Inline booster fans - hvac duct work

Would the warmer rooms be on the upper levels of the home? If so you might consider a squirrel cage type fan sitting over a duct in the upper level as long as there are no little fingers around. Not sure another fan installed in the basement level (where the duct is open to work on) would do any good. Cold air falls so pushing it up high is difficult, we lived in a 3 floor home once and the upper bedrooms were never cool in summer.

Before you add fans, be sure to seal your ducts, especially close to the blower, make sure your returns upstairs are open, and close the vents in the rooms that are too cold.

While I agree with the advice of sealing up the ducts, adjusting the dampers, and closing unused vents, four things were forgotten - replace the furnace filter as an old clogged filter can really reduce air flow, vacuum out the furnace especially around the filter, the heat exchangers and the fan as it does get dusty in there even with a good filter, vacuum out the cold air return grills and the order that these things should be done.

I figure that the order should be:

1. Check the furnace filter.
2. Vacuum out furnace area.
3. Vacuum out the cold air return grills.
(By doing these three first, you can verify that as much air as possible is getting into the furnace and out of it).
4. Using Aluminum HVAC tape for ducts (not Duct Tape), tape the seams of the duct work around the furnace. This area is usually the easiest area to get to and has the most air leaks as it's under the most pressure. Anything in the walls or in crawl spaces are secondary due to difficulties in access.
5. Open up all vents and adjust the dampers to fully open (the dampers adjustments are usually on the outflow side of the furnace ducts). Once they are all open, you can check which ones have the most air coming out and which ones don't. Adjust the dampers separately to see what damper adjustment controls what. Typically they go by floors but sometimes it's completely illogical so it's best to first that out first.
6. Once you know what adjust what, see what areas have a strong flow and which ones have a weak flow and adjust the strong flowing area's damper so that it cuts down the flow to those areas. This should in turn increase the flow to the weak flow areas.
7. Once you get the dampers adjusted, then you can use the registers to do fine adjustments between rooms connected to the same damper.

Thank you guys a lot for replies.
The duct system was renewed this year before I buy the house, I got a raised bangule bungalow: basment , lower level , main level and upper level.
Most of the room gets poor air flow so whenever the temperature is about 30s yu can say there is no AC at all ! Even the main level is not cool enough coz its an open concept living+ dining + kitchen
Thats what happened and thats why I am looking for a trusted company or guy based on your experiences

What do you mean by "the duct system was renewed"?

I meant they have installed a new duct system

DawoodA586582 wrote: ↑ Thank you guys a lot for replies.
The duct system was renewed this year before I buy the house, I got a raised bangule bungalow: basment , lower level , main level and upper level.
Most of the room gets poor air flow so whenever the temperature is about 30s yu can say there is no AC at all ! Even the main level is not cool enough coz its an open concept living+ dining + kitchen
Thats what happened and thats why I am looking for a trusted company or guy based on your experiences

*edit just read previous post*
Sounds like they did a really bad job rebuilding it if that's the case. You should be very sure that all of your returns are open, and all of the duct dampers are open. They're are usually just after the blower as the other poster mentioned.
You should also close the vent/damper to your humidifier, as that will reduce airflow as well.

If the airflow is poor than the problem is not the AC, either the HVAC blower is insufficient/failing or the duct system is undersized or very poor and leaky.

There are companies that can pressure test your ducts for losses, then spray a sealant into them to plug the holes. Costs about $2k (I think) depending on the size.

jackrabbit000 wrote: ↑ craftsman mentioned air filters, I'm using the 3M Ultra Allergan 1500 filter in my furnace. It has around 5-6x more pleats in the filter and should give you a higher air flow.

OP may also want to test his system without an air filter to rule it out (temporarily).