Spacepack High Velocity AHU Insulation blocking Fan intake

PC7060

I was working on a Thermostat no power problem for zone in my house which is serviced by a 24KBTU Spacepack system. The problem was pretty simple; EZ Trap condensation overflow switch reading false overflow. Toggled it a few time to reset trap switch; will replace if it occurs again. 

I removed the access panels to inspect the overall unit while I was up there and found the upper foam insulation panel adhesive had failed and the foam was blocking the upper intake of the fan. I cut a piece of 2”x2”x12” XPS foam board to act as a spacer above fan assembly to hold insulation away from the fan intake. Didn’t notice any adverse performance impact on the system but it must have reduced the static pressure of the discharge plenum.

Anyone else run into the panels coming loose like this on AHU? These air handler sit up in really hot attics for many many years not surprising the adhesive breaks down.  

As a side note to @ChrisJ and others comments (separate thread) on desirability of attic AHU, this AHU is located in a walk up attic and all of the duct work is very well sealed and buried in insulated plenums or under 11 inches of dense packed fiberglass (BIBS).  

clammy

It’s kinda common ,I ve ran across in both spacepak and unico systems . I usually use a spray adhesive and re glue and make up some corner sheet metal pieces in the corners of the access door to help hold in place . I guess all the tape was put there to stop air leakage . A r 8.5 duct wrap on the return would help . Peace and good luck clammy

PC7060

clammy said:

It’s kinda common ,I ve ran across in both spacepak and unico systems . I usually use a spray adhesive and re glue and make up some corner sheet metal pieces in the corners of the access door to help hold in place . I guess all the tape was put there to stop air leakage . A r 8.5 duct wrap on the return would help . Peace and good luck clammy

@clammy - thank for the response. 

I’m considering removing the fam from inside
the unit and using a 2” R10 panel on top.  I’ve got plenty of foam and is easier to fab up in the shop. 

Re the tape, installer (me, ) used the tape to keep system from pulling in attic air. Some of the gasket material was loosing its flex and seemed like simple way to tighten up system. 

I’ll be sure to add the insulation on the intake side. It’s just that last bit that’s in insulated so easy fix. 

Thanks.  

PC7060

I used screws with foam panel washer through foam in upper metal frame. Covered the top of the AHU with 2” XPS to cover exposed threads from the screw; protects maintainers and extra R value is a plus. 

Also followed @clammy advice and insulated the intake. 

Done! 

PC7060

Is it practical or common to insulate AHU located in attic spaces? 

Seems like it comes down to a compromise between reduced load on AHU and restricting maintenance access. 

pedmec

i agree @pc7060. unit jacket is insulated internally so your making it harder to service.

HVACNUT

If I need to service that air handler, I'll take the insulation off, but I'm not putting it back on. 

JUGHNE

I have wrapped attic AHU with a blanket of fiber duct wrap and even sometimes with "Bubble wrap" .

I staple it down to the floor on the back side, pull it snuggly over the unit and leave a 1' flap to lay on the floor on the front side. That flap is then weighted down with a wood plank.

This is just a compromise to cover 3 sides, but makes service easier.

I also foil tape the door seams. This is later cursed after perhaps years before needing to open it for repairs. I might remember to bring more tape up on the next trip.

I never put a filter in the attic. We have terrible attic spaces here for the most part.
Sometimes 3 to 4 filter grills in the ceilings of different rooms.
Gets rid of the trailer house hallway sound.

PC7060

I prefer the rigid foam over the blanket in situations where maintenance access is required.

Hollywood111

clammy said:

It’s kinda common ,I ve ran across in both spacepak and unico systems . I usually use a spray adhesive and re glue and make up some corner sheet metal pieces in the corners of the access door to help hold in place . I guess all the tape was put there to stop air leakage . A r 8.5 duct wrap on the return would help . Peace and good luck clammy

I might add, that attic is a "DREAM to work in"! Kidden me?...LOL

Hollywood111

Attic 135*f Cold beer, Priceless....