Boiler Replacement Q's

4Barrel

I am moving forward with a replacement boiler for my one pipe steam system. I am placing my order today for a Dunkirk PSB-7D, the same model that I am replacing, with exception the new one will be electronic ignition. Based on input from heating help, and reviewing some old texts for radiator output, i'm conformable that the prior size was/is correct for my premises. the last one (installed in 1993), for all it's decay and leaks, worked well, and quietly, when i had the presstrol set to a differential of 1.5psi, and when there was sufficient, or, ahem, not too much, water in the darn thing. i am hoping for some input on the following issues, each of which i will try and describe briefly:



Excessive rust /scale:

The old boiler has a great deal of decay, in particular in the first two sections of the side on which the supply water was connected. See pic. Are there certain environmental conditions that will produce this result and are there preventative steps i can take with the new install?





Main Flue vent:

It has been suggested to me that combustion air may not be exhausting in an efficient manner due to the flue pipe narrowing from 7" to 5" in the chimney, potentially accelerating the decay issue. See pic. I can't change the diameter of the chimney pipe, but a draft induced fan place in the flue pipe before the chimney was suggested as a fix. Is this a good approach?



Combustion Air:

There is a nearby basement glass bloc window with a square opening. Should I fit a duct to this to carry fresh air to the boiler (one foot above floor nearby)? Again, I am thinking this will assist with the decay issue.



Main Vent:

The existing near boiler piping follows the Dunkirk recommendations very closely. The one main vent is located on the main dry return. See pic. It is a Hoffman 75. Should I consider another make / model? I see the Gortons are mentioned here often. If so, what model should I consider?



Vaporstat:

I want to use a vaporstat versus the supplied pressurtrol on the new boiler. Can/should it be installed in the same location of the pig tail in the attached pic? Given that it old boiler operated at a cut in of 1.5 psi, what model should i get? should i be trying to measure this in the 0-16oz range?



Radiator Venting:

I experimented with a new Hoffman 1-A last winter, and as a result, have concluded that i need to replace all the vents with new. I've read at length on this wall about TRVs. I am inclined to stay with what i know with the Hoffmans, but will the use TRVs in particular "hot" rooms help reduce my heating cost? or is this too complex a question to answer just yes/no?



Reuse of near boiler piping:

I've de-constructed the old boiler, and to my eye, the risers from the supply tappings are in good condition. Are there steps I should take to clean them for proper reuse?



Thanks again to everyone out there... your input and advice is valued and appreciated.



Jeff

nicholas bonham-carter

boiler replacement project

by all means use a gorton #2 as well as the hoffman 75. when you are running at the optimum low pressure, it helps to get the air out ASAP.wait until the new boiler, and main vent is in before buying new rad vents, as they can often be cleaned up just with dish soap and a "shake".

do you have some sort of auto fill, which could account for the excessive oxygenation, and subsequent rusting out of the feed side of the boiler; or well-water? try to do without any sort of auto feed device, or chemicals if at all possible. a boiler installed properly in 1993, should have lasted longer [30 years?].

0-16 oz vaporstat, with a good low-pressure gauge, would be best; and you need to know from dunkirk which model they recommend.

i would be concerned about the combustion air duct. what would happen if the boiler did not fire, and 0 deg. air is coming down the pipe to it?

i don't think there is anything wrong with reuse of pipe and fittings-just clean the threads before reassembly.

chimney-there should be a flue requirement in the dunkirk inst. book. if it leaves the boiler with a 7 in. pipe, it is probably not good to be so narrow higher up, although the height may compensate for the restriction. perhaps others here will chime in on the flue, and combustion air questions.--nbc

4Barrel

autofeeder

yes, there was an autofeeder attached to the supply side, triggered by the LWCO. although the old one worked, i had planned on getting a new one. is this a bad move? how would i ensure the boiler is adequately filled without the feeder?

Steamhead

What killed the old boiler?

looks like it may have taken on too much feed water. Are there any obvious leaks in the system? Any underground return lines?



When you replace the feeder, use a Hydrolevel VXT. It has a built-in counter that tracks water input. You'll be able to see if it feeds too often. Any more than once a month is too often.

