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Duct fan installation: Dare I vertical it?  RSS feed

 
pollinator
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So... our crawlspace is unheated and our pipes are down there. I've been using a small fan to blow air from the upstairs through a disused duct into the crawlspace to prevent me having to worry about freezing. (The pipes are all wrapped but still.)

I finally went to the HVAC parts place and bought a duct fan the size of the old duct so that I can blow air down without the little fan. Everything seems to be no bigger a hassle than usual except that the directions for the new duct fan say repeatedly it's only for horizontal installation and I want it to be vertical, straight through the vent.

Anybody know that this is okay, or that it won't be? I guess I'm mostly worried about somehow the motor catching fire or something, though I can't think how. Can someone dissuade or reassure me?
 
gardener
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I can't see how it would be a problem to mount it vertically.  The only reasons for their warning that I can think of are:

1.  A fan pointing up that sits there for months in a dusty duct may collect dust and then cause a fire if it overheats.  If yours points down maybe the concern would go away.
2.  Maybe in a "duct boosting" application it won't work as efficiently (but I don't know why that would be)

There certainly could be a "real" reason for the warning but I can't think of it.  Hopefully the concern they have would just reduce its life or efficiency, not its likelihood of bursting into flame.  I horizontally mounted one in my root cellar two years ago and it just died.  So install it in a way that makes it easy to replace when/if it dies...

Here are two unrelated comments...  Would heat tape be a cheaper or more efficient way to protect those pipes?  Secondly, I often wonder if insulation around pipes is worth it (unless there's heat tape involved).  If the water doesn't flow through the pipe and is just sitting there for 10 hours, will adding a R1 or R2 pipe wrap really save it from freezing?  
 
pollinator
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I would just mount it in the crawlspace ,but add an elbow.
 
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Why not ask the company making the statement?
 
chip sanft
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Thanks for the replies. Mike, I'm hoping that the warm and dry air will help resolve another issue, or rather keep it resolved. There was a musty smell in the house when we moved in, which I mostly resolved by thoroughly cleaning out the trash from the crawlspace (which seemed to never have been done), putting down a vapor barrier, and adding a dehumidifier (w/ pump, so it runs pretty much 24/7). That works well most of the year.

In the winter, though, the dehumidifier doesn't work -- not well when it's cool down there, and not at all when it gets cold. I've read that current best practice in controlling an environment is to seal it and condition it and I'm hoping that sending warm, dry air into the crawlspace will keep the pipes from freezing and also help maintain a low humidity atmosphere. As for pipe wrap: It does seem to work. I don't remember what the R-value is of the foam wrap I bought was. But I gave a leftover section to my friend, whose pipes, also in a crawlspace, had frozen (luckily they noticed and he got in there with a hair dryer and unfroze them before any damage happened). According to what he has told me, that has been enough to prevent another occurrence. I'm just more paranoid. That paranoia has also put me off heat tape.

I though about adding an L just to meet the requirement, but that would add a lot of bulk to the installation. Admittedly it's just a crawlspace and no one goes down there except for me, generally. But I was hoping for a more elegant solution. I may well end up doing this.

As for asking the company: I bought this from a parts wholesaler who, unlike some such companies, is willing to sell to someone who's not a licensed contractor (namely me). But the manufacturer isn't a consumer manufacturer and doesn't give contact info. I asked the wholesaler about vertical installation and they didn't want to say "ignore that" for obvious reasons. The guy I talked to suggested the decreased efficiency that Mike mentioned. He also said repeatedly, though, that he didn't know. So I thought I'd ask for some other opinions / experiences.

I'm bouncing back and forth between just doing the vertical and seeing what happens -- the power draw is very small and goes to something surrounded by metal. It doesn't seem like a likely fire hazard -- and putting in an elbow. If I do an elbow I may use wingnuts to make it removable when not in use.

If anyone else has thoughts, experiences, or suggestions, please do add.
 
pollinator
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There are several different types of bearings/bushings used on fans.  Some types of bushings will wear out rapidly if the fan is mounted vertically.

If the instructions say to mount it horizontally only, then follow the instructions or buy a different fan.  That is unless you like replacing the fan every season, or perhaps twice a season.
 
William Bronson
pollinator
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I like your wingnut solutionšŸ˜
I have used Tees where a turn was too tight for an elbow, but it leaves a dead end on the unused side.
I have also transitioned from round duct to rectangular, to fit into a space.
I would probably try it vertical, knowing it might burn out,and if it did, my next installation would be horizontal.
 
John C Daley
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I have two ideas;
I can see what the issue with the fan is, its the horizontal bearings as suggested- So why not fit it horizontally and put a bend in the ducy to go through the floor?
Secondly, I use a Thermal Temp gun to measure temperatures on my racing motorcycle engines and tyres and I also use it to check temps around my house.
Such a tool if used in the crawl space and record the temps, may ease your concerns.
 
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If the fan has ball bearings that are pressed on the shaft then orientation does not matter. Roller bearings and bushings are loose on the armature shaft and allow the armature to float between bearings/bushings. A vertical installation will have the armature riding on the end of the bushing/bearing and cause improper wear characteristics. Roller bearings require the shaft to ride on the sides of the rollers not the ends (vertical application). The same applies to bushings. Ball bearings will wear on the surface of the ball regardless of the orientation. Vertical application increases friction and shortens the life of the fan. It may also limit fan efficiency. Maybe you could adapt a bath room exhaust fan to your duct as they are vertically oriented.
 
