Looks good / works poorly

[selfemployed]

This heat pump job has been in for 5 yrs. History is add gas in summer and take out in winter. 11 seer OD unit and TXV on ID coil. The equipment is not the problem. Why can't installers follow the directions?

http://hvacloads.com/talkpics/wall/98534_ruud.jpg.

[Joe_C]

How many sheath elements have they gone through?
I've seen many units like this.

[selfemployed]

The elements are green tip and none have failed. Plenums on both air handlers are being replaced this week. I wonder how many people have looked at the pic. and don't see anything wrong ? One contractor here has corrected 30 installs in one development. All done by the same company.

[cehs]

Are you refering to the condensate drain color, or the ductwork, or something else?

Please be more obvious (and specific). I don't see what you are trying to show us. What is happening to these units?

I want to learn, so be kind to those of us that don't see what you see as obvious.

[Edited by cehs on 02-10-2003 at 08:14 AM]

[billygoat22]

Don't those units have a 8" wide outlet on them?

[Breeze]

I see the drain clean out is past the trap and not capped or raised high enough to prevent a water leak.
Our inspectors would require the PVC to be insulated and all joints to have mastic on them.
The liq. line should be insulated on a heat pump to prevent condensation.

[workinlate]

Wrong indoor unit or a messed up: coil/cap tube/valve/airflow/lineset/tech/customer.......

"charge robber in the condensor??????"

[Edited by workinlate on 02-10-2003 at 09:54 PM]

[spike]

Not sure about my terminology, but on Rheems, the plenum should be designed/attached to the metal tabs from the blower assembly section, not the outside edges of the cabinet.

[james mo]

Well, It seems like we are talking about an airflow problem. Is it the plenum size? I don't see a place for a filter.....Damn......I'm not going to sleep tonight.

[selfemployed]

It is suppose to leave the air handler the size of the blower outlet, approx. 8x18 and continue for minimum of 12" - 14". There is orange tape on blower flanges that says, do not bend down.Installation instructions say that static pressure and air flow problems will result. I wanted to see how many people have run into this problem. It really will make you scratch your head the first time you run into it. Thats why I said, add gas in summer and take gas out in the winter. Head pressure reset starts tripping in heat mode after adding gas during summer to correct suction pressure in cooling. Sometimes it just heats and cools poorly with high heating and coolng bills. They finally put a filter door on the new air handlers instead of removing the coil door to change the filter.

[Breeze]

Down here fan coils are installed similar to your picture only we use fiber board and the return air is increased for heat pumps. Never had a problem connecting the duct like you are showing.
Do these problems happen when weather is mild? They do here, we sometimes have to install a mild weather kit. Most of the time the customers filter is dirty or return isn't large enough.

[icemeister]

I don't do much residential A/C, but I can say I don't remember ever seeing any Rheem/Ruud air handler installed per their instructions.

I installed a 4-ton 10 SEER Rheem heat pump in my own home three years ago. Standard setup, no TXV(s), just cap tube feed. The discharge plenum is full-size all the way to the attic space. My install manual says the discharge plenum must be the same size as the blower outlet for a least three feet or a loss of up to 0.1" static pressure will result. So? What does that really mean to me?

No apparent airflow problems, checked the temperature rise with the 10KW strips and its pretty close even with a slightly restricted return setup (I'll fix that one of these days).

I am interested in Breeze's post concerning a mild weather kit. What's that? I live on the Florida east coast and when we do use the heat, it's to keep the house at 75 Deg, not 65 like we did years ago up north. On a 60-65 Deg day if the heat kicks on and it'll usally trip the HP switch. So I let out about a pound and its fine. In March or April, I'll be putting it back in to get ready for the summer when we keep the house at 80 Deg.

[Breeze]

A mild weather kit is nothing more than a auto resetable high pressure switch installed in liq. line and cuts out the outdoor fan on high pres. this lowers the head pres.
Most come with a tee adapter.

