HVAC experts please help!

[zakthor]

Sure sounds like the ducting is an issue. The guy that installed our new furnace did an amazing job. And no extra charge he replaced a bunch that he didnt need to, just because he said it was manky. I didnt know what he meant until he was done, new was so natural looking. Find a good installer youll be happy.

That said, just because ive not seen it mentioned... big blower motor under load, could you have a problem with current? Could be heat at bad connection causing voltage drop?

Check and clean, then multimeter?

Good luck!

[cabmandone]

Sweet mother of pearl that's one jacked up duct system!

[Wayne 962]

Originally Posted by cabmando

The odd thing is, that return grille is a filter grille. It's designed to have a filter in it. From the looks of the pic, about a 2" thick 16x24 filter. If that 24" is oval shaped to fit that grille, it's part of the restriction as well. Then add all the kinks from going through floor joist spaces and you've reduced the effective size of the duct to a point that the static pressure can't be calculated.

Yup, I did notice that a while ago (last year) when I noticed there was no filter in it. When the testing on that fibrous material comes back, and if it's fine, I think I'm just going to tear into the thing, remove 10' or so of return vent, see what I can do to modify the intake vent to reduce the restrictions and see if that works. Disconnecting that big return line from the bottom of the convoluted vent and then testing the blower again will give many more clues. But - I want to make sure that stuff doesn't have asbestos in it. If it does, then the heater is indeed the least of my worries (just went through that with our other house in LA!).

-Wayne

[cabmandone]

Fly me out, buy me beer, and I'll coach you on how to install the ductwork properly. I won't install it! That'll be up to you. But I'll drink beer and watch you install it. It's what I do.
Ask my brother Gordo2, he'll tell ya.

[Wayne 962]

Originally Posted by sammyg2

you also reminded us what the American dream is all about and what makes this country great.
The land of opportunity, for those willing.

Glad to be an inspiration, but I don't consider myself too special. Just pretty good at looking at things and analyzing the best path. I credit the "mental pugh chart" for a lot of that...

-Wayne

[Wayne 962]

Originally Posted by cabmando

Fly me out, buy me beer, and I'll coach you on how to install the ductwork properly. I won't install it! That'll be up to you. But I'll drink beer and watch you install it. It's what I do.
Ask my brother Gordo2, he'll tell ya.

Contrary to popular believe by many (including my wife), I don't really enjoy the actual act of HVAC system design and installation. I do like problem solving though.

This house was a redo from a 1960 A-frame. The place is insanely cool, but it has some odd quirks, like this HVAC ducting, that show very clearly that it was a previous simple A-frame. The area where that vent is right now used to be a staircase to get down to the lower level (what we call the secret staircase). Behind the microwave was the entrance to the staircase. So, maybe they had to work with what they had at the time?





-Wayne

[javadog]

Long story short, you want the least amount of resistance on both the supply and return sides. In my world (commercial construction), we don’t use that flexible ductwork. In my opinion it’s crap and it gets used in the residential world because it’s cheap and easy, compared to making and installing sheet metal ductwork.

Anything you can do to shorten the return path, or straighten it, or make it larger will help.

[Wayne 962]

Originally Posted by javadog

Long story short, you want the least amount of resistance on both the supply and return sides. In my world (commercial construction), we don’t use that flexible ductwork. In my opinion it’s crap and it gets used in the residential world because it’s cheap and easy, compared to making and installing sheet metal ductwork.

Anything you can do to shorten the return path, or straighten it, or make it larger will help.

Cool, that was my thoughts - I just wanted to confirm it with the experts. I actually think perhaps the whole system has been "broken" since it was installed. I never noticed it until the whole system shut down the other day due to "repeated faults", which may have kicked it over the edge with a somewhat dirty filter. I.E. when I installed the new filter, it didn't start working property. Also, the thermostat (which is one of those newer wifi ones) told me "there might be something wrong with the heater because I've been calling for heat for the past two hours, and the temperature has dropped 3 degrees". Pretty clever design I thought. Although by the time I saw the message, the heater had "cycled" and started up again, and the temps were okay, so I shrugged my shoulders and ignored it (this was last year).

-Wayne

[cabmandone]

I've watched that first video several times and my head is still spinning! The duct that runs up the back side and into the crawl space, what size is it?

Where you say in the video it comes from here, to here, to here into the crawl, if that duct running up and into the crawl space isn't sized properly, you can change the flex and you might still have the same problem. It's all about the square inches... and the cfm those square inches can handle. If that drop duct is only good for 1200 cfm, as an example, and you have 24" that will carry 1800 cfm, it's only going to pull 1200 cfm no matter how straight that 24" is.

[Wayne 962]

Originally Posted by cabmando

I've watched that first video several times and my head is still spinning! The duct that runs up the back side and into the crawl space, what size is it?

Where you say in the video it comes from here, to here, to here into the crawl, if that duct running up and into the crawl space isn't sized properly, you can change the flex and you might still have the same problem. It's all about the square inches... and the cfm those square inches can handle. If that drop duct is only good for 1200 cfm, as an example, and you have 24" that will carry 1800 cfm, it's only going to pull 1200 cfm no matter how straight that 24" is.

Yes, that is smart to point out - the same principles indeed do apply when designing an air intake for a car. That is why disconnecting the flex and testing it without the convoluted intake vent thing will give some clues? I just need the results back on that vapor barrier / material...

I didn't measure the flex, but it looks to be about 24-30" or so.

-Wayne

[908/930]

Not a HVAC expert, but have done my fair share, had a problem years ago with with a Carrier Infinity 98, I turned the breaker off and when it went back on the motor would not run, fault code indicated motor failure, still under warranty service rep arrived did a quick test and replaced the wall mounted controller. That controller is where you set the speed for the motor. Any chance the wall mounted controller is not set up or working properly?

