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Bob Harper

Bob Harper

Joined on December 20, 2004

Last Post on April 16, 2014

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@ April 16, 2014 8:56 PM in Should a backflow prevention device be installed to prevent water from the boiler from flowing into the cold water supply?

Backflow prevention is required by the International Codes and the EPA. If the fire dept. catches a local fire hydrant, it can suck boiler water not only into the home but back into the neighborhood, too. That's why the house itself should have backflow prevention, too.

Failure to warn?

@ April 9, 2014 9:41 PM in Contractor kicked out of house for doing CO test

The legal principle upon which the contractor would be sued is a "Failure to Warn". Under this principle, the contractor would not have to be held to the 4 requirements for negligence (duty to act, damages, act or omission and proximate cause) but simply failure to warn adequately. In order to warn, you must prove you informed the plaintiff of the hazard, the effects of the hazard and sometimes even the effects of those effects. For instance, its not enough to say something constitutes a fire hazard. You would have to also show you informed them that a fire could cause personal injury and property damage, which could in term, result in death. You cannot assume they understand the sequelae of a hazard.

In the case with CO, you would need to explain how it affects the body, that at lower doses, it can cause permanent injuries and specify those injuries then what high doses can result in (death).

In order to prove you adequately warned someone who refuses to sign your form, you must send them a Certified Letter return receipt requested. I would also send a copy to the fire marshal and AHJ. If it involves gas or oil, I'd send a copy to the fuel supplier, too.

When I worked as a Regional Quality Assurance Manager for a large manufacturer with owned distribution, we wrote the policies for technicians. In cases where the hazard represented a "danger" as defined by ANSI Z535.4-2007 we were required to perform a Tag Out/ Lock Out even if against the will of the homeowner. That meant disabling the fuel by disconnecting the fuel line and capping it then attaching a tag and disconnecting the electrical control similarly. The point was to make it so the homeowner would have to use tools to re-connect the system. We drew up our own form for TOLO and asked the homeowner to sign. If they didn't, we filled it out and left it  attached to the equipment with two copies while we kept the original. This form instructed them to contact us for a post-view inspection prior to energizing the equipment or we would not accept any responsibility. If they refused to sign, a copy of the TOLO form was included in the Cert. Letter.

We never were sued for disabling their equipment though they sometimes cussed us out and refused to pay for the service call. At least they lived.

Also, take pics as you go. That means pics of the installation at various angles of perspective, close ups, screen shots of your analyzer, the equipment rating plate, etc.


NFPA 211

@ April 7, 2014 8:06 PM in oil and gas appliances in same masonry chimney

I don't know if NFPA 211 is referenced in any of the codes that apply in your area but it is the national standard for chimneys, fireplaces, vents and solid fuel burning appliance. It is referenced, for instance, by the International Building Code for heater flues and combustion venting other than fireplaces.

211 allows common venting of oil and gas IF:
-The common vent or chimney is sized for both appliances combined
-the common vent or chimney passes a Level II inspection, which will determine the suitability of that chimney serving both appliances.
-both appliances are equipped with "primary safety controls".

Now, it is up to your local code official (Authority Having Jurisdiction) to rule on what he will accept as primary safety controls. This generally means some device to shut off the fuel supply if the flame goes out so fuel does not continue filling the combustion chamber making it into a bomb. Another version of primary safety control is generally considered a flame proving system such as a spill switch on the vent system to safeguard against backdrafting.

take away fact

@ March 29, 2014 3:54 PM in The leak detection job from hell....

If you read Mark's case carefully, you'll note the static hydrostat test gave a false positive. How is this? Because much testing is done static and not dynamic meaning under the conditions of use. Things act differently when heated/ cooled, etc. That's one thing working in forensics and an R&D test lab taught me.

Good catch Mark and a good lesson in persistence and listening to that little bird sitting on your shoulder.

no relief from codes

@ March 28, 2014 7:13 AM in Gas piping

While a mfr. may claim their equipment is resistant to low inlet pressure regimes, that does not relieve the installer of the responsibility to pipe the appliance in accordance with the codes including the sizing charts. This valve may be a little resistant to sudden burps or dips but the bottom line is, you have to supply sufficient gas to the appliance to fire at its rating-period. 

suitable venting

@ March 21, 2014 7:12 AM in Wait on Liner?

The chimney must be suitable for the class of service. When changing appliances, it must be inspected. NFPA 211 dictates the levels and scope of inspection. If there is a single mortar joint failed or missing, you would need to reline even if all the flue tiles were visually found to be intact. Finding debris in the cleanout base means material is now missing above and thus compromised.

Your typical "8x8" flue tile measures about 6.5" ID. Now, factor in offsets, misaligned tiles and protruding mortar and yes, it gets fun pulling a 6" ID liner down one but it is done every day with no problems.

