like PABs, mixing devices etc.

This method could be used on conventional boilers, however, it would be wise to add mass in the form of buffer tanks to avoid short cycling. It was conceived for use in the super high efficiency condensing realm.

Hope I didn't cornfuse anyone out there. If I did, my humblest appologies.


ME

Keith M

modular boilers

There are pros and cons for a modular boiler and multiple boilers. I personally have over 20 years of experience with modular reverse return boilers and I assure you they are dependable and efficient.

If you are concerned about vent losses, use vent dampers on the modules. I do encourage their use.

When a modular boiler module stops firing the residual heat in the module's heat exchanger goes into the system water for a modular boiler because the water continues to flow through the modules, this becomes usable heat. This certainly minimizes the chance of thermal shock when it fires again. I do not know of any modules that have failed due to thermal shock in a reverse return set-up. I have asked the the manager of technical services of Slant Fin if he knows of modules that have failed due to thermal shock and he told me he does not know of any. He makes warranty decisions on failed boilers.

The cast iron sections used in Slant/Fin gas-fired Caravan modular boilers are the same sections used in the residential Galaxy boilers. In many ways residential boilers experience more stress than many commercial boiles. For many years residential hot water boilers systems have used multiple zones. Often a zone containing cold water opens and slugs a hot boiler with cold water. While I have seen many boilers condense, very few have failed due thermal shock.

Jackets are indeed insulated to minimize jacket losses. In addition a good modular boiler system uses outdoor reset, therefore the system water temperature flowing through the modules becomes lower as modules stop firing. This decreases jacket losses further.

A reverse return modular boiler is a boiler that consist of two or more modules.

Slant/Fin has supplied tens of thousands of modular boilers, they are indeed time proven. They are dependable working machines. Like any boiler sometimes a defective one gets installed and if Slant/Fin knows about it...we take care of it.

There are modular boilers installed as far north as northern Alaska and as far south as McMurdo base in Antartica...and indeed many countries between.

Indeed Slant/Fin boilers are installed in multiple boiler applications. The application should determine what the boiler set-up is. If you want to apply a modular boiler and are considering Slant/Fin please contact Slant/Fin technical services at 1 800 873 4346.


Keith Muhlmeister
Sales Manager Commercial Products
Slant/Fin Corporation

Unknown

Keith

In my post above that desribed various instances where boilers encountered difficuties due to control and piping problems, I was referring to instances where pressure-fire boilers with multi horsepower inputs. I apparently did not clarify that and for that I apologize. Correct me if I am wrong but I don't see these types of boilers in your product line, just atmospheric vent type boilers. As you stated, these types of boilers seldom encounter thermal stress difficulties.

I do have to disagree with you though on the reverse return modular setups not being problematic. Simple physics will dictate that if hot return water from the system is flowing through a module that is not firing at that moment in time, then its function changes from that of a boiler to instead that of a radiator. The standby losses of that system increase and the boiler room gets hotter than heck! As I stated, if there happens to be just one large system pump establishing the flow through the system, interrupting the flow through the reverse-return piped boilers with motorized valves is going to increase the desired flow through the operating module well beyond what you or any other company would desire to have. That is of course unless circuit setters are installed.

I believe in the newer technology that control manufacturers such as Tekmar employ and totally agree with their piping technology. I have grown up with this industry over the past 33 years and have been involved with all sorts of modular piping configurations. With the control technology available today and with the price of fuel what it is today, it is discouraging to walk into an Apartment building boiler room that is 115°F warm due to needless constant flow through the boilers.

