Forced Air blows cold air

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Old 02-02-13, 09:12 AM
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Forced Air blows cold air

I have a First Co. 36MBXB-HW system (a unit in my attic and one in the basement) and a New Yorker boiler. Last week, I turned on the heat on my second floor, it was about 10 degrees outside, and it only blew cold air. My heat on the first floor worked fine. I thought it might be the Grundfos circulator pump, which has failed before and I've already replaced once for each floor. Bought a new pump, installed and it still blew out cold air.

A few days later, the temp went up to 55, so I turned on the heat to the 2nd floor, and it blew out warm/hot air.

Yesterday, I turned the heat on to the first floor, and it was blowing cold air. Heat on 2nd floor still works now, but first floor is blowing cold. I cleaned out the air filters in both units, but that didn't fix anything. I doubt its the circulator pump because of what happened with the 2nd floor. The temp outside is 25 degrees.

Not sure why heat doesn't come on during coldest temps, or how to repair.
 
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Old 02-02-13, 09:36 AM
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Check the water coil pipes to see if they are hot? Is there a zone valve on them? Is the circ running for the floor that is calling for heat? Do you have a pump controller or zone controller?
 
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Old 02-02-13, 12:22 PM
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If I touch the pipes that come out of the circulator pump, the second floor is hot and first floor is cold. Last week, when the second floor was blowing cold, it was the second floor pipe tube that was cold.

There are zone valves, and they are all on in the same direction. When heat is called, typically the circulator pipe makes some clicking noises. Last week, the Grundfos was not, that I why I thought it was the pump and replaced it. However, when I did that, it did not solve the issue- the issue seems to have been solved when the temps outside increased. The pump zoned for 1st floor is not making those clicking sounds, but I am still hesitant to think it is that.
 
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Old 02-02-13, 12:25 PM
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Is it possible that the pump is air locked? Is it possible that the first floor line is froze somewhere? Pictures of your setup?
 
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Old 02-02-13, 01:29 PM
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Considering that it works in warmer temps, I am seriously thinking it might be frozen somewhere- although why would the circulator pump not make the correct clicks? Also, where could it possible freeze? I thought the unit in basement was for first floor, and unit in attic was for 2nd, but I might be mistaken.

I've attached some pics. Thanks.
 
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Old 02-02-13, 03:31 PM
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Make sure the pump is running with a call for heat by adjusting the speed. You should be able to notice a difference by feeling the pump while changing speeds. I don't see zone valves anywhere. Where is your zone controller?
 
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Old 02-04-13, 03:36 PM
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I went to the attic to inspect everything in detail. Some of the duct insulation has experienced cracking in its age (all of 5 years old). Because of this, I will buy some aluminum taping and tape any cracks where some heat was escaping.

The small plastic tubes that carry the water are not insulated. I assume after running, the water probably freezes. After the unit is calling for heat again, it can only blow cold air because the water is frozen in the tube. I think I will need to better insulate these tubes and protect them from the freezing temps in the attic.

Not sure what else besides this I can do. I am hoping all of that will solve the problem.

The release valves (where I can run the water) is located on the side of the furnace. I ran about 5 gallons of the first floor water to get it moving, then the heat seemed to blow warmer air.

I am not sure what a zone controller is.
 
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Old 02-04-13, 03:40 PM
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I think the zone controller is located on the side of the furnace- its an ARM-4P, Arco.

I checked it, cleaned it out. Everything seemed to be working correctly.
 
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