help needed for the bryant evolution furnace

[pathexplorer]

This is the furnace I bought.
http://www.bryant.com/products/furnaces/gas/evolution80.shtml
model number is 315AAV066135

I just installed the furnace for my home. It has two stage heating mode. But even the blower rpm is at least 800, air flow is at least 1400cfm at the low heating stage. Because of the size of my air duct, the noise is very loud at the setting.

My furnace guy told me the evolution system will set the blower speed automatically, he can do nothing about it. I am really pissed off, I paid more money for the system, but I don't have any control for it now.

Is there anyone familiar with the system, is there anyway to bypass the furnace and set the blower speed?

If there is no way to do it, I guess I would have to buy a new furnace. Any recommeand for a furnace that I can control the blower speed? By the way, my house is 2800sqft, and has a very limited air duct system. So the blower speed control is an essential for me.

Thanks for help.

[George2]

Because of the variable-speed motor, the blower will ramp up to compensate for the restriction in the ductwork.

I find that many contractors tell the customers that this is okay. That this is a "feature" of said motor.

What they don't tell you is that it'll makes noise and costs more to run (off setting the benefits of the motor).

The ductwork should always be the first thing to address before any furnace/A/C installation.

[pathexplorer]

I hope I know the place before I installed the furnace. So the only way to get rid of the noise is to get a new furnace ?

Do you have any recommandation?

[George2]

I hope I know the place before I installed the furnace. So the only way to get rid of the noise is to get a new furnace ?

Do you have any recommandation?

I don't understand the first sentance?

It's a very good furnace. The ductwork (just) needs to be improved which will help in so many ways.

The return air is probably short (first place I would look) but check the supply as well, of course.

[hidalgo1301]

The sizing and selection of equipment is based upon the heat load of the home. The most often overlooked aspect of this sizing is ensuring the properly sized and balanced duct work. Have you had a load calculation performed? Did you install this furnace yourself? If you change the furnace without addressing the duct issues, what outcome do you expect?

[notquiteamish63]

Dear sir. There are many possibilities to discuss. Blower speeds on infinity and evolution systems can be adjusted to some extent. However, you do need a certain amount of airflow for the corresponding amount of heat being produced or you will short cycle the furnace on high temp limit. The controls allow some adjustment, but not below the safe level of airflow for the corresponding btu output. Now, you said your fnc cfm was 1400 on low fire. Either you have a furnace much too large for 2800 sq' or you were on high fire and high cfm. Normally 1400 cfm would be high fire on an 80000 btu fnc. Is your evolution fnc using a thermidistat or a user interface to control it? Is the "system" in control or the furnace in control of the upstaging? If I get some more details, maybe I can help. Brian.

[pathexplorer]

I hired a contractor to do the job for me. He just simply measure the size of the house, and recomanded me the system. I also install the AC at the same time. The thermostat is the bryant smart thermostat. I could do all blower speed control, humidity and temp control from it. It also shows the blower and air flow speed.

In cooling mode, I am able to set the blower speed. It is running at 700 rpm and 1200cfm. It's very quiet and efficient.

However in the heating mode, the furnace itself takes over the control. The minimum blower speed I could obtain is 800rpm.

I also did some experiments. while furnace and AC is not working, I turn the fans on. My fan has four stages(auto, low, med, high).

Low: blower is 400rpm, airflow 700 cmf , weak air from register, very quiet
med: blower is 700rpm, airflow 1200 cmf, nice air from register, quiet
high: blower is 900rpm, airflow 1500cmf, too strong air, very noise

I tried to set the fan at med stage always. However when the furnace on, it will be override.

So I figured if I could find a way to let the blower running constantly at 700rpm, my house will be warm and noise will be small.


Thanks for your help











Dear sir. There are many possibilities to discuss. Blower speeds on infinity and evolution systems can be adjusted to some extent. However, you do need a certain amount of airflow for the corresponding amount of heat being produced or you will short cycle the furnace on high temp limit. The controls allow some adjustment, but not below the safe level of airflow for the corresponding btu output. Now, you said your fnc cfm was 1400 on low fire. Either you have a furnace much too large for 2800 sq' or you were on high fire and high cfm. Normally 1400 cfm would be high fire on an 80000 btu fnc. Is your evolution fnc using a thermidistat or a user interface to control it? Is the "system" in control or the furnace in control of the upstaging? If I get some more details, maybe I can help. Brian.

[pathexplorer]

I am using this thermostat.

http://www.ecrater.com/p/6520155/bryant-evolution-thermostat-control-systxbbuid01-a


I hope there is way to do it. Otherwise I have to buy another furnace.




Dear sir. There are many possibilities to discuss. Blower speeds on infinity and evolution systems can be adjusted to some extent. However, you do need a certain amount of airflow for the corresponding amount of heat being produced or you will short cycle the furnace on high temp limit. The controls allow some adjustment, but not below the safe level of airflow for the corresponding btu output. Now, you said your fnc cfm was 1400 on low fire. Either you have a furnace much too large for 2800 sq' or you were on high fire and high cfm. Normally 1400 cfm would be high fire on an 80000 btu fnc. Is your evolution fnc using a thermidistat or a user interface to control it? Is the "system" in control or the furnace in control of the upstaging? If I get some more details, maybe I can help. Brian.

[pathexplorer]

Instead of doing all the duct work, chaning a furnace might be a easy way to do it. They are all in the drywall.


