Commercial Boilers

StanH

What are the major differences between residential and commercial boilers? If this is requires too "big" of an answer, do you have a reference for a great book that tells about the differences or that zeroes in on commercial boilers?

SWEI

Size matters

Most states have different licensing and operating permit requirements that kick in at 400,000 BTU/hr (which is why you see so many 399,000 BTU/hr rated boilers.)  AFUE numbers are not computed above 299,000 BTU/hr so you could reasonably interpret 399s as being commercial.

RJ_4

boilers

 I agree, above 399mbh  considered commercial.  For a number of years now in San Francisco  any commercial boiler  400 mbh or higher can't be replaced with an atmospheric burner style boiler. It must have a power burner. This is to help with controlling flue gas emissions

Henry

Certification

The certification process and control requirements for boilers of 400,000 BTU and more are completly different from those under. That is what seperates residential from commercial.

Mark Eatherton

Never understood this requirement...

Boilers under 400K are required to have roll out detection lockout for combustion tray and vent hood to lock burners out if spillage occurs, but NONE of the appliances over 400K are e required to have them?



It's OK for big boilers to kill people, but not for small ones?



I've written nationally published articles about this provision, and requested that SOMEONE give me an answer, to no avail...



Care to comment Henry. I know you sit on numerous committees?



The particular app. I am thinking of was a copper fin tube atmospheric boiler used for snowmelt in a residential setting. They are lucky they didn't get more exposure to CO poisoning, and get sick, or worse.



ME

Henry

Roll out

I think it was due to resistance by some manufacturers who have had problems with roll-out due to heat soaking by the large boilers. Using a copper fin atmospheric for snowmelt, is stupid! The heat exchangers will block. Even with P/S the boiler will condense. Before we got good mod/con boilers around 2002 we used a thermodisc with a motorised valve on a bypass to keep return water at over 135F.

Our province passed an amendment to the national gas code regarding copper fin boilers. We are required to furnish outside combustion air to the boiler even if meet other sections that do not require this. If we install a cast iron boiler, no such requirements. The province thinks that if the heat exchanger blocks, there is less risk of CO entering the house. Give me a break! CO is lighter than air and goes up. How will it go down and up the combustion air duct?

Mark Eatherton

Installation was done way before the advent of larger modcons...

That is what I replaced it with, and it has worked flawlessly and reduced her energy consumption by 30%.



This room had code required C/A-V/A vents, and in fact NO other source of heat in this basement mechanical room, and THAT was why it would spill. No heat to maintain stack action, and it couldn't overcome the cold slug of air to establish draft.



Here's a link to the articles.



http://contractormag.com/columns/eatherton/watching_killer_work1_727



The second part somehow got lost, but it was spilling the products of combustion straight out of the combustion chamber ENTRANCE. I watched as the flames licked upward and burned the power wires to the point that they shorted out and blew the boiler transformer. Not a good roll out switch design...



Scary stuff here, and I suspect it happens a LOT more than we know.



ME

Henry

I have a problem

Mark, I read your article and I have a big problem. While I sympathise with you trying to solve a problem, but by law and code, you cannot change the way an appliance was certified. It can bit you in the but! One cannot not use a barometric when it is NOT in the certified instruction manual. You cannot ad control devices in the safety circuit if they are NOT in the certified I&O manual. If this went to litigation, you would be in deep doo-doo! I know as I have been there and testified. As well I am on the National Gas Code and 7 sub-committees. 

Mark Eatherton

I hear you Henry...

Thank you for your concerns...



If the customer has succumbed to CO poisoning (she was worth billions), what chances do you think I would have had, knowing that her appliance was spilling products of combustion into her house? I exhausted all reasonable expectations as it pertains to attempting to get the appliance to work correctly using conventional means.



So, if this is the way they want to play and I had installed a Tjernlund draft inducer (TERRIBLY noisy) do you think they'd (boiler manufacturer) have backed me up then? That requires modifications to the control logic and safety circuits as well and constitutes a modification that is not in their I&O manual.



Do you think the the boiler manufacturer would step up and back me up for NOT doing ANYTHING to their appliance?



IF, after installation of the barometric damper and associated spill/lockout switches, it had gone real bad, rest assured that I would have had Jim Davis standing by me in court, testifying that what I had done was a proper thing to do in that particular case. And this is not the first time I've had to resort to doing something like this to straighten out problems.