[icemeister]

Originally posted by Breeze
A mild weather kit is nothing more than a auto resetable high pressure switch installed in liq. line and cuts out the outdoor fan on high pres. this lowers the head pres.
Most come with a tee adapter.

Thanks, Breeze. I'll try that.

[james mo]

Of course you don't want the outdoor fan shutting off due to high pressure in the summer time.

[BamaCracker]

A builder called me once and offered to "let me" take over the warranty work for a competitor who went out of business. 21 brand new homes in this neighborhood, and two no cooling calls. I agreed to do the warranty work as long as I got to installo the HVAC in the remaining 40 homes scheduled to be built.

One of the no cools was low gas. . .gurgling metering device, low suction pressure, insufficient cooling. The other one was a small rock in the liquid line.

Come winter, Mr. Low Charge calls back on a no heat. Tripped pressure switch, gross overcharge. I figured the butt-head had added charge after I did. Come spring, back out for no cool and gurgling, added charge. Come fall. . .you guessed it, take charge out. I got the Rheem rep to come see the job, and as I opened the closet door, he said, "You can't install that plenum like that!" I tried to argue with him, because all 21 houses in that neighborhood with Rheem equipment (I was a Trane dealer :D) were installed just alike. But you know what? When I replaced that plenum per Rheem;s instructions, the unit worked great and I never had another call back!

So, not following the instructions about the duct hookup does not ALWAYS lead to a problem, but certainly can.

[dash]

We have found the same thing many times.Just because some of them work without the correct plenum,doesn't mean the are working at full capacity.

less static =less airflow =less capacity.Some don't need the lost static,due to the duct design.Some lose capacity but where oversized systems.

When blower flanges are left bent down,airflow is even worse.

Does anyone (except bama)know why they (rhemm/rudd)must be installed this way,or lose static capability?

[Edited by dash on 02-12-2003 at 05:34 PM]

[Breeze]

Originally posted by james mo
Of course you don't want the outdoor fan shutting off due to high pressure in the summer time.
Why not? If they are not going to have the unit cleaned every year they deserve to have the system shut off on the manual high pres. switch.

I can understand the blower needs the extra duct sized per factory instructions so it will get up to speed. My instructions (ESM Motor) Min duct length is 6" but they suggest 36". It says the same thing about a .1" of pres. loss can be expected.
For people that use metal duct (outside lined) it would seem to be more of a problem. Down here, as you know, everything is fiber board and flex duct so maybe that is why it works.

PS: since Harry James butt might see this let me add "10 gals of mastic" :D

[dash]

Originally posted by Breeze


I can understand the blower needs the extra duct sized per factory instructions so it will get up to speed. My instructions (ESM Motor) Min duct length is 6" but they suggest 36". It says the same thing about a .1" of pres. loss can be expected.
:D [/B]

Questions,"My instructions" what brands instructions?

"they say 36""who is they?

Why is that Rheem/Rudd different,than other brands?

[Breeze]

Originally posted by dash
Questions,"My instructions" what brands instructions?

"they say 36""who is they?

Why is that Rheem/Rudd different,than other brands? [/B]

Dash: I have a Rheem in my house so I said, "my instructions". Not sure if it matters but this is for a VS motor.

36" ? Rheem

I will take a stab at the why part: Rheem/Ruud have blower outlets right at the top, heaters are in the blower so you do not have the space other heaters have between blower and outlet. Most units have about 8" to 12" of space after blower, as you know Rheem/Ruud does not.

[dash]

That my understanding too.We also find ,water to air units ,similar fan setup,with the same problem,and solution.

I don't think enough contractors are aware of the problem.

If I remember correctly,to paraphrase the Trane manual,"stright duct, equal in distance, to size of blower outlet.'

[Edited by dash on 02-13-2003 at 11:14 AM]

[Irascible]

You'll have to excuse me for bumping an old thread. But I want to make sure I got this straight. That air handelr is an upflow and should have an 8x18 inch supply plenum coming at least 12 inches off the top before it transitions to a bigger size? And the reason Rheem is that way and not other OEM's is because they don't have much space between the fan and the top of the unit?