I don't understand the first sentance?

It's a very good furnace. The ductwork (just) needs to be improved which will help in so many ways.

The return air is probably short (first place I would look) but check the supply as well, of course.

[notquiteamish63]

I am still wondering the size of your fnc. I work on Carrier infinity systems everyday which are essentially the same as bryant. I need to know the btu of your fnc. By your air cond. cfm and tonnage I assume your fnc is 80,000btu with 1600 cfm blower. If all of this is true then I think your user interface is configured wrong. In the advanced features of the user interface is a section to decide if the fnc is in charge or the "system" which means the user interface controls staging. You want the "system to be in control, otherwise the fnc will run on high after a short time of running on low. Also, there is another feature in the user interface where you can choose comfort or efficiency airflow. This also changes how much air is moved during heating. Your selection of auto,low, med, or high airflow only applies when the unit is not running in the heating or cooling modes, in other words, continuous fan mode. I think your problem can be solved without changing units because of the airflows you reported in cooling mode and the size that I am guessing your furnace to be.
going to bed now. Will try to check on you this weekend. Brian.

[George2]

I am still wondering the size of your fnc. I work on Carrier infinity systems everyday which are essentially the same as bryant. I need to know the btu of your fnc. By your air cond. cfm and tonnage I assume your fnc is 80,000btu with 1600 cfm blower. If all of this is true then I think your user interface is configured wrong. In the advanced features of the user interface is a section to decide if the fnc is in charge or the "system" which means the user interface controls staging. You want the "system to be in control, otherwise the fnc will run on high after a short time of running on low. Also, there is another feature in the user interface where you can choose comfort or efficiency airflow. This also changes how much air is moved during heating. Your selection of auto,low, med, or high airflow only applies when the unit is not running in the heating or cooling modes, in other words, continuous fan mode. I think your problem can be solved without changing units because of the airflows you reported in cooling mode and the size that I am guessing your furnace to be.
going to bed now. Will try to check on you this weekend. Brian.

His original post said it's a 135,000 with a 5 ton drive.

[cboe]

if the furnace is close coupled like you say. meaning short run of duct. one way to quit down any system is sound deadner.. this is done by insullating the inside of both supply and return air . can also be done with sound traps,

[pathexplorer]

This is a way to do it. However another problem is air flow of a register is very weak in one of my bedroom while the blower is running at 800rpm. But it feel pretty good whilte blower is running at 700rpm.

So I would like find a way to lower the blower's speed instead of putting soundprood to my duct.

Thanks for your help




if the furnace is close coupled like you say. meaning short run of duct. one way to quit down any system is sound deadner.. this is done by insullating the inside of both supply and return air . can also be done with sound traps,

[commerce48]

That is a huge furnace! How big is your house?

Do you have the install manual for your thermostat? If so, you can lock it to medium stage. Of course, now you have a 70,000 BTU single stage. If that works for you all winter, you are way oversized.

[mike_home]

I am confused. The Bryant 315AAV series of furnace is an 80% AFUE two stage model. Your description sounds like it is a three stage furnace. Am I missing something?

The model number indicates it has a 135,000 BTU input. This is very big. What was the size of the previous furnace? Did you have this amount of noise with your old furnace? How did the contractor determine this was the right size for your house? Did you ask the contractor to increase the size of the furnace in attempt to solve the low air flow problem in one of your bedrooms?

If the contractor made all the decisions, then I feel he is responsible to fix the problem.

[Air Movers]

I agree alot of these shmucks out there think that a variable speed motor means they can get away with not sizing ductwork properly, well there is one reason why you always gotta make it right. My favorite saying that I hear from every idiot in the trade uses ( Its only the return).

[MoveOver]

My furnace guy told me the evolution system will set the blower speed automatically, he can do nothing about it. I am really pissed off, I paid more money for the system, but I don't have any control for it now.

Is there anyone familiar with the system, is there anyway to bypass the furnace and set the blower speed?

If there is no way to do it, I guess I would have to buy a new furnace. Any recommeand for a furnace that I can control the blower speed? By the way, my house is 2800sqft, and has a very limited air duct system. So the blower speed control is an essential for me.

Thanks for help.

Sounds like your system is way oversized for your duct system. What was the size of the old furnance? Did he do a manual J.
When we got our Infinity we went smaller based on manual J.

While in heating mode the system has to remove the heat generated by furnace and as such it will adjust volume so that the heat exchanger will not overheat. So you will never be able to control blower speed in heating mode outside of a certain range.

[notquiteamish63]

If I understand everything correctly, you have a 135,000 btu fnc coupled to a 3 ton ac system and the 3 ton ac at `1200 cfm has acceptable air noise. This really seems like a mismatch unless you have a huge heating load and a very small corresponding cooling load, but anyway lets see how your interface is configured and then you will know where you stand. Do you have the installers guide for the t-stat, not the homeowners guide? I would like you or your installer to access the setup menu for the furnace and make sure the airflow is on the comfort setting not efficiency. This reduces airflow in the heating mode. Also, do you have a humidifier? If you told the t-stat that you do it will automatically increase airflow by appox 10%. Also, you must let the "system" be in control not the furnace. This is also found in the installers advanced features. Also, this furnace can be locked into low fire only and if this solves your airflow noise and gives you enough heat in all conditions then your furnace is indeed waaay bigger than needed, but can work that way.