Is this bypass necessary on heat pump air handler??

[buddiez75]

Long time reader, first time poster....

Photo attached shows the unit in question.

Recently moved into a house that was more or less "home built" by the previous owner. I am currently rehabbing the HVAC system by sealing ducts, replacing insulation, etc and cannot figure out for the life of me the reason behined the black insulated bypass shown in the left side of the photo.

In essence, it allows air to be recirculated through the coils on the heat pump but my question is why?? As far as I see it, this only prevents the full pressure of the air flow from going to the house and would it hurt the system to remove it entirely??

Thanks guys in advance and this will save me not only money, but allot of sleepless night trying to figure it out....

Chris
buddiez75

[buddiez75]

Long time reader, first time poster....

Photo attached shows the unit in question.

Recently moved into a house that was more or less "home built" by the previous owner. I am currently rehabbing the HVAC system by sealing ducts, replacing insulation, etc and cannot figure out for the life of me the reason behined the black insulated bypass shown in the left side of the photo.

In essence, it allows air to be recirculated through the coils on the heat pump but my question is why?? As far as I see it, this only prevents the full pressure of the air flow from going to the house and would it hurt the system to remove it entirely??

Thanks guys in advance and this will save me not only money, but allot of sleepless night trying to figure it out....

Chris
buddiez75

[heaterman]

Interesting. I enlarged your photo as much as I could trying to figure out what is there. Looks like some motorized dampers in the system but can't really make anything out. Take some more pictures closer up and of individual sections including the panel on the return duct. Are there more than one coil in the system? Is there possibly a hydro coil for an add on wood/coal unit?

[buddiez75]

The previous owners hacked in 2 air controls and added an upstairs thermostat, so in effect it is dual zone. I replaced both of the dampers and it does help, but the workmanship of the overall system left allot to be desired.

My main focus is to cap all leaks and force as much flow as possible into the house. So thats why I cant figure out why theres a damper to bypass air from the bottom of the unit back to the air return at the top. Seems like it would only recirculate air through the coils but at the cost of air flow to the house.

[buddiez75]

Additional Photos

[behappy]

That looks like a barometric damper for a zoning system.

Judging by the pictures, you need to get someone in there that knows what he is doing with that duct work... :whistle:

[Tex76]

You are right the reason that a by-pass damper is there is to circulate excess air of the blower output across the coil when only one or sometimes two zones are calling. You must have at least 400cfm/ton across coil to be correct and more at higher elevations. You also can do this another way. I do this a lot I call it a bleed zone. Depending on duct layout I will not allow one or more zone dampers to close all the way on a no call. What this does is allow extra air to go into bleed zone doing the same function as a bypass damper across coil, and eliminating the need for bypass damper and extra ducting. We are primarily in a down-flow application world here, so we are always fighting for space. This works for me.

[fxb80]

I second what behappy and Tex76 have said.

My 2 cents:
1. Zoned systems, and zoned systems with bypass in particular, should have a discharge air sensor, and the DAT sensor should be set to correct values for heating/cooling.

2. A well designed two zone system will have oversized ductwork that should eliminate the need for a bypass during most modes of operation, making the bypass a safety feature that only operates infrequently. That is very often not the case, especially when an existing system has been changed to zoning.

If the system doesn't have a correctly set discharge sensor and oversized ductwork the system can still appear to be working OK when in fact the life of the equipment is being shortened. Which is why I second what behappy says about getting someone in there who knows zoning.

[buddiez75]

First, let me thank you guys for your responses. Outside of doing the basics of resealing everything and replacing the dampers, I am not up to speed on how the entire system is designed to act within itself and this is a big help.

Second, let me apologize for the multiple posts of not only the text, but also the photos. Lost connection in the middle of posting and didnt realize the board took the post originally....

Either way I appreciate the input.

[Armament]

bloody crafty. LMAO

[buddiez75]

Well--I am going to remove it from the system and sheet metal over the openings. As bad as the workmanship is and the fact I have had the damper closed on the bypass for over 2 years now dictates its removal.....