Two stage furnace question
#1
09-29-16, 04:59 PM
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Two stage furnace question
Just had a Daikin two stage furnace and single stage A/C installed today. It's working fine, but I got to reading the manual and poking around, and see that the installer left the furnace toggle set to single stage. Is there any reason you would want a two stage furnace always run in single stage mode? I paid extra for this furnace because the sales guy pitched the 2 stage as an energy savings feature in the winter, so I'm a little confused. Assuming I do want 2 stage, is there any reason I can't flip that toggle switch myself, or should I have the installer come back?
#2
09-29-16, 05:18 PM
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I would at least call the installer and ask the question, maybe the installer forgot to switch it, was the system tested to be sure it works correctly with both stages?
#3
09-29-16, 06:42 PM
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I don't know if they tested it or not. The book doesn't really say if it's unsafe to just flip the switch, but wasn't sure if I should or not.
I think I'll ask about it next week. Was thinking about having them come back next week anyway because it seems like a lot of air is leaking out around where the humidifier is, and where the coolant lines go into the case.
I think I'll ask about it next week. Was thinking about having them come back next week anyway because it seems like a lot of air is leaking out around where the humidifier is, and where the coolant lines go into the case.
#4
09-29-16, 06:45 PM
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Welcome to the forums.
Is that a gas furnace ?
That may indicate that a single stage thermostat is used but the furnace would still run in two stage mode. It would be a timed function.
For example it would come on running in stage 1 but after XX minutes it would shift to stage 2.
If you can't get an answer from your installer you'd need to post the full model number for the furnace so we could look it up.
Is that a gas furnace ?
That may indicate that a single stage thermostat is used but the furnace would still run in two stage mode. It would be a timed function.
For example it would come on running in stage 1 but after XX minutes it would shift to stage 2.
If you can't get an answer from your installer you'd need to post the full model number for the furnace so we could look it up.
#5
09-29-16, 06:58 PM
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Yes, it's gas, model GFDM80HS0604AX.
You are correct - I remember reading it is designed for a single stage thermostat, and it is a timed function. There is a second switch that gives the option of running in stage 1 for 5 min, or "auto" that says it runs 1-12 min. in stage 1 before ramping up to stage 2.
I was thinking I'd want the switch to put it in 2 stage flipped, and leave it in "auto" mode.
You are correct - I remember reading it is designed for a single stage thermostat, and it is a timed function. There is a second switch that gives the option of running in stage 1 for 5 min, or "auto" that says it runs 1-12 min. in stage 1 before ramping up to stage 2.
I was thinking I'd want the switch to put it in 2 stage flipped, and leave it in "auto" mode.
#6
09-29-16, 07:03 PM
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Hmmmmm..... 5 minutes or 1-12 minutes. I can see the 5 minutes although that's a little quick to change but 1-12. What determines the 1-12 threshold in auto ?
I have to look further.
I have to look further.
#7
09-29-16, 07:10 PM
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The book says setting the switch to auto: "enables an algorithm that calculates a delay period based on the heating cycle time and the total cycle time. The delay period can range from 1 minute to 12 minutes."
#8
09-29-16, 07:56 PM
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#9
09-30-16, 08:12 PM
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Finally got ahold of the sales guy that set up the install. He's going to ask the manager of the install team and get back to me next week he claims. My heart just wants to flip the switch and see what happens, but I'll wait and see what the guy has to say I guess.
Either way it's going to be a better furnace than the 20 yr. old one it replaced I'm sure.
Either way it's going to be a better furnace than the 20 yr. old one it replaced I'm sure.
#10
10-07-16, 05:04 PM
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They finally sent someone out today and basically just flipped the switch on. Guess there wasn't much adjusting they had to do. He said he left it in the position that runs in low mode for 5 min, then kicks into high. I might switch to that auto mode later, but for now I guess I'm happy.
Also made him seal some places that were leaking air pretty bad while he was there.
Also made him seal some places that were leaking air pretty bad while he was there.
#11
10-07-16, 08:08 PM
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I'll know now for future reference.
#12
10-08-16, 02:05 PM
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You were lied to and ripped off.
2-stage doesn't save any gas. In fact low can be less efficient than high especially if the furnace has a single speed inducer.
