Duct Size to small?

[Budreiser]

I am currently in the process of having a new heat pump installed in our home. So far we have had two quotes but with different opinion from each contractor.
The Trane dealer is recommending the x15i 15 seer 2 ton.

The Bryane dealer is saying I need a 2.5 ton (215b 2.5 ton)

Now I questioned both about the ton sizing and got two seperate answers.

Trane guy told me the duct work was too small for a bigger unit and at 1700 sq ft of my home the 2 ton should work just fine.

The Bryant guy told me the duct work should be fine because they can adjust the air flow of the system to work with our existing ducts.

We are so confused right now. Can anyone shed some light on what we actually need or don't need?
Thanks!

[REP]

The right thing to do is of course do a manuel "J" followed by a manuel "D" .Niether of your contractors want to do even those to get your money.Well you know I've been doing this for a million years so I know.Or all your neoghbors have this size and they don't complain,or a bunch of other excuses for not doing due diligence for your valuble job.
Why is that?its because when they are done they don't have to live in your house for 20 years nor will they have to pay the utility bills.
Your comfort and your finances are too important.Make them due the proper amount of work to get your job.
Now I'm guessing but You will probably need to make adjustments to your duct work both supply and return (this would be in your manuel "D" report).If you do then it will be the best money you spend on your comfort and pocketbook.
Then I would advise you to get a 4" media filter to protect your new equipment.The 1" filters are just not good enough.

[Budreiser]

Both contractors did some testing/measuring. I don't know what exactly as I was not home at the time. But my son who was, said they were taking measurements and inspecting the duct work. He said they even had the blower run and took some measurements.
The Trane dealer installed our current system 15 years ago, a trane heat pump 2 ton. Now if it's any consideration, the current system would run non stop on really cold days and non stop on really hot days, here in Ohio. But it did/does have a few issues itself.

[HVACTechNC]

Like REP said, there really is no way for one of us over the internet to be able to give you any real answers. A manual J will tell you the tonnage of the system for your home and the manual D will answer your ductwork questions. You need to get as much information from the contractors as possible, and if they are hesitant to provide it then call someone else until you find someone who is willing to answer your questions.

Now, I'm not there, so this is pretty much a worthless opinion, but a 2 ton system on 1700 square feet sounds a bit undersized to me, but hey, thats what Manual J is for.... It accounts for insulation, window quality, building orientation and a bunch of other factors that directly apply to the load for the house.

[udarrell]

Where do you live?

Is the duct system sized okay for the heating mode?

The 2.5-Ton's airflow can be reduced to 350-CFM per/ton of cooling or 875-CFM. The 2-Ton can be dropped to 700-CFM.

That will work well if you need a colder coil & longer runtimes to handle humidity problems.

It may or may not work as well in the heat-pump mode.
Do you also have N-Gas or oil heat?

Also, follow the advice of REP & HVACTechNC..

[Budreiser]

Ok just got off the phone with the Bryant dealer, again. He has talked with the manufacturer and his service tech. According to thier measurements and whatnot, they have suggested a 3 ton system, 226a. He told me the duct work is right at the limit for the air flow. He said only when the unit is in stage 3 air flow would there be little if any trouble. he also said because of the bigger unit it shouldn't go into the third stage except on extreme days.

[Budreiser]

We are in ohio, all electric home/heat pump. We burn mostly wood in the winter, so heating isn't as important as cooling. Right now we are compairing the XL15i Trane 2 ton with the Bryant 226a 3 ton.

[HVACTechNC]

I am either exposing my ignorance, or something... Stage 3?

[RyanHughes]

There is no third stage on that unit -- it's a two stage unloading scroll compressor, meaning 75-80% capacity on low stage (~2.25 tons). What size was the previous system? If it was a 2 ton, there is a good chance that ductwork modifications (adding return or supply) will be required to achieve proper capacity and efficiency. Many systems have marginally sized ductwork as it is. It doesn't sound like they're certain whether or not the airflow will be an issue. It could be oversized in low stage as well. They need to determine quantitatively that your ductwork is appropriately sized and that a 3 ton unit is required for the home. The idea of a 2-stage system is that it will run long cycles in low stage to remove humidity from the space. A 2 ton, (single or 2 stage) unit is what should be installed if the heat gain requires a 2 ton system. A load calculation must be performed to determine sizing.

[Budreiser]

Sorry the third stage was my bad, too much info going through my head at the moment....Should my contractors of done a load test, or is it something I need to pay for to have done?

[RyanHughes]

Is this a new install or a replacement of existing equipment?

[HVACTechNC]

Sorry the third stage was my bad, too much info going through my head at the moment....Should my contractors of done a load test, or is it something I need to pay for to have done?

A Manual J load calculation should be the starting point for ANY residential system installation or change-out. It should be done free of charge by any contractor who wants the OPPURTUNITY to EARN your business... If they give you the slightest hard time about it or act like they are doing you favors to go over the load calculations then kick 'em to the curb and call someone else. An honest and reputable HVAC contractor will have no problem answering your questions by doing a load calc and duct diagram and then going over the findings with you.

