Need some advice on HVAC air handler options

giantsean

Hi All,

I'll bore you with the history of why I'm asking, but suffice to say I fell victim to an HVAC setup gone bad (at least on the heating side - you can read about the saga in my old posts if you like). I'm posting this on the mail wall as it spans a few different areas.

So basically, I have a Trane TAM7 w/ a 2 ton evap coil and a hydro coil. Cooling works ok, heating not so much. Some techs have told me I need more CFM's to get air where it needs to go (it's at one end of the house and needs to get to the other), AND that a bigger heating coil wouldn't hurt either. I am trying to minimize costs since it's a brand new barely over a year old system, so replacing only what i need to is important.

That said, from what I understand the TAM7 is not particularly modular. If I want a bigger heat coil / more CFM's I need to upgrade, which means I need to get a bigger condenser as well. If there is indeed NO factory-friendly way to upgrade the wind or the heat I'm willing to try a new AH, so long as I can get a big variable fan, a big heat coil, and a 2-ton evap coil that will work with my existing 2-ton condenser. I'm pretty much open to any brand/combo as long as it's not total crap.

Sincere thanks for any advice or recommendations!

Gordy

If this setup is a poor performer from the start where is the original installer? 1 year old, and has performance problems since installation?

Mike

That a/h has more bells and whistles, than Carter has liver pills. IF not setup properly you'll get poor proformence from it. I would have a Trane dealer verify the system settings are correct . Then verify that the btus are correct. Then check the duct work, It does look rather large. What's the possibility , of moving the a/h and changing some of the ducts? Just a thought.

,

giantsean

@ Gordy. They are waiting for their last payment (which they'll be doing for a long time). I've already spent more than I owe them fixing their issues - not enough heat was the tip of the iceberg. Truth be told it CAN keep up when the weather is not too cold, but struggles from around 15F. I live in CT and we had a mild winter but the couple of very cold days we did have it struggled mightily.

@ Mike, I'm no designer but I'm pretty handy. I have tried different DIP settings to get the fan working the way I want it, and at the end of the day ironically they already had set it for the fastest that it can go. My last bullet is swapping the supply and return lines (which they plumbed backwards) which supposedly makes a difference. I also thought of placing the A/H more downstream so that it splits the difference. The 2-zone downstairs makes it a bit of a PITA but it's definitely possible. They used quite a lot of flex as well which would benefit from being tuned a bit. Still, having to grasp for every last BTU has gotten old enough that I'd feel better if I had an overpowered setup than a just-on-the-line.

njtommy

With almost 900cfm available depending on static pressure you should be able to heat your house.
@giantsean how many sq ft is the first floor.
flex duct kills air flow.

giantsean

Hey Tommy you probably remember my weird case (the hack installers and the swapped supply/return on the coil). Downstairs is about 1200sf and I think part of the problem is the distance the air has to move (the A/H is all the way at one end of the house in basement) There is a lot of flex which is certainly not helping matters.

The frustrating thing is that by the numbers this thing should work fine. It's just a perfect storm of a dozen little things all making it suck.

njtommy

I do remember all problems your facing. You said the first floor has zone dampers correct? So two zones?
What's size is the main trunk lines for those two zones?
If the main trunk lines are sized wrong you will not be able to deliver the cfm you need to heat or cool your house.

pecmsg

What does your building dept have to say about this situation?

giantsean

@ pecmsg...They have only done a half-**** inspection since these clowns also installed a condenser directly under the power meter, causing me to fail until I remedy it.
@ njtommy - yes correct two zones. I have not measured the trunk precisely but figure it's about 12x18 both supply and return.

For giggles I fired it up tonight and tried reading the closest register to see how hot it got on a spring-ish day. Was about 113F tops inside the boot after warming up (maybe like 105ish right at floor level. Ambient temp in the house was around 72 and the cellar where the ducts live was probably around 65ish. again water set at 180F with the circulator set to high (3 speeds)

Interestingly I was checking the delta T while it was warming up, and the gap narrowed as it heated up. At 150 it was sending back around 120... but at 177-180 it was sending back 160 pretty consistently. I am starting to wonder whether the supply/return orientation plumbing is truly affecting things.

One more note that I counted all the elbows for the supply.... from the circ it is 3/4" copper with 3 elbows, then 3/4 PEX with 3 elbows, back to copper and 2 more elbows where it hits the coil.

njtommy

Ok so a few things that going on here.
1. Duct design I will double check, but with both zones calling that would say give you 400cfm to each main duct with .01 static pressure which is very low. Should be up around .5ish is rule of thumb. We're lacking pressure in the duct to be able to move the air out to heat or cool the space properly. Even with only one zone calling you go to roughly .04" of static.

2. On top of that if you have crappy flex duct that's very long, pinched or restricted in any it will hurt your air flow.

