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Duct Pressure


mgbinspect
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Relocation inspection:

First visit: I find gaps in ducts and low differentials at both systems.

Second visit: HVAC Contractor shows up, throws a little refrigerant in the unit and leaves without addressing gaps in the distribution system. Differential barely fifteen downstairs and only ten upstairs.

Third visit (today): HVAC contractor has replaced an evaporator coil that the maker informed them was not up to snuff - and the HVAC contractor is, according to hear-say getting smart and uncooperative. Differential on both units low. I go into the attic and every junction taken apart to replace that coil is un-sealed. Just for the heck of it (vacant house now), I pull out my aluminum duct tape and start sealing it up. I'm tired of coming back! TWENTY-SIX FEET of duct tape later, I am able to get one unit to muster fifteen and the other still does only ten - both suction lines are nice chilly and sweating. When I left I handed the twenty-six feet of duct tape backing to the listing agent and told her to tell the HVAC contractor where to put it.

[:-censore

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Relocation inspection:

First visit: I find gaps I ducts and low differentials at both systems.

Second visit: HVAC Contractor shows up, throws a little refrigerant in the unit and leaves without addressing gaps in the delivery system. dIfferential barely fifteen downstairs and only ten upstairs.

Third visit (today): HVAC contractor has replaced an evaporator coil that the maker informed them was not up to snuff - and the HVAC contractor is, according to hear-say Getting smart and uncooperative. Differential on both units low. I go into the attic and every junction taken apart to replace that coil is un-sealed. Just for the heck of it (vacant house now), I pull out my aluminum duct tape and start sealing it up. I'm tired of coming back! TWENTY-SIX FEET of duct tape later, I am able to get one unit to muster fifteen and the other still does ten - both suction lines chilly and sweating. WHen I left I handed the twenty-six feet of duct tape backing to the listing agent and told her to tell the HVAC contractor where to put it.

[:-censore

Hey Mike:

Are you venting or looking for some help?

While I'll fix small things that take less time to fix than report I wouldn't put that kind of time in for someone that isn't family or friend.

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Mostly venting, and your point is well taken, Dr. McCann. I'll stop.

Oh, I get paid good money every time I come back out, but it begins to become an issue of who's right and who's wrong. And of course the inspector is ALWAYS suspect.

So, I just gave the listing agent a little demonstration regarding careless work and its affect on differential.

Normally I put don't put that kind of time into it either. I was making a statement that is going home to roost with this HVAC guy. That stuff is inexcusable, I think.

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Mostly venting, and your point is well taken, Dr. McCann. I'll stop.

Oh, I get paid good money every time I come back out,but it begins to become an issue of who'e right and who's wrong. And of course the inspector is ALWAYS suspect.

So, I just gave the listing agent a little demonstration regarding careless work and its affect on differential.

Normally I put don't put that kind of time into it either. I was making a statement that is going home to roost with this HVAC guy. That stuff is inexcusable, I think.

It's OK to vent - I just had a little spill over in the plumbing forum. When a psychiatrist, who has had enough, wants to vent who do they talk to that will understand? It's all good.

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Oh, I get paid good money every time I come back out,but it begins to become an issue of who'e right and who's wrong.

You sound like a pig headed Irishman [;)]

Eye, a touch, maybe... Kinda makes me think of the Family Guy Episode where Peter travels to Ireland to see his long lost dad, and they have their drink-down... "Mhe..mhe... mhe... mhe... me.. me.. me.."

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Get em' Mike! I suppose now would be a bad time to bring up how duct tape will fall off in a few years, so I won't.[:-dev3]

Anything under 12 degrees in differential is low in my book (measured at ceiling grille, not at the plenum), but an air conditioning system is far too complicated for a home inspector to even begin trying to diagnose. Air leaks in the ducts? That's just the beginning. When you touch that system by taping it up, you effectively put your name on it. Your name will pop up in the owner's mind as soon as any problem with the unit manifests itself. He won't understand how your work is not to blame.

I've pissed off more HVAC contractors than I can count on the fingers of both hands. Mostly because I'm so sick & tired of their funky workmanship that I just don't care for them anymore. Drew the battle lines a long time ago.

Marc

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Get em' Mike! I suppose now would be a bad time to bring up how duct tape will fall off in a few years, so I won't.[:-dev3]

Anything under 12 degrees in differential is low in my book (measured at ceiling grille, not at the plenum), but an air conditioning system is far too complicated for a home inspector to even begin trying to diagnose. Air leaks in the ducts? That's just the beginning. When you touch that system by taping it up, you effectively put your name on it. Your name will pop up in the owner's mind as soon as any problem with the unit manifests itself. He won't understand how your work is not to blame.

