Two-Stage firing on WM 580

Dave in QCA

I thought I would put out a question to the pros on here, or anyone else who might happen to have the experience.



Has anyone tested out the efficiency of a two stage gas burner operating in a WM 80 series boiler.  I am considering setting the low fire setting at about 60% of the boiler normal capacity.  (There really is a rational reason)  I'm running an orificed system.  Future plans are to reactivate and restore the steam system in the garage and chauffer's apartment which was shut off about 25 years ago.  Also need the two stage function if the heat is shut off in some of the rooms, etc.   Need to be able to control at 8 oz, plus or minus 2 oz.



I am considering a Weil-McLain 580 with a Riello 40-G900 gas 2-stage.  Ya, I know that WM doesn't show that burner for the 580, just the 680.  But, WM said to ask Riello if it is comparable to the single stage burner specd for the 580.  Riello said it's the same burner except for adding 2-stage firing and that it's applicable firing range is exactly the same as the Riello burner that WM calls out for the 580.



Presently running on a 37 year old Pennco atmospheric.  Rated input is 1,050,000 BTU.  Firing at about 550,000 BTU.  Ya, I know it's got a ton of excess air and the efficiency is horrible.   The age plus the oversize is the reason for changing out.  



Thoughts and comments will be greatly appreciated. 

Thanks!

Rod

Multiple Boilers?

Hi Dave-  I haven't really thought out the ramifications of this but the first thing that comes to mind is what about using multiple staged boilers?  I'm sure you have already considered this. I was just interested in what your thoughts were.

- Rod

Dave in QCA

Thinking, perhaps overthinking it!

Rod,

I have strongly considered using two small boilers set up in a modular staged setup.  Boiler Pro has done  those and shared his experiences on a job quite similar to mine.  He also mentioned, as I recall, that he had considered using one larger boiler with a modulating or 2-stage burner, but in the end opted for two smaller slant fin boilers (TR-40 as I recall.).  Redundancy and having a backup were a factor in the choice.  He set up the control with a 2-stage thermostat.  The second stage boiler does not run unless the first stage can not keep up with the load.  Even distribution was a little bit of a problem, but it was resolved by pinching down the inlet valves with future plans to install orifices.  I am not sure I remember this correctly, but as I recall there might have been some problems because of very low water content in the boiler and the need for a reservoir on the gravity return setup.  My apologies Dave, if I have any of this wrong.



So, I have thought and considered, looked at the situation from all sides and here is where I have landed (at least for the moment)  I appreciate the value of having a backup boiler, I ran a hospital plant for 17 years, everything has a back up!  However, while there is benefit, there is also a drawback as you have twice the chance for equipment failure-- essentially you have 2 boilers to maintain instead of one.   The following are factors I have considered:  (please do not take any remark that follows as a criticism of the Slantfin models, that is not my intent, I'm just trying to draw comparisons.)



1  The Weil-Mclain 580 (and the Burnham V-904, the other option) both have essentially the same efficiency ratings as the Intrepid. 



2  Also, both the boilers have a significantly higher water content than the Slantfin Models.  That water content is the same as my current old Pennco boiler and the water level only drops about one inch before condensate begins to return, where it remains stable until the boiler shuts off.  In about ten minutes the water level is back where it started.  I think that is stable enough.  So, it would stand to reason that the WM 580 water content would be adequate to operate without having to install a reservoir to increase the water content. 



3  I am controlling the system with a Tekmar 179.  It does not have the ability to control 2 stage firing.  So, if I opted for the modular approach, I suppose I could lock out one of the boilers based on outdoor temp but would lose the built in automatic redundancy.  I could control off of pressure with an additional vaporstat, as I would with a 2 stage burner, but in this case the lag boiler would fire on every cycle and that is not desirable and would negate the efficiencies gained by staging.  I suppose there could be a combination of a pressure control and outdoor temperature lockout, so that the second stage would never fire unless the outdoor temperature was say, less than 20F, and then it would be controlled off of the second stage vapor stat.  This same approach could also be used on a 2-stage burner.



