Hey guys, my wife and I recently got a new system installed in our home and we got a few quotes and decided on a company that we deemed reputable. A guy came out and said we currently have a 4 ton unit and said we needed another 4 ton unit. I was not aware until after the install and researching symptoms that a manual J is needed for the dealer to install proper size. I think the guy just saw we had a 4 ton and put in a 4 ton. I now have a brand new Lennox system 15 seer 4 ton that "short cycles" it comes on and runs for 10 minutes or even under 10 minutes, then turns off for around 10 minutes and so on. Now my humidity is 52-55% and the house feels clammy whenever the AC turns off. Is there anything that can be done? Should I insist on the dealer running a manual J now or is it too late? Am I screwed? If I keep on them will they take out this unit that is too big and put in the proper size? Something is wrong and I am not happy. Any advice please help. I feel it is the contractors job to install the proper sized unit, am I wrong? I am in San Antonio, TX

 

The "we will install same size as the old one" just doesn't get it. If this is a reputable company they should resolve this problem. Your absolutely right the contactor is responsible to install the proper size unit.

 

My old unit would keep the humidity at 45-48% all the time and it always felt nice and cool in the house. This unit just can't remove enough humidity because it only runs for 10 minutes. Is there anything I need to know to help my case? I had them come out today and check it out, they said the vent was blowing on the t-stat causing it to short cycle. I closed the vents and no change at all. Also said he adjusted subcool from 3* to 6*. Neither of these worked to extend the cycle time or lower the humidity. It's muggy instantly after the unit turns off, and while it's on its freezing!

 

I would start with a detailed letter to the company owner asking him or her to make it right. Send it by certified mail with a return receipt. And while I have very little faith in the Better Business Bureau I would send them a copy of the letter.

Do NOT make any accusations of impropriety in the letter, just state the facts, that the new system does not remove the humidity, it makes it too cold and that it short cycles. Do not try to tell the owner what is needed, just that you are not the least bit satisfied with the work done. At this point I doubt that you will get any satisfaction but you have to at least give the company the chance to make it right.

If nothing positive has happened after a week I would contact an attorney and also any consumer protection agency in your area. I would also consider the consumer affairs reporter at your local television station if they have one.

There is no excuse for what has happened.

 

Most homeowners demand oversize units from the residential contractors. A properly sized system will run 100% of the time at its top temp range which skeers consumers. If you have a split system most likely they can change the condenser to a smaller size and reuse the air handler (worst case change the air handler coil) If in fact that is your problem.You might have a issue with the tstat? I have seen some crazy things over the years. Once I had a unit that was short cycling because the tstat was mounted on a wall where an interior duct had separated and was leaking cold air. The cold air was pressurizing the wall cavity and blasting it out through tstat wire hole behind the tstat body causing it to cool almost instantly when the unit kicked on.............

 

I have a 3 ton handler, can I install a 3.5 ton outside unti to it. My old unit stopped working and was given the 3.5 ton unit

 

What is the difference between the input-air temperature and the return-air temperature, may be your delta-T is too high. Sounds to me, your new AC system works very well (too well), I wish I had one like that. Think twice before you go through the trouble to reinstall a smaller unit. may be your old system did not perform well and this new one is much more efficient. If I were the contractor, I may just do the same, 4T for 4T, make sense to me and I (most people too) do that all the time. I never trust Manual J anyway, too many variables, never got it right. find out what is the Delta-T now, if it is too high, just ask them to adjust it down, (for example from 20 to 15, or try to match your old system's delta-T) you will be OK, If I were you, I keep this unit, a few years later, you may need its full power. (the only question I have is why the stop time is only 10 minutes, should be at least 20-30 minutes unless your house is not well insulated, or your T-stat temp range is not set correctly)

 

Excellent advice, - Furd.
Get others to help you do a free load-calc; which that contractor should have performed!
HVAC Load Calculation - Maunualj - Whole House Loadcalc

 

Dan2696, Welcome to the best DIY forum on the Internet. Next time please start a new thread because it is too confusing to answer two different people.

The answer to your question is no. The evaporator (inside coil) sometimes may be oversized to a small degree but never the condenser (outside) unit.