You will also note, that I stated in the article that what I did was not recommended unless the person doing so was certified to do so through the organization (NCI) that had trained me to do so.



I had called the rep in and they had NO idea what to do to overcome the problem... "There's nothing wrong with the appliance..." Of course not, they were there when the room was 70 degrees F, and it was WARM outside...



In the end run, even THESE modifications failed to correct the cold slug condition that was keeping the appliance from drafting initially in this unheated mechanical room. I don't have to worry about it at all now, because it is a sealed combustion appliance.



What would YOU have done?



Not wanting to upset you, just asking questions.



The other part of the story that didn't get told, is that I personally exposed myself to over 999 ppm CO, (maximum read out on theCO detector that was in the room with me, that DIDN"T go into alarm status) with my head stuck up inside of the combustion air vent so I could see exactly what was happening when no one was looking at 2:00 AM. That's probably not one of the brightest things I've ever done, but it got me what I wanted.



W.W.H.D. .... (What Would Henry Do)



ME

Henry

Not essential

The snow-melt system is not an essential equipment. I would shut it down as the install was not right. Many atmospheric boilers are power vent approved, so there is a possibility to power vent with an approved unit. Was there a combustion air duct and the 10% that is required for appliances over 400,000 BTU? If the CO was that high, I doubt it.

We had one install that had a similar problem two winters after our installation. The CO alarm would go off on occasion. It was 180,000 BTU with an external insulated chimney. It had a combustion air duct as required by the province. After the second incident I went to check it out. You have to be the detective and ask many questions. I found out that the owner replaced the chimney due to some tree damage. The first thing that I found was the chimney did not meet code as It did not clear the lip of the flat roof sufficiently. After checking the model number of the insulated chimney, I discovered that it was over sized and had one inch less insulation. The chimney was installed by a licensed chimney installer. He cheated with the less insulated chimney. We installed a S/S chimney liner of the right dimensions and height, and everything is right now.

Of course, many manufacturers rep will not help you out on a venting problem! I can name a few manufacturers that won't help at all and only give vague instructions as saying that it must meet NFPA54 or B.149. There are very few that give detailed instructions on venting their appliances

Henry

Not essential

The snow-melt system is not an essential equipment. I would shut it down as the install was not right. Many atmospheric boilers are power vent approved, so there is a possibility to power vent with an approved unit. Was there a combustion air duct and the 10% that is required for appliances over 400,000 BTU? If the CO was that high, I doubt it.

We had one install that had a similar problem two winters after our installation. The CO alarm would go off on occasion. It was 180,000 BTU with an external insulated chimney. It had a combustion air duct as required by the province. After the second incident I went to check it out. You have to be the detective and ask many questions. I found out that the owner replaced the chimney due to some tree damage. The first thing that I found was the chimney did not meet code as It did not clear the lip of the flat roof sufficiently. After checking the model number of the insulated chimney, I discovered that it was over sized and had one inch less insulation. The chimney was installed by a licensed chimney installer. He cheated with the less insulated chimney. We installed a S/S chimney liner of the right dimensions and height, and everything is right now.

Of course, many manufacturers rep will not help you out on a venting problem! I can name a few manufacturers that won't help at all and only give vague instructions as saying that it must meet NFPA54 or B.149. There are very few that give detailed instructions on venting their appliances

Mark Eatherton

May not be essential in YOUR book....

But, Gawd forbid, she have to step out of her Jaguar into snow wearing her Gucci's... She could afford to burn money on the driveway to melt snow, if it weren't for the stink and the associated fly ash. She PAID good money for an automatic snowmelt system. And by golly, one way or 'tother, she WAS going to get it.



Trust me when I say I did due diligence.



The vent and combustion air were both properly and adequately installed, following applicable code.



The application of a draft inducer was out of the question due to proximity of sleeping quarters (directly above this mechanical room) so it was not considered. I ended up having to install a solid state relay just to get rid of the BANG associated with starting the main circulator.



The boiler WAS piped per the manufacturers requirements (P/S) with priority to the boilers operating temperature.



The boiler was BRAND NEW, remember, the installed control was never properly connected, so it never even fired for the first 4 years of its life.



The B vent was internal to the structure, 30' tall, with no adjacent impingement roof issues.



The biggest issue in this remote mechanical room was the fact that there was NO HEAT in this room. Isn't required by code unless there is a need for protecting water lines, of which there were none in this room.