A corrugated stainless steel liner typically must be de-rated 20% plus an additional 20% for any offsets. There are a few smooth wall liners available to buy back 20% when you're too close in your sizing.

Use a listed liner meaning UL1777 and install to the mfrs. listing and your codes. Usually insulation is not required for oil and gas but recommended. I use air insulation and it works better than blankets IMHO.


@ March 18, 2014 7:09 AM in Thermo couples

If the chimney is not venting properly, it can spill CO2, which displaces O2 causing pilots to snuff out. 


@ March 18, 2014 7:07 AM in New Flue

Chimneys have been required to be lined since 1927. Whenever you replace equipment you must inspect the chimney and repair it as necessary so its is suitable for the class of service. You got ripped off by this company. Even if the chimney looks ok, the material in the base tells us it is not. Reline it. Do not use this company again and I'd request a refund. Every standard in the industry disagrees with their assessment. including most IOM manuals. 

chimney inspection

@ March 13, 2014 9:32 PM in converting oil burner to gas

When converting fuels, NFPA 211 requires a level II (comprehensive) inspection. This will undoubtedly require relining if not already done and properly sized. The chimney will need to be swept as well. 

Level II inspection

@ March 9, 2014 9:36 PM in New Flue

I would ask the chimney contractor to perform a Level II inspection, which is a comprehensive top to bottom inspection. That will determine if the chimney is suitable for continued use and what repairs if any are warranted. Since there was material at the base of the chimney that means that material is no longer where it started up in the flue, hence your flue can no longer perform its intended function. You will need a liner. The liner must be suitable for the class of service. Since this chimney once served oil, any liner must be 316 alloy of stainless steel or better. Most liners are 316Ti these days with a pinch of titanium thrown in. Get one with a transferrable lifetime warranty btw.

The liner must be at least the size of the appliance collar. In addition, corrugated liners must be de-rated for corrugation (20%) plus an additional 20% for any offsets.

The vent connector galvanized steel pipe gauge thickness is determined by NFPA 211, which calls for 26 ga. below 6", 24 ga. 6-10", 22 ga. for 10-16" then 16 ga.above 16". You can drop one ga. size smaller if using stainless steel. In other words, for a 6" flue, you can use a 24 ga. galv. or 26 ga. ss connector. Follow 211 for pitch, connections, support, etc. No flat runs--min. 1/4" per foot slope upwards to the chimney.

You can not use B-vent inside a chimney that once burned oil--it will eat it up.

The barometric damper should be located close to the appliance but leave at least 2 duct diameters from the appliance collar and any ells to you can drill your test hole for combustion analysis. I try to locate them on the vertical rise if possible. If you must install it on the horizontal leg, you have to reposition the adjusting weight to the left side of on Field RC dampers. Bull head tees for baros. are not recommended for oil. See the diagram from Field Controls for damper placment.

clarification on the power of demi-gods

@ March 5, 2014 7:28 PM in Pressure Relief Valves on Expansion Tanks

While ME is partially correct, your local AHJ can NOT just indiscriminately require whatever he feels like. They are code ENFORCERS--not code legislators. Every jurisdiction must have a mechanism for implementing LEGAL code change. This is typically the submission of a proposed change with supporting data and arguments/ logic. At some point, three public hearings are held for stakeholders and citizens to voice their concerns. Then the local governing body votes it into law or rejects it. Only once it has been voted into law as a local ordinance does your AHJ have the power to enforce it.

Even that process has another level of review: The International Code Council. Where the I-codes have been legally adopted, local ordinances that go above and beyond the current I-codes can be reviewed and in most cases, overturned. This happened in Pa where right after we adopted the ICC suite in 2004, some jurisdictions adopted ordinances such as residential fire sprinklers. The builders went to the ICC and have 14 of 14 cases overturned.
An AHJ has the power to rule only where there is no applicable code. Even there, he is charged with relying, whenever possible, on reports, listings, or other credible data. In the case of the expansion tanks requiring pressure relief valves, the AHJ would need to show case studies where tanks failed during unfriendly fires that resulted in personal injuries or damage to the structure significantly over and above that which would have occurred anyway. He would have to present test data showing what sort of pressures these tanks could be exposed to and what form of relief would be warranted. For instance, do you install just a pressure relief valve or a temperature/ pressure relief valve and what ratings? TPR valve stems must be fully submersed in the liquid so how are you going to do that in the piping downstream of an isolation valve. Also, what is the incidence rate of such a tank being left isolated as opposed to online? If left isolated, the boiler's pressure relief will likely discharge during heating cycles letting you know something's up and call for qualified service.

