what size is this unit?

[jimpy]

American Standard

AUY080R9V3W5

It seems to not have quite enough CFM's to blow to far rooms. In other words, it heats the central portion of the house OK (just OK, though), but I have to choose to adequately heat either my kids' two BR's or my large LR. Can't have both warm. Cooling does not seem to be as much of a problem.

Can a slightly larger blower motor be installed or will this mess everything up RE: cooling, BTU's, etc. I have already adjusted dipswitch settings to higher CFM setting, so no further airflow there. What about an inline duct booster fan?

The system is five years old, has a heat pump with gas back-up and is otherwise serving well. But when it gets really cold, I have to choose where to be cold.

Thanks,

Jim

[saylor240]

do you have any balance dampers in your duct?

looks like a 80,000 btu furnace.

[jimpy]

yes, dampers are installed on most runs. I was not pleased with airflow to some rooms (as noted), so I adjusted some slightly (marked original settings, though). Now, I can get more than adequate heat to the bedrooms, but other rooms suffer. Will a duct booster just steal airflow from other runs?

[jimpy]

yes, 80K btu seems about right, but could a larger blower get installed, say bumping from 2.5 tons to 3 or from 3 to 3.5 tons? Can't remember what size this unit is and just wrote model # before leaving the house. If you need more info RE the system let me know.

[saylor240]

hummm how abotu returns...do the bedrooms have returns? but i agree with jimpy, if your out of cfm ...your going to have to go bigger, and yes a duct booster going to just couple rooms will only steal from other areas

[jimpy]

return in hall and another in DR.

[jimpy]

will adding more cfm reduce efficiency of cooling since more/faster airflow across coil? I guess it could be trimmed back on cooling side, right, so as to blow at same cfm (or nearly so) as currently when cooling.

will adding more cfm reduce ability of heat pump to deliver heat as more air will be passing across coil?

[saylor240]

when you change out blower motor and do not go with manf specs then its kind of a guessing game from that point. but you can always get a multispeed fan.

but you may want to consider adding more returns in the rooms to help circulate the air better.

[kontrolsfreek]

Have you considered a zoned system or is that not possible? Zoned systems do a great job redistributing the air around your house as the load changes. If the system is properly sized this may be your fix instead of going with a larger unit to move more air. Just an idea.

[jimpy]

The unit is five years old. The only other room that could use a return is the only place I can't get a return back to the unit. How much trouble is it to retro-fit a zoned system into an existing system. I assume zoned system needs a return in every room that is served by the zone system.

[jimpy]

how would a multi-speed fan differ from the variable speed blower motor I have now?

[kontrolsfreek]

A multi speed fan usually operates on only two speeds, one for cooling and one for heating. A varible speed fan starts off at a slow speed, then over a period of time begins to ramp up. At then end of the call the fan then starts to ramp down. Returns in each of the rooms would help with a zoned system but it is not critical for the zone system to operate.

[jimpy]

So, if a zoned system is out of the question and the unit is too new to replace and it is not advisable to install a larger than spec blower motor, does anyone have any other suggestions? I feel I have probably unbalanced the flow so bad from original installer balancing that maybe I should get them to come out and rebalance.

Thanks for your time

[kontrolsfreek]

A zone system may not be out of the question, unless the duct is unaccessable. If you have access the zone system can be a easy retrofit. Honeywell should have a list of contractors that can advise you on a zone system further. Also make sure that the heat loss/gain has been calculated to ensure that your system is properly sized.

[beenthere]

A larger motor is basically. A bad idea.

Can you measure the temp of the air at your closest supply to the furnace, and the air temp at the closest return register.

Good chance, its your duct system that needs alterations, and not the furnace.

[jimpy]

If the nearest supply and the nearest return are about 10' apart, around a corner, what would that air temps at the two spots tell me? Just curious.

I am in Knoxville, TN so if anyone has a qualified professional HVAC guy to recommend, please let me know.

I do suspect that a more efficient ducting might help somewhat. I have mostly round metal pipe (insulated), but there is one long run that has more flex than I would prefer. However, I can open up the damper to that run and blow my daughter out of her room, but then tweek it slightly and freeze her out, the damper does not seem to allow for much fine tuning. I will try resetting all dampers to original placement and see what happens. You know, I just hate to drop a lot more money on reworking duct or adding zone system to a five year old machine unless I absolutely am going to get noticeably better comfort/performance.

Again, thanks for the help. I enjoy reading other conversations around here from time to time and have learned a lot.

[saylor240]

you can get individual zone dampers. just for a couple of runs and set them up on thermostats, not to expensive to set up on couple runs. basically the zone damper would open or close on call for heat and cool, your local HVAC company should be able to set that up.

[beenthere]

If the air temps are very far apart. Then you have a large problem with your duct system. And it may be harming your furnace.

If its not real far apart. Then the air flow may be too much for the furnace, and may be harming it.

Post the readings.

[jimpy]

can I just use a standard air temp thermometer at the two spots?

[beenthere]

if it can go to 140 or higher yes.