Putting speed control on attic fan

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This is the one on Broan's website
http://www.broan.com/display/router.asp?ProductID )56
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I always call my whole house fan, an attic fan, because that's what it is, in the attic.
I use a green plug to slow it down a bit.
Greg
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On Mon, 1 Aug 2016 08:56:50 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

Sure you can - if you have the right roof fan.
More info required.
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My father had this same problem! When attic fan was turned on, the pilot li ght on HWH would get sucked out! Also sucking carbon monoxide back down the HWH exhaust. So I asked him if this was always an issue, and he said no. I knew he had the attic fan motor changed when I was living there. So I ask ed him if he had the booklet for the original roof fan and he did! After ma tching specs from the old motor to the one that was in there now I found th at the new motors RMPS were much faster. So I replaced the motor with one o f equal specs to the original motor! Problem solved. The house has plenty o f venting in the attic. The motor that replaced the original was just way t oo powerful! Also the attic entrance is in his bedroom closet accessed thro ugh a 3 foot by 3 foot opening. Just thought I would share. Good luck
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You have solved partially problem you will still get from time to time sucked carbon monoxide in because you are making up air through the exhaust of HWH. Suggestion get some one who knows how Ventilation works. It is better to pay then being dead.
wrote in message
My father had this same problem! When attic fan was turned on, the pilot light on HWH would get sucked out! Also sucking carbon monoxide back down the HWH exhaust. So I asked him if this was always an issue, and he said no. I knew he had the attic fan motor changed when I was living there. So I asked him if he had the booklet for the original roof fan and he did! After matching specs from the old motor to the one that was in there now I found that the new motors RMPS were much faster. So I replaced the motor with one of equal specs to the original motor! Problem solved. The house has plenty of venting in the attic. The motor that replaced the original was just way too powerful! Also the attic entrance is in his bedroom closet accessed through a 3 foot by 3 foot opening. Just thought I would share. Good luck
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I already told about my green plug, slows fan down 10-30% depending on motor and load.
Grab the old incense stick and check all wall outlets, switches, pot lights, etc. With Ac off also check all air vents. Most tend to have leaks to the attic when mounted in walls.
While your at it, you can do a check of leaks in windows, doors, etc.
I use my fans to do an energy audit.
Greg
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wrote:

Probably getting around the basement sill plates, HVAC ducting and piping, then up through the walls and into the attic. In my house, circa 1959, none of that is sealed. Haven't looked at the attic sills, but I'm sure they're not sealed either. I don't think they sell green plugs any more. You have the right idea, but he should go after the basement overhead first if wants to solve the attic fan induced downdraft in the water heater vent. Somebody wrote about a thermal switch between HW and attic fan and that's a good solution too. Personally, if the draft didn't take long to be established with the attic fan running, I'd put the horizontal diverter back in. This is what they look like, and Mike had one on his old heater. http://www.standexadp.com/specs.php?spec ( That would prevent pilot blow-out and overheating the top of the tank. I never had a pilot blow out with these but have with the hood style diverter. I'm not sure about spillage, but just guess it would be less. You also need a CO detector nearby to play it safe. This isn't a new draft problem, just a new water heater and venting.
--Vic
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wrote:

What exactly does that diverter do? It is open on the bottom, right? Thats what I had on my old water heater. Plus whoever installed the previous water heater eliminated the draft hood for some reason, and just put the 3" duct directly on top of the exhaust outlet. Now I'm wondering if they did this because of the backdraft problem.
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On Tue, 23 Aug 2011 10:44:32 -0700 (PDT), Mikepier

Diverts the backdraft, same thing the vertical hood diverter is supposed to do. But it works better. There's a flat baffle plate that runs half way down the box, interrupting the air/gas flow. A backdraft hits that plate and dumps out the bottom of the box. Never hits the top of the heater flue, where it can blow out the pilot. Hot gasses from the heater also hit the baffle, and drop down. But those hot gases rise back up at the bottom of the baffle, and continue up the vent.. Elegantly simple.