Glenn Stanton

Manager of Training

Burnham Hydronics

Keith M

Glenn

Glenn, in a modular boiler the maximum input for each module is 399M for gas and 3 GPH for oil. While I have heard of systems containing multiple modular boilers with over 60 modules most systems have less than 8 modules.
The debate about jacket and vent losses is interesting and there are indeed different schools of thought. The biggest reason I have seen for boiler rooms being hot is that the pipes are not insulated. As we all know a boiler heat exchanger is designed to transfer high temperature heat into low temperature water...boilers do not make good radiators. Most modular boilers use outdoor reset and with the resultant decrease in water temperature the standby losses decrease. Again it is good practice to use a vent damper. Oil fired modular boilers use residential type burners and there is very little air flow through the modules. Sealed combustion boiler modules can also be used in modular boiler systems.
With the exception of systems used for space and DHW we do not recommend the use of motorized valves in modular boilers. Flow rate is system dependant and should be taken into account when any product is being applied. In addition as you know the system circulator does not have to be the modular boiler circulator, again it depends on the application. Many use a 20 F rise in temp to determine flow.
I have visited many hot boiler rooms with all different types of systems and in these boiler rooms the pipes have not had proper insulation. This includes multiple boiler systems. The physics are not simple.
I think Tekmar manufactures many fine controls. I also think they tend to make things more complicated than they should be. I am not against multiple boilers, there are applications where they are the best option just like there are applications where modular boilers are the best option.
Burnham promotes multiple boilers and Slant/Fin promotes modular boilers. Both are good. There are mechanical engineers who like and specify one or the other.
Are you sitting in a hotel room tonight? I am.

Unknown

Yes I am

I am in a hotel room tonight as I am very frequently. Still wound up from a very interactive meeting tonight. I acknowledge your opinions but I don't neccessarily agree with them though. You are right that we all make modular systems and that the various engineers choose one brand or another based on their needs and preferences. One of those needs that I always encounter when speaking with engineers is floor space in the boiler room. Here in New England we tend to see more pressure-fire boilers being specified in modular applications for that reason.

By the way....say hello to Noel for me and as far as hanging out and posting on The Wall at all wee hours of the morning, I would think you might agree that we both "need a life". ;>}

Glenn Stanton

Manager of Training

Burnham Hydronics

jackchips_2

You gentlemen

who feed us this information provide a valuable service, add to our knowledge and therefore contribute a positive influence on society.

I'd say you have quite a life and offer my thanks for spending those long nights in those cramped, dingy rooms.

Hopefully, the family time and vacations make it all worth while.

Thanks to you all.

Jack

Boilerpro_3

Many good points

> I am in a hotel room tonight as I am very

> frequently. Still wound up from a very

> interactive meeting tonight. I acknowledge your

> opinions but I don't neccessarily agree with them

> though. You are right that we all make modular

> systems and that the various engineers choose one

> brand or another based on their needs and

> preferences. One of those needs that I always

> encounter when speaking with engineers is floor

> space in the boiler room. Here in New England we

> tend to see more pressure-fire boilers being

> specified in modular applications for that

> reason.

>

> By the way....say hello to Noel for

> me and as far as hanging out and posting on The

> Wall at all wee hours of the morning, I would

> think you might agree that we both "need a life".

> ;_}

>

> Glenn Stanton

>

> Manager of

> Training

>

> Burnham Hydronics

Keith M

Jackchips

Thank you for your kind comments. Please remember this is what we choose to do. Now if I could only convince my wife that going out to dinner is not the thing to do when I come home from a trip...
The hugs and kisses from my wife and daughter do make it worthwhile, for while I give and get them when I am home they do seem better after a trip. As a manufacturer I appreciate what engineers, wholesalers, contractors and end users do. Indeed, all of you folks make it possible. While without you I would be home, I would also have a different job. I like what I do...
Noel is good, does a great job and is a nice person. I am glad he is with us.
Perhaps Glenn and I will meet sometime and have a good and fun conversation. If all of us agreed on everything it would indeed be a dull life. Well, all packed and time to hit the road again. I hope I like the hotel I use tonight...
:-)

