thoughts on 1 vs 2 boilers

Adam_13

Hello all, looked at an old three story commercial building today. First floor is retail, and second and third floor is office space. The building was originally heated by radiators, but all the first floor and most of the second floor had the rads removed for separate HVAC units. The entire third floor is still using the radiators, and there are 21 of 'em. There are 5 radiators still used on the second floor in common areas. Currently there is one boiler for the steam system, and it is a two pipe system throughout. Traps are updated and all the rads have TRV's. Measuring the existing rads and using a pickup factor of 1.5 to account for the extensive piping system that used to supply many more rads the total DOE output load is 504,000 btu.



My question is should we recommend putting in one boiler or two boilers. I'm thinking two boilers might make more sense. First, during mild weather most of the TRVs will be closed so one boiler firing might be more efficient. Second, there will be redundancy so the building won't go down if there's a problem with one of the boilers. Finally, two smaller boilers would of course be more manageable to get into the basement.



If two boilers is ok would it make sense to split the load evenly between the boilers (i.e. two 250K boilers)?



Any thoughts or comments would be greatly appreciated! Thanks for your time, -Adam

nicholas bonham-carter

One or two, that is the question

If you install two boilers, will they be a "tag-team", or separate? It sounds like a more practical solution to have the second boiler come on when the pressure drops due to excessive condensing of the output of number one.

It would be important to keep the pressures very low, so that you don't have too much water in the active boiler pushed out into the inactive one.

Someone here must have done this, and so I will be waiting to see what the correct piping would be-maybe some sort of double false water-line?--NBC

jumper

multiple boilers

Somewhere there's an article named multiple boilers by Holohan on this site. After reading it you may be afraid to go that route. If you're not afraid then google Caravan modular steam. That being said, two boilers will work better. If you get it right. Undersize the main boiler and isolate the extra boiler for extreme conditions.

SWEI

two-stage burner

with a couple of Vaporstats sounds a lot simpler...

nicholas bonham-carter

One heavy boiler or two slightly less heavy boilers?

And why do we need steam boilers made of cast iron?

Why not lighter copper or stainless firetube boilers, with sections split in 2 parts, which could be carried into the basement so much more easily than 6-7 hundred pound cast iron sections.--NBC

Dave in QCA

I chose one Heavy Duty

I studied this issue for about 3 years.  There are very valid points for both approaches.  Both are good.  In the end, I chose a Weil-Mclain 680 commercial boiler with a 2 stage Riello power burner.  System is 2-pipe, vapor/vacuum, 8 oz max pressure.  Work is in progress, so I can't tell you how it runs until the end of the week.  There is a thread on the project under the title, New Boiler at Best Mansion.

Henry

Small load

For such a small load, a Smith 19HE-5 would be ideal with a full mod burner. We installed one this past winter. The modulation works great and the customer is raving about the savings.

If you go two boilers, you will need some Heat Timer controls. This and the extra piping would make you uncompetitive!

SWEI

19HE-5 with full modulation

I've been wondering about this application and would like to learn more.  Power Flame?  Midco?  Controls?





thanks~ 

jumper

lighter boilers ?

I may be mistaken but I believe that at one time Raypak offered steam. I never saw one but I imagine that it was a hot water boiler with a steam drum. In that case the circulator must have been special.

Adam_13

considering the extra piping

and issues when only one boiler is firing it seems that one boiler with a modulating burner sounds best. The two vaporstat control sounds interesting. The current boiler is oil but the owner wants to switch to gas. Any recommendations for a modulating gas burner? Is the smith boiler a push nipple or gasket boiler?

vaporvac

which Burner?

Henry, I too, would like to know which modulating burner you recommend. I was recently told all the modulating burners are for commercial boilers and are very loud...much louder than the normal power burner. There seems to be quite a bit of interest in this lately.

The Steam Whisperer (Formerly Boilerpro)

Quiet burners

The quietest out there is the Midco LNB1000.  The smallest is the 500,000 input with 4 to 1 modulation.  Not much louder than a louder atmospheric and the intake air can be ducted in to really quiet it down.   These burners have no burner roar.....mainly all you hear is the blower.  Midco didn't intend for this burner to be used in boilers, but they look great.  I hope to have one in soon.....Steamhead is working to put one in too.

vaporvac

thanks

Thanks for that info. It's probably too big for my situation (1460 edr with 2xSF TR50s), but I'm sure others can benefit from this. That's not too huge a burner and glad to hear it's not so loud. I wonder if other boiler can be installed the same way to reduce the noise? Hwever, if I do go with a single TR70 this may work.

The Steam Whisperer (Formerly Boilerpro)

Also.....