I've pissed off more HVAC contractors than I can count on the fingers of both hands. Mostly because I'm so sick & tired of their funky workmanship that I just don't care for them anymore. Drew the battle lines a long time ago.

Marc

Yep, wouldn't have done it if it wasn't a vacant relo - nobody to connect me with it, thankfully. And, the HVAC contractor STILL has to come back out and finish sealing up the swiss cheese ducts and low differential. I'm good.

Normally I just report it. I was just feeling particularly awnry and blew a gasket. Eh.. as Terence so eloquently put it, "got pigheaded." Yeah, that's the ticket... [:-banghea

PS. But, hey Marc, I usually draw the line at 14 degrees and below as needing attention. Talk to me...

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Jim K posted a temperature chart on another thread a while back that gives proper values of dry bulb temperatures for various combinations of entering dry bulb and wet bulb values but that chart likely applies only to certain model numbers or product lines with a specific tonnage value. Jim's input on this opinion of mine would be appreciated here but if I'm correct on this, it's not a 'one size fits all' type of chart. So, I just settle with 12 degrees for all residential split systems with attic ducts, measured at the air filter and at any ceiling register that isn't situated close to the cooling coil (to incorporate the effects of the duct system). I also use 18 degrees for a maximum. If it's over 18, then there likely an issue with inadequate moisture removal, called 'latent heat removal' by HVAC techs. At this time, I don't care to refine my benchmark values any further than that.

Of course, there's probably about as many different opinions about those two numbers as there are TIJ members so I've got my seat belt pulled tight now for a salvo of retaliatory posts.

Marc

Download Attachment: icon_adobe.gif Temperature_Differential_Chart_Carrier.pdf

75.86 KB

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Jim K posted a temperature chart on another thread a while back that gives proper values of dry bulb temperatures for various combinations of entering dry bulb and wet bulb values but that chart likely applies only to certain model numbers or product lines with a specific tonnage value. Jim's input on this opinion of mine would be appreciated here but if I'm correct on this, it's not a 'one size fits all' type of chart. So, I just settle with 12 degrees for all residential split systems with attic ducts, measured at the air filter and at any ceiling register that isn't situated close to the cooling coil (to incorporate the effects of the duct system). I also use 18 degrees for a maximum. If it's over 18, then there likely an issue with inadequate moisture removal, called 'latent heat removal' by HVAC techs. At this time, I don't care to refine my benchmark values any further than that.

Of course, there's probably about as many different opinions about those two numbers as there are TIJ members so I've got my seat belt pulled tight now for a salvo of retaliatory posts.

Marc

Download Attachment: icon_adobe.gif Temperature_Differential_Chart_Carrier.pdf

75.86 KB

Actually, I've found the chart to work equally well across the board. Air conditioner, heat pump, different manufacturers, Freon, Puron, . . . none of it seems to matter. They all seem to be engineered to pull the same amount of energy out of each cubic foot of air that passes by them, given a certain temperature/humidity point. The feedback I get from the techs pretty much always backs up the chart.

You've got a set of pressure gauges. Try it. Just remember that readings at the registers are going to be inaccurate if the ducts are screwed up. The best data comes from the plenums that are adjacent to the indoor coil. Of course the filter has to be clean and the coil can't be dirty, blah, blah, blah.

- Jim Katen, Oregon

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Mike,

I just talked to the head code compliance officer for HVAC for the state of Texas at the Department of Licensing. In Texas only the homeowner or a licensed HVAC technician can repair (seal ducts with tape or mastic). Anyone else that repairs ducts would be in violation of the state licensing laws and subject to a large fine. While I have no idea what the laws are in Va I would certainly check before I do any more repairs.

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Thanks for the heads up! It sure is sad when government authorities insist upon work being done by specialists who daily demonstrate that they have no pride in their work and really don't give a rat's butt. But, that's the government for you - always meaning well, but relying on the presumption that others do also... [:-banghea

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Jim K posted a temperature chart on another thread a while back that gives proper values of dry bulb temperatures for various combinations of entering dry bulb and wet bulb values but that chart likely applies only to certain model numbers or product lines with a specific tonnage value. Jim's input on this opinion of mine would be appreciated here but if I'm correct on this, it's not a 'one size fits all' type of chart. So, I just settle with 12 degrees for all residential split systems with attic ducts, measured at the air filter and at any ceiling register that isn't situated close to the cooling coil (to incorporate the effects of the duct system). I also use 18 degrees for a maximum. If it's over 18, then there likely an issue with inadequate moisture removal, called 'latent heat removal' by HVAC techs. At this time, I don't care to refine my benchmark values any further than that.

