ESP's above .50

[dazataz]

Hi all,
I'm designing a small residential system and am looking at one manufacturers' Air Handler ESP Chart that doesn't have Temp Rise above .50 IWC but does have CFM values @ .6, .7 & .8 ESP. The charts are bare (no filters).
This system is in central Maine and I've done both been heat and cool loads per Manual J but will only design with heat as it will probably never have a/c added. It's simply not seen as a neccessity on average people's homes in this area ( :.
So, while designing a duct system using Manual D, I'd like to leave out the coil in the FR Worksheet & use the values for .5 ESP in the charts (which seems correct with the heat only and temp rise).
My confusion occurs if I want to design for the possibly future add-on (slim chance). If starting @ .5 ESP and deducting another .25 to account for coil, we're left with only .06 total ASP. (.50 less .03 supply grille, .03 return grille, .03 damper, .10 filter, & .25 coil).
Seems wrong to me. Sounds like the system would certainly work in COOLING mode with no issue, but what happens during heating IF a coil is added later.

[sneep]

It'll work fine. Sizing for cooling is how it's usually done. Sizing for heating would actually shrink your duct size.
Your figures are exactly the kind of thing we see.

[dazataz]

Thanks!
Hmmm, please allow me to clarify a little more, I am ONLY designing for heat (The cooling loads in this scenario can be neglected as the duct changes wouldn't be noticible.
BUT, it would be wrong to design for Ducts with TEL's around 300 ft with a ASP of .06 IWC allowing a miniature FR of .02 IWC. It certainly would make much bigger ducts. ( :
So, to bring my FR into the Cone of .06/.18 FR I want to ignore the .25 loss for the possible future addition of a coil. But at the same time feel confident that the AH can handle it for heating IF there was a Coil shoved in it's heating path.
For furthur info, the manufacturur selected (Goodman) doesn't list Temp Rises above .50 ESP, others, like York, go all the way to 1.0 but don't list Temp Rises with the ESP's.
I believe we're fine but would like clarification on the Fan Chart not addressing the higher ESP's and Temp Rise. Attached is the Goodman Chart.
I suspect it's just a matter of convention - York doesn't supply Rise per ESP in their Fan charts.
Thanks again!

[sneep]

Temperature rise isn't used to size ductwork. Ignore it. Whatever is stamped on your furnace is the maximum static you can use. The what if chart is just that. What if. It’s useful in air balancing.

Your coil shouldn't exceed 40% of your static. Yours does based on your highlighted furnace at .25. Most residential furnaces are .50 static.
To be clear. You can't exceed the static thats stamped on the furnace.

Nobody can squeeze you the answer you are looking for. It’s all math and it does have to add up for a system to work properly.

You can see about a higher static system and/or a different coil. The combo you have won’t do it. That furnace barely supplies the required airflow at 1201 CFM @.50.

[dazataz]

Thanks again,
I'm aware the rise isn't a factor - except it is when this particular chart doesn't list a rise for a higher ESP. A higher ESP solves the issue, doesn't it. Other Goodman VariableSpeed units actually say "do not operate in heating mode with ESP higher than .5". BTW, York's charts go all the way to 1.0 ESP with no mention of the .50 max for heating.
So, I've not understood the elusive answer yet ( : Please slap or shake me ( : I'd like to understand Goodman's logic or rule of thumb or rule of physics.
IF I allow for a Design Value (not measured) of .25 IWC loss for a coil that will never be installed, then I need to cover the following DESIGN values.
.25 Coil
.10 Filter
.03 Damper
.03 Supply Grill
.03 Return Grille
.44 IWC TOTAL loss.
This simply can't be done with a ESP of .50 - For one run with 148 CFM, I'd need a 12" dia duct (that has about a TEL of 320 ft) to obtain a FR of .02 IWC with a whooping velocity of 189 FPM. It's way off the FR chart "cone".
In reality, I only need to design this system for the Heat Loss and for a air handler without the Coil so my total loss is only .19 IWC leaving me with .31 ASP which is perfect for a 320 TEL = .10 FR.
To me, I'm following the ACCA guidlines and things appear to fall right into expected ranges.
So, the $64k question remains, why the problem when (IF) a coil is placed in a Goodman unit and there appears to be no problem in a York?