4Barrel

leaky

i think the old one got into a viscous loop of leaking and replenishing w/ water, and then you have the resulting hot/cold cycles. before i bought this place a couple years ago, it had an absentee landlord that did not often service the unit. here are few more pics.



no, no underground returns. really, this thing is set up just like the diagram in the Dunkirk instructions. no leaks that i know of. I do worry though that i'm not getting condensate back to boiler fast enough. of course, those returns could be clogged, but I've heard that Hoffman 75 push a lot of air, so my hope is that they are clear. i checked the lines around this vent, with a snake, and they appeared to be so. my next thought is that better venting on the main return will help - is my thinking correct?

Unknown

Look up for the Answer !

Just read your latest post mentioning the need for possible better main venting and got a good laugh as all you need to do is look just above your post for the answer. Look the picture at the end of Steamhead's reply. It shows a multiple main vent setup using ( it looks like ) 5 Gorton #2s !    One should maximize their system's main venting as the faster the air exits the main, the faster steam gets to your radiators.

- Rod

4Barrel

Head's Up!

Thanks Rod! Ya know - I've been looking at that pic, and, yes, I get it! It looks cool too!



I've read a number of posts regarding main vents, and i know there's a way to calculate the amount of venting needed, but is it safe to say that you can't have too much? suppose I mounted two of those gorton's on a T off the current vent nipple, replacing the old hoffman 75. i'm thinking i could continue to add vents on the T if needed. is it safe to say that one gorton is equal to or better than one hoffman, or am i being to simplistic?

Steamhead

That boiler rotted out at the waterline

so I would say either your water has a high chloride content, or it was taking on way too much feed water.



Measure the length and diameter of your steam main(s) and we can tell you what vents you need.

Unknown

Main Vents

Basically a Gorton # 2 has twice the venting capacity of a Hoffman #75



You also might want to take a look at Gerry Gill's website as he has a good article on main venting

 http://www.gwgillplumbingandheating.com/

 .

I have also included a drawing of a vent "Menorah" / "Antler" sedtup. This drawing was done by Brad White and the interesting thing to notice is the use of the pipe union. With the union you can makeup, add to, or service the vents on your work bench and then attach them to the steam main using a single connection. Saves a lot of skinned knuckles trying to attach the vents and fittings up between the joists!



Steamhead is the "super pro" here so go with what he recommends on venting.



- Rod

4Barrel

will do

i'll measure them in the AM and post the result. do i include all piping to each radiator? i'll do my best to estimate the in wall portions...



THANK YOU!

4Barrel

great diagram!

i had read about this in other posts, but this illustration is great & very helpful. thank you.



do you recommend a similar set-up for the vaporstat / low pressure gauge, with a nipple off the vessel bulkhead?

Jean-David Beyer

Would you explain ...

Would you explain why you need a minimum of 15" straight pipe after the T in the "Menorah Arrangement," but you do not need something like that in the "Antler Arrangement."

nicholas bonham-carter

antler vs. menorah

the idea behind the 15 in clearance is to avoid placing the vent directly over [and thus in line] with a possible water-hammered slug of water shooting up the vertical pipe. the force of water-hammer is considerable, and could destroy the vent innards in a short time.

in reality, i think the menorah and the antlers are protected agaist that, by all their elbows, and each could be put on the riser without the setback.--nbc

Jean-David Beyer

water hammer

It seems to me that neither of these methods would help much with water hammer problems. It further seems to me that the best way to deal with water hammer is to put a "water hammer arrestor" right near whatever valve it is that is closing too fast; maybe second best is at the end of the line to at least prevent reflections. By "water hammer arrestor" I mean a gizmo like a sealed air chamber; a mini diaphragm type expansion tank, if you will.



But in a steam system, I do not see where water hammer would arise. Water is incompressible, but steam sure is compressible (you can compress it to the point it is denser than water at about 3208 psi), so the whole steam line would act as a hammer arrestor. Is there a likelyhood of water coming up the the return pipe of a two-pipe system? Would this ever be a problem on a one-pipe system?



