Heat Loss Calc for Steam Boiler Replacement

bowman

Applying for permit to swap-out existing leaking steam boiler with like-for-like replacement block.
Am not changing any piping above the header.
Current boiler is sized so the connected EDR is approximately 92% of its BTU capacity.
That leaves some room to add a radiator here or there, maybe; but otherwise seems perfect.
Anyway, am not questioning the size choice.
But the inspector wants a "manual J (???)" heat loss calc since we are techincally installing a "new" boiler.
Explained this is steam and we go by connected load, but he says they need that now, as if we are building a new house.
I understand the reasoning behind it; but does the Code provide an exception for like-for-like replacements of existing steam boilers where connected load is not changing?
Please advise.

Thank you

GGross

Locally they will not make contractors perform a manual J for like-for-like changeouts. They do make us for all new construction, and they ask for it when changing the size, or doing a remodel etc.

Unfortunately even if the code official misunderstands the code there are clauses in the ICC code book that the code is up to "interpretation by the code official" which has always bothered me since the whole point of standardized codes was to create equal enforcement across jurisdictions.

For me I have no problem asking inspectors the hard questions, but I work in sales and don't need to pull a permit so no harm in making them mad at me. What I always advise a contractor to do, if they don't want me to get involved, is to politely ask the inspector to cite the specific code section that enforces whatever issue you have, so that you may better understand it. At that time you can start a conversation with them if you are confident the code does not require a manual J in your situation, and show them the code section that agrees with you. I would be overly nice to them if I were you, at least locally the code officials are basically infallible, and the appeals process has to go through them, state appeals has 3 of the guys sitting on that board as well. Basically don't burn any of those bridges.

Steamhead

Show the inspector the sizing procedure in @DanHolohan 's "The Lost Art of Steam Heating" as well as from various boiler manufacturer's publications. It would be hard to argue with these.

Jamie Hall

No, you shouldn't need a Manual J heat loss calculation. However, if there is a requirement for one in whatever local Code being used, your building inspector is just as shackled by that as you are. It's all very well to say it's not needed -- and, privately, your inspector may well agree with you -- but he has to enforce the Code which he's given. Part of the territory. So don't be too hard on him or her.

GGross

OK so digging into my code book which is current Michigan Residential code you should check your own local energy code to see if something similar is written. Your inspector is likely citing the energy code, there is a section in the energy code about equipment sizing that reads as follows.

"Heating and cooling equipment shall be sized in accordance with ACCA Manual S based on building loads calculated in accordance with ACCA Manual J or other APPROVED heating and cooling calculation methodologies"

But there is a stipulation at the beginning of the energy code that reads

"Additions, alterations, renovations, or repairs to an existing building, building system, or portion thereof shall conform to the provisions of this code as they relate to new construction without requiring the unaltered portion of the existing building or building system to comply with this code."

Your inspector likely reads this (or however it is worded in your code book) as "all changes must comply to the letter as written in this book"

But, in my very feeble attempt to understand the code, let's say you change out a steamer, but leave the existing radiation. They can't make you change out these emitters anyway if it turns out your boiler is the wrong size. Additionally it would stand to reason that a home that has heated satisfactorily, and was legally installed under the codes of the time, could have the equipment sized based on existing emitters, never mind whether the inspector understands this is the correct way to size steam equipment anyway, the emitters were existing, and they were approved at the time of construction. Similarly if you change out a cast-iron boiler and size the new one based on the baseboard installed my local inspectors would approve this. The trick is to get the local inspector to agree that sizing the equipment to the emitters could be considered an "approved" method, as the code official it is his right alone to determine what is, or is not an "approved" method. Let them feel powerful as though they thought of it themselves, my money says they will work with you and you may even help out other local contractors bringing this up. We went through it back in 2015 when we adopted this code.

EBEBRATT-Ed

Don't know where your located but if it is Connecticut it is on the permit form and required in some towns. They dont care if the boiler is 3x oversized they just want to make sure it is big enough.