2-stage is for comfort.
and not using a 2-stage thermostat, having it shift to high after 5 minutes totally defeats the purpose of spending hundreds if not $1000 more on a two-stage furnace.
with the correct thermostat it will very rarely run on high.
you're a victim of the crappy resi hvac industry.
2-stage doesn't save any gas. In fact low can be less efficient than high especially if the furnace has a single speed inducer.
2-stage is for comfort.
and not using a 2-stage thermostat, having it shift to high after 5 minutes totally defeats the purpose of spending hundreds if not $1000 more on a two-stage furnace.
with the correct thermostat it will very rarely run on high.
you're a victim of the crappy resi hvac industry.
#13
10-08-16, 02:47 PM
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I agree with Muggle, a two stage furnace needs a two-stage thermostat.
My furnace NEVER goes into the high stage unless I move the thermostat (manually) more than three degrees above the current room temperature. I also run a 1/2 degree differential on the setpoint and I get very even temperatures throughout the house. Run time is typically ten minutes in mild temperatures but might be as long as 40 minutes during colder outside temperatures yet the inside temperature doesn't vary even a full degree.
My furnace NEVER goes into the high stage unless I move the thermostat (manually) more than three degrees above the current room temperature. I also run a 1/2 degree differential on the setpoint and I get very even temperatures throughout the house. Run time is typically ten minutes in mild temperatures but might be as long as 40 minutes during colder outside temperatures yet the inside temperature doesn't vary even a full degree.
#14
10-10-16, 02:35 PM
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Yea, I was wondering what the point of having it be time based instead of how many degrees it needed to raise the temperature. It was about a $550 difference between the two furnaces. Not sure there is anything I can do about it at this point. The strange thing is they were the lowest bid of all the others.
The installers also wired the transformer for the humidifier straight to the incoming line wires instead of through the accessory terminal, so it's hot 100% of the time. I turn the water off to the humidifier in the summer, so I didn't notice it until I tried to switch from A/C to heat the other day and saw it not working because the solenoid had burned out. I replaced the solenoid, and got the crap scared out of me when it suddenly came to life and sprayed water all over me - I was expecting it to be dead since I didn't have the furnace on at the time.
It's a simple 5 min. wiring fix, but I'm making them come out and do it instead of doing it myself.
The installers also wired the transformer for the humidifier straight to the incoming line wires instead of through the accessory terminal, so it's hot 100% of the time. I turn the water off to the humidifier in the summer, so I didn't notice it until I tried to switch from A/C to heat the other day and saw it not working because the solenoid had burned out. I replaced the solenoid, and got the crap scared out of me when it suddenly came to life and sprayed water all over me - I was expecting it to be dead since I didn't have the furnace on at the time.
It's a simple 5 min. wiring fix, but I'm making them come out and do it instead of doing it myself.
#15
10-10-16, 04:16 PM
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Two (and three) stage heating thermostats are pretty common these days, the only problem in retrofitting is when the cable between the thermostat and the furnace does not have enough individual wires. Even the lack of enough wires is able to be overcome with a few "communicating" thermostats that use digital technology to send all the thermostat signals over two or three wires to an equipment module located at the furnace that then separates the different signals for use by the furnace. Biggest downside to a communicating thermostat is the higher cost.
You may be able to pull a new thermostat cable with minimal difficulty depending on the house construction. Use a cable with a minimum of seven conductors and nine conductors is not too many.
You may be able to pull a new thermostat cable with minimal difficulty depending on the house construction. Use a cable with a minimum of seven conductors and nine conductors is not too many.
#16
10-10-16, 10:41 PM
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can u recheck the model? the model posted doesn't look right. have a camera or phone? could u post a pic of the rating plate?
odds are this company didn't set the furnace up properly.
Do you have a/c? if yes what size?
the fan speeds and gas fuel input may be wrong. u can't fix the fuel input yourself, so when they come to deal with the humidifier, insist that the gas pressure is checked in both stages.
odds are this company didn't set the furnace up properly.
Do you have a/c? if yes what size?
the fan speeds and gas fuel input may be wrong. u can't fix the fuel input yourself, so when they come to deal with the humidifier, insist that the gas pressure is checked in both stages.
#17
10-11-16, 02:50 PM
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Here's the link to the one I have: http://daikincomfort.com/products/ga...aces-80/dm80hs
I'll try to get some pictures tomorrow.
It's supposed to finally get down into the upper 30s tomorrow night too, so I was planning on firing up the furnace and watching/listening to it for 5-10 min. tomorrow to see if I can observe a difference in the flame and fan speed between stages.