Adam

[Budreiser]

More phone calls, more headaches.....Apparently they both did a load calculation. Trane said his numbers put me right at the limit for the 2 ton. But a 2.5 ton would be too much for the ducts. Bryant said he wouldn't go any less than the 2.5 because he feels the 2 is too small, and he thinks a 3 ton will be ok with the current duct work, even though he said it could have some resistence on high blower speed, and is putting in an extra air intake in the basement to help it.

[stonewallred]

Call a different company and ask for them to send a person out to inspect and do the load calculation. And pay them for doing so. Odds are they will also offer a bid for making your home comfortable, and take in consideration what you paid for the load calculation.

Cooling is cooling and it is all physics, except for spin and media hype.
There are good brands and there are bad brands (and don't ask me which is which), but the amount of cooling is not based on name brands but the way the refrigeration cycle works.

Good installation and design will make a system work well, while poor design won't work.

[btuhack]

A Manual J load calculation should be the starting point for ANY residential system installation or change-out. It should be done free of charge by any contractor who wants the OPPURTUNITY to EARN your business... If they give you the slightest hard time about it or act like they are doing you favors to go over the load calculations then kick 'em to the curb and call someone else. An honest and reputable HVAC contractor will have no problem answering your questions by doing a load calc and duct diagram and then going over the findings with you.

Adam

Hmmm,
An honest and reputable contractor who naively drives around doing time consuming calculations prior to compensation could make the craigslist contractors jobs very easy, just sayin'.

I'm all for helping and doing things correctly, just not a social worker.

If the homeowner really wants the all details worked out and documented as per J & D prior to deposit, "VISA is everywhere you want to be".

[lynn comstock]

.... The Trane dealer installed our current system 15 years ago, a trane heat pump 2 ton. Now if it's any consideration, the current system would run non stop on really cold days and non stop on really hot days, here in Ohio. That is ok. See "Bigger is not Better" http://www.proctoreng.com/articles/bigger.html But it did/does have a few issues itself. What issues? Also see: "Right sized Air Conditioners" http://www.energystar.gov/ia/home_improvement/home_sealing/RightSized_AirCondFS_2005.pdf

Going from a 2 ton to 3 ton sounds like a very bad idea.

[jpsmith1cm]

Tommy1010,

The rules have changed a bit in the AOP.


You can find the rules for posting and qualifications here (http://hvac-talk.com/vbb/showthread.php?t=957002).

[udarrell]

In Ohio, in the general areas of Columbus, Cleveland, & Cincinnati, a 2-Ton unit with weatherization work, could usually be made to work okay. Design humidity runs between 44%; & 46% for the Cleveland area 88F-dry bulb 72F-wet bulb, 2.5% Design.

Since they are concerned about the duct system's capacity, it is best to do the Retro-work to make the home comply with the duct system & the equipment capacities.

There again, it depends on the quality of the evaluations & the work performed to achieve a 2-Ton system that will Deliver close to its Capacity Ratings... otherwise it may fall short...

[tinknocker service tech]

i am at a loss on this
you have a 2 ton system and it has been working fine except maybe on the extreeme days with arent that many. The original istaller seems to have sized it a little tight but exceptable. Maybe an increase by half ton is ok to make up for the extream days and the ducts may as well be fine since it would be a increase of about 200 cfms and possible static pressure increase

to go to a three ton IMO will possibley cause humidity issues on not so hot days

if a load calc was in fact done then why such a differance in size
i tend to think the guy saying 2 to 2.5 ton is going from a load calc and also working in you complaints the other guy is just winging it and covering his butt

[genduct]

Let me just put an idea out there: Perhaps when you choose the contract, you might specify a clause in there requiring the static pressure to be within range for the blower's ratings. Many people speak of 0.5 (units inch water column) as a desirable number -- my old furnace clearly stated that as its maximum. After all the 3-ton guy does propose to add to the duct work. To say static pressure is "OK" is an imprecise goal, to say "under 0.6" is something that can be proven.

Would that be a deal killer with any good contractor?

Best of luck -- Pstu

Thing is that sizing the duct to work within the limits of the fan is what all contractors are suppose to know how to, AND DO! It would get complicated since would you spec at what speed setting you would need for a conventional unit and following that thought you wouldn't even know with a smart ECM motor how much energy you are wasting from a chocked duct system.

An interesting thought though that should be taken care of in the published ACCA Quality Standards

[genduct]

Seems to me the original installer knows he sized it for 2T, it works, and he is telling you that, since he thinks you are making a mistake considering the next size.
Another 200 CFMs for the bigger unit is not going to be noticed if you are happy with your current install

[genduct]

The word TURKEY comes to mind. Did this guy install even one pipe or duct hanger or strap in the whole job?
And this job was inspected?