How many supply registers on on each zones?

3. In order to get your maximum btu out put of your cool you would need to run 9gpm of water though the coil. 3/4 pex is really only good for 4-5gpm. I would recommend up sizing to 1" copper or pex piping.

giantsean

Thanks. Turns out I overstated the dimensions quite a bit... probably due to the insulation. They are more like 8.5" x 14" so hopefully that puts me closer to where I want to be. The flex however is definitely a problem... add the fact that some of the boots are poorly sized for the flex size and kind of mashed on there (think 7" flex on a 9" boot.

and yeah I do plan to address the piping when I drain it to reverse it, at least try to get the PEX part done and eliminate elbows where I can. the coil itself is 3/4 in and out which I'm not sure is a restriction in and of itself.

How about the Delta T being only like 15-20 degrees? Should it be higher?

njtommy

Port size or connection size of the coil does t really matter. If Trane says it will flow 9 gpms I believe it will.

A 15-20 delta on the system is normal it would be great to get a bigger split to keep you in the condensing range of your combi unit.

giantsean

Thanks again Tommy. How about the smaller duct size... am I more in the ballpark for that load as far as static pressure? Would hate to have to redo all the metal.. flex I can handle for sure.

njtommy

8x14 duct
If one zone calls its roughly .2 cfm at 850cfm.

Both zones call figureing 400-425 cfm to each zone it drops to .05-.06 static

njtommy

What condensing units do you have?

giantsean

They are AmStan - either the top of the line Silver or bottom of the line Gold (they were in the middle of redoing the lineup/naming). I think they are 16 or 17 seer.

Is it possible to use a 2 ton condenser with a 2.5 or 3 ton air handler evaporator/AH? I figured not but what do I know :P

njtommy

Yes it is possible. To run a 3 ton Ahu with a 2 ton condenser. New Ahu and hot water coil would not be cheap.

giantsean

True... but it would be a gen-u-ine bargain compared to the funeral expenses incurred after my wife kills me next winter. Then again I wouldn't be worrying about the cost...hmmmm....

No but seriously, I ask because I was afraid that in the worst case I would have to replace both the AHU and the condenser together... which would truly suck. I wish there was a way to just bump the fan in the AHU but I guess I'll work on making it make heat first. Thanks as always for your great advice Tommy!

giantsean

So today I'm doing some research on using a smaller condenser w/ a larger AH coil. While I am doing that I take another look at the manual for the TAM7/AAM7.

http://tranepennohio.com/secure/techdocs/TAM7-SF-2E-EN.pdf

I noticed from the fan performance settings that the pairing of a 2 ton condenser with a larger (2.5 - 3 ton) AH yields roughly the same CFM ranges. "Dafuq?" thinks I. Then it dawns on me.

Referring to pages 10-12, where it specifies DIP switch settings and also specs per each setting. I have the S1 DIPs set up for a 2 ton multiplier - since it seemed like the correct choice, because it is a 2 ton outdoor unit. This got me thinking... how the hell would the AH even know what is attached to it? If I set it as if it was a 3 ton unit, even though it's not, does that mean the fan will put out 1200 CFM?

I have not tested it yet... but it would appear I may be onto something. The downside is that (with my research in mind) that this is an all or nothing setting. It may well bump up the fan speed thinking it has a 3 ton condenser attached, but it will be blowing too much air for a 2 ton coil. Now, I'm not sure the overall effect but I am guessing it will cool faster, cycle shorter, and dehumidify less. Still, even if I have to reset DIP's every heating season, it's still much better (read: cheaper) than swapping out an entire AH.

Anyone know of an easy way to confirm whether a fan is blowing harder without an anemometer? :P

GW

Giant, I may have missed something but what was your past hvac system and how well did that work?

This is a new duct system?

It's very common to have a larger ahu compared to outdoor unit. Are you familiar with the AHRI directory? You can punch in your outdoor unit and it will give you all of the matching indoor units.

I am more curious about the infrastructure, not the equipment.

Gary

giantsean

Hi Gary.. the system is all new, as part of a large renovation of an existing home. So yes, quality of design or install notwithstanding, all the ducts are brand new, along with the equipment itself.

GW

Okay good, makes sense, so you're saying it is okay in cooling but it is not OK in Heating? If I were there I would be looking at heat loss issues in that particular room.

njtommy

Ok see here is the balancing act more CFM is equal to more btus per hour. Which is good news in your case, but you already run your boiler at 180f supply doesn't give you much room to play with water temps except to go lower. Lower is better with your high efficiency combi unit.
Bad news more cfm equals lower supply air temp, but if you can stay above 100-105 supply you should be fine to heat your home.
If you can get your fan speed and and water temps set right matching a good discharge air temp you maybe able to hook your ODR back up.

giantsean

@ Gary...yes that's right... cooling is sufficient, but being an old brick house the challenge has always been heating. I have done windows and upgraded insulation and air-sealed where I could, but it is what it is. I fear at some point incremental tweak improvements will stop paying off and a brute force approach may be needed.

