when should the A/C be turned on in a house under construction? there's painting still going on inside and lots of work to be done. It's mid 90's outside right now(and humid). Will the workers get mad if I don't run the A/C? (which was just installed). the HVAC guy said it's o.k. but never when floor sanding. Which brings up another question. Should I run it for the benefit of the floors i.e. to get them to an "indoor" humidity level?
There is a tremendous amount of dust floating around during construction. Even though you have filters the stuff will still get into the ducts. I would not do it unless a contractor needs it for the paint to dry or the floors to acclimate. If you do turn on the system, get a load of filters and replace them at least weekly. Use the good pleated filters.
You can run it, but plan on checking/changing/cleaning the filters on a weekly basis at least. The AC guy should have mentioned that you shouldn't run it if there's any drywall being sanded. That dust is the worst. And you should ask that any substantial cutting of any materials be done outside - unfortunately that's going to be a tough sell with a nice cool house sitting there.
I don't know if the workers will get mad, but you might return to the house to discover that it's already been turned on and nobody knows who did it.
If you do decide to run it for the workers, they'll appreciate it, you'll get better work out of them and won't have all of their sweat dripping on your new house, but you should make it clear that the system is not to be abused. If someone doesn't obey your house rules, you'll turn it off. Turning it off once it's on _will_ come across as punishment and that's not a good thing when people are working on your house.
If you don't want the system running at all, you should make it clear that the system is not operational and if there is any damage due to unauthorized use, you'll be charging the contractor.
Another suggestion. If your new system has one of the high efficiency 5" thick filters, like a lot of new ones do, then take that new $50 filter out and put in a stack of the standard 1" filters. After all the work is done, then put your good filter back in.
If the filter is in the filter grill and it a high efficiency filter and the ducts do not leak the ducts will stay clean.
If the filter is at the furnace no filter will keep the return clean.
If the filter is not a high MERV rating the system will get dirty no matter where the filter is. a. High MERV rated filters produce high static pressure and should not be used unless the return grill is sized properly.
If the return ducts leak (always do unless duct sealing and testing is performed) and any of it is in the conditioned space.
If all the above is correct I=92d get a good supply of filters and it checked daily to be sure it is not plugged. Better yet have a static pressure probe installed and replace as the static pressure goes up. This is how all systems should be set up to determine if the filter is producing too much static pressure.
Let=92s think about putting 5 low MERV filters on top of each other. It does not make the hole size smaller. The size of the hole is what removes the smaller particles. It may catch a small amount more dust but not sufficient enough to keep your HVAC system clean.
If one installs 5 high MERV filters it will restrict the air flow and likely ice the AC coil and this can cause issues like sending liquid refrigerant to the compressor and this will shorten the compressor life.
So in conclusion: Install the 4-5=94 or a 2=94 over sized pleated filter (I would hope this is what is in the system and is at the return grill). Check it every day and replace as needed. Yes it is going to cost but it=92s your choice. Spend some now or have your ducts cleaned and spend more later.
Cleaning ducts is not a perfect science and will not clean everything. There is also the concern of tearing the duct lining. So if you have ducts cleaned there should be a duct test for leakage before and after. Good luck finding a company that will do testing and if you do you will not like the price.
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