Question about opening heater duct to warm up crawlspace


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Old 11-28-16, 06:10 AM
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Question about opening heater duct to warm up crawlspace

Hello could use some advice, we have a secondary heater in a crawlspace on top floor that is unheated and we were told by a technician that we need a 4 inch collar with dovetails, cut 4 inch round hole in supply duct and attach to supply duct work and point to condensation pump. Duct water is freezing up in supply drains in below zero and can crack the condensation pump. Also to use a damper.
Apparently the job was beyond the technicians capacity. So we cut a hole in the large rectangular supply duct that goes under the heater and into its side, far from what looks like some sensors in duct closer to heater. Got a dovetail and elbow. As for the damper, i know that they sell ones that open and close with flow and ones that go inside the 4 inch duct and just regulate how much flow. Not sure which i need because i wasnt the one who spoke to technician. Is the idea to close the duct when its not blowing warm air completely? Not sure if this affects sensors etc in any way like it would in a car. Im assuming what he called the supply line is hot air going out of the heater. Thanks for any tips.
 
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Old 11-28-16, 06:50 AM
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Not a hvac pro but I'm lost. I usually think of a crawlspace as being below the house and you refer to yours as being on an unheated top floor. Is this an attic space? If an attic space outside of the conditioned space for the house there would be several concerns about blowing hot air into it.

Can you clarify?

Bud
 
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Old 11-28-16, 07:14 AM
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Sorry i just used a term someone used to describe it i guess because you cant really stand up, its right under the roof behind wall of a bathroom on top floor of 2 story house accessible by a crawl door at floor level. Its where secondary heater and ac unit is along with some insulation and a sub floor to walk on
 
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Old 11-28-16, 08:23 AM
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That sounds like a side attic. Has this space been sealed off from the outside or is it attic space with ventilation?

Still not certain I'm on the right page, pictures would help a lot.

But, here are my concerns using the assumption that this is essentially a vented (cold) attic space. Blowing warm air into that space would deliver a lot of moisture and create condensation problems and potential mold issues. In addition, for every cubic foot of conditioned air you blow to the outside of the conditioned space a similar volume of outside cold air must return through whatever leaks it can find.

I assume your problem is a drain line freezing and for that one of the hvac pros will have to comment.

Bud
 
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Old 11-28-16, 10:45 AM
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Ill try to get some pics the original issue was not freezing lines (that was technicians comment) but rather a lot of condensation water building up from ac which caused a leak and damaged floor which was the ceiling of a room downstairs. There were several battery powered water sensors under heatet when moved in. I think there is some sort of condensation system installed on roof. I have to see how cold it gets seemed warmer than freezing in there on a cold day not too sure why he told me to cut hole. But youre saying if there is no opening to outside moisture can build up more than if it was open and cold? Ill check with a flir to see if cold comes in/if there are real openings, cant see much theres insulation.
 
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Old 11-30-16, 08:34 PM
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Attached some photos. Looks like it is pretty much sealed room. I closed the hole in duct that I cut to see how cold it really gets in there.
 

Last edited by PJmax; 11-30-16 at 10:19 PM. Reason: added space between pics
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Old 11-30-16, 10:11 PM
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Welcome to the forums.

a lot of condensation water building up from ac which caused a leak and damaged floor which was the ceiling of a room downstairs.
Now I'm confused. Condensation from an A/C system running in the cool mode is a normal occurrence. Your description of the problem made it sound like a winter problem.

It sounds more like you had a drain line plugged and the condensate drain pan overflowed.

I see roof/gutter heating cables. The reason you need them is from the heat being released into the attic from your heating system. Adding additional warm air into the attic will increase your snow melting/freezing water in the gutter problem.

An A/C - furnace needs to really be in a conditioned space.
 
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Old 12-22-16, 05:47 PM
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Sorry didnt see your reply. The leak was during summer months when ac was on but i cant tell which part of system is ac and which furnace, the whole thing fills up the small room. THe pump failed and it overflowed I am just quoting what the repair person said should be done for winter. The space doesnt get as cold as outside because its sealed but from what youre saying without actually moving the sytem out of that space it would be a bad idea to follow what he said and cut a hole to release heat into that space correct? I cut the hole but sealed it back up.
 
 

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