This September, we had a furnace installed to heat the basement. It's an Armstrong, two-speed, 95% efficiency unit. The specs say it can do 57,000 BTU/hr, and my basement is 1350 sq ft.

Yesterday was a cold day, so I had my first chance to try it out. The temp in the basement was 61 degrees. It took 4 hours for the furnace to heat it up to 71 degrees.

This doesn't seem right to me. I've never seen a furnace take this long. I called the furnace company, and they said the time doesn't matter, just so long as it can eventually get there and *hold* the 71 degrees. But that doesn't seem right either, because my furnace must be creating 57000 BTUs an hour as it's going full speed, which means I'm not efficiently heating my basement.

What do you guys think on this?

How about a link to the manual and model #.

Ok, so it's two speed or two stage?

It could be stuck in low fire mode or it may not have a two stage thermostat installed. Sometimes a furnace control bump things to two stage with a single stage stat.

In any event, I would probably expect it to either start in high speed because of the temperature difference if the thermostat was doing the controlling.

If the furnace board was staging, then I might expect around 30 min of low speed/low fire and switch to high fire.

How many W terminals are connected to the furnace? W, W,W1 or W/W2

Thanks for the reply. Sorry for not having the full details, I'm just a lowly homeowner learning about this stuff for the first time. :)

It's an Armstrong G2D95CC060V14B. Info on it here: http://www.armstrongair.com/pdfs/ag2d95-100.pdf and http://www.armstrongair.com/pdfs/506244-01.pdf. It's a two stage furnace (not speed).

Based on what I've seen, it starts at the first stage for a few minutes with slow airflow. Then it kicks into the second stage and really blows out air and stays there for hours until it gets to the target temp. Only other info I know is that the thermostat is connected to the furnace with a 2 strand wire, not a 5 strand wire.

I'll research and figure out how many W terminals are connected to the furnace if it's needed.

Yep, two strand wire. Only W1 is connected.

I'll try to look at the manual, but hopefully there is an observation window. The flame should get bigger when the blower goes to high speed. The air temp should be hotter too.

Can't seem to find an install guide. Usually the contractor should leave you one.

Since you just purchased that unit and it is still under warranty I suggest you call the company back and tell them you want someone to wire it correctly so both stages kick in. There are many different ways that furnace companys have to activate the second stage. Some need an additional wire from the thermostat for the second stage and some brands have a circuit board setup that works on a timed/temperature function so when the first stage is running if it will not bring the temperature up quick enough it will automatically kick in the second stage. Goodman brand has this feature on some of there units. This way if you do not mess with it they cannot say you violated the warranty since some HVAC companys will violate the warranty if they can tell you changed something or tried to make an adjustment.

A basement which is not hard to heat to start with at 1350 sq ft should have no problem with a 57,000 BTU unit.

Seems to me it is working. If the fan kicks from low to high then it must be controlled from the 2 stage switch on the control board. Is this basement fully finished? Or is it all block and concrete? If it is not finished it will take a long time to heat up. If it is a finished space why was the stat set so low to begin with?

What you might want to do, is take a reading of the gas meter at full fire and one 30 min to an hour later with the furnace in high fire mode.

Use the conversion of 1028 BTU/cubic ft and see if the BTU/hr is not way off.

A four hour burn at 57,000 btu's per hour gives a total gross available heat gain of 228,000 btu's during the four hours. With a 10 degree temp gain on 1,350 sq ft in a basement setting it should do that gain in a lot less time. I cannot believe the second stage is working or it is being delayed for way to long of a time. Divide the total btu's by the square feet and see what you get. It is a big number per sq ft.

This may not be a furnace problem at all? Was all new duct installed when this unit was put in? It may be a airflow, or registar problem! Or lack there of.

Thanks all. I'll be doing some meter tests later today, grabbing lots of data along the way. Luckily I have an upstairs floor furnace of very similar characteristics (and the floor layout is almost exactly the same too). I'll run the same test against the upstairs furnace, so I can compare how much gas it uses to heat t Just to answer some quick questions:

1) The basement is finished. However, it's an older block house. Half the walls have great insulation (I just put that in), the other half has poor insulation, using R-7 (I didn't even know they made that!)

2) I looked at the manual, and it seemed to indicate for it to get to a second stage, it needs the W2 wire, and the thermostat controls it. A picture also seems to show that several speeds will be reached as it climbs to the second stage.

3) The reason we let the basement get so cold is that we don't live down there. I'm currently renovating it. It was recently that I was down there working that I got cold and decided to try out the new furnace.

How many supplys and how many returns do you have down there?

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Originally Posted by Joshdta

This may not be a furnace problem at all? Was all new duct installed when this unit was put in? It may be a airflow, or registar problem! Or lack there of.

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You know, this may be the issue.

The device is counterflow, so the ducts run under the slab. I know some vents seem to blow out slightly warm air, but a few don't seem to be of normal warmth. (One vent even blows cold air, so I blocked that off). I do know though that there is plenty of room through those ducts, and all vents really kick out air fast.

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Originally Posted by Joshdta

How many supplys and how many returns do you have down there?

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6 supplies (there are 4 rooms, the two larger rooms get two supplies). There is one return, it's on a wall adjacent to the furnace. (It's a very large return, and it's positioned about 10 feet from the thermostat.)

Your ducts are under the concrete? Were the insulated? I would think for 1300 sf you would need at least 8 to 10 6'' supplys, inless the supplys you have are large.

There is also the possibility as not enough gas flow. i.e. pipes not sized properly

The heaters are the most energy consumables in the house and you have to plan for two in the piping design.

So, consumption verification would indicate that there is a problem. It doesn't say where.

Quote:

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Originally Posted by Joshdta

your ducts are under the concrete? were the insulated? I would think for 1300 sf you would need at least 8 to 10 6'' supplys, inless the supplys you have are large.

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I know that right before we put the furnace in, I saw a pit with three 4 inch metal pipes heading out towards the rooms.

At the supply ends, it almost looks like the ducts are a trough, a foot deep and about 4 inches wide. The ducts appear to just traverse the perimeter of the foundation. There is no insulation in the duct work. In fact, the walls of these ducts are just pure concrete. (Again, it's an older home).

So, you could be heating the slab. Nonetheless, the contractor probably goofed.

Given the fact that your ductwork is concrete, I would jumper your furnace so it runs on high fire all the time. As you are heating the concrete thus not getting the temp out of the registars, expecally on low heat.