Long Beach Ed

Your jurisdiction may require it. We had a place in NY where the locality required any replacement boiler to provide no more than 80% of the Manual J heat loss to meet efficiency requirements. We were able to circumvent them with a letter from a licensed professional engineer who took responsibility for the carbon crime against the environment

Jamie Hall

Long Beach Ed said:

Your jurisdiction may require it. We had a place in NY where the locality required any replacement boiler to provide no more than 80% of the Manual J heat loss to meet efficiency requirements. We were able to circumvent them with a letter from a licensed professional engineer who took responsibility for the carbon crime against the environment

That should be criminal. Who takes the liability when you get a design day and you can only heat the place to 50, and the people die of hypothermia? Or in an effort to avoid that they use a couple of space heaters from Walmart and burn the place down? There is a special place in Hell for the folks who dreamed that one up.

The Steam Whisperer

Jamie Hall said:

Long Beach Ed said:

Your jurisdiction may require it. We had a place in NY where the locality required any replacement boiler to provide no more than 80% of the Manual J heat loss to meet efficiency requirements. We were able to circumvent them with a letter from a licensed professional engineer who took responsibility for the carbon crime against the environment

That should be criminal. Who takes the liability when you get a design day and you can only heat the place to 50, and the people die of hypothermia? Or in an effort to avoid that they use a couple of space heaters from Walmart and burn the place down? There is a special place in Hell for the folks who dreamed that one up.

Jamie, that's been my thought with this whole idea that a steam boiler must be sized to the heat load calcs.
I would present that the requirement of sizing steam boilers to heat loads is against the industry and manufacturer's requirements and if the building does not heat properly, they will be liable. I imagine having an attorney tell them this would make it pretty clear the problem they could be facing.
However, the idea of using 80% of the manual J calculation is not far fetched. It was discovered many years ago and real life has shown that heat load calculations typically grossly overestimate the loads. I believe this is especially the case in high mass structures where ground contact tempering is occurring or in well insulated structures. Heat load calcs assume no person in the building giving off heat, never any sunlight, no electrical usage, cooking, showers, etc.. They pretend that there are no internal gains from any sources to come up with the number.
We all know this is simply untrue.
Example: I sleep in an unheated room (I like it very cool) with 1 exterior wall measuring 13 feet x 9 feet ( (overall 120 sq ft) that contains about 42 sq ft of windows and 180 sq ft of exposed ceiling. However, despite steadily dropping outdoor temperatures overnight, when I wake up in the morning, the room is noticeably warmer. Body heat is enough to raise the temperature several degrees, even when it is zero outside.

I think that probably the structures that this 80% requirement may not work is with large, wood frame private homes that have been extensively remodeled with drywall or newer construction, and have not used any type of airsealing methods on the interior side of the exterior surfaces. I believe typical drywalled exterior frame walls leak profusely, so heat loads tend to be really high.

Jamie Hall

I agree with most of your thoughts, @The Steam Whisperer , but I would argue that carefully done a manual J or other heat loss calculation is not likely to be more than 10% off -- and is more likely, in an existing structure, to underestimate the load than to overestimate it. In a new structure it shouldn't be more than 5% off. This assumes, of course, that the individual doing the heat loss calculation is actually doing it correctly and conscientiously, and not just throwing darts at the walll.

Now then. If, in some other engineering discipline, I make a careful calculation of the loads and then deliberately design for 80% of that load, when the system fails I have both a civil and criminal (for example, if the part fails -- say a beam -- and someone is killed, that's manslaughter) liability. This has been held up in court any number of times. This is, of course, in addition to any moral or ethical shortcoming on my part.

I don't see that there is any difference here, only in this situation it seems that the regulation is intended to force the engineer and installer to deliberately install a defective system; the writers of the regulation will, no doubt, escape liability. That's modern society. As I say, though, in my belief structure there is a very special place in Hell for them, and that's where they are headed unless they repent. But.... that's me.

ethicalpaul

I kind of can’t see how a boiler at 80% of heat loss could kill anyone.  The rhetoric I think hurts your argument my friend.

I agree it sounds odd but I’d have to see the regulation to have any hope of understanding.

Jamie Hall

well, @ethicalpaul , it wouldn't -- provided the occupants of the structure either are young and vigorous, or have somewhere else they can go. However, let us consider the recent little cold snap we had. The temperature outside was -15 for two days straight, with a wind. The design temp here is 0. A full power boiler would, then, be able to maintain the interior temperature for those two days at about 55. That probably wouldn't have killed me, although it would have hospitalized me unless I had auxiliary heat. An 80% boiler would have only been able to maintain 40. That would have, again, unless I had auxiliary heat and a lot of it. Hypothermia can and does kill older people, particularly those who may not have the ... um... padding that many people do these days.