As you can tell, I know nothing about steam systems except what I read here.

nicholas bonham-carter

water-hammer and vents

that chamber type of water-hammer arrester is for evening out a pressure pulse in a water pipe due to uneven flow caused by a loose washer in a valve, etc.

the type of water-hammer, we are protecting the vents from, is caused by a bubble of steam; which becomes completely surrounded by water. when this happens the steam suddenly condenses, and leaves a complete momentary vacuum. the surrounding water then rushes into this vacuum, and the resultant force can send the water shooting from one end of the pipe to the other at high speed! some pros have reported fittings cracked [even in our low pressure systems].

this is one reason not to allow sagging pipes in  which collect pools of water, because of incomplete drainage. i like to think also that  NOISE=WASTED ENERGY in any system.--nbc

Unknown

Vent Arrangements

Hi JD-  The 15 inches on the "menorah" drawing represents the "ideal" and the "antler" mounted on a tee at the end of the main represents what you typically find at the end of a lot of mains though it is usually a special reducing  elbow with a separate small  FPT hole to attach the vent,  rather than the tee show in the drawing. I don't know what this type of elbow is called but you see them frequently on old steam systems.



When the radiators are cold and steam is really condensing at a fast rate, the amount of condensate at the end of the main is quite considerable. It's more like a "river" than "drainage". The pipe can be quite full  of condensate moving at a rapid speed. This collides with the elbow / tee at the end of the main and the idea of the (15 inch) setback it to help prevent water/rust /dirt from being forced into the vents and destroying them.

As creating a new place to attach the main isn't always practical, the "antler" shows what you can do instead. Keep in mind that the original vent fitting probably was installed directly on the elbow for years so the "antler" is obviously an improvement on this. The idea is to keep the "ideal" in mind and work towards achieving that.. Working with old steam systems and the modifications that have been done over the years I find you just try to go in the direction of the "ideal" as far as it is practical both physically and economically.



"Water hammer" - What you're describing is classic hydraulic water hammer like the type you get when you quickly close a valve on a solid stream of running water. This confused me a bit at first and then I realized that with steam the term "water hammer"

also refers to the collision of steam and condensate with each other or parts of the piping system.



Edit - NBC brings up a good point of what collapsing steam (vacuum) plays in steam "water hammer".  A cubic inch of water makes 1700 cubic inches of steam at atmospheric pressure. When steam instantly collapses (back to 1 cubic inch.) you can see how much vacuum comes into play.

4Barrel

measurements

steamhead-

thanks for your offer of help. really, what i'm picking up here is fantastic. when you asked me to measure, i didn't think much of that exercise, b/c i was in the process of trying to figure out how much insulation i needed to purchase. but when i actually spent the time to look at every line, the system took on a whole new dimension. i was able to recognize where pipe size reductions took place, some by design, and some that may have been the result of later repairs. also illuminating were radiators that i believe are connected to undersize valves. i don't have too many of these, but it explained why last winter they were so slow to heat up.



anyway, here are the figures. i included everything from the boiler out: header, header risers, mains, branches, sub-branches, sub-sub branches, risers, all the way to each radiator. had to guess in some spots, but i think i'm 90-95% accurate. also included the dry returns. note, note every steam line had one (some branches are counter-flow, but then connect to a union that has a drip on it).



Steam Pipe Tally

Size Total Feet

2-1/2" 14

2" 84

1-1.2" 60

1-1/4" 175

1" 22



Valve Count

1-1/4" 13

1" 4



Dry Returns

1" 73'

3/4" 74'

4Barrel

thanks rod,

for the clarifications/explanations. great info! look like i'll have enough room for the menorah set up. i do hope the additional venting will solve issues i had last winter.

Unknown

Menorah (cont.)

Jeff-  The "menorah" is just an example of what one can do with main venting and might not be necessary for your system.  If you had a Hoffman 75 and replaced it with a Gorton # 2, you have doubled your venting capacity and that maybe all the venting you need. 

As Steamhead mentioned you can calculate the amount of venting

necessary for an individual main (by calculating the volume of each

individual main. - you need to measure the inner diameter and the length of each main to do the calculation)  or you can do it by trial and error timing. You can always add more venting if you find it necessary. There is no point of having / paying for more venting than each main needs.