I did look up the AHRI number for that condenser and it just told me that the coil is designed for 800 CFM. Not sure if blowing more over it is worse, or like I said I can just

@ Tommy... Thanks I will play around with it... as well as fix the backwards supply/return and check the coil for buildup/dust. If time allows I will see if I can address the PEX supply (or at least change over to 1" pex w/ less els.

The reason I was running 180 was to try to pump as much heat as possible through the coil. However we know it is only sending back 160-165 degrees hopefully there is some room even with higher CFM's... of this I have no idea.

One of the guys who advises me on the side (but doesn't live close) said worst case I can just change over the 1/F unit to a gas furnace and leave the attic (which works ok) a hydro system. I realized later the side benefit would be that this unit could keep heating during a DHW call (this boiler can do one or the other)

njtommy

I will take hydro air over a regular furnace any day of the week. I really like the lower supply air temps 105ish better. Doesn't dry out the air as bad and keeps long even run times. Which makes the house feel more comfortable.

GW

Raising cfm won't increase BTU. If BTU is what you're looking for, you need hotter water.

Hotter water with same cfm= more BTU
More cfm with same boiler temps= no gain
Hotter water with more cfm= much more BTU
Lower water temp = less BTU
Hotter water, more cfm, faster pump speed, much much more BTU.

What's your house like, two floors? And where is the problematic room? Seems like you need someone that undestands how houses lose their heat.

Beat case is lower your heat loss, not add more heat.

njtommy

Gary I'm going to have to disagree a bit on this one.
The Manufactures of hot water coils read and show differently.

Yes All three are key components and need to be matches and balanced together.

http://www.aquecoil.com/specs/hhuspecs/files/AQUECOIL_HHU_RH-Series.pdf

giantsean

@ Gary the problem I'm having is multi-layered.

At the heart of it, I am not able to get the hot air the full distance to the farthest duct and gets enough airflow to the room it is in. If in simplest terms more CFM / same temp = same heat, but it gets there, then that's wonderful.

The house is a 1951 brick on cinder block cape, 2 floors / 3 zone (1 up 2 down), 2 air handlers w/ hydro coils (50K down, 70K up), navien CH240 boiler. All ductwork new in 2015 as part of a larger reno. It works ok when it's above 20 degrees out, but below that and it can't keep up on the 1st floor (AH is in the basement). Metal/flex is all R8 insulated (I think, worst case R6). On a day like today (80 degrees in CT) it can crank out 110-115 at the closest duct all day. When temps drop, it barely cracks 80. My feeling is that by the numbers, 50K is enough BTU, but there are several contributing factors working against me:

- The cellar is a walk out and very leaky.. it gets cold down there
- The 1/F floor joists are not insulated, though I am not sure how much that matters to be honest
- There is an open chimney chase which sucks heat out of the basement to the attic
- The hydro coil (Trane/AS BAYWVxxxx) is plumbed backwards, which I've been told makes a difference in a counterflow coil
- The AH has a max CFM (when dialed in correctly) of 800-850 CFM. It is situated in the basement on one extreme end of the house and needs to feed 2 zones, one being at the other end
- The coil supply is half made of 3/4" PEX with a lot of 90's. That said, I am getting 180 degree water to the coil and 160-165 back
- The house is old and built in the days when building science was, if not non-existent, at least in it's infancy. I have replaced windows in the 1st floor and air sealed considerably which has certainly helped.
- One room on the 1st floor is over a crawlspace which exits into an unfinished garage, creating a wind tunnel effect. It is insulated and somewhat air sealed (this part is new construction) but on a cold day that floor is COLD.

All that, and the fact that it was pretty much assembled by hacks who have little knowledge of the Trane/AS brand, and made a multitude of stupid mistakes and general hackery (using the cheapest stuff that works)

Phew

BobC

Insulating the basement ceiling would help but it's important to seal and insulate the band joist that runs around the cellar. That is where you will get the worst air infiltration in really cold weather.

Then seal up that open chase with some metal sheeting and fire caulk.

Bob

GW

Ok so more cfm will help a tiny bit.

But I still think lowering heat loss is better than pumping out more BTU.

Yes, that wind tunnel is getting you, just wind washing the floor above it.

I bet of you can get the basement under control, you'll be in much better shape next winter

How about ice dams? Yes , no?

Did anyone attempt to balance the duct system?

This is a cape?

I don't see how your sysyem can be dropping 30-35 degrees when it's cold out. Does your rerun ducts suck? I mean do they suck in that nasty cold air you're describing?

