[Mr Blotto]

Hi All,

I bit the bullet and had a 95% effecient gas furnace installed today to replace my old clunker. I had a few questions:

1 - seems like I am getting WAY more air flow out of the registers and into the intakes now (so much so that one of them almost whistles). But the new blower motor looks like the same size as my old one was. Am I imagining the increased air flow??

2 - I swear my house seems more comfortable/evenly heated, but it also seems that the air coming out is not as hot as it was before. Is this because the air is moving so much faster throught the furance and out the vents so it feels cooler than slower moving air over the same amount of heat.

3 - They had to install a condensate pump - anything I need to know about maintenance of these things? They are new to me.

Thanks

 

[digitalplumber]

Post the make and model.

 

[techpappy]

You should have received a manual with the new furnace and condensate pump complete with maintenance guides. Most brands also have web sites with this info including technical bulletins. Might help you to understand a lot more about the products but all questions are welcomed here. Just some food for thought. Congrat's on your new furnace. Sounds like it is performing well.

 

[gregzoll]

Also post the thermostat make and model.

 

[hvaclover]

Hi All,

I bit the bullet and had a 95% effecient gas furnace installed today to replace my old clunker. I had a few questions:

1 - seems like I am getting WAY more air flow out of the registers and into the intakes now (so much so that one of them almost whistles). But the new blower motor looks like the same size as my old one was. Am I imagining the increased air flow??

2 - I swear my house seems more comfortable/evenly heated, but it also seems that the air coming out is not as hot as it was before. Is this because the air is moving so much faster throught the furance and out the vents so it feels cooler than slower moving air over the same amount of heat.

3 - They had to install a condensate pump - anything I need to know about maintenance of these things? They are new to me.

Thanks

1) No. The air flow on higher efficiency furnaces is markedly higher to maintain higher efficiency. Air flow can be so high that undersized returns can whistle. This can be be remedied with grills with more free area or gearing down the blower (assuming the the temp rise stay with in specs).

2) yes. The aim to size the new furnace to the correct size for better comfort and less gas consumption. Faster moving air seems cooler..but if you keep your hand in the air stream you will fell it get warmer(more btus per cfm at higher speed).

3) Your contractor should be the one to answer maintenence questions. But your owners manual can answer those questions too.


Can't believe a retired mechanical inspector could/would not answer this for you.

 

[techpappy]

HVAC lover...if you were really sharp you may have noticed that the Retired HVAC inspector's BIO reads.. Commercial/Industrial applications...not so much on domestic so, rather than blather, just offered a tip in the right direction...did know increased air flows on new units but now know a bit more..thanks...anytime you have a commercial/industrial question, particularly about boilers...give me a dingle...CHEERS:whistling2:

 

[carmon]

well then..... a hissin match...lol registers should not whistle.... house will be more comfortable..... lower supply air temp is due to lower td newer furnaces are set up for....condensate pump...no worries there..... change it every 5 years and you will be fine.... mine is 11 years old know...i dont mind a wet floor though.....:thumbsup:

 

[Mr Blotto]

Thanks for the replies. My new furnace is an 80k BTU American Standard Model # auh1b080a9421a. I am still using my old Honeywell thermostat that I got about a year ago.

 

[raylo32]

Not sure I'd be happy with whistling.... these furnaces have jumpers on the control board that can adjust the blower cfm. Lowering the airflow a tad should help the whistling and it will also raise outlet temps. The tech needs to measure the temp rise and make sure that any adjustment in airflow keeps that in spec. Your installer should be able to tell you if this is practical or not. Such an adjustment and temp measurement would take only a few minutes.

 

[gregzoll]

Thanks for the replies. My new furnace is an 80k BTU American Standard Model # auh1b080a9421a. I am still using my old Honeywell thermostat that I got about a year ago.

If your thermostat is not a dual stage thermostat, they would have the furnace set for a single stage thermostat, which the circuit board would control the ramping.

Also, your ductwork could be undersized for the new furnace, which may also be causing the whistling. Are all the ducts at the same output, or different? Your HVAC installers should have one of these
http://www.amazon.com/Extech-AN100-...UTF8&qid=1353419303&sr=8-3&keywords=cfm+meter and can take readings to check all registers.

If only one is whistling, maybe upsizing the duct vs the register.

 

[Mr Blotto]

Thanks - let me refine my statement. There is no whistling perse, but one of the two intake registers make a pretty good sucking noise....nothing that wakes you up, but it is louder than it was with old furnace.

So is my new furnace a 2-stage? If so, i would have gotten a new thermostat to take advantage of that! I thought it was single stage....

 

[digitalplumber]

Thanks - let me refine my statement. There is no whistling perse, but one of the two intake registers make a pretty good sucking noise....nothing that wakes you up, but it is louder than it was with old furnace.

So is my new furnace a 2-stage? If so, i would have gotten a new thermostat to take advantage of that! I thought it was single stage....

Increase your return air size, whistling will go away. Or if you can, add a return air in a room.

If your filter is pulling in, its asking for more air. Also, becareful of the type filter you use, they can be too restrictive.

 

[gregzoll]

If it is your return, a larger return would be in order. What is the current size of the returns? HE 95% systems are variable or dual stage.

 

[hvac5646]

HVAC lover...if you were really sharp you may have noticed that the Retired HVAC inspector's BIO reads.. Commercial/Industrial applications...not so much on domestic so, rather than blather, just offered a tip in the right direction...did know increased air flows on new units but now know a bit more..thanks...anytime you have a commercial/industrial question, particularly about boilers...give me a dingle...CHEERmmmmm

 

[yuri]

If it is a metal return grill and whistles or is noisy you can sometimes buy fancy wood grills from HDepot to replace it (or a handy guy could probably make one if he does woodworking) and wood won't whistle. The installer shoud check the temp rise and adjust the blower speed accordingly. Also the new furnaces start the fan on a timer after 90 secs and none of them will run higher than 135 deg supply temp or shouldn't. The old ones started the fan at 150 and ran higher. With plastic parts/hybrid plastic they cannot run these furnacse too hot or they get damaged.

 

[digitalplumber]

We dont know what his old was, so its quite possible that if the new one is larger, the return air is too small?

As yuri states, could be on wrong blower speed for heat? Could be wired for high heat all the time instead of low then high if necessary.

 

[Mr Blotto]

So back to the blower speeds, my furnace is a single stage with a multi-speed blower. Is there an easy way (when my furnace is not on) to make the blower run at a very low speed? As a bandaid while I was waiting for my new furnace to be installed, I had to run the fan continuously and was amazed on how balanced it kept the house (temp-wise).

Do I have to get a special t-stat to do this? Will the furnace need to be re-wired? Is this just not recommended?

Thanks!

 

[digitalplumber]

Dont know your thermostat but you should just be able to switch it over to "fan" from "auto".

 

[beenthere]

Slowing the blower is not hard to do. Should check temp rise across the heat exchanger before slowing it, and after slowing it. if you had a contractor install it, you cn probably have them come out and slow it for you.

 

[raylo32]

Exactly, as I said above slowing the blower is a 2 minute job by moving a jumper on the circuit board. Like BT says make sure the tech checks the temp rise before and after to avoid approaching the high limit.