Rudd Furnace Jet Engine

Unknown

A dammper somewhere near the furnace if there's room?

Derheatmeister

Rudd Furnace Jet Engine

Just got done with a Rudd(RGPR-10 EBRMR 278) with an ECM Motor retro furnace replacement.

I like the furnace construction and the install was great..

BUT after the weekend the customer was complaining about elevated noise levels due to high CFM air flow which i thought i can adjust.

After checking the instructions on how to lower the RPM's to the Blower and calling support i was told that the furnace only does 1 Speed which is very annoying to my Customers in fact it is so loud that they cannot sleep and when they are watching TV they need to turn up the Volume so they can hear it over the blower(Not the Draft inducer!)

Must i remove the Furnace with the ECM and install a "Regular Furnace" so that i may adjust the blower to a lower setting ? Or is there a way to keep this furnace at a"Low fire" Mode which will also keep the furnace from "Cycling" as well? How about the P7 jumpers at the none setting?

Any Ideas will be Great! I need to make this right by my customer .Richard.

don_205

You spoke

You spoke to the wrong person.Every ecm motor comes with a
board that has dip switches that will let you change the cfm.Follow the wire from the motor back to the board and you will find the dip switches.

Sometimes you will also find that your diffusers are to restrictive on the supply and return.

I would say to you that you should be checking static pressure and temps rise across the system but it would be reductant at this point.

Lets us know what you find.

Edit..I did some research on the web and see you have a 100.000 btu furnace.It also show dip setting for cooling only.So,I was wrong it looks like the heat cfm are fixed.

I wonder if you were to set the cooling cfm to a lower value would that some how work off like a diff for the heat.

I also wonder would a tstat that energize the fan in heat/ac mode has anything to do with it.
Example..the stat energize the fan in ac mode and with a call for heat the furnace control energizes the fan.

If not,then maybe a smaller furnace or some work to the distribution system.

Ranger

Ductwork & Heatloss

It's alittle late,But with the advent of the modern electronicly commutated indoor fan motor and the modulating furnace, these products are great BUT there is no longer any room for error. If the ductwork cannot support the minimum cfm necessary for proper operation the ECM motor will try to achieve its programed cfm until it dies.Oversized furnaces and/or undersized ductwork are by far the number one operational problem with these products. In some instances due to ductwork limitations a furnace with a PSC motor is your only option.I have been to new jobs also unfortunatly where the ductwork is inadequate. Measure the trunk duct size and note the branch sizes and see if thay add up to the manufactures minimum cfm requirements.(supply and return)I would take a system static with your manometer also.The maufacture will surely require these and other readings to solve this problem.

Derheatmeister

Lessons Learned !

I will start using Manual J/D from now on!

Especially in a retro, but most of the times the duct work is under cover!

So i guess that in these chases i will no longer offer
ECM driven furnaces.

One more small trick i was thinking of is to install a Bypass type Humidifier to reduce the airflow to the registers? hence reducing the noise level!
Could this work?
If this does not work i am changing the furnace and will "eat" it..this is also very embarrassing!

I have been starting to see air movement Differently now !
Just like everything planning and having the proper tools is half the Battle !

Again respect to the Air guys and thanks for all the input !

Unknown

Is it possible

to just replace the ecm motor with a straight 3 speed? Rather than change the whole furnace? Just a thought.

[Deleted User]

Sure...

Air is just another fluid. I see no reason why a bypass around the blower wouldn't work. You may have to put an additional bypass in but is should make a difference.

Maybe one for the humidifier, and one for an air cleaner/UV air treatment system. UPSELL!

I've always had a healthy respect for a good force air guy. I LOOK at sheet metal and my hands automatically start bleeding. I go through a case of band aids just changing the filter on one...:-)

ME

Ranger

The short answer on any bypass with your issue is "depends". Short on return will give you the same symptom as short on supply. Remember,that ECM motor will try to give you whatever cfm it's programed for no mater what.Even if your tring to push/pull air thru a garden hose! It doesn't know any better.

If you can,pick up a copy of Airside System Analysis by Norm Christopherson. (JCI publication No:257095) It's akin to The Lost art of Steam Heating (but not as colorful!) on the air side. Also,I have it on good authority that some NATE testing questions were taken from the information in that book.

