Should returns size in each room match supply

[jpsmith1cm]

taxman

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[54regcab]

Anything less than 300-fpm velocity is wonderful; the lower the velocity through an extra large effective sf area filter the better.

Hart&Cooley Engineers say NOT to go over 400-fpm with a new clean filter; especially with a cheap throw-away filter; that only provides 100-fpm increase for debris loading of that particular fiber glass filter...

The velocity should never exceed 500-fpm when using a cheap fiber glass throw-away filter; pleated filters can go higher but the 1" thick pleated filters have too much pressure drop at those higher velocities.

Filter area sizing can gain or lose important efficiencies in important HVAC arenas; both filtering health & cleaner blower wheels & coils plus airflow efficiency areas.

While we're at it let's not forget unbalanced returns. It isn't uncommon to find 75% of the air going through one of the returns while the others barely move any air. Especially true when one return is a lot closer to the air handler.

[mudgod]

@udarrel/welling service
I use angies list to look up providers (calling up the higher rated ones). I've called 4, 1 of whom refused to do a Manual J / D, two said they don't do it at all and one said they'd have a senior guy give me a call back. I'll be trying a couple more

@udarrel
I've currently got a 1" 18x20 filter installed (The return plenum is 21*22*20). From what i'm reading on here. It sounds like I should have a 4" filter of 20*25 size (2.5 tons = 1000 cfm and 1000/2 = 500 sq inch of filter). Should I ask them to replace the plenum and get a bigger one installed with the capacity for that sized filter.


@54regcab
The BR2 is getting too hot while BR3 is getting too cold.
I've measured temperatures of
MBR (location of thermostat) = 75, BR2=81, BR3=70
Keeping the doors of all rooms opens its much more even +/- 3 degrees

None of the guys so far have mentioned installing dampers on the returns or anything like that, what do you mean by unbalanced returns? and how would that be rectified? closer ones needing to be smaller not to pull all the required air?

[mudgod]

One other thing, reading the forums here it seems that the Ductboard triangles are the worst thing to do and that is what I currently have. Three Flex take-offs going to triangles. One for the MBR, one for BR2 and one for BR3/4 and then flex ducts going to the registers from the triangles.
I read that the best thing to have is wye's. I would eventually like to upgrade that to a 3 zone system and therefore the triangles made sense from that perspective.
None of the techs commented on them being bad. One mentioned that they prefer using metal junction boxes instead but nobody recommended changing them out.
Would the square metal junction boxes be better then the triangles or have the same problems. Basically should I keep the triangles or spring for an upgrade

[54regcab]

I find if very odd that BR2 and BR3 are 10 degrees apart even though they both are the same size rooms and have the same size and length of ductwork. Does BR3 face North or have lots of glass areas? Is BR3 hotter than other rooms in the summer? Does BR3 vents seem to have lower airflow coming out of the vents vs BR2? Is BR3 conductor pinched/blocked or obstructed in some way?

[jtrammel]

@ 54regcab
I'm not sure, but the distances are also proportional to size (neglecting bathrooms/hallways) so not sure which is factored in more
BR4=10-12ft run/ 160sf/7" flex (off of 10" trunk)
BR2=20ft run/ 200sf/7"+6" flex (off of 10" trunk)
BR3=20ft run/ 200sf/7"+6" flex (off of 10" trunk)
MBR=30-35ft run / 420sf/7"+6"+6" flex (off of 12" trunk)

@dan sw fl:
I've had three contractors out so far. Two used a manual slide rule to calculate sizing (I believe a ductulator). One simply took measurements and left and I haven't heard back from him yet. None of them suggested a Manual D or a Manual J


@Udarrel: Yes I have but I wasn't sure of what I should be looking for. From the companies I looked up they seemed to be offering widely divergent services with a good deal of them being tied into weatherization (things like 300 off weatherization if you get an energy audit). The place itself is relatively new and is well insulated with high efficiency double glazed windows, weatherstripping on all doors etc. I didn't want to waste money if it was going to suggest the obvious things which I've already taken care of. Is there a specific kind of audit that I should be looking for in relation to HVAC?
Also the place is around 4500-4700 sf with the basement being around 1100 sf and the main / upper levels being around 1700 sf each (50*34 footprint)

A lot of times new construction homes have worse air leakage and pressure imbalance issues than older homes. Check out this site www.comfortinstitute.org to learn more about a home energy audit/home comfort checkup