I saw somewhere that the hood type diverters came into play in 1992. Your old heater was probably just an original installation. Unless you know the heater was put in after that time. I noticed the one in the pic showing your old installation, and remembered examining and moving mine while doing some chimney sealing in my old house. I figured out its purpose out of curiousity. I also think I left it on when I put in a new heater with a dome vent. But it is really amazing how you can find absolutely no information on horizontal diverters on the net. Everything I said is from memory, not the net. All the so-called experts in the HVAC forums never mention it when answering questions about how to stop downdraft from blowing out pilots or melting plastic on the top of tanks. Now me and the other folks in this group who happened to read this are the only ones who know about horizontal diverters.
--Vic
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Vic Smith wrote:

This guy doesn't need a horizontal diverter.
His pilot isin't being blown out.
If you've got a constant down-draft in the chimney caused by negative air pressure inside the house, your horizontal divertor will do squat at helping exhaust from the water heater to make it up and out the chimney.
So are you going to keep telling him he needs a horizontal divertor?
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I must have confused that with the match blowing out during his testing, and all the crap I've read on the net.

Maybe, maybe not. It for sure would dump the heat elsewhere instead of melting the plastic atop his heater. And he never said how long it took the draft to get established when the heater went on with the attic fan running. My reading indicates spillage is pretty standard for up to a minute.

Only if it's acceptable to him, and it works for him. Since his pilot isn't blowing out it would just move spillage away from the heater top. Burnt plastic atop the heater appears to be a fairly common occurrence. Here's my order of preference, "by the book." 1. Crack open a basement window during attic fan season. Easy, and he said that works. 2. Thermal switch between heater and attic fan. Moderate job. 3. Seal the basement so attic fan has no effect. Big job. 4. Modify chimney for better draft - if possible. Big job.
Throwing out most of the book, here's what I'd do. 1. Crack open a window if it doesn't affect anything else. 2. If the cracked open window wasn't acceptable, I'd measure how long it took a draft to establish with attic fan running. If less than a minute I'd forget about it except to make sure I had a working CO detector near the heater. If the heat melting the plastic bothered me, I'd add a horizontal diverter. Then I'd check spillage again. That would the interesting part. Anything I did that wouldn't keep spillage under a minute would get me back to the "by the book" list.
--Vic
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Vic Smith wrote:

What the hell is wrong with you people?
He holds a match near the gap where his draft hood meets the water heater, and the match goes out.
He says his pilot (way down at the bottom of the heater) does not get blown out.
Why he even thought he should even check to see if he's getting a breeze blowing out of the draft hood - I don't know.

I see that basic physics is beyond your grasp.

He doesn't have a problem with "dumping heat".
And by the way, if a divertor is dumping heat to some other place besides the flue, what does that tell you about where you're dumping the combustion exhaust gases?

I don't think he even said it ever gets established with the roof fan running.

He's a boob because he doesn't want to climb a ladder or pick up a saw and cut some more holes in his soffit.
I wonder if he really knows how much of his soffet venting is actually clear vs obstructed?
Does he have insulation jammed into the corners of the roof line, obstructing his soffits?
He obviously must have a direct path in his house from attic to basement that he doesn't know about.

What spillage?
WTF are you talking about?

The OP (Mikepier) has NOT SAID (at least not in this thread) anything about burnt or melted plastic on his water heater.

Bullshit.
If you don't have enough ventilation in the attic (soffits, gable ends) then why bother running the roof fan in the first place?

More bullshit.

He should find out why there is such an easy path between his attic space and the rest of the house / basement, and close that path.

That won't help if there's still a negative pressure inside the house or basement caused by the roof fan. Why is that concept so hard for you to understand?
The **ONLY** way you can have proper drafting for the furnace and water heater in his case if he allows his house to achieve a negative pressure is to seal the room or the area where his furnace and water heater is, and give them a new combustion air intake from the outside.
Or he can turn his furnace and water heater into a closed system by bringing sealed ductwork directly to the combustion air intake vents or the cabinets and running that ductwork to a dedicated outside air intake, and then use lots of aluminized tape to seal up his furnace and water heater so there is a completely closed path from from the outside air intake to the furnace / WH to the exaust flue to the chimney.
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" snipped-for-privacy@optonline.net" wrote:

I don't know what you're talking about.
The ONLY posts that I see Mikepier posting in is this thread, with the subject "Putting speed control on attic fan". If he started an older thread about melted plastic on water heaters, then I didn't read it at the time, or he didn't post it to this newsgroup.
He hasn't said anything about melted plastic in this thread.