I've got an appointment for them to come out a week from today and wire the humidifier properly.
I'll try to get some pictures tomorrow.
It's supposed to finally get down into the upper 30s tomorrow night too, so I was planning on firing up the furnace and watching/listening to it for 5-10 min. tomorrow to see if I can observe a difference in the flame and fan speed between stages.
I've got an appointment for them to come out a week from today and wire the humidifier properly.
#18
10-11-16, 03:18 PM
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#19
10-11-16, 05:01 PM
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This furnace can't be used with a 2-stage thermostat.
Also has a single speed venter motor. The first stage is less efficient due to having too much combustion air.
It's rated at 80% (the minimum) but that's on high only. It could be a few % points lower on low.
If u care about comfort it can be set to time out after up to 12 minutes.
If u care about efficiency it should be set up to run on high only. personally that's what i would do.
This is a builder's grade furnace and the price u paid reflects that. As a single stage furnace it looks like a decent product but as a 2-stage it's the cheapest thing out there.
I suggest clocking the gas meter when it's on high and telling your installer if it's off. Ask for a temperature rise test too.
------------
Do you have a/c? part of the setup process is setting the fan speed right for the a/c size.
Also has a single speed venter motor. The first stage is less efficient due to having too much combustion air.
It's rated at 80% (the minimum) but that's on high only. It could be a few % points lower on low.
If u care about comfort it can be set to time out after up to 12 minutes.
If u care about efficiency it should be set up to run on high only. personally that's what i would do.
This is a builder's grade furnace and the price u paid reflects that. As a single stage furnace it looks like a decent product but as a 2-stage it's the cheapest thing out there.
I suggest clocking the gas meter when it's on high and telling your installer if it's off. Ask for a temperature rise test too.
------------
Do you have a/c? part of the setup process is setting the fan speed right for the a/c size.
#20
10-11-16, 06:01 PM
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I figured it was lower quality than the Lennox it replaced, but I didn't care since I'm so warm blooded and like to leave it set at 60-65 degrees all the time. I purposely stuck with the 80% since that what I had already - for the price difference I figured getting a 90+% efficient one would never pay for itself. Thought the more I look at it you're right - I should have just got the cheaper one that was identical except for being a single speed fan / single stage gas valve.
Not much I can do about it now other than keep bugging them until they actually get it installed right I guess. On the bright side it has a 12 yr. full parts warranty, and they gave me a 12 yr. labor warranty on top of it. So by the time it needs replaced again I'll probably be dead or moved out of this house.
It has an AC on it, and I do remember them adjusting that fan speed.
Not much I can do about it now other than keep bugging them until they actually get it installed right I guess. On the bright side it has a 12 yr. full parts warranty, and they gave me a 12 yr. labor warranty on top of it. So by the time it needs replaced again I'll probably be dead or moved out of this house.
It has an AC on it, and I do remember them adjusting that fan speed.
#21
10-12-16, 12:57 PM
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As a single stage 80% furnace it's a decent unit.
It has a stainless steel heat exchanger that not even lennox, carrier or trane use.
Daikin has some nice proper 2-stage furnaces -> naturally, they cost more.
Lower cabinet quality aside (if a goodman i saw is any indication -> it's basically the same equipment) -> ie sharp edges, thin metal, poor paint job I think their stuff is pretty decent overall.
It has a stainless steel heat exchanger that not even lennox, carrier or trane use.
Daikin has some nice proper 2-stage furnaces -> naturally, they cost more.
Lower cabinet quality aside (if a goodman i saw is any indication -> it's basically the same equipment) -> ie sharp edges, thin metal, poor paint job I think their stuff is pretty decent overall.
#22
10-14-16, 12:43 PM
Banned. Rule And/Or Policy Violation
Unfortunately, this thread indicates that it's wise to read the various manuals BEFORE you have a new furnace installed!
It's interesting that manufacturers are finding ways to offer cut rate two stage furnaces that tend to ignore the reason why a two stage furnace might be worth buying.
Personally, my bias is for a single stage 90% gas furnace. 90% efficient furnaces have real savings over an 80% efficient furnace, and single stage 90% efficient furnaces offer greater simplicity that 94%+ efficient furnaces and two stage furnaces.
Those are my biases, anyway.