Perhaps you are right, though, and I shouldn't be concerned about my own health and that of my family, in light of the Greater Good for the Common Society.

dabrakeman

I was a little surprised to see how moderate the design heating temperature ratings were per locale when referencing recommendations used for Manual J calculation. I am sure there is plenty I do not understand about the intent of these ratings but 3F @ 99% for where I live certainly does not fall into what my uneducated expectation was of a reasonable worst case temperature. Probably get a half dozen nights well below that each year. -2.5F appears to be the value for 99.6% according to the second link. Tend to get below that once or twice per year at least. So what % rating typically gets used?


https://farm-energy.extension.org/wp-content/uploads/2019/04/7.-Outdoor_Design_Conditions_508.pdf

https://captiveaire.com/CATALOGCONTENT/FANS/SUP_MPU/doc/Winter_Summer_Design_Temps_US.pdf

mattmia2

The worst case is probably not the lowest temp but windy at a somewhat warmer temp. Modern hydronic heating goes in to the math in a chapter. Not sure where manual j is factoring in wind because it is part infiltration and part disrupting the air at the surface of the structure and reducing the r value.

mattmia2

I'd be interested in seeing a cite of the New York regulation.

ethicalpaul

How many hours would people sit in 55 degree temps without calling someone for help? They have to have support, just like they would have if the heating failed outright. But again, I'd have to see the regulation to judge it.

Jamie Hall

mattmia2 said:

The worst case is probably not the lowest temp but windy at a somewhat warmer temp. Modern hydronic heating goes in to the math in a chapter. Not sure where manual j is factoring in wind because it is part infiltration and part disrupting the air at the surface of the structure and reducing the r value.

The windspeed adjustment for the boundary layer should be part of the determination of the overall u value of the wall assembly -- and it can be significant, depending on a variety of factors. Among other things, it varies substantially depending on the elevation of the wall or roof in question above the ground. It wasn't part of the old Slant/Fin on-line calculator, and probably isn't in most other simpler calculators. It is a different calculation (and effect) from the infiltration adjustment. Not taking it into account properly is one reason why many such calculations underestimate the design heating or cooling loads -- or, if a high value is assumed in the calculation, why an overestimate can occur.

I will only address @ethicalpaul 's comment on seeking support to the extent of noting that it -- and my comments on the same area -- are actually part of a much more profound ethical, moral, political, and indeed religious question which really doesn't belong on The Wall -- and which I apologise to you all for having brought up.

GGross

mattmia2 said:

I'd be interested in seeing a cite of the New York regulation.

Yeah I would like to see it as well. There are sizing limits in the Michigan energy code, but it's like no more than 150% of the load calc or something like that. They actually called out a customer of mine on that one time for a modcon install, they forgot to read the last bits if the code that talk about modulating equipment, there is also a stipulation that FA can be oversized to meet the cooling load, and any equipment can be oversized if the next size smaller is undersized, OR you can tell them you can't get the correct size equipment. There is honestly more code support for oversizing equipment in MI than undersizing.

gmcinnes

*If* you can have your manual J done by someone who never has to work with the Inspector directly, like a salesman or someone from a supply house, and *if* you explain the situation to them, and *if* you have "had insulation added" or "have a lot of infiltration" you may find, like me, that the manual J numbers suggest a boiler pretty close to the one you want to install.

Still a totally unnecessary PITA though.

@EBEBRATT-Ed In my town in CT they didn't just not care if my new boiler was 3x larger than needed, they were very anxious to make sure that it was. Weeks of fighting to get them to right-size it.

EBEBRATT-Ed

So you fudge the manual J up 20%. You don't think those idiots are going to be smart enough to catch it do you?

Jamie Hall

Why not have the Manual J done by a really conscientious and honest person, who knows what he or she is doing, and have the equipment sized and the installation done likewise? Such people do exist -- thogh it would seem they are getting kind of rare...

The building inspector or code enforcement officer should accept that. Although with everyone trying to cheat the system, it's not too surprising when they are suspicious, is it?