[sneep]

So, the $64k question remains, why the problem when (IF) a coil is placed in a Goodman unit and there appears to be no problem in a York?

Forget the other ESP’s are there.
It goes by what the equipment is rated at. What is stamped on the sticker.
You can use a higher static if it's stamped on the sticker. Or you can talk to the manufacturer and see what replacement blower/equipment they have to get you what you need.
If the furnace is rated at .5”WC than that is all the static you have to play with.
You cannot design to .8 regardless of what York’s chart shows.
Doesn’t matter what the paperwork says. It’s the sticker. Most residential furnaces are .5”WC

Lots of equipment gets thrown in and runs at less than 60% of what it's rated at.
Many people size their ductwork at .1 for everything they install, supply and return. Hart and Cooley recommends .06 & .08.
Some recommend less than that for good reason.
What you’re seeing is what gets ignored a lot in our trade. It’ll run but you’ll pay in reduced efficiency, higher bills and shortened life.
A system is considered good if it delivers 90% and above. Welcome to the dark side of the trade.

[dazataz]

The darker side :) Yes, I didn't mention, I owned a small Mechanical company that had to close due to the fallout of 9/11. One of my partners son's was the HVAC guy...long since gone. I do NOT relish (from an engineering viewpoint) the days of dealing with supply houses or manufacturers or their reps.
Unfortunately, I will not be calling a rep or manufacturer on such a trivial question...it will not get answered or explained in sufficient detail. From an engineer's eye, I'm going to design the York into it and know that it'll work based on published data.
I don't like rules of thumb, but they are good for confirmation. I'm sticking with the ACCA FR range of .06 to .18 IWC, specifically, I like the .10 that happens to be what everyone does.
Anyway, one last head-bang :rolleyes: --> the Goodman system would be fine for heat only - adding the coil puzzles me, I have a couple coworkers that have Goodmans, I'll go and check the working SP with a u-tube of the one that has the 90k btu version of this furnace with a 4t coil. It was a recent upgrade to a system from the 80's. I'll also check the design of just any random Runout and see what it's design loss is and if it relates to the observed SP. Just for fun ( :

So - what does the average general trade still do? In this design, I assume they'd still pull out a ductulator and go for .10 FR all-the-while disregarding the coil/filter/ and grilles.

I should forget the engineering side of it, right? :D

[sneep]

[QUOTE]Unfortunately, I will not be calling a rep or manufacturer on such a trivial question...it will not get answered or explained in sufficient detail. From an engineer's eye, I'm going to design the York into it and know that it'll work based on published data.
Won’t get you where you want to go. Using any data published or not that exceeds the design stamped on the equipment, is an instant fail. You’ve already read some of those warnings. Reread 8-3 in the J-manual. Engineer’s are great are screwing this up. Balance reports prove it.


I don't like rules of thumb, but they are good for confirmation. I'm sticking with the ACCA FR range of .06 to .18 IWC, specifically, I like the .10 that happens to be what everyone does.
They use it because they either don’t know better or don’t care about the performance of the equipment. Higher statics on paper allow them to use smaller duct to undercut on price. Doesn’t make it right and no reputable company or knowledgeable contractor advocates using .1.


Anyway, one last head-bang :rolleyes: --> the Goodman system would be fine for heat only - adding the coil puzzles me,
You’re adding resistance.


I have a couple coworkers that have Goodmans, I'll go and check the working SP with a u-tube of the one that has the 90k btu version of this furnace with a 4t coil. It was a recent upgrade to a system from the 80's. I'll also check the design of just any random Runout and see what it's design loss is and if it relates to the observed SP. Just for fun ( :
You will learn a ton doing that.

So - what does the average general trade still do? In this design, I assume they'd still pull out a ductulator and go for .10 FR all-the-while disregarding the coil/filter/ and grilles.
Of course. Thats why they are average and the systems they install don’t deliver what it’s rated at. However they are tons of contractors who actually can verify rated operation after installation.

I should forget the engineering side of it, right? :D
No. I’d temper it with some classes. ACCA’s EPIC classes, NCI etc. Plenty of reading on this subject.
http://contractingbusiness.com/enewsletters/cb_imp_69579/