Can You Solve This Unsolvable Home HVAC Problem?

Try to use a small video camera like in a surveillance systems. some can be found for around for $30-50 range and can be connected to AV jacks on a tv.

Use something that you can use to feed down through the vents that have the most debris.

Now as to the debris it sounds like vermiculite and or coal cinders. The house I live in is block construction and the voids are filled with it. A pain in the butt fixing problems.

One thing you have left out is where the debris is coming out of. And if those vents have had any modification done with any of the HVAC work. Also if only a few are doing it they could be on the same branch line.

After rereading your commit the duct work in the outside walls may not be sealed and with the air blowing out the return it could be picking up some of the old insulation from the wall cavity.

This is the best guess I can give. good luck and let us know what you find.

Charles

metalSmith's

you could try having someone come in and clean the inside of all the ductwork,or at least the old work, i know where i live there are several companys that do this as well as video the duct work. if the ducts were reversed, i am sure alot of dust and stuff collected in the returns and now its all just blowing out, sounds simple enough. having someone do a video inspection should give you a pretty good idea where the debris is coming from. even someone with a sewercam can do duct inspection. good luck!!!

Presumably you only have the problem in summer?

What is the weather like? Humid, dry, wet? Daily temperature range?

Years ago had a problem in a ship air con. Turned out to be the galvanizing inside the duct corroding under some fairly special conditions and blowing out a whitish powder. (The situation was a little more complex than that, but my simplification should serve the purpose here). At the time, all the experts were stumped.

This doesn't sound like the same thing, but it won't hurt to eliminate it as a possible cause.

It sounds more likely that you are picking up vermiculite or perlite from between the walls or somewhere, but you have undoubtedly been checking that.

May I ask why the supply and return were swapped?

When this was done was the filter relocated to what is now the new return? Is the filter at the unit or on the central return?

Were the former return ducts cleaned? Were the individual return filters removed from the grills?

Is the flex duct in the basement insulated? Have you checked for damage to the insulation? Does the insulation get wet? Why is there flex ducting there to begin with? Is the flex on the supply or return?

You could try individual filters on the supplies to determine where, if it is only one duct, it is coming from. Cheap foam insulation can be used for this. Is it in all rooms?

Do you have a separate air unit for the second floor? If not, do you get this debris on the second floor as well?

I could go on for ever. Far too many choices.

description is not complete, though it does seem debris is coming out of (former) return chases in outside walls that are now forced air supply? Are the air flow passages in 'the outside walls' simple uninsulated chases, or are they sealed and insulated ducts? Running A/C chilled air in uninsulated exterior wall cavity WILL cause mold, mildew, rot from water condensation during hot, high humidity periods. With the old heat only service, uninsulated wall cavities were commonly used as return air 'ducts', since the air was cooler and energy loss was not a consideration in 1940. (propane in 1940 was $0.03gal or less)

Thorough cleaning of those former 'return air' passages is essential, as is adequate insulation to prevent moisture ingress and subsequent mold/mildew, yuk.

When the flow was reversed, all of the debri that had accumlated in the ducting since the 1940's was now blown back into the rooms.Apparently, the debri has reached the AC unit itself, and becomes airborne every time the unit operates.The unit should be removed and thoroughly cleaned.The ducting should be cleaned or replaced, and all seams should have mastic applied(sealer).This should be on the HVAC company's dime, not yours.You paid for a properly designed and functioning system and you still do not have one.If you have trouble with them complain to the BBB or License Board in your state.

FWIW

-----------------------SSB-------------------------

Exactly what he/she said! The air flow had been flowing in one direction for a great deal of time... The got stuck at some point with that original air flow direction... Now when you reverse the air flow... The debris that got stuck has another chance to become free and therefore airborne again...

Replace the ducting.

Pl check your AHU rooms for the source of the dust. If not already done, re-install all ducting after cleaning. What about the filter material itself? Is it checked?

Score 1 for Good answer for Ed Weldon, he backs up lynlynch in post #3

my guess would be something like this (lived in an old place) most likely the interior wall "ducting" was just the stud cavity.

the following post regarding LATH and such furthers the explanation. although replacing the LATH and all seems a bit extreme. I think the right contractor could line the stud cavities, or selectivly replace Lath and horsehair with sheetrock in affected areas.

(just make sure it's not the rotting chinese sheetrock that just hit the news!)

more frustrating to me is the fact that all these "experts" have not found anything.

I deal with "experts" on a daily basis. amazing what a title can do to common sense!

cheers!

JB

Please keep us posted on what the final outcome is.

Your comment:-

I deal with "experts" on a daily basis. amazing what a title can do to common sense!

...was BRILLIANT! I could not agree more. GA for that alone.

I have "S**T" experts!!!!

Many is the time where I have done a job where I had little of no prior knowledge. Sometimes I screwed up, but buying the parts (sometimes for the second time!!) was NEVER as expensive as getting a "so called Expert" to do it even once!!! I also learned a lot each time!

I am exceedingly careful when I pick my "Expert" nowadays.....

I think you have a case of modern construction conflicting with the old. Buildings in the 1940's were constructed using rough cut lumber, lathes, mud and straw. The lathes were nailed to the studs and then covered with a mixture of clay and straw. The walls were then filled with shredded paper. When the walls were disrupted installing the new system, the seal from the wall was compromised. There is probably a ton of mud and straw in the house and removing it one little dustpan at a time could take around 3,235 years to remove it. I can't think of a way to reseal the walls, but a solution is to remove the lathes/mud and replace with dry wall. I hope this not the case.

