Posted: 4/19/2011 4:55:04 PM EDT
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I have a question for your HVAC experts. My home heater/AC blower does not seem to be working right. The blower that blows the air out of the vents is blowing, but it does not seem to be blowing as hard as normal. The central unit in the garage sounds like it is vibrating a little too. I turned off the AC compressor and had just than fan running and the blowing/vibration sound is the same, so I do not think it has anything to do with the compressor or the coils in the inside unit. My question is do the blower motors go partially out? I can spin the squirrel cage of the blower by hand and it appears to move freely and easily. I am guessing that it is either the motor or the start capacitor. Any ideas or am I completly wrong? TIA
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Last summer the air coming out of my vents was not very strong. Check the outside unit and lines were icing up, A-coil in the inside unit was froze. Put some more R-22, worked great.
This winter my blower would not always starting when the heater kicked in. Put a new control board in and that fixed it. I think the same control board is used in a whole lot of blower units. I called Johnston and told them I needed a control board for my heater and before I said the part # he said is it part # we have in stock. The control board runs the blower motor at different speeds for heat or air. The little black relay on my board was bad, I could hit it with handle of my screwdriver and the blower would start. This happened the night it got down -17. I'm sure the HVAC guys will correct me |
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Quoted:
Last summer the air coming out of my vents was not very strong. Check the outside unit and lines were icing up, A-coil in the inside unit was froze. Put some more R-22, worked great. This winter my blower would not always starting when the heater kicked in. Put a new control board in and that fixed it. I think the same control board is used in a whole lot of blower units. I called Johnston and told them I needed a control board for my heater and before I said the part # he said is it part # we have in stock. The control board runs the blower motor at different speeds for heat or air. The little black relay on my board was bad, I could hit it with handle of my screwdriver and the blower would start. This happened the night it got down -17. I'm sure the HVAC guys will correct me The copper lines were frozen up a week ago when the blower sounded like it was running, but hardly any air was coming out. I turned the unit off for the rest of the night and the next morning it seemed to be normal again until today. Are you saying low refrigerant causes it to freeze up? |
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Quoted:
Quoted:
Last summer the air coming out of my vents was not very strong. Check the outside unit and lines were icing up, A-coil in the inside unit was froze. Put some more R-22, worked great. This winter my blower would not always starting when the heater kicked in. Put a new control board in and that fixed it. I think the same control board is used in a whole lot of blower units. I called Johnston and told them I needed a control board for my heater and before I said the part # he said is it part # we have in stock. The heat has to build up in the furnace to a certain level before the fan will kick on. The control board runs the blower motor at different speeds for heat or air. The little black relay on my board was bad, I could hit it with handle of my screwdriver and the blower would start. This happened the night it got down -17. I'm sure the HVAC guys will correct me The copper lines were frozen up a week ago when the blower sounded like it was running, but hardly any air was coming out. I turned the unit off for the rest of the night and the next morning it seemed to be normal again until today. Are you saying low refrigerant causes it to freeze up? If enough air is not blown across the evaporator, it will freeze up. The evaporator (inside coil by your blower) takes the heat out of the air blowing through it. If enough heat is not present (i.e. enough air blowing through), it will freeze up. Too low a freon level means the pressure is to low and it will freeze up faster. You need a certain pressure on the low side - approx 65 lbs for Freon 22 which will blow 35 to 40 degree air. Lower pressure will give lower temperature on the coil and the condensate will freeze up on the coil. If your charge is not low, you will be adding 30 to 35 degrees to the ambient air outside on your condenser. If it's 90 degrees outside, the air coming off your condenser should be 120 degrees. It should read around 250 lbs on the high side. You probably have a fan problem. It can be a bad winding, bad control board/relay, or even a bearing causing it to drag. It sounds to me like you have an electrical problem in your furnace. But hey, I'm just a licensed electrical contractor and don't have my HVAC license anymore. I let that go last year and I got pretty stupid about refrigeration problems in the interim. 
ETA Be sure and check your filter. If it's clogged, not enough air going through will freeze it up. You could have a bad capacitor but that usually kicks a thermal in the motor pretty quick. Take the capacitor loose, short between the contacts, then take an analog meter to read across the two contacts. It should spike up, then drop slowly as the charge builds up in the capacitor. It's a good capacitor if that happens. If the meter needle stays swung over and doesn't drop, the cap is bad. |
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Dan has a lot of good info there, just adding a little.
Coil could be dirty if filter wasn't catching everything, do you have dogs in house? Have seen coils plugged with dog hair. If it is an older furnace and the blower motor has bushings instead of bearings they could be dry, dragging motor down and reducing air flow. Blower wheels can build up a crust on them which will reduce the efficency of the wheel reducing air flow. Try pulling the blower section out if you are comfortable with doing so and visually look at the blower. Is this a direct drive blower or an older belt drive? Good luck, if all else fails call a reputable contractor. |
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Probably.
You know how a glass gets wet on the outside when you have ice on the inside? That is the moisture in the air condensing on the glass. The same thing happens when a copper line gets cold. If the pressure is too low the line gets colder than 32 degrees and the condensation freezes on it. Or if enough air is not blowing across the coil. Obviously all the ice on the coil melted overnight. You said your fan was running slow earlier. You either have low freon and/or not enough air moving across the coil. Get someone to put gauges on the unit while it is running to see if you are low on gas. Then check the fan speed out. Have someone put an amprobe on the fan while it is running. You could have a two fold problem, low freon and not enough air flow. |
| Just wanted to post an update. The retired HVAC guy from my church came over last Friday to check out my system. He found a small leak in the fitting where the line comes in to the inside unit. He fixed that and had to add 2lbs of freon. The unit is running fine and blowing hard now. Just wanted to say thanks for all of the info you guys gave me so I could understand what was going on. |
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