The attic eaves in the 3rd floor located in Richmond VA (mild climate) are insulated with R-30 behind an uninsulated kneewall with open framing (24" oc) in the HVAC closet for an existing unit 2.0 ton split system heat pump with gas heat mounted horizontally supplying the 2nd floor.

There does not appear to be enough clearance for a 1.5 ton split system heat pump with electric heat strips to be mounted vertically in the existing HVAC closet. There is open framing into the attic eaves on each side of the 13' wide, 6' deep HVAC closet. The R-30 insulation is along the rafters with styrofoam air baffles from near the soffit vents to the ceiling, the house has ridge vents. There are diagonal supports for the trusses which could make installation tricky with bulky items. For this reason, I am considering the following products:

Goodman 14 seer variable speed modular blower MBE 1200aa-1, whatever is the corresponding evaporator coil, and the GSH 140181a outdoor compressor. 1.5 ton is all that is necessary for this 500sq ft room, and is a bit oversized. A ductless system isn't practical for the length of the room with a barn-style roofline.

Are there any issues with mounting a unit in the attic eaves that should be of concern regarding truss supports such as clearance? I understand that there needs to be adequate space for maintenance and repair. The trusses are spaced at 24" oc, any issues with getting the unit back there? Have condener lines and properly sized lineset run when the house was being built, this project is for finishing off the 3rd floor. An experienced technician will certainly perform the install and connections, but I'd like to know if it is possible to place those units in the attic eaves and any issues in getting them in there.

Here is a picture of the trusses, there is no R-19 in the kneewall as shown in green.

 

Id call around and get 3 bids for the job the hvac guy will know what will work and not work for you.

ED

 

For the modular system, there is supposedly about a 3" gap that needs to be sealed between the blower and evaporator coils. There is no gas heating element, using electric (5Kw). Could someone explain in layman's terms what connections or concerns there are in a modular split system such as this? I am having problems finding hvac contractors that have installed a modular system before, but it appears to be the best solution for placing in the attic eaves.

-- Richard

 

Go check out on a www go to Samsung. They have the ductless split system with electric heat and cool if that is what you mean. they also come as a heat pump if you want. also check out Fujitsu and Comfort-aire both are ductless ht and AC. There is the spacepac high velocity but dont like them .

ED

 

Never seen a ductless split system that could be installed on a 3rd floor and the condenser on the ground level.

 

Im not sure im understanding your question but... there shouldnt be any problem installing the air handler in the kneewall, as long as you maintain your clearances in front of the unit for service and have a main power disconnect. usually i would cut two doors into the wall to open up to the airhadler so you can save space. not sure about the lift maximums for a ductless system. i know Trane makes a compact airhandler for tight spaces such as that. otherwise as long as the airhandler is sealed and the ductwork is insulated than you should be fine.

 

The kneewall is only 50" from the floor, so getting the supply and return ductwork in a vertical configuration is a concern. Horizontal installation would permit easier ductwork I would think without tight bends.

That TRANE 2TFB-B model with multi-speed for the 1.5 ton has a height of only 37" -- very impressive. What would the height be expected with the ductwork if installed vertically?

 

it depends, your best bet would be to go with the horizontal, because like you said 50 inches isnt gonna be enough to mount a return box with an emergency pan and a supply plenum. another option if you do want to go vertical would be the carrier apartment/base series air handler with the return basically being the lower half of the airhandler. not sure on the dimensions but it is also around 37 inches tall and can be set directly on the emergency pan if im not mistaken taking return air from the front. that would give your 13 inches clearance to mount a plenum for supply take offs.