Powerflame makes a 11 to 1 mod burner, max input of 400,000.  I believe Midco may make a smaller one too...you just have to ask for it.

Mark N

TR70

TR70 is only rated for 1108 sqft EDR, you have 1460 sqft. Are you sure you want to be undersized.

vaporvac

Dave's posts

I've just been reading Dave's posts on the Btu ratings for orificed systems such as mine. I think you can size the boier smaller, but I actually don't plan to do that as I want a HW loop at some point in the nearer future. I'm really wanting 2xSF TR50s. Just having a hard time finding out from the rep what exact burner to order. He never calls back and his suggestions have been running counter to advice I get here. I think Midco or the Carlin EZ-gas has been hightly recommended and is approved by SF for use with the TRs.Thanks.

SWEI

twinning boilers

You really seem to have your heart set on this configuration.  Dual-stage or modulating burners combined with multiple boilers will require some not-so-typical controls.  While I'd really enjoy designing that, I don't think I'd actually recommend the configuration for anything under several MM BTU/hr.



A Smith 19HE with two stage or modulating burner won't work for you?

The Steam Whisperer (Formerly Boilerpro)

Here's what Vaporvac is thinking

These two TR-40 , 200,000 input boilers heat over 70 radiators in a 10,000 sq ft 1930's home with no insulation.  All windows are leaded glass with no storms.  Highest winter bill is about $700.00 here in Chicago.   Control is a simple two stage thermostat.  It been running a couple winters now, but the system is awaitng orifice plates to get the heating even.   The only problem we'rehaving is the water content is so low, that we may have to had a holding tank at the water line.  

Dave in QCA

The expert on modular Steam Speaks

Dave, I am glad you jumped in on this.  I had told Vaporvac about this same install that you did and that it worked very well.  What burners did you use?  Would you advise 2 stage or modulating or would your consider the fact that 2 boilers=2 stages to begin with and that is good enough?

nicholas bonham-carter

2 boiler setup

Boilerpro, are these boilers fired at the same time, or are they staged?

If staged,was there any problem with water being blown out to the inactive boiler?

Nice piping!--NBC

SWEI

the cavalry arrives

I've been hoping you'd jump in on one of these...



Caveat:  I'm a controls guy who's just getting his feet wet in steam (that has to hurt somehow.)



From a controls and functionality standpoint. I see two boilers with single-stage burners as being equivalent to two stage firing of a single boiler.  Two vaporstats or a two-stage thermostat -- something a reasonable portion of HVAC techs will be able to diagnose and correct problems on if they are given a system diagram.  Which of these two options is less expensive/difficult to install and which to own is what really interests me.



Full modulation of one or more boilers (or two-stage modulation of multiple boilers) is something that cries out for good DDC work.

vaporvac

That's it!

On the nose! That's exactly what I mean...I had read about this (thanks again Dave), but had not seen the end game. Wow! That piping is rad  I'm interested in how you chose the TR40s for that Btu.. I figured two Tr50s for my 1460 edr . SF suggested a 2gph gas burner which would almost perfectly match my edr. Did you figure this for a system with orifices. It seems like I should definitely be able to get by with the 2x Tr49s. SF said I definitely need a reservoir to accommodate the small water volume.At the rate I'm going you might actually be available.

tim smith

Re: Midco burner

I saw that burner about a month ago and talked to one of the heads at Midco, he said testing on boilers is to follow. I like the mesh head for mixing quite a bit.  I guess the main thing they would have to adjust is the burner tube length and blower speed.  I think will be quite interesting.   Boilerpro, what do you think of Powerflame X4?  Have you installed any with mod.

The Steam Whisperer (Formerly Boilerpro)

Details

The two stage thermostat controls a simple 2 zone hydronic pump relay panel with each relay firing one boiler.  The boilers have on/off Heatwise Burners( Heatwise was a casualty of our bad economy).  The second boiler almost never fires, as can be expected.   The boilers capacity was matched to the heat loss of the home, not the installed EDR.  This makes the need for Orifice plates part of the bargain.  It really doesn't make sense to use two stage pressure controls with this set up, as the only thing that matters is the temperature at the stat.  If you install TRV's on all the radieators, then a pressure control would make sense (probably in addition to the stat), because the load on the boilers may drop and you may end with two boilers firng when only one is needed.

A big advantage of using the power burners over the atmospheric is not only the higher thermal efficiency, but the stand by losses of an off, but steam hot boiler are lower than with atmospheric.  Unless you install motorized valves on the supply and return of the second stage boiler, it will act as a condensor for the primary boiler and be kept hot all season.  This is a big difference from hot water,where flow through an off boiler can be stopped just by P/S piping.   I've done a few mulitple atmospherics and with stack dampers the boiler rooms are roasting from all the heat fromthe second stage boilers dumping into the boiler room.