I find this a pretty rare hazard and think its just paranoia. Often, AHJs will read of one isolated incident then make a name for themselves locally by instituting changes based upon imperfect information. Most of the stories about losses are just heresay and not evidence-based from litigated cases. Also, if this was such a hazard, believe me the CPSC, ICC, NFPA, etc. would be all over this.

joist shrinkage?

@ February 25, 2014 6:39 PM in Has anyone ever heard of this?

When you have engineered joists and still see shrinkage, its usually more the mudsills the rim joists are sitting on or interior columns on poor footings. If the floor is still level, then its probably not the mudsills. Engineered joists shrink very little in my experience and when they do, the similar components shrink uniformly. Did he measure the thickness of each plate? 


@ February 24, 2014 9:03 PM in How many of you carry

I carried a Scott Bacharach personal CO alarm set to alert at 35ppm for about 12 years. It has been replaced by a CO Angel set to 35 as well. They have gone off so many times I couldn't count. They have drawn a lot of inquiries from homeowners which led to sales of low level CO monitors and repairs. They gained respect from mechanical building inspectors, fire marshals, etc.

I'm a retired paramedic and have transported quite a number of CO victims. I've had CO poisoning myself back when I worked for someone else.

Personally, I think its irresponsible to send any employee into any buildings without a personal CO alarm. Note that in the recent Long Island incident, three paramedics had to be treated as well.

A local EMS responded to a call at a grocery store that ended up transporting 31 to the ER. They discovered the reason granny zonked out at the bakery counter when their personal CO alarm sounded. BTW, their dept. responded wearing SCBA and screened everyone in the store with Masimo Rad57 CO pulse oximetry units and transported anyone with a COHb of 5% or higher. BTW, 6 were transported from the adjoining drugstore.

Anyone entering a crawlspace should wear a 4 in one confined space alarm: LEL, O2, CO, H2S

another case for pesonal protection

@ February 23, 2014 9:22 AM in another case for pesonal protection

Sad case but it hopefully makes you aware that almost NO buildings
in the US, residential or commercial, have adequate CO protection, are
not required to have periodic maintenance that includes CO testing with a
professional combustion analyzer, no requirement or standard for the
techs using such equipment, no requirement for professional periodic inspection
by qualified inspectors of the venting (because HVAC techs are not so
qualified--trust me!), and the UL listing for carbon monoxide alarms
prevents alarms from sounding until you have CO poisoning (10%
carboxyhemoglobin level). Those alarms are designed to protect you from
CO death--Not from CO poisoning and apparently there were none at this

So, what can you an I do? I wear my own personal
CO alarm, which alerts at 35 parts per million after 60 seconds. It is
an electrochemical sensor and very accurate. I take it everywhere. Note
many of the victims in this case were cops and first responders. We walk
into toxic atmospheres all the time and don't know it. We drive in
traffic, fly in planes, stay in hotels or friends homes, shop at stores,
are admitted into hospitals, etc. but there is only one place where you
will routinely find adequate CO monitoring--parking garages. They are
required to have low level sensing linked to alarms and exhaust fans
depending upon the level. Don't be a victim--get your own personal
protection for everyone one you know and wear it or put it in your
pocketbook. Humans cannot detect CO. Very preventable. BTW, the manager
may have died from the trauma of falling down stairs or even had an MI
(heart attack).

We had a similar incident at a local grocery
store where about 30 were transported for treatment. The local EMS had a
personal alarm that sounded when they responded to an elderly lady
collapsed at the bakery. 6 patients were from the attached drugstore
next door. 6 months later, it happened again in the same store from the
same oven! Don't assume anything!


@ February 22, 2014 10:01 PM in Tim; New IFGC Question

Washington Suburban Sanitary Commission. They are the AHJs from western MD down around DC. I've had many a "discussion" with their inspectors.

I'm not sure what the OP is referring to but I'm thinking its one of those chimney kits that acts like an axial draft hood on 80% furnaces.

As far as the requirement to reline, you must inspect the chimney when replacing equipment. The Std. for inspecting chimneys is NFPA 211. A proper level II inspection will undoubtedly reveal the chimney is no longer suitable for continued use for the intended purpose and therefore must be relined with a listed liner and in accordance with the IFGC, which back references 211 for heating chimneys and vents.

Basically, you have to prove a chimney does NOT need to be relined. You'll find a suitable chimney maybe one in ten thousand. Code compliant chimneys do not exist in the wild.

You reline when the flue is oversized, eroded or improperly constructed such as gaps between flue tiles. You also reline to size the flue to the appliance for performance. You reline exterior chimneys that run cold and don't draft reliably. Relining does not overcome structurally unsound chimneys, short chimneys or other major structural defects.

got carried away!

