I have been struggling with issues related to my furnace for months now so I hired a 3rd party HVAC company I trusted to inspect and document issues with the design and install which produced a lengthy report. The key findings were:
The above was after I had them address install issues with the drain and exhaust pipes and not adhering to manufacturer requirements.
Their recommendations were a lot of duct design changes such as going from a 6" to minimum 10" w/ access door between furnace and coil, increasing size of supply and return plenum (to change duct connections) and adjusting duct flow via dampers. They also noted the furnace being excessively oversized (well beyond 200%, upwards of 300%) to the homes needs and should be downsized.
After the installing company sent a rep and confirmed the report they are going to address the duct design issues and replace the furnace but leave the coil (CHX35-42C), the new furnace will be a EL296UH045XV36B so it will output into a larger coil box (C chassis). There is a CHX35-42B coil and an AHRI match reference that pairs the outdoor 3ton coil with this furnace (202363347); is it a big deal that the coil is a C chassis instead of a B chassis as long as the furnace to coil transition accommodates this size change? The coil is in the optional flow direction (horizontal) due to the space available in the encapsulated attic thus the need for the larger transition.
- The furnace tripping the temp sensor on our Harmony III unit
- Static pressure reading over 1"wc from the input and output of the furnace though set for 1400CFM max (5 ton capable blower; 60% on the return side, pressure dropped from input to output of the coil though)
- Over-firing based on meter clock rate and pressure
- Poor duct design with sagging, remote plenums and no balancing between zones (causing extreme variation between floors when all zones called).
- Furnace to coil transition not sized correctly creating choke point (small and narrow)
The above was after I had them address install issues with the drain and exhaust pipes and not adhering to manufacturer requirements.
Their recommendations were a lot of duct design changes such as going from a 6" to minimum 10" w/ access door between furnace and coil, increasing size of supply and return plenum (to change duct connections) and adjusting duct flow via dampers. They also noted the furnace being excessively oversized (well beyond 200%, upwards of 300%) to the homes needs and should be downsized.
After the installing company sent a rep and confirmed the report they are going to address the duct design issues and replace the furnace but leave the coil (CHX35-42C), the new furnace will be a EL296UH045XV36B so it will output into a larger coil box (C chassis). There is a CHX35-42B coil and an AHRI match reference that pairs the outdoor 3ton coil with this furnace (202363347); is it a big deal that the coil is a C chassis instead of a B chassis as long as the furnace to coil transition accommodates this size change? The coil is in the optional flow direction (horizontal) due to the space available in the encapsulated attic thus the need for the larger transition.
source https://hvac-talk.com/vbb/showthread.php?2225787-Furnace-chassis-size-difference-to-evap-coil&goto=newpost
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