Negative pressure in new studio need help

BlandStudios · #1 2014-03-19, 10:17am

I just had an addition added to my home to use as my studio. I have a 750 cfm inline exhaust with a large cone shaped entry. I had a portable ac unit installed that has a fan mode or ac mode but this is not bringing in enough air.

The ac is immediately sucked from the room when I turn on the exhaust and I start to feel sick after a short time at the torch. I am in Florida so I don't want to open a window. My desk is stainless steel and I can't add a vent under the desk.

I can have the contractor add a 6" vent to bring in return air ( I have 6" exhaust vent). I don't understand the best place to direct the return air for safety and to try to keep the ac from being sucked out my exhaust.

I would love to hear some suggestions.

silverlilly1 · #2 2014-03-19, 10:27am

You want the air to flow over your bench from the inlet to the exhaust. The air inlet should not be within about 6 feet of the exhaust vent on the outside of the building (there's a bit of margin of error in there - for safety, vent lines for natural gas appliances can't be within 1 m of a building opening (window, door, dryer vent, etc) by code in Ontario. A similar rule of thumb should apply. If you can get it on a different side of the building, that would be ideal.

Alternately, you really shouldn't have an issue with getting enough air in if you can even crack a window or door 2 - 3 inches (as long as it's not beside the exhaust vent).

getdul981 · #3 2014-03-19, 10:39am

Quote:

Originally Posted by BlandStudios

I just had an addition added to my home to use as my studio. I have a 750 cfm inline exhaust with a large cone shaped entry. I had a portable ac unit installed that has a fan mode or ac mode but this is not bringing in enough air.

The ac is immediately sucked from the room when I turn on the exhaust and I start to feel sick after a short time at the torch. I am in Florida so I don't want to open a window. My desk is stainless steel and I can't add a vent under the desk.

I can have the contractor add a 6" vent to bring in return air ( I have 6" exhaust vent). I don't understand the best place to direct the return air for safety and to try to keep the ac from being sucked out my exhaust.

I would love to hear some suggestions.

We just had an addition built onto our garage/house for the purpose of me torching. The builder asked if I wanted AC and I told him no, because I would have to leave the door open anyway for the make-up air for the exhaust fan. I live in Florida also and I hope I will be able to tolerate the heat this summer. I do have a fan that sits on the floor which I can turn on if I get too hot. So far, it's not been too bad.

BlandStudios · #4 2014-03-19, 11:53am

Thank you Mellisa. We did cap off a dryer vent on the opposite side of the room almost directly behind my chair. I can open up that vent to bring some return air in from the garage. I can also try cracking the sliding door that leads into the main living area....that way I shouldn't loose too much ac.

Thanks again :0)

houptdavid · #5 2014-03-19, 1:54pm

Exhaust should be at least 10' to any intake makeup air

Add some makeup air under/in your bench

Good luck with the A/C

750cfm is going to change the air in a 10'x10' room with an 8' ceiling about every minute

BlandStudios · #6 2014-03-20, 5:00am

We have decided to put register vents in the ceiling with dampers. We will position them behind the desk so return air is coming from behind me and across the room towards the torch and exhaust.

Thanks everyone

BlandStudios · #7 2014-03-20, 5:04am

Greg,

If it gets too hot for you with just a fan, let me know. I can send you pictures of the portable ac unit we got from SAMs Club. We piped it to the outside during construction. It gets pretty hot in the summer.....

Happy Torching

Eileen · #8 2014-03-20, 7:57am

I'm in Florida too. I have a separate shed for my craft shack, and we added a room a/c because of the heat. I have a small window behind me that I leave up about 2-3" when I have the torch lit, and running the A/C doesn't keep me cool, but it keeps things bearable, and cooler than the outside in the middle of summer. My fan isn't that strong though.

Dale M. · #9 2014-03-20, 8:01pm

FYI .. For all those under misconception that airconditioning is part of ventilation (fresh air inlet - makeup air) most system do not supply fresh air, they just recirculate room air.....

If you want to keep room cool and still have plenty of make up air look at second graphic in this write up on ventilation...

http://www.artglassanswers.com/forum...php?f=22&t=150

Note a large percentage of make up is flow through confined area and does not pull much "room air" that you have spent $$$ heating or cooling...

Dale