Do I need a new Thermostat? with New Furnace?

Problems related to residential installations.

Do I need a new Thermostat? with New Furnace?

Postby jannie » Sun Oct 28, 2012 8:33 pm

Oct of 2011 Old (vintage 1950's furnace broke) American Standard had two blower motors. We were using a WX500 thermostat (setback - which worked fine). Purchased a Luxaire furnace. I believe it is a single motor. It makes a huge racket, but I can live with that.
However I set the thermostat for 69 and get up in the morning and it's 64 degrees and it hasn't kicked on, I have to punch the temperature up to 70 before it will go on. It finally gets the temperature up to 70 and goes off and then goes back down to 64 before it will go on.
Question 1. Is this because it is a new furnace and we are suppose to have a different thermostat - this is not an old thermostat (maybe 4 or 5 years old). It worked great with the old furnace.

2. Also, the "air that came out of the vents was hotter when we had the old furnace, is there a way that that can be changed?

Thank you.
jannie
New Contributor
 
Posts: 5
Joined: Sun Oct 28, 2012 8:15 pm

- Do I need a new Thermostat? with New Furnace?

Postby Freon » Mon Oct 29, 2012 8:15 am

Describe your old thermostat... make and model. Does this thermostat control only your heat? If you remove the cover are there only 2 wires and a mercury switch? Did the installing company do anything to the thermostat?

What is the make/model of the new furnace? It is possible that the blower is set to too high a speed. That will cause noise as well as cooler air coming from the registers. However to know for certain, you need to take a thermometer and when the furnace is running, measure the temperature entering a return register closest to the furnace and also the temperature exiting a supply register closest to the furnace. The difference between these temperatures is the temperature rise across the heat exchanger. Add 10 degrees to that number and compare it to the temperature rise the manufacturer says the furnace is designed for.

If your calculation is well below the design temperature rise, you may try a lower blower setting. However I would check with the installer so you don't disturb any warranties.
Freon
Most Valued Contributor
 
Posts: 732
Joined: Sat Jun 18, 2011 11:26 am

- Do I need a new Thermostat? with New Furnace?

Postby jannie » Mon Oct 29, 2012 10:51 am

Furnace is Luxaire TG95080B12MP114 When it was put in this is what the person put on the paper on the side of the furnace RA 72 degrees 122 I complained because the furnace blower is so much noiser than the old one and he came and adjusted it RA 69 128 degree. On the invoice it states adjusted blower speed and changed filter. Blower on medium-high 59 degrees rise and blower medium-low 71 degrees rise. Blower is now on Medium high.

The machine is still noisey, but will live with that. (house is 1930's stucco about 1500 sq feet ) heat register for living room is near inside wall the cold air return is directly opposite to that across the room under a window about 12 feet away. There is an open staircase to the right. That is the only cold air return. DR, K, Den on main floor each with heat register. Upstairs bath & BR with heat register.

Thermostat - I can find no company name except that WX 500, It is digital set back (We don't use the setback because of this issue). It can control the AC and the heat.
jannie
New Contributor
 
Posts: 5
Joined: Sun Oct 28, 2012 8:15 pm

- Do I need a new Thermostat? with New Furnace?

Postby jannie » Mon Oct 29, 2012 2:10 pm

- The Thermostat is LUX 500 Programable Thermostat.
jannie
New Contributor
 
Posts: 5
Joined: Sun Oct 28, 2012 8:15 pm

- Do I need a new Thermostat? with New Furnace?

Postby Freon » Tue Oct 30, 2012 2:17 pm

From your descriptions the thermostat and furnace should work fine together. The thermostat seems to be behaving like it has a 4 degree temperature differential setting. Check the thermostat setup for the differential.
If this is a new furnace and under the installer's warranty, the installing company should be told since the system they installed is not working correctly.

As for noise, if the furnace is close to the return you will hear the noise conducted by the air in the duct and the duct walls. If the ducting is round metal duct, you can inserts a short piece of flex ducting thereby isolating the noise transmission through the metal ducting. If you have the room and can make the flex do a gentle 90 degree bend, you'll help mitigate the noise transmitted by the air in the duct. Also possibly slide a piece of carpet under the furnace to help absorb motor vibrations, furnace installation safety permitting.
Freon
Most Valued Contributor
 
Posts: 732
Joined: Sat Jun 18, 2011 11:26 am

- Do I need a new Thermostat? with New Furnace?

Postby jannie » Thu Nov 01, 2012 4:57 pm

Thanks for the info. It's suppose to have a 2 year warranty. I'll see if setting it with the difference helps. There's no way to put the carpet under to silence the furnace. It is all round piping going to the vents. Most were convented by us some years back to the smaller round pipes. I'm wondering if putting insulation around the pipes would in some way keep it so the air coming out of the vents wouldn't be so cold to start with. I guess as someone who's not in the business I don't understand why the air from the furnace that goes upstairs isn't as hot with this furnace as with the old furnace. It's good to know the thermostat is normal.
jannie
New Contributor
 
Posts: 5
Joined: Sun Oct 28, 2012 8:15 pm

- Do I need a new Thermostat? with New Furnace?

Postby Freon » Fri Nov 02, 2012 2:40 pm

If we assume the BTU output rating of this furnace is the same as the old one, then the reason the air exiting the supply registers is colder is because it is traveling faster through the heat exchanger. That is where the temperature rise is important. By slowing the blower down, you slow the mass flow rate of the air through the heat exchanger thereby allowing for more heat transfer from the furnace side of the heat exchanger to the house air flow side. More heat transferred means higher exit temperature.

But you have to never have the exit air higher than the manufacturer's specification call for or you'll prematurely kill your heat exchanger.

Insulating the ducts will help depending on how cold the space is where the ducts travel through.

Sometimes removing one section or metal ducting and replacing it with flex will greatly reduce noise.
Freon
Most Valued Contributor
 
Posts: 732
Joined: Sat Jun 18, 2011 11:26 am

- Do I need a new Thermostat? with New Furnace?

Postby jannie » Sat Nov 03, 2012 11:13 am

Final Update - Thanks for the info & we may try insulating the duct or flex hose.
- I turned it up to a higher temperature as was "cold" in the morning and had not started. I pressed the button to raise the temperature (override) & the Panel that shows the temperature time went blank & showed "low battery", so... furnace kept going & going. We went & purchased a battery and by the time we got back it was showing 81 degrees (although the temperature was set that high). Took old battery out and furnace didn't shut off. Put new batteries in and it immediately shut off.
One of the old batteries had started to leak so the problem was eventually the batteries. We hadn't even remembered anything about batteries and they were probably never changed. It makes sense to hold the memory if the power goes off. The thermostat now shuts off on it own and is ok with one degree of what it's set. I believe that problem is solved now.

I still believe the furnace that we have was a poor choice and should not have been recommended to us because of the type of home and location of cold air return, but that's a "live & learn" on our part.

I think the thermostat problem is solved. Thank you
jannie
New Contributor
 
Posts: 5
Joined: Sun Oct 28, 2012 8:15 pm


Return to Residential

cron