Taking on a steam system can be a bit overwhelming at first. You need to break your steam system down into sections and evaluate each section individually.  ( I haven't included the boiler, burner and controls in this as you should leave that to a professional)

   The first section should be the piping near the boiler - the risers, the dropheader, the uptakes to the mains, the equalizer and return piping.

The next sections should be each main from where the steam enters each main down to the far end and the main vent and then back through the dry return to the boiler.You need to evaluate each individual main's venting.  You also need to evaluate whether the slope of the main is correct and that there are no sags in the mains where condensate can pool. 

   The next sections are each radiator "system"- the radiator piping , the radiator valve ( the tap) and the air vent.  You need to check each for function and be sure the radiator (1 pipe steam) is adequately sloped.    You mentioned that your system may have  undersize piping, valves etc.. This while not ideal can still perform okay . With small diameter piping what you have to be careful of here is to not vent the air too fast from the radiator as the steam coming in through the pipe/valve will collide with the condensate returning and this stops steam entering the radiator. Slower venting helps keep the volume of return condensate lower and the radiator working though a bit more slowly.



- Rod



 

4Barrel

details... and conclusions

rod -



yes, i am getting sense of the details here. last winter, i came to understand the boiler issues, mainly because it was failing. now, i see the piping, and understand the relationships that impact how a particular radiator may behave. like i said in another post, the system, when it had the right amount of water in it, ran OK.



thanks for the tip on the main venting. it reminded me that i need to focus on key issues, and not get too lost in all the permeations. that said here's where i'm at:



1) i've validated the boiler size against my calculated load, and in fact, the same size (in fact same model) boiler will serve my needs. this will allow me to reuse the near boiler set-up, which was piped according to Dunkirk spec. there is a possibility to add a drop header (which i will post on separately), and i plan to insure everything is pitched correctly.



2) i've got a recommendation on an in-line draft induced fan (TJERLUND D-3) to assist with exhausting boiler combustion gases. it not exactly inexpensive, but i think a worthwhile insurance policy.



3) i'll wait for the final calcs, but i'm pretty much sold on the idea of using a Gorton #2 instead of the Hoff 75 for main venting, and will use that as a starting point.



4) similarly, i'm ready to move forward with the low pressure vaporstat and pressure gauge.



5) i liked the recommendation to use the Hydrolevel VXT, in order to measure the amount of water supplied. although the prior set up utilized a water feeder, i had no way to determine if the system was calling for too much water. now i'll have a way to determine that, and hopefully prevent a premature demise of the new boiler.



lastly, i do think i will be making changes to piping & supply valves of the identified troublesome radiators (two or three).



whew... please comment if my approach needs tweaking or re-evaluation.



thanks to all.



regards,



jeff

Steamhead

What we need to know

is how long each steam main is, and what pipe size. If there is more than one steam main we need info on them all.



BTW- you don't need that Tjernlund unit if the chimney develops proper draft.

nicholas bonham-carter

steam boiler replacement

why not reuse the hoffmann 75 plus the new gorton #2 on an antler?

also suggest, piping the make up water-feed into the wet return, as far upstream from the boiler as you can. this mixes any makeup water better with the returning condensate, and reduces thermal shock, and oxygen shock.

i have no auto feed on my 1,000,000 boiler, but check it once a day. i just don't trust "auto-feed" to be not "over-feed"!

don't remember mention of smaller than nec. steam pipes-only the flue. why not see how those pipes behave with the new boiler and pressures before changing them, unless you are very sure. the increased venting will make a big improvement, as will correcting any low spots.-nbc

4Barrel

here are the lengths:

there are two mains (and two risers from the header). the measurements here are from the point at which each main meets its respective riser:



main 1: 2", 31' length - serves 6 rads, w/ total load of 260 EDR

main 2: 2", 44' length - serves 11 rads, w/ total load of 340 EDR



(for main 2, there is a 1.5" branch at 6', which sorta looks like part of that main, but it only serves two radiators. the 2" section winds to the back to he house, and serves the rest of the radiators on main 2).



more info that you wanted, but there it is



as for the inducer, yes i do believe that i am not getting enough draft. the spec requires a 7" , and i only have 5" sleeve in the chimney. do you think this may not be the best solution?