I get the noisy furnace phone call at least once a season.Hope this is helpful,







Ranger

Unknown

I had to trim a piece of 6\" pipe back yesterday,

it wasn't pretty. LOL...

Ranger

ECM to PSC

You could replace the ECM w/a PSC motor on a non modulating furnace by matching the ECM horsepower and using a 115v coil relay to be energized by the EAC contacts on the control board (so the IFM will come on with either a call for heat or cooling) but that is usually ment as a temporary set-up upon an ECM motor or endbell failure. And you can only use one speed (normally high) with the PSC.

Ranger

That's what...

...the left over napkins from breakfast and electrical tape are for!

BRIAN SMITH

ADJUSTING BLOWER

THERE IS ALOT OF ADJUSTABILITY ON THOSE, DROP ME AN EMAIL AND I WILL SEND YOU ALL THE SETTINGS!

John Mills_4

Common

This can happen with VS equipment, especially if oversized. With a small house and not having a lot of choice in small furnaces, I've had this for a long time. Fortunately I use a 2 stage thermostat and the furnace rarely goes into high. In fact, I have a switch on the furnace to keep high off except in bitter weather. On low, both my last furnace & new furnace are virtually inaudible in the house. How is this furnace sized? Big? Right at the loss? Do you have on a 2 stage stat? Could use a switch to keep off high except in very cold weather or use an outdoor stat between W2 at the stat and W2 at the furnace to do it automatically.

This furnace wants to move a lot of air to keep the rise in the middle of the range. With a PSC motor, you could drop it down and run the blower close to limit. Of course if the HO let the filters go, you could end up with a stuck open limit. And hot running furnace isn't near as efficient, another reason they want to move a lot of air.

Unknown

Ah!

The old construction site bandaid trick, eh? lol...

Wayne_16

bypass

Installing a bypass humidifier on the plenum to the return, will increase the return air temperature the furnace sees, moving the discharge air temperature closer to the upper limit of the safeties. A better choice would be to dump some discharge air into a room that would not matter.

As a check for suppy problem or discharge air ducts, using a magnahelic to measure, both the supply and discharge static air pressures. This measurement will tell you where the problem is. Most residential furnaces are designed around a .5"w.c..
Add the return static measurement to the supply for the total static pressure.

If possible check each component, the return duct, the air filter, the blower, the heating coil/het exhcanger, the air conditioning coil, and supply duct.

Futher testing may require removal/temporary disconnect of the return duct to verify the return.

As some else stated, there is no excuse not to do a manual j loac calc of every building to deterime the proper equipment to be installed.

Mn Wayne

Derheatmeister

Thank you Brain! will do

Marty_7

Where are you

I have a technical advisor in New England who I am sure can help you with this. If you are in the New England area give me a call 603-518-1453.

tim smith

Heating mode on ECM controlled motors with staged heat

do not allow for much airflow adjustment due to having to maintain a proper temp rise. We do a fair amount of air retros and the first thing we do is figure heat loss and then we look for the right blower capacity for duct system. This is a very common problem we see. Sometimes due to heat loss, we are stuck with larger blower than we like but if the client really wants the higher end furnace, we write in on contract and also tell them about the higher airflow noises than there old belt drive blower or whatever. Also we may give option for added ducts if they want to go that far. I have found just giving all info up front to client saves a lot of headaches.. Old retrofits on 100+ yr houses with some older clients requires some thought.

Mitch_4

Big unit

at 95% you have 95000 output..as some consults I do for these EXACT issues, it is generally that the unit is Too large for the application.

at a 50° delta T (usual for a high) you need about 1750 CFM.

keeping the optimal flow rates for noise issues in mind (700 fpm) a 5" round will carry 80 CFM, and 6" 100.

you need 17-18 6" rounds or 20 5" in the supply system.

a 100,000 will do about 7000 sq.ft of new construction here in Canada. How big is the house?

Some things to consider...

Mitch

Derheatmeister

Did the right thing

by changing the furnace out and lowering/adjusting the speed to the required delta tee from the supply to the return air duct...less noise = happy customer and some lessons learned! Thank's for all the replies Richard..