W/A HX question

[dogwood]

I am putting a water to air heat exchanger over my updraft forced hot air furnace on the air supply side. There are already a/c coils in place over the furnace. I read that a water to air heat exchanger has to be located before the a/c coils on the air supply side. The concern was if the a/c coils were before the water to air heat exchanger, the cold air could cause the w/a heat exchanger to freeze and crack when the a/c was on in the summer. Anyone know if this is true or have had this happen to them?

Also, there is a fairly recent thread that addressed the possibilily of a water to air heat exchanger interfering with the a/c output. Does anyone know where it is? I can't locate it with the search function or otherwise. It had some nice pictures. Thanks.

Mike

 

[goosegunner]

I am putting a water to air heat exchanger over my updraft forced hot air furnace on the air supply side. There are already a/c coils in place over the furnace. I read that a water to air heat exchanger has to be located before the a/c coils on the air supply side. The concern was if the a/c coils were before the water to air heat exchanger, the cold air could cause the w/a heat exchanger to freeze and crack when the a/c was on in the summer. Anyone know if this is true or have had this happen to them?

Also, there is a fairly recent thread that addressed the possibilily of a water to air heat exchanger interfering with the a/c output. Does anyone know where it is? I can't locate it with the search function or otherwise. It had some nice pictures. Thanks.

Mike

I set mine up so I can take it out in the summer. I wanted max airflow for air conditioning in the summer.

gg

 

[rkusek]

I leave my water to air HX in year round. It is mounted after the output of my heat pump but I have ball valves that i close off to prevent water from circulating through it. I used some aluminum angle iron pieces to make a "tray" to support the HX. I did this so I could slide it out in the summer, but the heat pump seem to cool our house no different than before so I had no reason to mess with it. Since the water doesn't circulate in the heat exchanger the energy wasted is minimal. I sealed it all up with some of the tape that the HVAC guys use on all their joints now. I have never heard of A/C output being cold enough to freeze anything. I believe rule of thumb is 20* differential between incoming and outgoing air which would mean your home would have to be something like 52 degrees.

 

[Duetech]

Before it would freeze the water in your W/A X it would frost and freeze up your a/c coils as that would be the first place the condensation would form. Besides that I think that a/c coils never go below 34* and 80* going across the coils will emerge at a rough 60* so if the W/A X is in a 60* flow it will not freeze.

 

[dogwood]

Thanks Cave2K, huskers, and goosegunner. It will be easier for me to put the w/a hx above the a/c coils. I think I will try to make it removable as you suggest goosegunner. I wish I had the know how to make the A/C coil removeable as well so I could swap them out seasonally. I don't know that the 1/3 hp motor on my Lennox Pulse furnace is going to have enough oomph, even at high speed, to blow through both the a/c and w/a hx, and deliver enough cfms throughout the house. Its fairly big, 3000sq, feet. Maybe I'll have good luck like huskers and can leave both in.

Mike

 

[dirttracker]

I have an older Lennox pulse with a 1/3 hp blower and water to air HX and AC coil installed. I have to blower set up to run on high speed for both heat and AC and don't have problems with either AC or heat operation. My house is only 1500 sft (2000 sft including the basement), you are heating more space. I'd say try it and see what happens. Depending on the size of the water HX, you may not see much change in flow. I'd suggest you build in a means to access the HX for cleaning. After 8 years, I had a fair amount of dust trapped on the blower side of my HX.

 

[dogwood]

Thanks for your input dirttracker. I am encouraged that you have had good results with the same Lennox Pulse furnace. I'll take your advice and put both the A/C and heat on the high blower speed and see what happens. I've got an oversized, custom built heat exchanger. Maybe it will let air flow more easily. Good idea to have the hx removeable too for cleaning.

Mike

 

[markmudd]

mine is located above the AC coil. No problems other than it seems to form a little condensation where my HX coil is exposed on the side. I plan to cut a vent into my furnace room to cool that room, which should eliminate the problem. I leave it in year round, and have no noticable difference in cooling in summer.

 

[dogwood]

Thanks mocus. I'd like to leave it in permanently like yours, but will install it so I can take it out if need be.

Mike