Mike Jay
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Ok, now the devil's advocate is coming out.  I'd assume that most duct fans that people want to install vertically would be blowing upward.  I presume that the OP wants to blow his air downward.  So if bearing wear is the manufacturer's worry, would it be negated by the fan blade pushing air down?

And now to over-explain it...  If a fan is mounted so it blows upward, the bearings have to resist the weight of the blade plus the force from the air it's pushing upward.  If a fan is mounted the other way, the bearings fight the gravitational forces of the blade but are helped by the lifting action of the fan.
 
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into  fn  n is  

chip sanft wrote:So... our crawlspace is unheated and our pipes are down there. I've been using a small fan to blow air from the upstairs through a disused duct into the crawlspace to prevent me having to worry about freezing. (The pipes are all wrapped but still.)

I finally went to the HVAC parts place and bought a duct fan the size of the old duct so that I can blow air down without the little fan. Everything seems to be no bigger a hassle than usual except that the directions for the new duct fan say repeatedly it's only for horizontal installation and I want it to be vertical, straight through the vent.

Anybody know that this is okay, or that it won't be? I guess I'm mostly worried about somehow the motor catching fire or something, though I can't think how. Can someone dissuade or reassure me?



We had problems with occasionally slightly moist air being ducted in to the roof void by some Bodgit & Scarper kitchen fitters , who vented the hob extractor directly into the roof void , leaving the purpose cut vent hole & pipe work unconnected  .
The insulation the roof void got wet .
Which  caused the ceiling boards to sag & increased our heating bills no end as we were heating up conductive moist air in the bungalow , things started to go mouldy & we got chest infections several times till the problem was found .
I rectified it by venting by the cooking moisture  in to correc sized good fitting solid plastic pipe work for some 14 feet horizontally , then out the brick work gable end via a tube & a self closing louver vent on the end  .


The warmed air you are intending to use may well have a fair amount of moisture in it which will tend to condense in a long run when it's cold making your roof space insulation & wood work wet & likely to go mouldy . In a damp state your roof void insulation will be almost useless.  Eventually damp & mould will almost certainly start to also develop in the home .

Once you go past a certain level  of condensate in the pipes it will  either get in the motor or run back down the inlet pipe in to the point of extraction . The fan motors on our new fans have a degree of water protection but they will not run underwater ... neither did the last set of the same model


 In August 2016 .of sair out
Our fully tanked  wet room has our toilet pan ,  shower & tub  , has underfloor electric heating & a two  horizontal low voltage ( 12 volts ) extractor fans with 12 volt LED lights included in the housings , pushing 2.7 cubic yards of air out a minute from each fan set up ,

One in the shower area ceiling & one above the bath tub .   Both were connected to  8 foot long vertical vent pipes & taken out through the roof tiles .by the building contractors ..... Disaster !

We actually got rain coming down the vertical pipes , the water passed under the fan blades to a lower point in the wire plastic vent pipe where it formed a puddle which eventually filled the sag in the plastic hose that developed & started to get very smelly .


I strongly suspect that the following will have a degree of bearing  for you too .
We couldn't work out where it was coming from.  Our fans were on with the lights & for an automated 40 minutes after , which we found was not quite long enough to fully vent the moist bathing room air if all three of us had had showers one after the other .. So when the fan is off there is still warm slow moving high moisture trying to escape out the ceiling set extractor vents .

I've sorted the rain coming down the vent pipes by putting a cowl over each vent pipe tube .
The moisture is now removed by leaving the fans on for at least two hours continuous & then switching the lights & timed fans off manually ( thank goodness for low current 12 volt LED lights & fans )  
 
John C Daley
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It seems wasteful to leave a fan on, to dry out an air tube.
Why not replace it with a steel or smooth plastic duct and eliminate the ponding of water?
 
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It seems to me that blowing hot air down into the crawl space is just a band-aid temporary fix for a larger problem.

I would also assume that the previous owners didn't have a fan down there and the pipes did not break due to freezing.

The best method of fixing potential pipe freezing is insulation for the pipes.  As for moisture the fix is to find where the water is coming in, dig and lay in a sealant - because most likely you have to dig around your foundation and tar the outside of the foundation with weeping tile to move water away from the foundation.

As such you need to plan out when you are actually going to address the underlying issues, and decide if putting in this more expensive vent fan is even worth the expense as it is, or if using your small fan would cover the short term issue and then aim for doing the duct-work properly (with your vertical only fan vertical) and addressing moisture and pipes.

Or, if you don't mind throwing money away, just use the new vent fan as you need and just keep an eye on it and see what happens.
 
David Gould
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Ha ..just read the thread again ... here in the UK a crawl space is the roof void of a low roof ... I now suspect you are talking of a craw space under tthe floor boards on the ground floor level ... am I right ?
 
Mike Jay
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Yes David, you're right.  I was really wondering what you were going on about

A crawl space over here is a shorter version of a basement.  Often it's accessed from outside the house primarily for maintenance activities.  Over here the floor the front door is on is the "first" floor.  The basement or crawl space would be underneath.  I've learned that in the UK the "first" floor is what we would call the "second" floor.  Fun times!
 
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