Heat coming from the return

[Phillip]

Yesterday The inspection was on a bank owned home. I had done an inspection for the client before and he made sure every thing was turn on to inside the house.

The package heat pump (14 years old and a 3 ton) was running when I got there. I when inside when the door was opened and after I talked to my clients I when to shoot the temps to see what the unit was doing.

The supply was in the sixty's and the return was in the eighty's. There was air coming out of the return.

Later in the day I turn the unit to cooling, It can on and I let it run while I was doing the crawlspace.

When I return to the inside of the house. there was no air flow any here.

I changed it back to heat and when it came on the supply was blowing like it should.

Have any one of you run into anything like this?

The ductwork is installed on the properly sides of the unit and it is a single phase electrical.

[Scottpat]

So when the unit was set to the emergency heat the air was coming out of the return? Then when you switched it back to the normal heat pump mode the air was coming out of the supply registers, like normal.

About the only thing I can think about is that the blower fan is running backwards when the unit is switched to the emergency heat.

[Jerry Simon]

When you say "shoot the temps", I'm guessing you used an infra-red thermometer, and maybe you measured the temperature of perhaps a portion of metal heating duct versus the actual air temperature.

'Course, that would not explain why air was coming out of a return.

[inspector57]

Fan motor or blade is backwards.

You would be surprised how often this happens on both indoor and outdoor blowers.

The compounding factor is (at least it used to be back in the dark ages when I was in the business) the different motor manufacturers call their motor rotation differently from each other. For one it is CC or CCW when looking at the shaft end of the motor and another is is CC or CCW when looking at the lead end. Put a CCW blade on a CW motor and it will run and heat or cool but not properly even if the air is coming out of the right vents.

Bottom line is get a good tech.

[Phillip]

So when the unit was set to the emergency heat the air was coming out of the return? Then when you switched it back to the normal heat pump mode the air was coming out of the supply registers, like normal.

About the only thing I can think about is that the blower fan is running backwards when the unit is switched to the emergency heat.

Scott,

it was in normal heat to start with, then normal cooling then back to normal heat.

[Phillip]

When you say "shoot the temps", I'm guessing you used an infra-red thermometer, and maybe you measured the temperature of perhaps a portion of metal heating duct versus the actual air temperature.

'Course, that would not explain why air was coming out of a return.

Jerry you are correct.

[Phillip]

Fan motor or blade is backwards.

You would be surprised how often this happens on both indoor and outdoor blowers.

The compounding factor is (at least it used to be back in the dark ages when I was in the business) the different motor manufacturers call their motor rotation differently from each other. For one it is CC or CCW when looking at the shaft end of the motor and another is is CC or CCW when looking at the lead end. Put a CCW blade on a CW motor and it will run and heat or cool but not properly even if the air is coming out of the right vents.

Bottom line is get a good tech.

Jim,

To me if the fan blades where wrong the air flow would have been the same as it was when I check it the first time.

when it was put back into the heat mode from the cooling the air flow was coming out of the supply side like it should and a good flow of air,

[qhinspect]

For the blower to run backwards (lets call it counter clockwise) then forwards (clockwise) would be impossible for a single phase motor (Three phase yes since all that is needed is an extra contactor).

The only thing I can think of is that the blower motor didn't run because it was overheated. Then the burners heated up the heat exchanger and would eventually turn off by its limit switch. That heat would then seep into the house from the return air register (Central return on a horizontal furnace would make the most sense). Then the blower came on after the motor cooled down resulting in the air blowing out of the proper registers.

This would be the only thing that would make sense to me.

[inspector57]

I changed it back to heat and when it came on the supply was blowing like it should.

Sorry, I failed to read this all important detail.

Intermittent blower operation sounds the most likely.

Still needs a tech.

[SonOfSwamp]

Have any one of you run into anything like this?

Yeah. A few years back, co-inspector Rick and I inspected a RE agent's newish (Pulte) house, in which the blowholes sucked and the suckholes blew. Both HVAC units were located in the attic (the usual for Pulte here.) Sure was hot in the kitchen.

I did not offer any handyman advice. I just said something like, "This thing's hooked up backwards. Call an HVAC man, but don't call the one who put in this system."

WJ

[Jason B]

I've had this happen once a few years ago with a packaged unit as well. I was told it was a loose piece of insulation at the elbow duct that would cover the supply side occasionally which then forced the air back through the returm. Don't know that I completely believe it. Then again I didn't believe it when the air came out the return and the after letting the unit sit for about a half hour it came out the supply registers when I went to show the buyer and their agent. Luckily the seller was there to confirm the first as everyone thought I may had been drinking at lunch.

[Scottpat]

Are all blower motors AC or are some DC? I really never gave that much thought before.

Heck, I just found my first DC garage door opener the other day. It was a German brand (Herman, I think) and was about half the size of a normal opener.

[hausdok]

I've had this happen once a few years ago with a packaged unit as well. I was told it was a loose piece of insulation at the elbow duct that would cover the supply side occasionally which then forced the air back through the returm. Don't know that I completely believe it. Then again I didn't believe it when the air came out the return and the after letting the unit sit for about a half hour it came out the supply registers when I went to show the buyer and their agent. Luckily the seller was there to confirm the first as everyone thought I may had been drinking at lunch.

I find the sound deadening insulation loose in plenums all the time. It usually on the intake side where the owner will loosen it by not being careful when installing the filters. Sometimes it's the insulation on the sides of the air handler. In a case like that, it sometimes gets pulled loose and sucked into the sides of the blower. I suppose if there were a big flap of sound deadening insulation loose on the outlet side of the air handler that was hinging up ward and closing off part of the outlet side - at least enough to push air backward, it might force some air out the returns. It's certainly a possibility worth exploring.

ONE TEAM - ONE FIGHT!!!

Mike