I have laid out and priced the cost to do 2 atmospherics staged with zone valves, etc.  It gets pretty pricey.  In addition, after doing some efficiency analysis with atmospherics, it appears its a bad idea to split the heat loss (not radiation load) into two equally size boilers.   You're better off using a 60 to 65 /40 split so the second boiler only fires in very severe weather.    This is probably why the traditional split was 50/50 but included the 33% to 50% pick up factor.  Esentially you ended up with a 65/65 split, when looking at heat loss.



2gph burners would be about 280,000 input, I was only at 200,000 input, so the TR-40 are fine.  Also, the TR-40's use only one riser, greatly simplifying the pipng.

ttekushan_3

letting the second boiler get warm. . .

I think letting the second boiler get warm through condensation has a minimal effect on overall seasonal efficiency but may, in the long term, prevent it from corroding. So long as the bolers are truly piped in parallel, any carbonic acid formed in the idle boiler should dissociate into the active boiler's water thus preventing both oxygen and acid corrosion of the "off" boiler.



[This is a big issue in the large steel steam boiler end of things, where oxygen content in the "off" boiler can be quite high if left cold.]



In other words, foregoing the expense (and added complexity) of fulling isolating one of the boilers may have an unseen benefit.



But I like your idea of "vapor-systeming" the steam with orifice plates or valves and using boilers based on the heat loss. And using an off the shelf two state thermostat is wonderful.



I've restored several vapor systems and they are a wonder to behold when they are working as designed. But your thoughts add a new wrinkle to even the intact original systems, making me think that further throttling the inlet valves and controlling a two stage burner or two boilers with a modern thermostat is the way to go.



Between your meddling with the rules of steam heat, and Gerry Gill's revival of the minitube steam system (thus throwing out all the traditional rules of steam heating), this Steam Heat Anarchy may become a threat to the republic!

The Steam Whisperer (Formerly Boilerpro)

Yes, I've done a couple.....

they are a pain to tune in, but do work.  I'm itching for the midco for a couple of reasons.....it uses a variable speed ECM blower with a negative pressure gas valve 4- to 20MA input for speed control, just like all the HW modcons, only bigger.  Also, it sounds like it has a very high radiant output, so I be the efficiency in wetbase boilers will be exceptional. The current burner lengths available fit very nicely with the Peerless models.

The Steam Whisperer (Formerly Boilerpro)

Staged

The large header and return piping act as equalizers between the boilers, just like between the sections of the Mills boilers.  Slant Fin has been doing them this way since the 1960's I understand.  When new with dirty water , the waterlines can get a bit wild, but after some cleaning they settle down.    I am not sure I would want to try more than 2 this way, since getting them absolutely level with each other would be a challenge.

vaporvac

Compatible burner option!!!Yeah!

Thanks for all the great options listed on this thread. I gave up on the rep as I have lost over 2 weeks of time and a window of good weather and available help, trying to get the info it took me less than 6hrs to get..

So it looks like Carlin is out for the TR 50 as they are only approved for the tr30 and smithg8s.

The RielloG400 series is go : on/off and 66 decibels.

Becket is a go and is actually under the Adams or Dornbeck Manufacturing name for the gas conversion. It  is also on/off.

Midco EC300 is approved for use. They did not have a modulating one for a TR50.so On/off. only...

Powerflame X4 is a go.. The powerflame can be purchased as an on/off, h-l-h, h-l-off, or fully modulating HDT with a 10-to-1 turndown.!!!!!So, if you want hlh or modulation on a smaller sized boiler this is the one (and apparently only)! Yeah!

So based on this is anyone know of any advantage of one over the other ie. noise, etc.?

Unfortunately, everyone now goes off for Xmas break and then inventory in Jan, but I think I may be able to get them even if the install has to wait.

My only question is with the condensate make-up tank and what size to get. This is NOT a float type thing. I'm a little unclear about it myself. Any input?

I hope this thread has helped Adam.  Didn't mean to hi-jack his post.

The Steam Whisperer (Formerly Boilerpro)

Another burner

Midco RE4400DS  HTD (High Turn down),  400,000 to 20,0000....20 to 1 downturn.



For a bigger boiler  Midco RE6110B HTD  1,100,000 to 40,000  ..27.5 to 1 downturn.

 3 or 4 to 1 downturn is probably all you need, unless you are running mulitple zones or TRV's

The Steam Whisperer (Formerly Boilerpro)

I forgot to add

the Midco' are ;linkage less, so they should be easier to set up.

vaporvac

thanks.

Thanks for the head-up on that Midco. I guess they forgot. I'll just have to check into the $ differential and see how much that option is worth to me when it gets down to $ and sense.