I just have to make sure I get it. Though I may have seen one and forgotten, I don't recall every seeing one with a supply plenum as you describe it should be in my entire 9 years in the trade. Is that true of most Rheems or just heat pumps or just a specific series of Rheem heat pumps?

[selfemployed]

That style (family) of air handler. Should hace taken a pic when I was doing a PM on one the other day. I'll post a pic next week.

[Irascible]

So it's just a particular series. I'll have to call Rheem and get the details. Thanks.

[selfemployed]

All the air handlers that look like the one in pic posted.

[rottenfoot]

For those who haeven't seen one, here is a pic of the a/h in question.

http://www.wwwebworks.com/talkpics/wallofshame/rp_ah.jpg

We install lots of these down here. Have fixed numerous that were installed wrong.

[Edited by Boss on 12-29-2003 at 11:57 AM]

[rottenfoot]

Originally posted by icemeister
I installed a 4-ton 10 SEER Rheem heat pump in my own home three years ago. Standard setup, no TXV(s), just cap tube feed. The discharge plenum is full-size all the way to the attic space. My install manual says the discharge plenum must be the same size as the blower outlet for a least three feet or a loss of up to 0.1" static pressure will result. So? What does that really mean to me?

No apparent airflow problems, checked the temperature rise with the 10KW strips and its pretty close even with a slightly restricted return setup (I'll fix that one of these days).


You may have the RHQA (or UHQA) model which has the full size supply discharge.

[Irascible]

Awesome. Thanks for the pic Rottenfoot. Someone mentioned that the flanges are or get bent down. Does the air handler come shipped with those flanges down and you have to bend them up? If anyone has a pic of a correct installation of one of these, that would be awesome. Now that I've seen the pic, I know that IF I've seen this air handler in the field it wasn't installed correctly.

[rottenfoot]

Originally posted by Irascible
Awesome. Thanks for the pic Rottenfoot. Someone mentioned that the flanges are or get bent down. Does the air handler come shipped with those flanges down and you have to bend them up? If anyone has a pic of a correct installation of one of these, that would be awesome. Now that I've seen the pic, I know that IF I've seen this air handler in the field it wasn't installed correctly.

Usually comes with a bright orange sticker over the air discharge so that you have to remove it to hook it up. Unfortunatly, very few tech and installers pay any attention to that stuff now.
All the different manufacturers give FREE seminars down here that any company or tech can attend whenever new designs come out.They usually provide free food. Most companies and techs don't take the time. I wonder what will happen in 5 to 10 years when you will have to have a laptop to hook to the new system to troubleshoot.

BTW: I will get you a pic of a correctly installed unit soon.

[DeltaT]

Check out this article as to why these systems might act the way they do.
http://www.achrnews.com/CDA/ArticleInformation/features/BNP__Features__Item/0,1338,98984,00.html

Above won't work. Go to http://www.achrnews.com and search for the words "system effect"

[Edited by Boss on 05-19-2003 at 07:32 PM]

[Irascible]

"We're sorry. The page you attempted to access requires a valid subscriber number."

I suppose I should subscribe. It seems that The News is one of the few that are actually worth paying for. You think?

[DeltaT]

Try the page again. I can get through now that boss fixed the line. But I also subscribe. It's a very good article and addresses this problem from the design stand point.

[1coolhall]

I have found that reehm uses very small blower motors and stange blower wheels. Somthing like 1/8 h.p.(on 2 ton) Prety low air flow. I think I will use a 1/4h.p. if I have to replace one. in cool weather they run prety low suction (61 pounds).

[Dawlfandav]

acually the instructions if i recall correctly are 12 inches per ton, of duct on the supply plenum from the unit, the size of the opening. which is wider as cabinet size increases.