4  I am already concerned about the sound level, but figure I can tolerate the Riello burner with its acoustic cover.  However, not so sure about the sound level of having two of those running at the same time.



So, the unknown to me, is the combustion efficiency while firing at 60%.  It would seem to me that if the excess air is tightly controlled, the boiler would be equally as efficient at 60% as it is at 100%.  I note that the Intrepid models such as the TR-50H, (high efficiency model) is simply the TR-50 with a firing rate 10% lower than the regular model.  This is a case where turning down the fire increases the efficiency. 

I'm hoping that someone out there has done burner tuneups and checked efficiency either on the 2 stage burner or any other scenario where the boiler was being fired significantly lower than than design maximum firing rate.



While I'm writing.... a good time so say Thank you Rod, for all of the hard work, dedication, thought, and expertise that you bring on a daily basis to the forum.



I apologize to all for my inability to be consise.  I know that my great weekness is my ability to take any short story and make it long!  HA! HA!

 

The Steam Whisperer (Formerly Boilerpro)

you may want to check this out...

http://www.midcointernational.com/.

these are 5 to 1 mod burners with no burner roar.  The blower motor is an ECM  so electrical usage is a fraction of typical power burners.   Steamhead came into Chicago and we visited Midco together, and we both agreed that this burner is a game changer for the steam heating field.  It also runs very quiet quiet if you address the air intake noise (which can be ducted remotely).  Also, Midco tests these burners in Peerless steamers.   I am itching to get one of these in.

Dave in QCA

WOW! Interesting!

Dave, thanks for this information.  It is a very interesting burner!  Years ago, when working at a hospital complex, we had an old 1960s vintage incinerator that had an incinomite burner on it, from this same company.  The thing was quiet and trouble free.



One thing I was attracted to the Riello burner is that it is only 1/8 HP-- much less than most of the others. 



Thanks for passing this on.

The Steam Whisperer (Formerly Boilerpro)

Yea...

It's great to get the bump in combustion efficiency of a power burner, but the increased electrical usage( and complexity) can wipe out the gains.  This burner, however,  should help address that issue.

Dave in QCA

which burner?

Dave, I ahve been looking at their website, but I'm not sure which model you are referring to.  The new LoNox?

Steamhead

That's the one

it's a "radial-flame" burner.

SWEI

Midco Low NOx

Looks like a great design!



Install manual is quite specific to the MUA application.  Not a lot of detail on modulation control, though it seems there might be 0-10V along with PWM input options?

Rod

Weishaupt Burner

Hi Dave- Thanks for the kind words though I’m only echoing what I have learned from Dan and the Pros who graciously share their knowledge with the rest of us. Thanks also to you too for your input. I always enjoy reading your posts and learn a lot from them.

    I can see where the economics would be better using only a single boiler. Since the boiler you require is a fairly large capacity. you probably have a better chance finding a unit that is staged /modulated. Have you looked in Weishaupt Burners at all?  http://www.weishaupt-corp.com/local/documentBase/2050-CA-10-04.pdf

They appear to have both staged and modulating units though their presence here in the U.S. seems to be rather limited as least at the lower btu level. In the U.S. they are based out of Chicago so maybe being close to you would be a positive consideration.

-Rod

Charlie from wmass

You guys find the best things

keep us posted. what is the range for a burner like that? How big, How small?

The Steam Whisperer (Formerly Boilerpro)

Midco Radial burner

These burners are available in two sizes.  100,000 to 500,000 input and 200,000 to 1,000,000 input.  A 2 million input model is currently in development.  I invited Steamhead to join me at Midco to look at these burners and we both agreed that they are a game changer for the steam heating industry.  We now have a very efficient modulating gas burner that cna be used in residential applications where noise is an issue.  (Chicago is completely dominated by huge atmospherics largely due to this issue) Since they are radial design, they have little burner roar and can have a remote air intake, so noise is drastically reduced from typical power burners. Also of great interest, is that they appear to produce much higher levels of radiant heat than equally sized power burners, so I would expect a nice bump in efficiency when these burners replace an equivalent "flame thrower" type burner.   There will probably be much better transfer of heat to the heat exchanger in the combustion chamber with these burners.