Where is the building geographically?

People are much more likely to guess at local building practises, if they know where it is.

You did not mention who did these installations...but it sounds perhaps amateurish. Recommend collect but do not touch or breathe the stuff coming out the registers. Have the stuff analyzed by HVAC company or appropriate local lab to make sure it's not asbestos...which was commonly used in heating systems about the time of construction of that house. Call in a legitimate contractor to analyse and repair/redo this seemingly misguided installation.

Quote "Original system had return in each first floor room (6) in the outside walls, supply in interior walls. When AC was installed returns and supplies were reversed in each room. Central return added in a central return."

Did they have any explanation on why they did this? Seems to me it makes more sense to have the returns in the outside walls rather than the inside walls. And a return in each room also seems better than a central return on each floor. Why would you change a system so dramatically when it was working well to begin with?

As far as the crap coming out of the returns. Its probably like someone else mentioned. After all these years of the air flowing in one direction thru the vents. Now its flowing the other way and all the stuff in the little nooks and cranny's that was trapped before is coming lose since the air is moving in the other direction.

A really good cleaning of the duct work will probably solve the problem unless its actually sucking the debris form a new source shuch as your walls insulation.

We can simulate the conditions Can we talk to the HVAC supplier?

If flexible ducting was not properly sealed at the joints, the air pressure could be causing the fiberglass to breakdown and become air borne. Have the ducts checked by installing inspection ports. If any lined galvanized ducts where part of the system, again if the edges of the liners were not sealed properly,they may breakdown and become air borne particles.

Hope this helps.

When the installer reversed SA & RA ducts, that could be a problem. Sometimes installer save money and/or space by using three sided duct screwed on board wall for return duct, specially when the duct passes thru wall behind dry wall. Wooden board may be rotten/partially burnt by the heated air thru supply (now) duct and that may be causing of dust particles out of supply air.

Hello,

35 years ago I worked for a large midwest hvac company. Return ducts were panned in every chance they could due to costs ( this is where one simply nails tin over the wall, floor, or ceiling joists rather than using ductwork and tin close the ends). A few years back, we remodeled our parents house (built 1942) and it was done the same way. Reversing the original duct blindly (and I don't know if they did this in your case) sounds like a bad idea to me. I would check this out ASAP.

Since you describe the particles as mica, this appears to be to be a vermiculite problem. Vermiculite was a popular insulation material but is now banned due to lung problems it can cause similar to asbestosis.

The insulation may be in the attic which is now being pulled down interior wall voids due to the reversal of the air pressure in the interiors walls since the AC retrofit.

1. In the 1940's into the 1950's a Thick cardboard type duct material was used in some homes to duct the supply and return lines, sometimes this material disintegrates due to moisture and causes problems similar to what you are experiencing. The glue that holds it all together also will flake when moisture gets to it. To determine the exact problem hire a company that has fiber optic video camera equipment and allow them to run it through the ducts you will probably find an area that has wasted away and you are getting wall and or decomposed duct material. This whole process was accelerated because while air conditioned air does not carry as much water as warm air it does cool the plenum of the wall at which wil cause dew point in the wall and duct causing condensation to form in and on the wall ducts (Not as likely in the floor). This is also the reason no problems were noted when just heated air was forced through the ducts.

Regards

Hi,

You've received plenty of advice on what must be an extremely unpleasant 'investment' with an ongoing saga.

Clearly your contractor/supplier had a reason for reversing the polarity of the ventilation ducts and thereby created all the allergic problems due to bringing the 'crap' of decades into your living spaces.

What next? Put things back the way they were is the only practical solution for overcoming the main problem. But what about the actual performance of this system?

Does it deliver the comfort conditions required and if so how much energy is it consuming? All these old ducts etc particularly the extract ones will have either none or little insulation and plenty of leaks! All serving to boost the cost of ownership. Therefore having overcome the most apparent problem there are possibly others just waiting to be realised.

Were you given any performance guarantees? It seems as though you have a system which is 'unfit for purpose' and therefore you should be considering what form of remedy to seek, eg, a full refund and re-instatement of the installation to an 'as before' state.

This looks like a rapid parting of the ways as far as convivial contact with the provider is concerned and an imminent appearance of legal eagles on the horizon.

Good luck what ever way you go.

Had a similiar "debris" problem on a house only 5 years old. HVAC man pointed out the problem to be aged mulch around the flowers bordering the unit pad. The old mulch had rotted to the point of just being dust and small fragments that was being pumped into the house by the AC unit. Noticed the debris in the house mostly around the ducts in the floor.

Sounds like insulation is being transfered from a source. Also you have new and old duct pipes. When was the last time the duct work on the older system was vacummed out ? Also what kind of insulation is in your attic ? Also look at presure differential between the systems etc. Is there negative air presure in the house Vs outside or positive presure when the system is running. Did this gray matter start showing up after the new duct system was installed ?

You might try a series of air transfer experiemnts. Shut off the old duct work and run the system if you can with the new duct work. OR you could put vent filters in your duct discharge vents and findout which vents are discharging the gray matter.

My bet is the older duct system is falling apart. Newer air systems these days move air much faster thn older system.