Keith Muhlmeister

Sales Manager, Commercial Products

Slant/Fin Corporation

Boilerpro_3

Many good points

and both of you very able gentlemen are thanked. I do have agreements and disageements with some points, however.
I typically set up my systems as multiple boilers, as it allows for isolation of the units for service during the heating season. Operationally, I don't see how much difference it makes whether it is modular or multiple, size may change but principles are the same.
Typically I pump each boiler seperately using paralell P/S piping. However, I use standing pilot or allow a small amount of flow through off modules to keep them up to a reasonable temp to prevent shock from hot system water hitting the casting at full flow when a cold module is called on in a hot system. Cold shock protection is provided by return mixing valves, injection pumping, etc.
I do nearly always use stack dampers on atmospheric units due to standby losses either directly from a hot boiler, or from all the cold air entering the boiler room, being heated, and exiting the stack. However, when those dampers are closed on a hot boiler, there is a very large amount of hot air exiting the draft hood, especially the mushroom type. There seems to be less heat lost from lower built in divertors, and very little to none from the air trap type like on Lochinvar minifin boilers. This hot exiting air is at least not going directly up the chimney, and tends to heat the boiler room, but is used for combustion, probably slightly improving efficiency here, or is lost up an operating modules draft hood as dilution air.... a large waste.
As to the current boiler jackets on typical American cast iron boilers, if they really were there to reduce standby losses, all the piping openings would be gasketed to prevent large amounts of air leakage driven by stack effect through the jacket and its fiberglass (think air filter) insulation. This is not the case, so a large amount of heat is lost here. I'm sure the jacket greatly reduces radiation loss, but it increases convective loss since the air moves easily through the open spaces of the jacket and through the fiberglass, greatly reducing its effectiveness. Just gasketing the upper penetrations of the jacket will work wonders, I would think.
As to shock issues, they are real in any piping configuration that allows a boiler(module) to go dead cold, while the system is hot. I have sat and watched a cast iron boiler go from room temp to 200F in less than 60 seconds as i heard the casting groan and thump under the strain of rapid temperature change. It is NOT something nice to here. I already stated above how I deal with this problem.
To me the ultimate solution to these problems is to move modular or multiple smaller boiler designs from draft hoods to power vents to eliminate the loss at open draft hoods on "off" modules or the indirect losses of stack damper equipped off modules through open hoods of "on" modules. Some simple upgrades to jackets with gaskets on penetrations and maybe thicker insulation would be great too.

Unfortunately, in the cast iron market, package power vent boilers are made in limited sizes, with the largest (sorry guys) being made by Dunkirk (225,000 in) and Weil (recently upped to about 230,000 in), that I've seen. The copper tube companies, however, have a much broader range, and its forcing me to their products if I want to continue to improve the efficiency of my modular or smaller multiple boiler heating plants that I install nearly exclusively in commericial and large single family applications.

Adding power vents to the Slantfin Galaxy and Bunaham 8B lines and extending them in current lines such as the Burnham 2PV and Slantfin VPlines would really gie you gentlemen somehting to compete against the likes of Raypack's proven smaller copper tube boilers that can be had in atmospheric drafthood, powervent, and if you ask, barometric.

Just my thoughts

Boilerpro

Unknown

Jack

I'll have to ditto what Keith has already said so well. We do truly enjoy what we do and that makes it worthwhile. My wife and I have been married for 24 years and have 3 boys that are now 18, 21 and 23. Being away from home is not as difficult on us now that they are all grown up.
Besides my wife needs a little time to herself too! All I can say is that it works and we all get along well.

Another hotel tonight after a great day of training today in the Albany, NY area. Stayed in Hadley, MA last night after a half day meeting in the Taunton, MA area. Two job visits at 7:30 this morning in the Hadley area and then across the Berkshires to Albany for a 6 hour meeting. Its a good thing that I enjoy driving!

Glenn Stanton

Manager of Training

Burnham Hydronics

Rheff

Parallel boiler piping and control

I've been reading the posts on piping and control of multiple boiler systems and still wondering how to resolve an issue I have. Although there has been mention of schematics and diagrams, I haven't been able to see them.

My problem is this: I have a customer with an oil-fired, 5-zone hot water system. It's a huge house and he complains that the house never gets warm enough. The existing boiler uses a 1.65 gph nozzle fired at 140 psi (approx. 277,200 BTUH). I was considering adding a boiler in parallel but would like some advice as to how to pipe it and what controls to use to stage the boilers. All of you guys sound like you know your stuff. I'd appreciate your advice. Thanks.

nicholas bonham-carter

New thread required for this

Otherwise you will get lost in this old stuff.

I am assuming that this is a hot water system?

Is this the maximum firing rate for the boiler?

Have you done a heat loss for the house to see what additional heat would be needed?

What is the water temperature-supply, and return?

Has this system ever worked properly?--NBC

Outofmydepth

Reading this I am embarrassed to say most plumbers don't work like this in the UK.

Zman

How is this post still open?

nicholas bonham-carter

Now we can have a nice discussion on the differences between U.K. Proffessionals, and those here---in another thread!--NBC