BRIANJ

Connect to hot water?

Would connecting makeup to a hot water supply eliminate the boiler shock? I also don't like automatic feeds nor low water syphon cutoffs. I check the water level visually and add accordingly.

4Barrel

do you guys mean...

1) putting the water feeder input on the same side of the boiler as the wet return



and/or



2) making the supply come from a hot water tank



for #1 - i was thinking of doing this, but not for the reason you state. makes total sense that this would be the better side to feed from, and just plug the other side.



for #2 - the hot water tank i would feed from is not proximate to the boiler, but there is line from it nearby, and could easily be tapped into.



both of these steps seem like good preventative measures to reduce cold water shock. should i do both?



as for the autofeeder itself, i do need to have something in place as i am not here all the time.



great input guys!! keep it coming!!!

Unknown

Makeup Water

Makeup Water- While you need to keep thermal shock in mind when thinking about adding boiler water, the volume that is added is so small it shouldn't be a problem as long as you don't introduce it directly into the boiler. 

If you want to add water manually, one of the best items I have seen is to use a spring loaded tap like they use in high school showers. This stops the problem of opening the valve and then forgetting about it which then results in a flooding boiler and possible water damage. The setup i saw also had a ball valve upstream so you had to turn that on before operating the spring loaded valve. On automatic feeders you might want to look at Gerry Gill's sight that I posted in an earlier post. He has a good discussion about  how they should be wired.



Details- Carefully thinking out the details to each part of the system makes a big difference. You might want to take a look at the Videos under` Resources  above and take a look at the Steam videos and the one Dan does on Near boiler plumbing. While the master valve on the steam supply might be a bit much (due to cost), having shutoffs and drains in appropriate places really helps making the maintenance easy. I didn't have any originally on my wet return and so renewed it (with copper) and put in  the shutoffs and drains. Since you're using you original piping you might want to renew the wet return section as this is usually quite "crudded up" and it's easier to just replace it than try to clean it out. The piping around the boiler needs to be carefully considered as this is a "make or break" area of how well you system works both from a comfort and an economy standpoint.



I see Steamhead doesn't feel the Tjernlund is necessary. He's the real expert here so I'd definitely follow his recommendations.



Small pipes- I think I'd really consider following NBC's advice and just see how well they work with the new boiler before I'd tackle them. Running at a lower pressure and with good main vents  you might  get a pleasant surprise. If that doesn't work you can always do them later.

4Barrel

wet return

hi rod - yes good point, my next step is to disassemble the wet return / loop assembly. more than likely this will replaced. but we'll see if anything can be reused.



on the fan, you made me think to call Dunkirk, and they validated that as a class one boiler, the spec is for 7" flue through the chimney. so my options are: 1) re-sleeve a 40'+ chimney with a 7" flue, 2) power vent out the basement window or 3) in-line draft inducer. #1 - yikes!, #2 is pricer an more involved than #3, so i'm inclined towards #3 at this point...

Unknown

Power Venting

Hmmm- Chimney / Powerventing decisions are way above my paygrade  My understanding was that this was a straight boiler swap - using the same type/size of boiler as the previous one. If so, it occurs to me If the previous one worked okay, why would you need a big (and expensive) modification on this one? 

Just food for thought.

Big-Al_2

Possible vent issue?

From the photo, it looks like the ceiling above your main vent has spent its life in a sauna. Could the system have been running for a while with a main vent that never closed all the way and constantly let out steam?  That might account for a large quantity of makeup water.



At my house, the main vents are pretty close to the subfloor.  I stapled up a decent sized  square of aluminum sheet right above them.  That way, if one of them fails open when I'm not home, maybe the hardwood floor right above it won't buckle.  It's probably not necessary, but it lets me sleep a little better . . .

