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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7501
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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We have a complete new heat pump system in our Florida home.

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We have a complete new heat pump system in our Florida home. We found out that the old pellums were not replaced when the pellums started leaking. The HVAC company replaced the pellums with new ones. After the repair was completed and the service installers left our house, the one pellum started leaking from the bottom that is next to the air handler and the air handler now having condensation on the entire bottom and side of the unit and is dripping water too. We know there is something wrong with the unit. Our question is: Should we have the company replace the entire air handler replaced because of this problem? Does it problem mean that the unit was improperly installed from the beginning? Also if they say they can repair it,
should we be concerned that the water that was in the air handler will rust the unit? The unit appears to be all metal on all sides and our concern is that there may be some hidden problem that has developed from this leak, etc. Give us some ideas as what we should do when the service/installers come to repair it and their manager comes to inspect the unit. Thank You for you help.
Welcome to Just Answer!.

I hold questions open after positive ratings to allow for unlimited follow up. Please be patient though. The research & typing take time

There are many aspects to this problem.

1. The air leak problem is normally repairable. Air leaks in Florida can run your operating costs up dramatically. There are superb duct sealing compounds in calking tubes that can be used to seal the plenum to the furnace. Many companies use duct tape... that tends to fail in many cases.

2...Of more concern is that the plenum is running cold enough to condense moisture. In Florida that is generally cooler than 45 deg F...

Normally a system should put out cold air 18 to 22F cooler than the room air... so if the room is 72 then the cold air plenum should run no cooler than 50F... 55F is the national design standard however....and not condense any water onto the duct work where it can do the damage you have mentioned... and worse, leak water from the duct joints that support mold growth in the wetted areas of the house framing and ceilings etc, a very serious problem.

The problem is normally caused by duct work that is too small to move enough warm air... so that the smaller amount of air it moves gets too cold. The cure is larger ducts, and possibly running the fan at a higher speed if it is not already set at high speed for cooling.

The proper solution is to have the system 'air balanced' by a testing and balancing specialist so that the system is moving beween 400 and 500 CFM, per ton of cooling capacity. These companies and most high quality air conditioning contractors use 'air flow test hoods' to put over each supply air register to measure that air flow. Beyond that there are sizing issues that affect the ability of a system to dehumidify the air properly.


If you found that answer useful and will rate it positively, I will hold the question open for an unlimited amount of time and address the special humdidity control requirements in Florida. and the complex issues of good system design that top quality HVAC contractors are familar with. It seems likely that this contractor is not up to speed on this range of issues.

Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7501
Experience: Retired HVAC/ Electrical & Boiler contractor. Industrial
Phil and other HVAC Specialists are ready to help you
Customer: replied 3 years ago.

Will the water that is condensing in the air handler cause the unit to start rusting some time down the road at a later date even though it will be

repaired? We are concerned that because there is water inside the unit now and if it eventually evaporates it will still start to rust the unit from the inside out. Thanks again for all your help.

Hello again! Thanks for the positive rating.

The water that has covered the sheet metal so far will dry out and not be a problem later... but... unless the cold air situation (below 45F) is corrected you will continue to have condensation over the air handler.. that will cause significant rust damage and can leak onto the electronics control card if the cooling coil from the heat pump is above the blower section.

The cold air situation, (below 50F needs to be fixed for sure)....

Let me know how deeply you want to get into the engineering issues. Let me know if you understood the air flow issues i mentioned earlier. We can go from there.

Customer: replied 3 years ago.

Thank you again for your excellent info. This info will help us when the Operations Manager comes to inspect the unit and work that was done. We just want to be sure this person will not give us some off the wall explanation to the problem which is not correct. We wanted to have some info to back up the problem in case he does not address nor solve the problem correctly.

Thanks again for all of your help. You problem solving was great.

You are welcome, feel free to post this thread again if anything else comes up.


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