No TRVs or Xzones. My goal is to put in any missing orifices.I don't know what lingaeless means, but easier set-up is always better, as you said the Powerflame were a bit fiddly.

For some reason I hadn't really noticed that 2nd riser on the TR50. Oh well, I don't think I can go with the 40 even if it's simpler.

what did you ever do for a receiver tank given the low water content of these boilers?

The Steam Whisperer (Formerly Boilerpro)

Don'thave one....

yet.  They are on the edge and maybe the orifices will do the trick to get the condensate back faster.

SWEI

two-stage X4

I figured they might have that option, given the full modulation configs they offer.



Still curious about off-the-shelf steam controls for modulating boilers.

Henry

Burners

We did one with a Powerflamme full modulation and that was no trouble. We did a small 28HE-5 with a Carlin 2 stage modulating oil burner. That one was full of trouble, from the ignition card going to the modulating motor. We had to clean that boiler several times as it sooted up. All of our larger Smith installs, all have now Powerflamme modulating burners.

SWEI

modulating burners

What controls did you use on the Power Flame?



thanks~

vaporvac

Burner Updates & a Question

Happy New Year everyone! I thought I'd update this post while waiting for some answers from the boiler distributor. Slantfin was closed completely for the holidays.

I spoke to Midco about the modulating burner and that is also compatible, but they couldn't give suggestions concerning controls, plus it's 6hp!, so i'm assuming LOUD. The others are only a fraction of the power. He was able to explain what linkageless meant in terms of the set-up so that was helpful.

However, the awesome tech guy at Midco is going to use a sound meter to give me an accurate measurement of both the Midco RE4400DS HTD (High Turn down), and the Midco EC300. It should be next week before he can set up this testing, but then we can compare apples to apples when talking about the loudness of the powerburners. (This is mostly for homeowners.)

As the modulating powerflame is still in the running I'm curious as well, which controls Henry used.



I'm still pondering the orifice/boiler sizing thing. It would be so much easier to use the TR40 with the single riser and Carlin ez-gas burner, but I'm afraid if it wasn't enough it would be a costly mistake.



One slightly off-topic question: one of the boiler distributors sells the Intrepids as a package with an oil burner. If they won't swap out the oil for gas, is it possible to sell the oil burner? Obviously, my installer will price it all out, but if I could recoup that it might make a difference.

Dave in QCA

orifice calculations

I don't know if I have gotten back to you with the results on my boiler install and firing rates, etc.

My new boiler is firing at 390,000 on low fire.  It is running at 83% efficiency on first pass of tuning.  We'll see if we can get it any better.  Here is the big part for orifice systems... I am making enough steam to hold 8 oz in the mains (that is how my orifices were sized) for 1269 EDR.      I beleive that I had given the example of the calculations before, and the indeed are correct.  NO Pickup factor needed.  My calculations had told me that I needed to fire at 378,000, I'm firing at 390,000.  Maybe I am running a hair over 8oz.... dont know for sure.  Either way, the numbers are pretty much spot on.

vaporvac

Decisions...decisions

I may actually have to run those numbers for my own system. Did you include any sort of piping loss? I've decided I will need to turn the ceiling radiator on in the basement if the boiler puts out less heat so I need to keep that number in the calcs.

I also need to decide if I have serious intentions of heating the "pool room" during the winter using a HW loop. I'm not sure how to calculate how many xtra btus I need to do that. Is it based on square footage? I suppose this indecision is part of the reason I was looking at a variable speed burner.

Your new system sounds amazing. You were lucky to find some steam guys willing to help with something a bit new to them. I couldn't even find someone to follow through with an estimate. i guess since it was out of the usual install they didn't know how to price it. Hopefully, between my plumber/pipefitter/boilerman and burner guy we can figure it all out. I'm sure I'll post pics before the finish to get a critique and correct any problems before hooking it all up.

The Steam Whisperer (Formerly Boilerpro)

6 hp

I bet it's 1/6 hp.  The RE6850 is only 1/7 hp and fires over 1 million btu.  The LNB's have small ECM motors that use about 1/2 teh power of standard motors.

vaporvac

I'll ask again!

I'll ask again, but I am pretty sure that's what he said, especially as he mentioned the others were 1/10 the HP and I probably wouldn't want to have two of those in my basement. It was a shocking number, but I see what you're getting at with those other burners. I hope you're correct because it was some off-putting info even without a $differential.

SWEI

horsepower and noise

are loosely related at best.  Noise comes from the fan and the housing plus a tad from the motor bearings.  Single phase fractional horsepower motor efficiency is horrific. The ~50% which does not become useful work turns into heat and noise.  A reasonable ECM can exceed 90% efficiency.