Sad situation.

ethicalpaul

Long Beach Ed said:

Your jurisdiction may require it. We had a place in NY where the locality required any replacement boiler to provide no more than 80% of the Manual J heat loss to meet efficiency requirements. We were able to circumvent them with a letter from a licensed professional engineer who took responsibility for the carbon crime against the environment

There have been a dozen or so messages freaking out about this, all based on possibly a single locality in NY, can we calm down a bit? I'd still love to see this requirement.

gmcinnes

@Jamie Hall In normal situations yes, honesty is the best policy, but this is a very specific, broken, situation. Correct me please, but isn't this a case where the heat loss calculation could differ from what BTUs would most effectively be provided by the connected EDR?

@bowman original boiler was working. If the manual J heat loss calc indicates a different size boiler is needed.. How do you reconcile that with the connected EDR?

If everyone involved knows that the previous setup was satisfactory, and no other changes are being made, I don't see this as ethically problematic. Just a bit of fudging to get around some mis-written policy.

Falsifying a manual J for a new build or a new system in order to save a developer or an installer some bucks on a system, or to beat a heat loss mandate, totally different story.

In my case I had a manual J done by two people. In both cases it was estimating heat loss *way* too high. I knew that because I had years and years of data rather than estimates. Data always beats estimates. When I explained it to the first guy, understandably, he didn't want the liability of changing things. The second guy was more willing to look at the data with me and look to where he could make his values more conservative and get us close to agreement.

After the recent weather (-20F, -30F with wind chill) if I didn't feel vindicated before, I do now. I would guess the boiler was active less than 30% of the time. And I'll tell ya, my installer *still* felt skeptical it would be big enough, and I *still* thought I could go a size smaller

GGross

@ethicalpaul

Considering most local codes are based on, if not complete copies of, the ICC books, I remain entirely skeptical that there is a NY locality that has a written code demanding equipment be sized at no greater than 80% of the manual J. I checked NYC codes and their sizing requirements are exactly the same as they are here in MI. Size to manual J, Or any "approved" method, where approved means any method the building official accepts. This allows for the building department to make some "common sense" exceptions for things such as, existing steam systems that have heated correctly for 50 years, we know the radiation is sized correctly, so just size the equipment to the radiation.

Now I could believe that there are some building officials out there who either misunderstand, or choose to misunderstand the code, that is why you should always ask them to cite the specific code section when they call out stuff like this that doesn't make sense

Jamie Hall

@gmcinnes has an interesting -- and valid point, although a slightly complicated one. There are, fundamentally, three possibilities.

First, you are looking at a new build or a gut rehab. In that case, there really is no excuse for a Manual J -- or equivalent engineered heat loss analysis -- to come within about 10% at most of "real life" experience, and equally no excuse for the system -- SYSTEM, not just the boiler -- to be chosen (not just hot water or hot air or whatever, powered by whatever) to be correctly designed and sized for the application.

Second, you are looking at a system -- pretty much anything other than steam -- which needs a new power plant, but the rest of it is in good or at least usable condition. There the heat loss calculation is again used, and again the power plant can and should be chosen and sized on that basis. I would expect, however, a greater margin of uncertainty -- 20 to 30%

The third choice is steam, and there, unless one is willing to do a lot of work on the system, the power plant must be sized in accordance with the power requirement of the rest of the system -- the EDR -- and NOT according to the building heat loss. This can be hard to explain to building inspectors (and many contractors), but is the correct way to do it.

Anything else is at best sloppy engineering, and shouldn't be tolerated.

Long Beach Ed

You can't ask an inspector to cite the code here. Here they are free to "enhance" the code as they see fit. The "Chief Code Enforcement Officer" in the jurisdiction can say "I don't like that part of the code. You must do it my way" This has been upheld in NYS courts time and again for over a century.

The only challenge then is to have a licensed engineer write an adverse opinion. Since most of these boneheads have credentials, are truly indifferent or personally agree with you and are simply satisfying a political mandate, more often than not the engineer prevails.

The problem is that this can add months to a permit application, so it's easier to work around the obstacles.

ChrisJ

I'll tell you what should be criminal.

Those who have no idea how to install or size a steam boiler, but take the work anyway and then proceed to install one that's 50-100% oversized with a "vertical header" or whatever other 3 stooges contraption they slap together, and then say "That's just how steam is, I've been doing this for 50 years" when the system heats poorly, bangs, blows water out the vents etc and then leaves the homeowner with a pile of garbage and disappears with their money.