It's interesting that manufacturers are finding ways to offer cut rate two stage furnaces that tend to ignore the reason why a two stage furnace might be worth buying.
Personally, my bias is for a single stage 90% gas furnace. 90% efficient furnaces have real savings over an 80% efficient furnace, and single stage 90% efficient furnaces offer greater simplicity that 94%+ efficient furnaces and two stage furnaces.
Those are my biases, anyway.
#23
10-20-16, 06:57 PM
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They finally came and fixed the humidifier yesterday. The dipstick that installed the furnace and moved my existing humidifier to the new furnace wired up the transformer straight to the incoming 120V wires, so it was hot all the time no matter what. I think it's finally set up and working now. I'll probably just switch it back to single stage when it gets cold enough to fire up the heat - probably later this month.
Thanks for all the advice!
Thanks for all the advice!
#24
10-20-16, 07:01 PM
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#25
10-20-16, 07:12 PM
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Try it in both modes and see what works best.
the two stage mode should offer better comfort and less noise while the single lower gas consumption on your specific model. had daikin made the unit maybe $100 or less more expensive and put a two-speed inducer on it, it would be nearly as efficient on low as high. u would have paid more too.
There used to be a middle ground where you could get a decent 2-stage without all the expensive electronics like communicating controls, ecm motors.
That's fading away especially with a government push to eliminate psc motors.
the two stage mode should offer better comfort and less noise while the single lower gas consumption on your specific model. had daikin made the unit maybe $100 or less more expensive and put a two-speed inducer on it, it would be nearly as efficient on low as high. u would have paid more too.
Personally, my bias is for a single stage 90% gas furnace. 90% efficient furnaces have real savings over an 80% efficient furnace, and single stage 90% efficient furnaces offer greater simplicity that 94%+ efficient furnaces and two stage furnaces.
That's fading away especially with a government push to eliminate psc motors.
#26
10-24-16, 08:28 AM
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How quiet is the sound coming from the furnace cabinet of DM80HS0604A in both stage 1 and stage 2?
Quiet enough to be located in a living room closet in a condo?
Sounds like I could upgrade thermostats to a two stage thermostat with either added wiring or a 2-stage thermostat that can manage on 1-stage hard wiring?
This topic is very timely... I have an HVAC installer willing to install both the single stage (DM80SS0603A) and the Dual Stage (DM80HS0603A) for the same price.
The original poster had installed the DM80HS0604A (dual stage) but with the max 1600 CFM fan (1/2 hp) whereas apparently I only need the 1200 CFM (1/3 hp) fan.
My question, since I can get both for the same price, am I getting a quieter Furnace with the 2 stage than 1 stage unit?
I realize that the 2 stage is < 80% AFUE in stage 1.
That is:
- Efficiency is NOT important to me (rental unit and tenant pays heat)
- Acquisition cost IS important (hence 80% and not 90%... also I can't cut holes in condo walls for PVC intake/exhaust).
- Quietness is CRITICAL/IMPORTANT as the unit is in a living room closet in a 2 bed condo.
Thanks in advance
Quiet enough to be located in a living room closet in a condo?
Sounds like I could upgrade thermostats to a two stage thermostat with either added wiring or a 2-stage thermostat that can manage on 1-stage hard wiring?
This topic is very timely... I have an HVAC installer willing to install both the single stage (DM80SS0603A) and the Dual Stage (DM80HS0603A) for the same price.
The original poster had installed the DM80HS0604A (dual stage) but with the max 1600 CFM fan (1/2 hp) whereas apparently I only need the 1200 CFM (1/3 hp) fan.
- I thinking 1/3 hp (with a smaller fan cage) might be quieter than 1/2 hp?
- But is 2 stage unit quieter than 1 stage unit?
- Am I correct that the first stage is quieter and second stage is same noise level.Am I correct that the induction motor is the same between both units and same sound in both stages
My question, since I can get both for the same price, am I getting a quieter Furnace with the 2 stage than 1 stage unit?
I realize that the 2 stage is < 80% AFUE in stage 1.
That is:
- Efficiency is NOT important to me (rental unit and tenant pays heat)
- Acquisition cost IS important (hence 80% and not 90%... also I can't cut holes in condo walls for PVC intake/exhaust).
- Quietness is CRITICAL/IMPORTANT as the unit is in a living room closet in a 2 bed condo.
Thanks in advance