[rimide]

well-well-well I dun learned something new--have a friend that has that exact same prob-now I can be of some help

[-80guru]

Characteristics of air flow are a funny thing. For those who still do not get it. Rheem/Ruud went to all that trouble to make that discharge panel the way they did just so some unlucky bas$&*d would have to make a transition. Install it according to Manuf. specs/instructions and prevent the head aches.

[ga-hvac-tech]

Good read here! I installed a RUUD H/P at my friend's beach house and had this problem (RUUD UPPA 030 with UBHK VSM A/H). We have been adjusting the charge as was described.

Tried to get into 'NEWS' to read the article, but they will not let me in (do not subscribe).

If I remember correctly (it was a year and a half ago :) ) I did read the installation packet, but do not remember seeing anything about the duct being the size of the 'outlet' (I do remember bending the tabs up). What I do remember is wondering why the supply plenum needed to be 36" long (made it 30" to compromise).

Now if I am understanding what is being said here (?): If I cut the first 12" of the supply plenum and change it to the size of the output flange of the A/H, this will change the airflow characteristics and the charge issue will be resolved???

THX in advance for any help on this issue.

GA-HVAC-tech

[dash]

The ones we have reworked all improved air flow dramaticly,be sure and check the charge after the air flow is increased.

[selfemployed]

Keep in mind that there is 1 1/2" duct liner inside so the OD of duct is larger than the flanged outlet. http://hvac-talk.com/vbb/showthread.php?threadid=75076

[Edited by selfemployed on 10-07-2005 at 06:23 AM]

[warp1]

If the plenum is installed incorrectly, will the airflow issues show a high static pressure? I used a square-round transition on the ones I have installed. The square matches the discharge opening but obviously changes shape to the round part. One unit has lower than normal suction pressure, but static is well below .5. Any tips, sorry - dont have a flow hood yet :d

[warp1]

Dash? Anyone...still curious as I havent had any experience with this problem.

[spackard]

Originally posted by warp1
Dash? Anyone...still curious as I havent had any experience with this problem.

If you join a small circumference pipe to a large pipe without
a gradual transition you have a lot of turbulence inside the first few feet. Should make lots of noise, vibrate the walls of the duct, but move less air than a calm, gradual change of circumference.
You'll also get a venturi effect in the beginning of the mismatched duct and air/fumes outside the joint will be sucked in through any cracks in the joint.

[dash]

Originally posted by warp1
Dash? Anyone...still curious as I havent had any experience with this problem.


As I understand it ,when you don't bend the tabs up and provide the proper lentgth duct ,sized the same as the blower discharge,air flow and static will be lower then the specs.

The purpose of the staying the smaller size is to allow the conversion of velocity pressure to static pressure,so with out it the static will be low,but so will the air flow.

Now your square to round is likely better than a plenum the size of the cabinet,which is all we we from the Rheem Team around here.

[Edited by dash on 10-13-2005 at 05:45 PM]

[drcustom]

We are a RUUD dealer and whenever one of their A/H's go in we fabricate a simple 26ga. rectangular collar (L X W corresponding to the opening off the blower cabinet) that is 12" long. Each open end of the collar has a 1" X 4 side flange--one end for attaching to the unit, the other end's flanges provide rigidity for the collar.

1. Fold down the flanges off the blower cabinet (without this step, bizarre air flow characteristics frustrate you beyond belief).
2. Attach the collar to the blower cabinet around the blower opening--essentially this collar is the true plenum.
3. Encase this collar within a larger plenum, usually insulated and sized per man D, also flanged and attached to the blower cabinet. It's dimensions can be 2x, 3x larger. So long as the Manual is adhered to, airflow is now perfectly within limits. Larger take offs are now acheivable without an expensive transition, yet there is no diminishment in system performance--a home run.

I learned this from a former employer who would ship his ductwork out to be fabricated and its cost was about that of say, a 10" X 10" steel diffuser. Hope this helps.

[warp1]

Thanks guys, exactly the kind of info I was looking for. I guess I still need a flow hood or at least an anemometer to get decent airflow readings. I dont doubt the experience on here, so will start fabricating plenums before the square-rounds.

Thanks again