Of course, there's probably about as many different opinions about those two numbers as there are TIJ members so I've got my seat belt pulled tight now for a salvo of retaliatory posts.

Marc

Download Attachment: icon_adobe.gif Temperature_Differential_Chart_Carrier.pdf

75.86 KB

Actually, I've found the chart to work equally well across the board. Air conditioner, heat pump, different manufacturers, Freon, Puron, . . . none of it seems to matter. They all seem to be engineered to pull the same amount of energy out of each cubic foot of air that passes by them, given a certain temperature/humidity point. The feedback I get from the techs pretty much always backs up the chart.

You've got a set of pressure gauges. Try it. Just remember that readings at the registers are going to be inaccurate if the ducts are screwed up. The best data comes from the plenums that are adjacent to the indoor coil. Of course the filter has to be clean and the coil can't be dirty, blah, blah, blah.

- Jim Katen, Oregon

I'd love to behold that chart. Can I? Can I? Can I? Huh? Huh? Huh?

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I'd love to behold that chart. Can I? Can I? Can I? Huh? Huh? Huh?

Marc posted it at the end of his message.

- Jim Katen, Oregon

Oh, OK. I thought maybe you were alluding to a new one you had come up with you liked more than the one Marc had posted. But, now that I re-read your post, I realize I read too fast. Thanks

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That unit is likely losing about a third to half of it's tonnage via those air leaks. When I see this, I inquire of the seller about the most recent electric bill.

Marc

Marc, Words cannot adequately describe my feelings when I behold a mess like this. It's the kind of stuff that makes ripping the yellow pages book in half easy. What ever happened to tradesmen?

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What ever happened to tradesmen?

There few and far between. We just lost our lead installer at my day job, he left for greener pastures. We have hired two guys, each with a dozen years or more of experience, to replace him. These guys are so green that I have been out in the field doing installs two or three days a week to keep the schedule moving. I have been in sales for the last twelve years and have gotten fat and a little bit rusty, but I can work circles around these guys. These two are the best of over a dozen candidates that we talked to.

The trades is where you go when you can't make it anywhere else[:-banghea

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Times have changed. It's not necessarily a bad thing, as long as the homeowner responds to it. Contracting is driven by dollars now because homeowners usually hire a different contractor every time they need one. There's so many of them and so many different specialities that the homeowner doesn't get a decent chance to get to know which ones possess good workmanship. Service ends at the point of sale instead of when the job is finished, like it used to be. A wise homeowner in this climate is better off getting representation from a home inspector each time they contract over $1,000. You don't need a different home inspector for every type of work done on the house. This way, the homeowner has a chance to get to know, and trust, a particular home inspector and get their repair work done right.

Educating the public is key. The national associations should be doing that, but they too have become driven by dollars. You figure that one out, I done figured the first one for you.[;)]

Marc

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What ever happened to tradesmen?

There few and far between. We just lost our lead installer at my day job, he left for greener pastures. We have hired two guys, each with a dozen years or more of experience, to replace him. These guys are so green that I have been out in the field doing installs two or three days a week to keep the schedule moving. I have been in sales for the last twelve years and have gotten fat and a little bit rusty, but I can work circles around these guys. These two are the best of over a dozen candidates that we talked to.

The trades is where you go when you can't make it anywhere else[:-banghea

Tom, this is a true story - I was taught masonry from a real stickler for perfection, from Holland, who always told me, "Learn it right and the speed will come." He would go BALLISTIC if he ever heard you touch a brick with the handle of your trowel - a waste of time. If your mortar is perfect, you can merely roll a brick to the line, cut off the excess mortar and clip it on the next brick to lay and keep on keepin' on.

Consequently, when I worked commercial jobs, I could be on a LONG gymnasium wall and TWO men would be FRANTICALLY working their asses off to meet me in the middle of the gymnasium wall, and their work LOOKED LIKE HELL and mine didn't even need to be cleaned! Funnier yet, they went home beat and I went on to lay another four more hours of brick on a side job.

Best of all, because of my speed and clean work, when the economy tanked in the mid-70s, they laid off HALF of their 150 man work-force before they finally laid me off, even though I was the last bricklayer they hired. I was making them too much money. [:-eyebrow Only when they finally got down to the bricklaying families that were two and three generations deep in thier workforce did they finally lay me off. Now and then, one actually gets rewarded according to their capabilities.

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