The production of CO is compounded due to flue product spillage, and regurgitation back into the combustion process, no?. The only thing that saved these people is the fact that the associated CO2 levels got so high from spillage that the pilot and main flame were self snuffed due to the lack of oxygen. (CSD1 ignition module, immediate lock out) Had it not been for that fact, this most probably would have ended up as a VERY serious situation.



As the room sat there, getting cold, waiting for a call for snowmelt, there was NOTHING to maintain a proper draft in the associated vent system. Snowmelt systems don't fire when its warm outside...



The application of the barometric was to "enhance" stack draft operation, and control the flow of primary and secondary air as well as dilution air through the combustion process.



This is when and why I apply them to these fixed hood appliances, which in my professional opinion (fixed draft relief hoods) are pure B.S. I am not alone in that assessment. I have asked for and received the permission of the local utility and the AHJ to apply these devices in the field, per the barometric manufacturer. Hell no, the appliance manufacturer won't give permission (although I have seen a few I&O manuals where it IS allowed) to apply a baro damper to their product. Why would we want to do THAT? But again, will they come and stand next to me when their appliance maims someone or worse, even if it was installed to their instructions and code? I (we) will be VERY lonely in the court room... If I have to put my self in front of the jury, and I explain what I did and why, the jury WILL get it, and I feel I will be absolved of any wrong doing. If I did nothing because it violated the manufactures approved installation methods, I WILL get hung out to dry, and will most probably lose in a court of law. Not enough due diligence performed, and not enough caution exercised. "Industry Standard of Care" be damned.



I do NOT throw these things around with abandonment. I must exhaust all other avenues before applying them, and you would be AMAZED at what these things can do for the combustion process in fixed hood appliances. Especially when "controlled" with a barometric damper...



Have you ever had an atmospheric appliance where the CO was all over the board, and climbing steadily? Try blocking the draft hood off (temporarily of course) and see what happens to the numbers. They clean right up.



These boiler manufacturers test their appliances under IDEAL conditions, that rarely occur in the field. When the appliances get to the field, and start acting up like this one did, they are lost, and try pointing the finger of blame at everyone but themselves. Been there, seen that SO many times, I can't recount them. And it's not just THIS manufacturer, it's like EVERY atmospheric appliance manufacturer I've ever had to deal with, and that is a BUNCH over my 36 years of field experience.



Now that the minimum appliance efficiency is going to 90+ percent, all of these venting issues will disappear, but I guarantee you that something else they never expected will raise its ugly head, only to be answered with "It didn't do that in OUR lab's".



Kinda like the typical manufacturer reps initial response of "Geez, we've NEVER seen that before...."



Thanks for keeping the discussion civil. Hopefully many people will learn from this.



ME

Ironman

Question, Mark

I'm in agreement with your handling of this job. However, would another viable approach possibly have been to keep the boiler hot by bringing it on when the o.d. temp dropped to about 35*? Then let the SIM control activate the circs?



I know it would waste some fuel, but would that have been an issue with the kind of money this woman has?



Just a thought, not questioning your approach.

Henry

Nicely said

Well said but, we do have to be carefull about what is done by us and putting it on this forum when we bend some of the rules. There are too many DIY that think that they could play with gas appliances.

BTW, this is also my 36th year full time in this industry. But I did pass my fathers contractors tests in 1972 ( we were allowed then to have help). He had me doing threading during the mid 60s during the summer.

jumper

outside air control ?

Is it legal to install thermostatic dampers on outside air ? Otherwise hood sucks frigid air into boiler room all the time.

Mark Eatherton

That might have worked...

But I can just about guarantee it would have led to anther complaint about noise in the middle of the night. And even tho she was (still is) worth billions, she doesn't want to intentionally waste money, unless it has benefit, like melting snow:-)



Thanks for the thought in any case.



ME

Mark Eatherton

AIr dampers are allowed...

Provided that they have a safety interlock to the ignition to guarantee that they are open before firing...



I have YET to find one that seals worth a darn. Too many moving parts.



ME

jumper

in the good old days

A barometric damper sufficed to limit draft. Another one was for outside air intake and it didn't have to be ducted to floor level. No diverter but how often was down draft a problem? Pressure in the basement should always be higher than in a chimney ? Plus today CO and CO2 alarms are available. So codes seem to be designed to sell electrics and electronics. Plus everything ties into an irreparable circuit board. Is the utility room really safer? Or are we going backwards ?