Rod

Midco Radial Burner

Hi Dave- Thanks to you and Frank for info on this burner. It looks VERY interesting! As was pointed out, from the literature, it would seem they are aiming at the spray booth heating market at this time.  Any ideas to when we might see a unit that could be used in a residential steam boiler?

Having good circular radiant heat, one would think that this burner would do well in a wet based boiler.  If I understand the operation of this burner correctly, one of my concerns would be that very well filtered intake air might be necessary otherwise internal clogging of the cylinder burner grid might become a problem.

- Rod

   

The Steam Whisperer (Formerly Boilerpro)

Burner

The burners are run regularly in Peerless and Smith(?) steam boilers for testing, so thier use in a steamer is not an issue.  The burner is essentially the same as those found in most mod-con hw boilers, so the same precautions would apply, I suspect, regarding clean air supply. The burner head is only about 12 inches long in the small model, so they will fit most mid size to larger residential units.  Steamhead has a Slantfin TR-40 that he hopes to retrodit  withthis burner due to noise issues with the current "flame thrower".  I am working with a local controls company to come up with control packages for a fixed pressure mod output and an outdoor reset pressure with mod output.

Rod

Midco Radial Burner

Hi Dave- Again thanks for the further info on the Midco Radial burner.  It's nice to hear that this burner is close to becoming a reality.  A good modulating burner system for residential level steam boilers will go a long way to keeping steam heating viable. 

    With a modulating burner on a one pipe steam system, what do they do control wise so that TRVs are able to work properly?   It seems to me that with TRVs and utilizing the 33% pickup factor, you would save a lot of fuel and have a very efficient system.

- Rod

JStar

Awesome

This is the kind of product that makes you stare off into the distance, daydreaming about that mystical condensing steam boiler.

Dave in QCA

WOW

When I posted this thread, I didn't imagine that it was going to become the forum for announcing the debut of a revolutionary new burner! 



This new Midco burner is truly amazing, but simply borrows the existing technology that has been used in Mod-Con type boilers for quite some time, and in fact, for some boilers prior to the advent of the Mod-Con, such as the Weil-Mclain Gold series, which is a "kinda, sorta" condensing boiler.



I have been dragging my heals to replace a very inefficient boiler, thinking that something new would hit the scene soon.  Then, when I was all set to move forward, BANG!  Here it is.  I wonder when Midco is going to get around to testing on W-M? 



At any rate, it seems to me that the new Midco burner answers the question, that a modulation burner produces efficiency by matching firing rate to the load, and therefore avoiding short cycling on pressure.  It also, if I understand its operation and design, constantly maintains a perfect gas/air ratio, no matter what the firing rate is.  WOW!!!!



While no one has answered my original question directly, I think the answer lays between the lines.  Firing at a lower rate does not cause a loss of efficiency as long as the fuel mixture is maintained so that there is not too much excess air.  That of course, is if it within reason and the simmering pot phenomenonis avoided.  I am thinking in the range of a firing range that varies from 100% down to 60%, maybe 50%, but certainly not lower than that.



I may have to get a bid on the Midco and the Peerless Boiler.  We just don't see much of them in this area.   Another option would be for me to go ahead with a W-M 580 with a single stage Riello.  It will work fine for me if it is set up for a lower firing rate.  Then, at a later date when I bring the back building back onto the steam system, I could upgrade to the Midco.  Hopefully, it will have been tested by then and will be commanding a great share of the market!

