Your furnace is grossly over sized. It sounds like your furnace contractor installed a bigger furnace then what previously existed and then cut a hole in the return in order to compensate for the insufficient air flow.

Your duct work is probably too small to handle a 100K BTU furnace causing it to overheat and shut down.

Is the HVAC contractor licensed? What is his response to your complaints?

Thanks for your reply mike. i told him and he didnt give me a good reason but he said he was going to come back to fix it so i got my house contractor involved and she will bring him to fix it up but can that be possible to do? also what can i do in regards to the oversized unit? would it cause me problems ? or would it blow out my condenser?this unit is like 7 months old prob and i know he didnt do a good job and we had words with him and he said he was going to fix it up. also i have little water drops dripping inside the unit prob from condensation which is prob due to pressure switch issue. any suggestions would be helpful. i will post pics up when i get home today. based on the models i gave would i have any issues with AC in the summer ?

sorry yea hes a licensed contractor, he does alot of commerical hvac to. i think with my job he took few shortcuts.

What thermostat did this contractor install?

You should not have a problem with the AC assuming it has been set up correctly.

You should have a drain connected to the furnace and the coil to collect the condensation. You should not have any water dripping inside the unit and is unrelated to the pressure switch.

currently i have a regular thermostat, i am aware that i need a 2 stage one, which the guy said he is going to be bringing. please see pic 1

pic 2 of the hole on side of return air vent.

pic 3- return air- i think its 2 small. what should the size be.

duct work pic

i just noticed some ducts are 8 inches and some are like 10. does that make a difference for the 100k btu.

It looks like this furnace is installed in an uninsulated attic. What is your location? The condensate line has no protection from freezing.

I am sorry to say this but your contractor is a hack. The hole he cut for the return is allowing unconditioned air into the furnace. In addition all the debris of the attic will enter the furnace and go through the duct work. This is unacceptable. Is he going to fix this?

Thanks Mike, i am located in NYC. "The condensate line has no protection from freezing." what do you mean by that. he said he would come back and fix the issues and install a new humidifier and thermo but i would have to pay him 1k, which im soo hesitant to do, but i feel like going with someone else who will do the job right and give me the peace of mind. i dont want the heating to mess up in another month or year. also the duct work is that fine or do i need to change that as well ? i know the return air issue has to be fixed up and i need another extension for the plenum which he prob wont do.

thanks

The attic temperature could fall below 32 degrees which would cause the condensate line to freeze. The furnace will shut down and you may get a water coming through your ceiling.

The return duct work needs to be fixed. It looks like your filter is installed at the return intake. I can't tell the size but it looks too small.

What was the efficiency rating and size of the original furnace?

Your issues have been going on for 7 months. I have no confidence in this contractor. I recommend you either get him to remove the furnace and get your money back or hire someone else to try to salvage the installation.

this is a complete new install, i did an extension upstairs so i put a new unit upstairs since the one i had downstairs wouldnt be able to support the whole house so i have 2 diff units. so i wonder if the ducts the guy ran from pendlum to the rooms are sized right, they are 8 inch and 2 10 inches one. what can happen if i have an oversized unit? would it still function fine ? yea im going to have to get another guy to clean it up completely.

If you install a 2-stage thermostat, what will probably happen is the furnace will operate in the low stage most of the time. You currently don't have a 2-stage thermostat. The 2 stages are probably being controlled by the furnace. I assume the furnace starts in the low stage and then goes into the high stage after some set time.

You paid for a big 2-stage furnace which you will use mostly as a small one stage unit.

The reason your air is dry is because of the big hole in the furnace return. Cold dry air is entering the house. Adding a humidifier is not the solution.

Is the Carrier AC also new? Your contractor recommended installing a Luxaire furnace and an Carrier condenser?

well he brought some cheap one and i had a luxaire downstairs so i told him to get a luxaire one dual stage, thinking he would bring the right btu one but i realized it after when another hvac tech told me its 100k btu. yea he brought the carrier ac condenser. is there an issue with 2 diff brands ? would the ac condenser outside blow bec its 3 ton and the furnance is 4 ton ?

Ask neighbors and friends who they recommend to get someone in there that knows what they are doing. There are so many things wrong with that install that I wouldn't know where to start. I'm guessing that no permit was pulled for this. If the install manual is with the furnace read through the drainage part. I bet it says something about a trap for the condensate. The rest just has me shaking my head.

The furnace and condenser are not a match. It will work but you don't know what efficiency the AC will have.

The AC is also over sized. I estimate 1.5 tons would have been adequate.

Thank you all for your help. The dumb ass contractor didnt bother to prob read the manual its sucks how ppl get cheated. tinmantu, mike can you please list the things that are wrong so i know exactly what to expect when another tech comes and fixes the job so im more prepared.
appreciate it.

Here is my short list of things that I see wrong:

- no heat tape wrap on condensate line
- no condensate trap and clean out
- no condensate overflow switch
- condensate line is not pitched properly
- PVC exhaust pipe going up through roof (might be OK)
- PVC intake pipe does not go to the exterior
- line set missing insulation
- hole in return in take
- return supply too small
- return filter too small (prefer 4 inch media filter)
- where does condensate drain terminate?

Mike pretty much nailed it on the obvious. I'd also consider a larger secondary drain pan that goes underneath the furnace as it also makes water. I looked at a very limited install manual and it warns not to have an outside trap on that model.

Couldn't find the specs for venting, but I would think that 2" pvc that appears in the pic should go to 3" for that size of furnace. Get someone that knows what they are doing, and don't be shocked if they say to start over.

Also on further look at plenum to coil change in size is a concern. The furnace size to coil, can be overcome if proper transition but this guy is a hack. Do not call him back.

i have a drain that goes straight into the gutter. that pvc pipe thats underneath the duct work is connected to gutter for the bathroom below, so the water drains into the bathroom gutter pipe. i read the booklet and says a 2 inch pvc pipe out the roof is ok for this unit since its a high efficiency one. thank you guys for your help, someone is coming to take a look at it tomorrow so ill b prepared and know what to expect. thanks again.

What happens with over size units is that they cycle too often (short-cycle). For AC, this means that it doesn't run long enough to extract humidity and your home becomes cold and clammy.

It could also be said (and some may argue this) that the frequent short run times are hard on the equipment leading to early failures.

thanks guys, i had a hvac guy come in and knew what he was talking about and told me that i would need to have a plenum for the return air and has to be bigger and the drain issue he would fix up, re-pipe it where its needed and add a bigger tray re-wire the unit, add a 2 stage thermostat and add a new vent in hallway also add a extension for plenum for the duct works so that there is less compression in the flexs. also he said we can add 2 vents in attic since i have no insulation and heat which would kinda help me out with the coverage of the sq ft since my attic is about 700 sqft. and he did tell me the unit is oversized. all this he said would come out to 3500. is that a reasonable price. he said if i wanted to change unit and condenser outside it would cost me 3k total for both units. so i am not going to change the units right now as i dont have that much money. so does the price sound reasonable to fix up all the issues for $3500.

Labor rates from region to region vary so much it's hard to say if it's reasonable. My advice is to get another bid or two and then compare to them.