That should be criminal.


Regarding manual J's.......they're far from perfect and I wouldn't be surprised if they tend to run 10-20% over what's actually needed. However, design day temperatures also aren't the actual real low temperature and area experiences. My area's design day temp is +6F but our record low is -19F and I've personally experienced -8F there in the past few years. I believe we use design day temperatures because extremes are only momentary and not long enough to truly matter but in my situation my calculated manual J was 66K and my actual usage on that -8F night was 72K. I think that had mostly to do with infiltration which it seems like manual J doesn't really consider.

GGross

@ChrisJ

Most codes state that equipment should be installed according to manufacturers instructions, or per code, and generally the most stringent one applies. So it is very likely that there already are rules in place to stop bad steam installs in your area, but many inspectors are not going to check the install against the manufacturers instruction. This wording is used in all of the codes that use ICC as a basis that I have found.

Manual J does account for infiltration, in fact its usually one of the largest loads for a structure, in older or poorly built structures it can be the largest load. There are many reasons manual J is not 100% accurate but generally it is because we do not have the correct values input to simulate real world conditions.

Design day, as you mention is not meant to be the absolute coldest day you will ever experience, that is not it's purpose and is never stated to be the lowest temperature day. For heating it is usually 99%-99.6% of heating days that are warmer than design day, averages put about 35 hours per year below design day conditions. To get around this you can size equipment for lower temperatures, even if you must submit a manual J based on design day, just figure your load for a lower degree day. As long as the resulting equipment is within the acceptable oversizing range for design day, or it has multiple heat stages or modulation, you'll be fine. Issues can arise from this with people designing at -30 when design day is +5 and then oversizing the equipment even based on that -30 number.

Also consider that equipment has fairly standard sizes, so if your load is 60K btu/hr and the two available boiler output sizes are 59kbtu/hr and 75kbtu/hr every code I have read will allow the oversized equipment to be installed, even if it were outside of the acceptable oversizing range. This is part of the reason why "design day" is not the absolute coldest day, because by the nature of sizing equipment via manual J/Manual S the equipment must meet or exceed the load, and there is almost never a scenario where a piece of equipment absolutely perfectly matches the exact manual J, so they are all slightly "oversized" already based on manual J numbers alone.

Sorry for this wall of text, this whole subject of codes, sizing, manual J, is something I spend the majority of my day doing already so I can really go on and on about it

ChrisJ

GGross said:

@ChrisJ

Most codes state that equipment should be installed according to manufacturers instructions, or per code, and generally the most stringent one applies. So it is very likely that there already are rules in place to stop bad steam installs in your area, but many inspectors are not going to check the install against the manufacturers instruction. This wording is used in all of the codes that use ICC as a basis that I have found.

Manual J does account for infiltration, in fact its usually one of the largest loads for a structure, in older or poorly built structures it can be the largest load. There are many reasons manual J is not 100% accurate but generally it is because we do not have the correct values input to simulate real world conditions.

Design day, as you mention is not meant to be the absolute coldest day you will ever experience, that is not it's purpose and is never stated to be the lowest temperature day. For heating it is usually 99%-99.6% of heating days that are warmer than design day, averages put about 35 hours per year below design day conditions. To get around this you can size equipment for lower temperatures, even if you must submit a manual J based on design day, just figure your load for a lower degree day. As long as the resulting equipment is within the acceptable oversizing range for design day, or it has multiple heat stages or modulation, you'll be fine. Issues can arise from this with people designing at -30 when design day is +5 and then oversizing the equipment even based on that -30 number.

Also consider that equipment has fairly standard sizes, so if your load is 60K btu/hr and the two available boiler output sizes are 59kbtu/hr and 75kbtu/hr every code I have read will allow the oversized equipment to be installed, even if it were outside of the acceptable oversizing range. This is part of the reason why "design day" is not the absolute coldest day, because by the nature of sizing equipment via manual J/Manual S the equipment must meet or exceed the load, and there is almost never a scenario where a piece of equipment absolutely perfectly matches the exact manual J, so they are all slightly "oversized" already based on manual J numbers alone.

Sorry for this wall of text, this whole subject of codes, sizing, manual J, is something I spend the majority of my day doing already so I can really go on and on about it

Please never apologize for posting accurate educational material.