Read my statement more carefully. I said "at least not in this thread".
My 4-year-old water heater also has melted disks of read and blue plastic surrounding the two water pipes (hot and cold) at the top of the tank. I don't have a negative air-pressure situation in the house. The melted plastic doesn't bother me.

Why can't you read properly?
Look what I said:
"and give them a new combustion air intake from the outside"
Look what you just wrote:
"by providing a fixed ventilation opening to outside for the basement"
You look like a fool when you disagree with me, and then go on to give the same answer using different wording.

If he doesn't want to actually fix his home's internal air circulation and attic venting problem, then he doesn't have many other alternatives to deal with a negative air pressure. I'm not saying that pulling a rube-goldberg ductwork job on his water heater and furnace is the first thing he should do - I'm saying it's the last thing he should do.

It doesn't matter when you've got a negative air-pressure situation in the house that you need to deal with first.
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His first words in this thread were:
"A few weeks ago I posted a problem with too much negative air pressure in my house caused by my attic fan."
I even provided youi with a direct link to that post yesterday. Seems for someone so interested you would take a look.

Still to lazy to read the other thread?


Not the same answer at all, you claimed he had to seal the area around the water heater or the room. He's already proven that just opening a basement window fixes it.

You didn't specify first or last, you just said he should do it. Whether it's first or last, I think everyone else here would agree that it's wrong to be using tape to fashion some kind of hack job connection from the water heater and furnace to outside air. You think that will pass inspection?

Again, there was no qualification in your blanket statement saying that correct chimney sizing does not matter. Correct chimney sizing does matter, as you've apparently now learned, so you're trying to now get around it with a qualification. That's like saying it doesn't matter if you use a ground conductor to carry current because someone is having a problem with a switch. Code is code and it always applies.
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Sound like you have bad draft. Shouldn't be that much spillage. Probably won't matter though. Do you have a CO alarm? That's a good safety measure.
--Vic
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You've probably never seen a horizontal diverter. I can make a good case why they're better than a dome for establishing draft, but won't And why do you think a downdraft that blows out a match can't be overcome with heat to establish an updraft? Lots of houses have negative pressure. Depends how bad it is.

That's what melted the plastic on top of his heater. He seems to think that's a problem. I wouldn't like it if it happened to mine.

I don't want to confuse you here, and since I don't have all the info from Mike I could be wrong. This assumes he had the same attic fan running before with the old heater and hasn't tightened up the house. The downdraft existed before and nobody was poisoned by CO. He only noticed it now because with the horizontal diverter gone the dome diverter on the new tank spilled enough heat before it established a draft to eventually melt the plastic. If he has a working CO alarm and there was no draft established it would have went off. Mine went off when a squirrel got in the vent. Mike can say if my assumptions are wrong.

I don't think he tried. He's not too talkative. But if he has a CO alarm and no draft with a firing heater it would go off. And he'd most likely smell it and feel the heat if he was nearby.
snip soffit vent stuff.

That's what HVAC guys call gases escaping diverters until draft is established. They also test with negative pressure in the appliance room. http://virginiahomeperformance.com/yahoo_site_admin/assets/docs/Gold_Sheet.185172811.pdf You can get an idea of how many houses are under negative pressure here. Pretty good study they did when homes were near an airport were soundproofed. http://www.state.mn.us/mn/externalDocs/Commerce/Ventilation_and_Depressurization_Research_022003031343_VentilationReport.pdf

He mentioned it in a prior thread.

Got no idea why you say that. It already worked for him.

So you think that because an attic fan causes some negative pressure in the basement it's not cooling the attic? Nonsense.

Somebody else did it to solve the problem.

Already been covered, And it doesn't have to be an "easy" path. Older houses have hundreds of paths where air can migrate.

You still don't understand a negative draft can be reversed by heat.
--Vic
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Mikepier wrote:

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No. The frequency of the mains controls the speed. The voltage has minor influence, and low voltage can damage the motor by overheating it.
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