4Barrel

i know what you mean...

but, input from the supplier led me to believe that the diminished flue diameter could have caused the boiler exhaust - which is acidic, i believe - to possibly condense and help accelerate the boiler decay. he suggested a new chimney liner, but i know this old place, and that there is reason for everything. my bet is that the max width of the masonry opening probably wouldn't allow for anything larger than a 5" liner. i decided to look into options, and the inducer seems most cost effective, and straightforward to install, versus the other options. so, we'll see. in the big scheme of the project, this seems like a reasonable insurance policy. you're right, in the main aspect, this is a direct swap, but the things i'm looking at will hopefully make the new one perform better, and last longer. thanks for testing my assumptions... again, keep it coming!

4Barrel

the location of the main vent

is where the Dunkirk specs say it's supposed to be, but ya know, i've always wondered about whether or not the thing is working right. the staining you see in the ceiling has been there since i owned the place (3 years now). the old boiler was installed in 1993, as best i can tell, and i'm confident when i say the prior owner probably never touched the vent from the time it went in.

Unknown

Venting & Chimneys

I must first state that I know virtually nothing about chimneys/draft.   It just seems to me that if an acidic condition resulted from the combustion byproducts was the cause of a boiler's demise,  that it would be readily seen inside the boiler on the walls of the firebox / crown plate (that is, on the fireside of the boiler). If the corrosion is on the water side of the boiler, that's a boiler water issue.



Exhaust gases can be very acidic but with a steam boiler it is my understanding  this is more of a chimney issue that a boiler one. While I can see where a good liner would be benefit in containing chimney erosion I'm just not sure in an old chimney (having recently had two of them redone) just how much benefit one would get with a positive draft setup as a lot of the old house chimneys don't have separate individual flues. I'd really check out this area a bit as there is no sense spending money on the unit and energy to run it, if it isn't really necessary.



I' d really be interested in what  the pros have to say on this based on their experience.

Steamhead

Vent

the shorter main with two Gorton #1 vents, and the longer one with a Gorton #2. The branch line may or may not need a vent, see how those rads heat up when the Gortons are in place.



Was the chimney relined at 5" when the old boiler was still there, needing 7"? If so, you may need to go after whoever re-lined it......

4Barrel

where should i locate

the vents you suggest? the hoffman is currently located on the dry return, just before the drip connection. see attached pic (the green vent is partially hidden). this is where the Dunkirk spec says to put it.



i should note that there is a "sub-main" the runs off main 2, and parallel to it. it serves 5 rads. it goes like this: 5 feet of 2", 4 feet of 1.5", and then 16 feet of 1.25". there are branches off it and then hit the riders for each rad. should this "sub-main" be vented?



as for the chimney, i don't know the answer, unfortunately. i believe it was all set up that way at the same time back when the boiler was installed.

Steamhead

What does that Hoffman

vent- main 1 or 2?



The sub-main will probably need something, probably a Hoffman #4A at the end. I don't have my chart handy for pipe smaller than 2", so I may need to update that.



Have a chimney pro look at your chimney.

4Barrel

the hoffman

vents the whole system. there are no other vents. it's near the end of the dry return piping (although, the dry return for main 1 comes in to the main return just after the vent and just before the 90 degree bend back to the boiler). you can see this in the pic.



is it possible to place the vents you suggest in the position of the current vent?



will do on the chimney.

Steamhead

Ahhh

That's something else that needs fixing. Each dry return should drop below the boiler's waterline before tying together. That way, water standing in the drops will keep air and steam from passing between the two dry returns, and you can vent each one with the proper size vents to make the system heat up evenly. 

4Barrel

i think i'm getting this

so, if i understand you correctly, each dry return should drop 90 degrees to the floor (like the drip connection in the picture), and THEN tie into a common WET return below the boiler water line. before each of the DRY returns turn towards the floor (15" i think) i should place the vent appropriate for the main(s) those returns serve. Is this a better design?



it would be quite difficult to place the vents at the physical ends of the mains themselves, so i'm hoping the above makes sense.

Steamhead

It does

and given the difficulty of getting at the ends of the mains, I'd do what you're going to do. 

4Barrel

Thank you

for all your help! I have a much better grasp on the main venting now.

nicholas bonham-carter

vent location

if you are going to rework the dry/wet return, you could always mount those vents for each dry return on the vertical drop, just underneath the elbow. some where here there is a picture of that arangement. it solves the headroom issue, but must be well above waterline height.--nbc