@ December 15, 2013 12:07 AM in On an atmospheric boiler

Sorry to steal your thunder Timmie. Please feel free to expand on any of these concepts. I'll chill and let some other people comment. You are da' man always. 

disconnect switch at CAZ entry

@ December 14, 2013 5:03 PM in Second shutoff for boiler on stairs?

Required for oil under NFPA 31--not required for gas.

primary aeration effects

@ December 14, 2013 3:52 PM in On an atmospheric boiler

In addition to the points Timmie made, let me offer these additional concerns:
High primary aeration with a low manifold pressure may result in flashback
High primary aeration with a high manifold pressure may result in flame lift-off
Low primary aeration with moderate to high manifold pressure may result in yellow tipping.

The higher the primary aeration, the greater the velocity of air being entrained at the venturi and not just volume. Therefore, subtle increments can have a significant impact. This can be beneficial such as with LP where we need that turbo-boost to help shoot the fuel/ air mixture down the mixing tube towards the burner ports and create turbulence for better mixing.

One side negative of primary aeration is the propensity to cause poor combustion from the recirculation of combustion products, which is why we add in secondary air. This recirculation is mainly seen on a cold start, which can be seen on a combustion analyzer. Once secondary aeration is established, there is better flow up the stack and removal of combustion products. Too much secondary air can cool the flames resulting in poor combustion, which is one of the drawbacks of high excess air. Each fuel gas has its own specific properties in these regards, which is why it can be very difficult in some units to get them to behave when performing a fuel conversion.

With regards to flame speed as Timmie pointed out, the flame front moves faster at higher air/ fuel ratios. This is all very specifically calculated, engineered and tested with burner designs, venting, etc. One example of flame speed is on an Oxygen Depletion Sensor safety pilot of all ventfree appliances. As the ambient O2 drops to 18.5% the pilot flame appears to advance out past the tip of the thermocouple causing the pilot to dropout. This is because the flame is burning slower back towards the pilot burner thus creating the 'gap'. Now, if you have too much air, the flames can race back so fast that, depending upon burner design, port loading and esp. temperature of the burners, the flame front can run down through the burner causing flashback or extinction popping.A narrow mixer tube and smaller burner ports can increase primary aeration without flashback or extinction popping.

Lint can stop burner ports causing major changes in aeration and fuel/ air mixing so cleaning burners is very important to good combustion. Engineers have to figure what method they will use to eradicate lint from the burners such as incineration, filtration, re-directed airflows, etc.

It will be interesting to see the effects of high Wobbe Index fuels with time. The studies thus far indicate no major concerns but those were conducted by agencies with close ties to the fuel providers and government so I don't trust them one bit. I think you and I will inherit a mess of problems if LNG becomes more prevalent either straight in or mixed with existing stocks of pipeline NG for peak shaving during high demand periods.

prv release

@ December 13, 2013 1:36 PM in Boiler Pressure Spike while under heat

Undersized or failed exp tank. If not on an isolation valve, install one so the pressure can be tested with it isolated from the system without dropping the system. If you get water out of the Schrader valve, the diaphragm is blown and the tank needs to be replaced. The charge should equal the operating pressure of the boiler.

Failed feed valve. Isolate the valve to test this. If bad, clean strainer first.

Bad PRV. Test annually and replace every 3 yrs or as needed.

Yes, leak from hot water coil but this would be constant as would bad feed valve. PRV release on firing generally from undersized, waterlogged or otherwise inadequate exp. tank.


@ December 13, 2013 1:27 PM in What is the definition of

2009 IRC G2403 General Definitions
Air, Makeup. Air that is provided to replace air being exhausted.

[me] This includes combustion, dilution and excess air through combustion systems but it also includes air exhausted by fans such as kitchen hoods, dryers and fart fans in bathrooms. There are several specific places in the code, such as M1503.3, which require MUA. This this case, it is referring to exhaust hoods >400 cfm requiring dedicated powered MUA interlocked with a damper and sized to equal the exhaust.

KAIR method

@ December 13, 2013 1:17 PM in What does

Known Air Infiltration Rate for calculating MUA requirements. IRC G2407.5.2
Used only when ACH 0.40 or less. Otherwise, use Std. Method.


@ December 11, 2013 12:16 PM in 5 Die of Carbon Monoxide Poising

I has never been proven scientifically that CO has any odor. You may, however, smell aldehydes, which may or may not accompany it. With fuel gases, they typically do not have an odor of their own so producers are required to add various types of odorants depending upon the application. Not everyone is sensitive to these odorants and one person might be sensitive to one odorant but not another. You couldn't tell which stink gas was used without a gas chromatograph and someone who knows how to use and read it.

Would be interested to see if there was a UL listed CO alarm present in that house.
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