SNations

I've seen something like this once before. That house was in . . . . Oak Park, IL. There was also a grease trap outside. Mine was also very near the laundry sink. (Based on the paint color of the floor it is most certainly a different house.)

The consequences of high CO concentrations in the flue of a residential appliance being what? If you don't mind educating me. Marc I didn't write the BPI standards, of course, so don't hold me to any of this. For sealed combustion appliances I believe that it's just an efficiency issue. For atmospherically vented appliances spillage is a huge concern, and worst-case depressurization testing is also required. If you were to argue against raising much fuss over an elevated reading in a direct vent furnace you would have a lot of company, from what I can tell. But that's what the standards say.

I agree with Kurt and Mike regarding the benefits of CO testing during a home inspection. But . . . . According to the Building Performance Institute (www.bpi.org) guidelines: You should definitely be at steady state, and I would think 10 minutes is plenty. But I think this allows the CO level to drop, not rise. You were right not to drill through a power vented flue, and to measure at the exterior outlet. I hope the tech recognizes this. CO levels should be below 25 ppm, and in no case should it be above 100 ppm in undiluted flue gas. As to why you and the tech got such different readings: there are probably a million possibilities and that's one reason why testing for CO might be futile. Way too many false positives and false negatives.

Yes, well, that's what I mean. I'm not separating the actual physical equipment from the way it's installed.

Bill, it seems that we agree that the problem is likely to be the manometer itself. I don't want to put words in your mouth; am I reading you right?

You are absolutely 100% correct. But this forum is full of people who complain constantly about crappy installation, so I don't understand why you feel free to use the qualifier "if properly installed." Heck, the whole system is extremely unlikely to have problems, if properly installed. I would start with the manometer partly because it's likely, and partly because it's easy to investigate. I'd rather rule that out before I climb on the roof to look at the top of the discharge pipe. My favorite story along these lines comes from the movie Apollo 13. (It all comes back to that movie for me.) There is a scene just after Jack Swiggert replaces Ken Mattingly as the command module pilot. The crew is in the simulator, and Swiggert makes an error that causes the simulation mission to crash and fail. The mission control folks are lamenting the error, and one of them says, "I sent him a faulty indicator light. Mattingly didn't get it right the first time either." So, an enormous amount of the best scientific and engineering talent that this country could must went into designing, manufacturing, and installing that indicator light. But the message to the astronauts was: Don't trust the gauge. It might be wrong. It might be simple, but don't trust the manometer: If it's giving you a faulty reading it might be wrong.

The manometer tube could easily come loose from the pipe.

Les, I see what you're saying. And that makes sense. If there's a blockage, the fan creates a partial vacuum in the pipe, and this shows up in the manometer. But under normal conditions, when air is just flowing freely through the pipe, that airflow creates a reduction in pressure, the same way that air flowing faster over the top of an airplane's wings creates a reduction in pressure that causes lift on the wings. It's not clear to me which condition would cause a greater pressure differential, or if they'd be about the same. Personally, I think the original problem is the result of a faulty manometer, but I'm just guessing there.

Les, I don't understand your reasoning here. If the suction pipe is wide open and the discharge pipe is wide open, and the fan is running, then air is moving through the pipe and the manometer should show a pressure differential. This is Bernoulli's Principle.

I don't mention every item in my reports. That would make the report a long, unholy mess. And it wouldn't serve my client's interest. I also don't use a canned report system. My report and my agreement reference the SOP's under which I work. I think that should do it.

Adding more insulation to the ducts or a pipe or the water heater won't increase the heat loss. Not in any residential setting, although it can increase the heat loss in some situations. There are two basic types of heat flow that we need to consider. Conductive and convective. (Radiation plays no part in this discussion.) Conductive heat transfer will always be reduced by adding insulation. But convective heat transfer can actually increase, because you're increasing the area available for heat transfer. Convective heat transfer from a pipe can be greatly affected by the orientation of the pipe (vertical, horizontal). But as a simple approximation the critical radius of insulation (beyond which you're actually hurting rather than helping) is = k/h, where k is the thermal conductivity of the insulation and h is the convective heat transfer coefficient. Notice that as h goes to zero, the critical radius goes to infinity. Meaning that if conductive heat transfer dominates then you can just keep piling on insulation. This is the condition we encounter in a home inspection with ducts, pipes, and water heaters -- particularly if the outer shell of the water heater is at the same temperature as the home's environment (always the case, right?). To get convective heat transfer you need the surface of the pipe/duct to be dramatically different from the surrounding medium (not likely, especially after you've added the first layer of insulation), or you need a fluid moving over the surface of the duct/pipe (again not likely in a residential setting). Otherwise conductive heat transfer dominates. Here's a good link: http://www.cdeep.iitb.ac.in/nptel/Mecha ... 2.6.4.html

If there was no problem with condensation with the existing insulation, I can't see how adding anything more would cause condensation. We all know why condensation happens at the surface of a cold bare pipe. But insulation doesn't change the temperature of the surface of the pipe. In fact, if anything it makes it colder. So what insulation does is keep the air and water vapor away from the surface of the pipe for enough distance that the temperature can rise above the dew point. So if there was no condensation before, there really can't be any condensation if you add more insulation.

