Hi Lee,
Can you tell my how many CFM the engineer and contractors proposed to exhaust. Is it ultimately a flat roof on top of the building directly above the attic space ?
Thanks
Mark
Hi,
Did they specify a certain of duct for this ?
The raw price of a 2,000 CFM make up air unit with heat and exhaust costs about 2,000 dollars roughly. The rest of it is installation , wiring, piping etc. 30,000 seems like a lot unless the installation is incredibly tough. I recently installed a 2,000 CFM class 1 hood system in a restaurant for less than 18,000 dollars, wiring piping complete including the hood at 6,000 dollars.
Do you have any idea if you have any excess steam capacity ? My thought is that you may be able to use your central steam boiler to heat the necessary fresh air.
No, I don't know the type of duct, but I would assume it's nothing more special. They said it cost around $10,000 for the system. I probably don't have excess steam capacity. We have a little left right now from our boiler, but it's for the future machines that we will install for pressing. The installation is not easy, but I don't know if it's incredibly tough. Basically they cannot put it on top of the attic, so they will put it at the back of the shop, and then duct the exhaust part to the front of the shop, and then leave the make up air at the back. I have another quote for $20,000 with a 45x94" canopy, 2 speed exhaust fan up to 5000 cfm, make up air unit HE-50 (roofing, electrical, gas costs excluded from price). So at the end it's going to be close to $30K. We are hoping for some creative way, maybe even internally so we don't have to go through the city inspection. But if we have to install something new, or touch the roof, then we need permit for it. Or maybe someway to modify the existing system... but it's not that strong at all as it was installed for a regular space, not a drycleaning shop. I just don't have the money and probably exhausted all the answers for more economical ways, but still hoping for someone who may know something that no one else does....
I'm sure the second option was a class 2 hood which sounds like a reasonable answer.
Reality is that you need to exhaust the steam because the cost of dehumidifying it would be very expensive. I don't know that there is a shortcut and as you have said you have already tried the obvious things such as just running air through the area. I don't know why they were going for a 5,000 CFM hood though when the engineer only asked for 2,000. That's quite a bit of cost difference in the two systems , initial installation and operationally.
You could try opening the outdoor air damper all of the way on the rooftop unit and using 100% outside air on it , this will cause the unit to exhaust all of the air it sees from inside the building and bring in all new fresh air. That's the easiest thing you can do and see if it helps.
Sorry for the little time off - I was trying to figure more things out with the shop. We went up to the roof and had a look at the unit, and not sure how you would open the air damper 100%. I am new to all of this, and to me, it seems to open and close on its own -someone told me it depends on the air coming in or out or something. Now we are wondering if the system is working properly because when we were there, we turned on the fan/cool and it did not seem to suck a lot of air out... it was very very weak. The A/C was working though.
What do you think of this proposal so that I can get away with the city inspection? Are we allow to distribute air around the shop internally? What if I install an exhaust fan with ducting so that we will distribute the hot air from the hot area to the back of the shop where it's near a door. If we have the door closed, the hot air at least will stay in the back where we don't go to often. If we have the door opened (which is 99% of the time), I would think there will be some outside/inside air exchange since we will duct it pretty close to the door.
At the work area, I am also thinking of getting a good capacity portable evaporative system, and use what they called "air sock" or "plastic piping" to pipe the cooled air to each station and have it blow at the workers' body to help cool them down.
Combining the redistribution of hot air, and the cooling air sock, I know it's not the best way, but to us, it is much cheaper. Or is it? Do you think it will work? And if it does, since I don't know what they are selling out there, what exhaust fan and what evaporative system do you recommend?
I would check with the inspector if any of that will meet code, it probably won't.
On the unit, I was referring to making a modification that will keep your outdoor air damper open anytime the unit is running, you can try this by just unlinking the damper and seeing how it works but to make it permanent you will probably need an HVAC service company to devise a control for it to operate correctly in the winter. Your rooftop unit can probably also be fitted with an exhaust fan. I would look into those options first as it is going to be the least expensive options that have a real chance of working in my opinion. Any refrigeration equipment you add to this system is going to cost megabucks to run.
Journeyman Technician
UA Journeyman Pipefitter , HVAC, Refrigeration, DDC controls. 26 years.Commercial & residential
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