Gary

njtommy

@GW yes lower heat loss will help his problems.
I believe all his duct work is wrap/ insulated from the previous posts and pictures. All these problems he has talked about have been on going for several winters now.

GW

Tommy yes I guess I missed all the previous posts.

I'm no engineer but I don't see how the coil being backwards can make a big difference. Just think of all the calls the manufacturer would get if they 'didn't' label an 'in and out'---it would be pandemonium.

Seems like the return is pulling some cold basement air.

15-20 split on the coil water temp is fine, sure you'll get some more BTU if you tighten than temp drop. I'd focus more on the air infiltration and possible leaky ducts on the return. Once your leaky ducts and cold basement issues are corrected I bet the temp drop will steady out at 15 all winter.

njtommy

Gary the supply and return question comes up every single time. I'm not sure if it would change anything and neither is anyone else. It's ran in 3/4 pex pipe from the combi boiler to the Ahu coil. So it would be very easy and take very little amount of time to swap lines.

Looking at the charts of his coil from Trane to get the most BTUS out of it he needs 9gpm and 800 plus CFM. This is only 1 part of the equation tho. Like you said sealing up ducts and insulating the basement. Will help.

giantsean

Thanks guys and sorry for the pause. Glad this thread has built a following though

@ Gary - yes it's a cape, ice damming has never really been a problem for whatever reason. The heat (also hydro) works ok upstairs and the attic (gable vented) tends to hold it's temps well. The soffits have those styrofoam vents as part of the reno but I need to get some vented soffit material to make it all work.

Anyway as to sucking... I never really thought about it until now but it is likely it's pulling quite a bit of cold air from the cellar (and/or air is infiltrating) as nobody ever bothered to foam around the register boots. I'm sure that will help a bit.

Duct balancing... maybe? These guys did SOME things right but I got the impression that design was not their strong suit. At least I got returns in all rooms etc. To be fair some things weren't their fault like the geography of the basement and overall cobbled construction of the house.

The band/rim joists are interesting as it's a cinder block house. I have been sealing the gaps on the sill where the joist ends meet the wall, the problem is that the house was framed with a small gap between the block and the joist. I will probably need to drill some holes in it to properly deal with it.

As for the coil, the best explanation I have received is that because it's a counter-flow coil it is designed for the hottest water to enter at the top and exit at the bottom. Now, being it's a two layer coil it may truly make zero difference, but the manual clearly states piping it a certain way. We shall see (I know many are interested :P)

I really like the hydro too, but I'm not sure this house will ever be tight enough to make it ideal. Right now I'm torn between just going for it w/ a larger kick-**** heating unit that is grossly oversized, or seeing how we do next winter so that I can gauge it properly. The curveball has been that the house has never been "done" enough to really tell if the performance is what is will always be, or that we'll see some improvement.

Thanks again and will keep at it!

giantsean

Here is the not-so-ancient history thread
http://forum.heatinghelp.com/discussion/157442/more-winter-more-problems#latest

SWEI

giantsean said:

I am not able to get the hot air the full distance to the farthest duct and gets enough airflow to the room it is in.

What you described above sounds like a ductwork issue.

giantsean

So for those curious (this means you Tom :P) I have FINALLY swapped the supply/return on the coil to the right direction, and made a couple of other changes, including swapping out several of the PEX elbows for bends or sharkbite elbows to maximize flow as much as I could (using what I had available). I also needed to swap out the power circuit from Romex to MC to pass inspection so took care of that while I had it all apart (thinking even if the temp did not change, it wouldn't be a total waste of time).

As far as results, I was able to get the temp up several degrees both at 120 but especially at 180. A small probe hole drilled in the plenum helped immensely, and as it turns out the unit appears more or less to spec. I couldn't get the whole coil unit out as the AC lineset is in the way but the half I could clean did not seem overly dusty. Best news is that the closest register temp jumped from 113 to over 120. Now whether this was due to me waiting longer for it to heat up or what, or the changes actually helped is the question, but either way it's right now, and I'll take it

To Gary's earlier question about my returns sucking, while mucking around I noticed many large gaps around the corners of the return duct where it meets the handler, that apparently nobody ever sealed (see pics). I assume all four corners have this problem, and during winter time these holes would be pulling in cold air from the floor area of the unheated basement. That can't be good...

GW

very good sounds like you're making progress! Just a quick note though, your numbers won't be the same as they are in the winter months, so you may be able to see a glimpse but not a true comparison.

Yes, keep hunting down those gaps!!

SWEI

Plug those holes for sure. Insulating the pipes (and the return ducts where they are in unconditioned space) should also help.

njtommy

Awesome news. Hope to hear even more good news in the colder months.

giantsean

I hope to have some good news to give