Drywall contractor wants to bankrupt me!

[Ford850]

You can also tape filters together to form a box to cover air returns, adding 4 or 5 times the filter area.

Those butt board backers for non-tapered seams is fantastic! Butt joints are always difficult for me, and those backer boards would solve the problem.

 

[Ford850]

Yep. Your vacuum example is a good one. All the air in a free-flowing vacuum puts a load on the fan.

Plug the hose = no air = no load = motor revs up freely.

Think of a boat propeller on an outboard motor. Lift the outboard up and the prop comes out of the water and the engine revs up because there's no load.

Air is a fluid.

I've heard this many times but never took a minute to think about it until now. It makes perfect sense, since a lugged motor does not rev, it slows down.

 

[MossRoad]

I've heard this many times but never took a minute to think about it until now. It makes perfect sense, since a lugged motor does not rev, it slows down.

I remember the first time someone explained it to me, too. I stood there blinking into space for a few seconds. :laughing:

 

[dnw64]

I've heard this many times but never took a minute to think about it until now. It makes perfect sense, since a lugged motor does not rev, it slows down.

I think the reason some people (myself included) tend to/have think/thought about it in the reverse is because a typical small engine is designed with a governor to increase output under load. It doesn't (generally) actually increase RPM, but the increased power output has a similarity to increased RPM. So when you hear increased RPM the resultant thought is typically "increased RPM".

 

[Industrial Toys]

Funny, it always sounds like the vacuum cleaner is in great distress when you block off its air supply!

 

[Oldstuff]

I have always heard that drywall should be maintained at 40 degrees or more-year round. I have a house on a lake development where there are houses/cabins and some of them are heated year round and others drain the plumbing during the winter months and do not heat them. After looking at many many of them I can tell you that the ones that are NOT heated year round almost all have drywall cracks.

 

[quicksandfarmer]

This may sound counter-intuitive, but the opposite is true. The reason a vacuum cleans revs up when you plug the intake is not because "the governor is telling it to send more power", it's because there is less air moving through, which requires less power.

I learned this after installing a VFD on our dust collector. All the blast gates open - maximum amperage draw. All blast gates closed - minimum amperage draw.

You are correct, but it is not the fan that is the component of the HVAC that is stressed by clogging. If the filter is clogged there will be insufficient air flow. In heating mode, this means that the heat won't be moved out of the heat exchanger, which will cause it to overheat and the burner will cycle on and off. Meanwhile the house doesn't get heated. In cooling mode it's even worse, if the coolant isn't warmed enough it can return to the compressor as a liquid which can destroy the compressor.

 

[dnw64]

If the filter is clogged there will be insufficient air flow. In heating mode, this means that the heat won't be moved out of the heat exchanger, which will cause it to overheat and the burner will cycle on and off.

Good point. I would hope that the filter would be changed before it got to that point though! Speaking of which, do modern hot air systems have sensors that will send an alarm when the negative pressure in the blower gets too great? Our spray booth has a gauge that shows the pressure drop so we know when to change the filter based on how dirty they are.

 

[civilian]

Ooo, I like that hose trick!

I killed one shop vac doing drywall cleanup during my reno. I'll try one of those bucket cyclones if I have to do more.

What I have is that same sanding pad with a hose connection to a shop vac. But from the sanding pad, I run the hose to the bucket cyclone filled with water. Drywall dust goes into the water, the clean air goes to the vac. When done, pour off the water and you have drywall mud slugdge, that some have told me they us on the walls again. I don't do that, though. I also wash the drywall tools/pans, in the laundry tub, BUT I wash over a bucket. All the dirty water goes in the bucket and gets dumped outside. Jon

 

[plowhog]

I have always heard that drywall should be maintained at 40 degrees or more-year round. I have a house on a lake development where there are houses/cabins and some of them are heated year round and others drain the plumbing during the winter months and do not heat them. After looking at many many of them I can tell you that the ones that are NOT heated year round almost all have drywall cracks.

I have a cabin in the Sierra Nevada mountains with a lot of drywall. The only source of heat is a wood stove, and I visit maybe once per month in the winter-- sometimes not that often. So it sits very cold for long periods but I have never seen any drywall issues. Next visit I will examine the drywall much more closely.