But only about 1/3 of the fuel energy supplied to coal and natural gas electric power plants is delivered to homes as electricity. The rest is lost in transmission inefficiency. So that's a huge knock against electricity. I would refer you to Home Energy magazine Nov./Dec. 2008, and a follow-up article in July/Aug. 2009. They make the point that CFL's save energy, but there is definitely a take-back effect of up to 40% in heating-dominated climates when switching to CFL's and giving up the heat generated by incandescent bulbs. Of course in cooling climates there's an extra boost in efficiency. The follow-up article makes the point that the only situation in which switching to CFL's is less efficient is with an electric furnace with leaky ducts. An electric furnace with well-sealed ducts will still benefit overall with the change to CFL's. www.HomeEnergy.org

I believe that NEC requires smoke alarms in bedrooms to be AFCI protected. Some jurisdictions give exceptions to this rule. Supposedly, there are reports of fires starting at smoke alarm wiring. From 2009 IRC: E3902.11 Arc-fault circuit-interrupter protection. All branch circuits that supply 120-volt, single-phase, 15- and 20-ampere outlets installed in family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreations rooms, closets, hallways and similar rooms or areas shall be protected by a combination type arc-fault circuit interrupter installed to provide protection of the branch circuit. Exception: 1. xxxx 2. AFCI protection is not required for a branch circuit supplying only a fire alarm system where the branch circuit is wired with metal outlet and junction boxes and RMC, IMC, EMT or steel armored cable Type AC meeting the requirements of Section E3908.8. I believe that exception 2 makes it clear that a smoke alarm must have AFCI protection if it's wired along with the rest of the bedroom. So your case may be different if your alarm is wired separately, but it's not the case where the smoke alarm is not allowed to be on AFCI.

I also love the view of anybody in the yard who wanders by, looks in the door, and sees the home owner soaking in the tub. Now that's shocking.

If it's a condensing furnace (the original topic) then there is almost certainly a trap either installed or built in. A trap is needed to form a plug so that the forced exhaust doesn't spill through the condensate drain and into the house.

Don't forget that there's a trap in there somewhere. Not all the condensate drains away when the furnace shuts down.

Kurt, even in Oak Park in the last year I've heard more regularly of elevated radon levels. Nothing crazy -- in the 4-8 range -- but still above the recommended action level. And I work out in the western suburbs regularly, where it's even more of a problem. From my experience, radon is not much of a problem in Chicago proper but becomes more of an issue the farther away you get. Where are you testing mostly?

You can have some of ours if you want. We have plenty.

Randy, I think you should put in a radon mitigation system. I was at a ventilation conference in Wisconsin a few years ago and the instructor had some pretty impressive stories about how sub-slab radon mitigation systems helped cure moisture problems in basements. I like this idea better than dehumidification or an HRV because it's attacking the problem at its source rather than letting moisture get into the house and dealing with it there. Source control is always the way to go if it's possible. Good luck.

I'm new to this forum, and I've been perusing old posts. So nobody may see this, but here goes anyway. In some cases, adding insulation to a cylindrical or spherical object can increase, rather than decrease, heat flow. (I don't believe this would ever happen to a water heater, but I suppose it's possible.) There are two basic types of heat flow that we need to consider. Conductive and convective. (Radiation plays no part in this discussion.) Conductive heat transfer will always be reduced by adding insulation. But convective heat transfer can actually increase, because you're increasing the area available for heat transfer. Convective heat transfer from a pipe can be greatly affected by the orientation of the pipe (vertical, horizontal). But as a simple approximation the critical radius of insulation (beyond which you're actually hurting rather than helping) is = k/h, where k is the thermal conductivity of the insulation and h is the convective heat transfer coefficient. Notice that as h goes to zero, the critical radius goes to infinity. Meaning that if conductive heat transfer dominates then you can just keep piling on insulation. This is the condition we encounter in a home inspection -- particularly if the outer shell of the water heater is at the same temperature as the home's environment (always the case, right?). So the myth is true, although not something we'd ever encounter in a home inspection. Here's a good link: http://www.cdeep.iitb.ac.in/nptel/Mecha ... 2.6.4.html Steve

It's a poor picture, but I believe it's a higher quality light. The globe is heavy glass with I assume a bulb inside. I applied reasonable counter-clockwise force on it with 2 hands, couldn't budge the globe. Just out of curiosity, if you couldn't budge the globe and there (presumably) were no obvious connectors/fasteners, how is the homeowner going to replace the bulb when it goes? (I hate getting questions like this from clients, because I always feel that my answer is inadequate and unhelpful.) Steve

Oh Kurt, you're killing me man! From my copy of "Lost Moon", personally autographed by Jim Lovell -- "To Steve -- Best Wishes", Chapter 10, page 251: In order to make the oversized command module cartridges work in the inhospitable LEM, what Smylie envisioned doing was inserting the back half -- the outflow half -- of the bulky lithium hydroxide box into a plastic bag and taping the bag in place with heavy, airtight duct tape. An arched piece of cardboard taped inside the bag would hold it rigid and prevent it from collapsing against the outflow vents. Smylie would then punch a small hole in the bag and insert the loose end of one of the pressure-suit hoses into it, making this connection airtight with tape as well. From page 256: Swigert swam back up into Odyssey and collected a pair of scissors, two of the command module's oversized lithium hydroxide canisters, and a roll of gray duct tape that was supposed to be used for securing bags of refuse to the ship's bulkhead in the final days of the mission.

Did you all see the movie Apollo 13? While in space their CO2 scrubber became overloaded and they had to configure a new one. The solution, as devised by the engineers on the ground, included ordinary gray "duct" tape. Duct tape is great stuff, provided that 1) it only has to last for a couple of weeks, and 2) you need it right NOW or you might die (think astronauts in space or soldiers in war) Steve

This is what the installation manual for my condensing furnace, built and installed in 2004, says: “IMPORTANT: The condensate drain should be installed with provisions to prevent winter freeze-up of the condensate drain line. Frozen condensate will block drains, resulting in furnace shutdown. If the drain line cannot be installed in a conditioned space, then heat tape should be applied as required to prevent freezing (per manufacturer’s instructions).â€