[cabmandone]

Went back through all of your replies in case I missed something. In post 24, you mention no code with blower door open and furnace running and then blower door on furnace running you get the code. The answer is the return duct. I think it will likely also work with the large flex duct disconnected from the duct that runs up into the crawl space. Only reason I tend to think it will work is, if the size of that duct is "close" to right, the furnace will compensate. Once the flex duct with it's length bends and kinks is added, the furnace can't overcome that added restriction.

You can't mess things up by shortening the return duct. You can only mess it up by restricting it. The only thing you might get by shortening the duct is some whistling or vibration through the return vent. If it does this just take a pair of needle nose plyers and open the louvers a bit.

[Wayne 962]

Originally Posted by cabmando

Went back through all of your replies in case I missed something. In post 24, you mention no code with blower door open and furnace running and then blower door on furnace running you get the code. The answer is the return duct. I think it will likely also work with the large flex duct disconnected from the duct that runs up into the crawl space. Only reason I tend to think it will work is, if the size of that duct is "close" to right, the furnace will compensate. Once the flex duct with it's length bends and kinks is added, the furnace can't overcome that added restriction.

You can't mess things up by shortening the return duct. You can only mess it up by restricting it. The only thing you might get by shortening the duct is some whistling or vibration through the return vent. If it does this just take a pair of needle nose plyers and open the louvers a bit.

Awesome. This is the answer I was looking for. I will take a closer look at it on Thursday when I get the test results back!

-Wayne

[908/930]

If you are going to replace that flex return are you able to get pipe into that location? A smaller diameter rigid pipe will still flow better.

[dad911]

I'll throw out my 2 cents.

Almost 20 years old, that unit reached end of life. I'd change it. Without AC it's a simple swap, easier than a 2.2 in a 1971T. Probably quicker than the time you will spend debugging.

I'm also not a fan of common returns. I don't know the layout of the house, but imagine adding a few additional returns in other rooms would reduce the load and help balance the system better.

Flexible duct is cheap. I'd replace that return before cleaning. Probably less than $100.

[nota]

Originally Posted by cabmando

You can't mess things up by shortening the return duct. You can only mess it up by restricting it. The only thing you might get by shortening the duct is some whistling or vibration through the return vent. If it does this just take a pair of needle nose plyers and open the louvers a bit.

in a perfect world totally correct

but in the early pictures in inside the bent restricted ducts red area
sure would flow better if longer sweeping curves and less crushed joints

but I still suspect a monster dust-bunny is lurking behind a turn near the air to the box red area
as 24'' ducts should flow no matter how twisted or bent

[fintstone]

You simply do not have enough return capacity to run on high heat. You need another return to increase capacity. Look at Appendix E.

http://www.graycoolingman.com/uploads/1/0/6/6/10667336/58mvp-_2_stage_variable_speed_troubleshoot_guide.pdf

[Zeke]

Originally Posted by Wayne 962

The code is indeed 44 right now. Nothing else either. I bought some stuff at the hardware store to clean out the vents. The trouble is, I found some stuff down there that looks like it might have asbestos in it, so I FedEx'ed it to the testing lab in Los Angeles and I'll have them check it (by Thursday morning). Then if that comes back all clear, I will crack open the return pipe and tape a filter to it and suck air from the basement area and see if that makes a difference. I'll also clean all of the dust out too while I'm there.

-Wayne

Don't do that. And it takes special scrubbing equipment plus the best HEPA vac you can buy to accomplish anything but making a mess.

In another post you said "intakes" as in plural. Is that correct? Your drawing doesn't seem to indicated more than one.

It's a long return air and I think some critters may be involved. Obviously this is a 2nd home so who knows what goes on when you're in SoCal. Or while the home was on the market and maybe not inhabited.

IDT it's that expensive to do a whole duct system clean by a pro. Sorry about your wife not wanting anyone in the house but it is what it is. They disinfect as part of the process.

[cabmandone]

Today is the day we find out what the mystery stuff is! Wooo Hooo.

BTW Wayne, if ya get a chance post the A/C Model number and the High Fire rate for the furnace. I think I can put to rest a lot of assumptions by knowing these two things. I could tell you more if I knew the total number of supply registers and the corresponding duct size for each. If you're wondering where I'm going here, the rule of thumb is 6"=100cfm 7"=150cfm 8"=200cfm on the supply side. If add up the cfm for your supply, the return duct needs to be able to draw that much back. The big thing to know would be the exact size of that drop duct coming from the crawl space down into the bottom of the furnace and exact size of the flex duct. Again the variable being how kinked the duct is in the points you have pictured.

[Wayne 962]

cabmando - I'll get you that info soon, heater is apart and it's getting cold so I need to work semi-quickly.

So, I disconnected the return line - what a convoluted POS setup this is. BUT - disconnecting the line did not make a difference! I ran the heater with the return line disconnected, *and* with the filter removed (just for 20 seconds during the test mode), and it still came back with the 44 code. By the way, it shut down last night for it's "3 hour reset cycle" on its own.

So, with the return disconnected and the filter out - it still gives me the 44 error! Running the motor with the cover open (so it gets air from the room instead of from the return circuit) resulted in no errors. So, is there an obstruction in the return duct all of a sudden? Is the line just so long it can't get air? I thought for sure removing it from the screwed up intake vent (semi-crushed by the beam ) would help, but it did not! Right now, I'm headed back down there, and I think I'm going to chop about 20' off of the return line and see what happens. I have to be careful not to screw up the entire setup. We do have another FAU in the house, and we do have a wood burning stove, but I wouldn't hear the end of it if the unit was down and inoperable for several days...

-Wayne