Need Home HVAC help

Por_sha911 · Por_sha911's Garage

I know this is a shot in a million but its worth a try since my repair guy can't get here til Monday.

8 Yr Old Lennox heat pump HVAC. Plenty big for my house (as per HVAC repair dude). New squirrel cage last summer. Recharged refrigerant last winter (a had line was rubbing and over time leaked). Has been running perfectly until recently. Out of nowhere, the volume of air coming out the vents is almost nil. The coils are not frozen, there are no obstructions around the outside, everything sounds normal, I took the cover off the unit and the fan is running fine but there's very little air coming in and its not ice cold. If I shut the unit down at the fuse box and let it sit for a while it seems to come back but then later it starts slowing down. If I shut the unit down for just a minute, it takes longer than usual for the unit to kick in and the flow is the same. It sounds exactly like a frozen unit but there is no frost or ice anywhere. Suggestions?

rattlsnak · rattlsnak's Garage

do you have a "fan" option on your thermostat? try to run the fan alone, (with the A/C off) or run the heat for a while and see what happens. Make sure that the returns are not blocked by sofas, charis, etc.

bottom line is, if the fan is running as normal, but no air is coming out of the vents, there HAS to be a restriction somewhere.

Por_sha911 · Por_sha911's Garage

Once the airflow is reduced, if I run the fan alone it does the same. I just shut the unit off again to "reset" it. When I powered it back up the unit didn't come on even after a minute. When I switched it to heat, it came on in 5 seconds. I immediately shut the heat off and switched it to AC and the unit came on. I would run just fan but it still cools somewhat and I need all the help I can get (93 degrees today).
I have one huge return. Nothing blocking it, clean filter.

billybek · billybek's Garage

Check your filter. Low air flows would lead to a frozen coil though. You may have more than one problem.

Is the suction line (big one) cold going back to the condensing unit cold when it is running?

Does there seem to be more air at the vents if you run the air handler without the access door on it?

billybek · billybek's Garage

Is the fan on the out door unit operating?

URY914 · URY914's Garage

You may have a duct connection blown out. Get up there and check all the duct work for and leaks or broken connections.

Por_sha911 · Por_sha911's Garage

No change in air flow with or without the access door in place. I checked the ducts in the attic and didn't find any unusual air blowing or noise (4 ton unit blower can really push some air). I dread crawling under the house to check the downstairs ducts but, why would it not be blown off after being shut off for a while? I admit it seems like a clog since the coils aren't freezing up. I'll see if I can check the suction line without killing myself. The entire unit is outside with a cooling fan above the compressor surrounded by the coils (with a lot of space between them). The blower is to the side. I'm assuming the condenser would be between the blower and the coils surrounding the compressor.
The fact that the heat comes on immediately but the AC takes a while is making me wonder if theres a problem with the reversing valve. I can't service the unit but I was hoping to find a simple solution before Monday.

Brian 162 · 06-25-2010, 06:20 PM

Maybe something has come loose inside the blower compartment and is blocking the squirrel cage.Or the blower wheel is loose on the motor shaft.

idontknow · 06-25-2010, 07:12 PM

Quote:

Originally Posted by Por_sha911

I know this is a shot in a million but its worth a try since my repair guy can't get here til Monday.

8 Yr Old Lennox heat pump HVAC. Plenty big for my house (as per HVAC repair dude). New squirrel cage last summer. Recharged refrigerant last winter (a had line was rubbing and over time leaked). Has been running perfectly until recently. Out of nowhere, the volume of air coming out the vents is almost nil. The coils are not frozen, there are no obstructions around the outside, everything sounds normal, I took the cover off the unit and the fan is running fine but there's very little air coming in and its not ice cold. If I shut the unit down at the fuse box and let it sit for a while it seems to come back but then later it starts slowing down. If I shut the unit down for just a minute, it takes longer than usual for the unit to kick in and the flow is the same. It sounds exactly like a frozen unit but there is no frost or ice anywhere. Suggestions?

