NG Furnace Time to Raise Temp x Over x Time


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Old 01-03-18, 08:15 AM
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NG Furnace Time to Raise Temp x Over x Time

I have a 2500 sqft home, pretty standard 2 story with basement built in 2003. Have an NG furnace. I recently installed a Ecobee4 and a whole house humidifier, but even before that it seems like it would take a while to raise the temp in the house. I have read however that in the coldest months (which we are certainly in here in PA with the temp being 6F currently, and was sub 0 last night) it should run almost non-stop if sized correctly. Prior to the real cold snap, when it was ~35F during the day, I read that if we are not home I should be dropping the temp to at least 60F. I could only take it down to 67F as it takes about 30 min to raise the temp 1F. I'm not sure if this is somewhat 'normal', or to the point I should be having it looked at. Today for example it would take it 2 hrs to get from 67 to 71F, at least. I've been firing up the kerosene heater lately in the basement to assist it in raising the temp on the coldest days. Let me know any feedback or anything I can check before paying a $60 service tech fee just to look at it.
 
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Old 01-03-18, 09:19 AM
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g,
With the limited info I can offer my insight.

First off, warm air heat is the fastest heat you can have and your system to me seems excessively slow to recover.

That being said there are a few things that determine how fast your temp will rise.

How tight the house, how well insulated.

The temp of the air being delivered.

The speed of the blower delivering the air

The size of the furnace, if it sized properly and the duct work also.

Check to make sure all dampers are fully open. Usually installed on each line coming off trunk (mainsupply) in basement.

Adequate return air. You will only get as much supply air out as you have return coming back. If you want to check the effects of not enough return air cover up your return vents and watch the result of the supply air.

If returns are blocked supply becomes non existent. It's like filling a straw with water and putting your finger over the top. Without return you are basically pulling a vacuum.

This should get you started for now.

Hope this helps a little.
 
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Old 01-03-18, 09:57 AM
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First verify that it is indeed producing heat the entire time it says it is. Could be cycling on and off due to problems.

Otherwise there is a remote chance that it is a multi-stage furnace but only the first stage is hooked up to the thermostat.
 
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Old 01-03-18, 09:59 AM
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Thank you. I figured with a warm air source it should be heating much quicker too. Tonight I'm going to check pre and post furnace air temps (already a probing location from a prior service tech, for the AC). As for the dampers, I have a finished basement and when finishing it did not see anything that looked like and adjustable damper anywhere on the plenum. All fiberboard plenum. Returns I make sure are all open, but I do throttle some supply vents in certain rooms (mud room and bathroom right above the furnace) as they get really warm and figured it was taking some heat from the neighboring family room. I closed a few vents in the upstairs too in bedrooms that were getting warmer than others to try and balance it out a little. Otherwise most vents are fully open. 2 yrs ago I had and HVAC tech replace the heating coils as they were corroded and not allowing proper burning of the gas and shutting down the system. I'm not sure how to determine if that was done properly, or if it could've been done incorrectly?
 
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Old 01-03-18, 10:06 AM
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Well, about 3 yrs ago I got a programmable thermostat and hooked it up myself. Using the same connections as what was on prior. I now have a Ecobee4 installed, and the only difference was that the instructions said I did not need the jumper from R to Rc like there was on my old Honeywell stat as there is no R on the Ecobee. Any chance this jumper would have anything to do with it? Anything that could've not gotten hooked up correctly on the 2 thermostat swaps? Pics of the honeywell and ecobee setups attached.
 
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Old 01-03-18, 10:19 AM
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The wiring looks fine. Ecobee wants a single red wire to be connected to Rc like you have. Jumper not required.
 
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Old 01-03-18, 11:14 AM
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It's unfortunate that dampers weren't installed at the beginning of each branch off the main trunk going to each room.

That would be how you would balance your system by throttling down the air in some branches to divert the air to others that needed it.

By throttling the registers, although it may be more comfortable for you, the air is still being delivered down the pipes instead of being cutoff or cut down at the source, so for the purposes of your problem isn't really doing much in the way of delivering more air to the cold rooms.

You mentioned that some rooms get to warm which means your furnace is probably putting out enough heat. It sounds more like a distribution problem to me.

Where is your stat located, cold room or warm room. Is the furnace cycling on & off or running constantly and just cannot keep up.

Just a couple of thoughts.
 
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Old 01-03-18, 12:50 PM
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So should I try opening all vents? Also going to check supply and return delta T at the furnace. However, could someone also address the notion that I've read more than once now, that a unit is sized properly if it runs near 100% of the time near or at it's highest load point (with sub 0 temps I would think we are near that point, for this area of the country).

Also, sounds like I had the wrong interpretation, that if I closed off vents in our bedroom for example, that was always warm, that it would push more air out the vents in the lower level. From reading above it this thread, that is not the case? All vents should be open in the whole house?
 
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Old 01-03-18, 03:55 PM
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Just checked and with the thermo set to 71 on this 25deg day the return is at 72F and the supply is at 144F. Opened all vents upstairs now so well see what happens. Let me know if those readings are on par.
 
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Old 01-03-18, 05:32 PM
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When you subtract the two that leaves a heat rise of 72...... which is pretty hot. If you take off the burner access door..... there will be an ID tag on the side wall near the burner with the model number on it. The heat rise will also be listed on that tag. It may say something like 40 - 70.
 
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Old 01-04-18, 04:21 AM
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Spoke to the tech last night who’s been servicing my system the past few years. He said that delta is on the high side, and said I might benefit from an increase in fan/blower speed. However, did not seem like something that was a glaring issue. Also said that I should not be lowering the thermostat during the day as it takes way too long for it to catch up, contrary to what I’ve been reading in a lot of the smart thermo forums. We keep it at 71 while we are home and will only lower it 2deg now while away.
 
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Old 01-04-18, 10:00 AM
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PJmax, when he replaced the heating coils last winter he also installed a new board. Is there a chance he hooked up the mid-low wire for heating blow speed vs the mid-high that could've been hooked up prior? This should be easy to tell by looking at the control board, correct?
 
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Old 01-04-18, 10:01 AM
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Heating coils.... in a furnace ?

Post a picture or two of the control board.
 
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Old 01-04-18, 11:54 AM
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Originally Posted by PJmax View Post
Heating coils.... in a furnace ?
Sorry, secondary heat exchanger.
 
 

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