The Steam Whisperer (Formerly Boilerpro)

I've run much lower than that

on a slant fin with the Power flame xm burner.    I was at least down to 30%.  At the low firing rates you have to watch out for the gas flow going laminar in the heat exchanger.  This happens quite suddenly as flow drops and then efficiency drops suddenly.   However, I have never gotten there yet on the boilers I have worked on. 30 % minimum rate is pretty standard in the industry.  The Power flame tended to run with alot of excess air at the bottom end, but combustion test efficiency improved.

When they were running the New radial burner in the Peerless, combustion efficiencies were around 86% at low fire with fairly tight excess air. STack temp was under 300F, IIRC.  However, the boiler was a 2 million btu boiler and they were running the burner at 100,000 btu/hr.

The Steam Whisperer (Formerly Boilerpro)

It is not mystical, it is real

condensing steamers have been around for quite some time now.

Charlie from wmass

This will speak volumes for what I think of this burner,

my Father wants me to find out more info on this. He seldom thinks much about new things in the industry.

Dave in QCA

Amazing!

Dave, I guess you are saying that it will be more efficient than my 1,050,000 BTU Pennco, that is downfired to 600K BTU?   heh heh!

Charlie from wmass

I will need to contact them later in the week

it is not listed yet as Massachusetts approved

The Steam Whisperer (Formerly Boilerpro)

Just a little....

those boilers are at about the bottom for efficiency to start out with...probably at best 75% when combustion tested and with all the losses from being so oversized it's got to be down in the 50's I bet.  did you orifice the system?

Dave in QCA

Orificed ? Yes

Yes, installed orifices last fall.  System was plagued with balance issues.  No amount of venting would correct it totally.  Found that it was probably a result of oversized inlets on the rads plus the very high venting ability of the Dunham traps.



Interesting to note that early on, Dunham was specifying that "regulating plates" be installed in the inlet valves to provide even steaming.  Actaully found an old regulating plate in one of the valves as I opened it to install a new orifice plate.  I sized the new orifices at 8 oz pressure drop but pressure usually runs about 10 oz.  I had already repaired/replaced all of the traps, so am not operating as a true orificed system without traps.  Since I'm sized at 8 oz. and have an adequate B dimension, I could actually operate at 16 oz. if I needed to.   That adds about 50% to the steaming capacity of the orifices and would prevent short cycling on pressure.  However, it seems to me that the slow gradual steaming at a moderate fire would be the better way to go.



Have you ever used the Riello 2 stage?  

The Steam Whisperer (Formerly Boilerpro)

With orifices you open up some wonderful possibilites...

like outdoor reset of pressure feeding back into a modulating burner.  Nothing new about this,  it's been done before with the Vari-vac systems.

Fizz

Trapped orifice

What type traps did you use?

Dave in QCA

The Traps are...

The original traps were Dunham #2.  There were serveral still present.  They were rebuilt with Barnes-Jones cage units and replacement caps.  The great number of traps were Dunham 1E, the were repaired with new discs.  I also purchased several new Dunham-Bush 1-E and or Mepco 1-E traps on Ebay that were used.  I also used a few Armstrong TS-2 traps, which have a high venting capacity.  Early on in the project I discovered that if I used a trap that had a low venting rate, such as the new type Hoffman 17c, it greatly affected the balance, so I opted for Dunham or equal in an effort to get the system balance.  Eventually, the need to better balance the systme lead to orifices.



See the original thread at http://www.heatinghelp.com/forum-thread/131216/The-Best-Heating-System 

Dave in QCA

Modulating & Vari-Vac

Dave- Yes, the thought had occured to me as well.  Vari-vac intrigues me, but I had wanted to get to the designed vapor system operation and see how well the self induced vacuum works and whether with low firing rates the system will produce subatmospheric vapor at moderate temperatures. 



If not, the vari-vac system has great appeal to me.  And, as you say, the modulating burner would be a PERFECT fit.  Vari-vac seems to combine the best features or a steam system with the best features of a hot water system.  I have lived with hot water systems for many years, and only two residenctial steam systems.  I operated a facilty with high pressure steam, but that is a whole other animal.