Windings are burnt out on the blower motor.

billybek · billybek's Garage

I am not sure if he is referring to the blower motor speed or just the airflow slowing down.

futuresoptions · 06-25-2010, 09:01 PM

get a flashlight and look at the return side of your evaporator... you may of sucked something up into it..(it happens) with the squirrel cage being replaced last year I would doubt dirty fins to be the problem unless you don't run a filter... sounds like to me to be a duct failure of some sort... as long as the big line is cold and the skinny line is not too hot to the touch you should be okay as far as refrigerant goes... this will not cause a decrease in air flow unless the coil freezes up... if you find out that a section of duct has failed, pay extra and once they have repaired the failure, have them coat all your duct with mastic...

futuresoptions · 06-25-2010, 09:04 PM

Quote:

Originally Posted by billybek

I am not sure if he is referring to the blower motor speed or just the airflow slowing down.

If it is airflow he is referring to it could be the coil icing up... or if it is a high efficiency unit, it could be having an issue with its logic control board...

Heel n Toe · 06-25-2010, 09:16 PM

You ought to be able to get a repair guy quicker than Monday... what is up with that? Can you call someone else?

If there's no help 'til Monday, go to K-Mart, Walmart, Best Buy, Lowe's, Home Depot, etc. and plop down $90-100 on one of those Haier or similar 5-6000 Btu window units, install it in a strategic location, crank it up to eleven, close off any rooms you can, move air around with a box fan or two, and you will be amazed how much good it will do. Ask me how I know.

Best money you will ever spend.

mattdavis11 · 08:03 AM

I'm just beginning to learn some of this stuff, but I hear that some techs are putting in a device to manage flow. I think he said they are leaving the existing expansion device in place. The concern was that some units are chugging too much oil causing problems. I forget what he called it, but it's similar to an expansion valve, orifice tube, capillary tube, what ever it was.

Hijack, the a/c system at my brothers place was low on freon, somebody here said they are all sealed up, soldier, no unions nuts, yada, yada. I guess an a/c tech made the system serviceable because you can remove the cooling coil (evaporator). I thought it was brilliant. All I have to do is close the discharge valve for a few minutes with the system on, shut the valve, turn the system off, loosen and separate the lines to the evaporator, then take the coil and clean it in the yard.

I might loose a bit of refrigerant, and will have to replace 2 orings, but that's to be expected. There will be service ports added at the coil so I can read those pressures. I can't believe this isn't done everywhere. A/C isn't rocket science but they are making things less serviceable with all the electronics and braised connections.

If you have to have a new system installed, I'd demand that they do it with the aforementioned features. If they won't, tell them to do everything short of vacuuming and opening the valves, then cut the lines, install some unions, flare the copper and make that sob serviceable. Installing service ports is optional, but if you can vacuum from inside and read the pressures, why not?

Por_sha911 · Por_sha911's Garage

As already stated: Blower squirrel cage and motor (one unit) are 6 months old and I pulled the service cover to see that it is running fine.
The air flow I am referring to is what comes out the vents.
If the coil is icing up, wouldn't I see it somewhere on the coils around the unit?
Lastly, why would it run better after I shut the unit down for 15-30 minutes?
To make matters more confusing: last night it started working fine and has been OK ever since. This is the 4th time its done it (and then the problem went away) in 2 weeks so I'm ready to pay the HVAC dude but the guy I use for the last 20 years is out till Monday. I would rather wait since I have tried 2 other companies and been cheated, overcharged, and had shabby work.
In the meantime, thanks for the group problem solving session. Any other ideas between now and Monday?

scottmandue · 06-26-2010, 10:19 AM

If it is low on charge (freon) indoor coil could be iceing up?

mattdavis11 · 11:01 AM

Is it draining the condensate? I'd say you're fuched unless you have gauges and can tell us more. Your blend doors, what's going on there?

rattlsnak · rattlsnak's Garage

Where are you looking to see if its iced up? The evap coils are in the furnace area usually above the heater element, not on the condensor coils. Its not easy to see without removing panels.

A930Rocket · 06-26-2010, 07:56 PM

If it's low on freon, the coil will freeze up and start working it's way outside. By turning it off, you might be thawing it out enough to blow air through it. Then it freezes back up.

Do you see any frozen line sets? Do you have one or two systems? Check for dampers being closed and blocking the air.