Choices on better thermostats for my vc97 furnace

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Old 03-30-13, 03:52 AM
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Choices on better thermostats for my vc97 furnace

Hello,

I have this furnace and if possible, please give me some advice:

KeepRite® Air Conditioning & Heating

I've had it for a year and I've realized that it was a big mistake not to upgrade the thermostat as well. There was no point in getting multi-stage/2-stage if the thermostat can't do it properly. The sales dude did not give me enough information to make a better decision sadly.

I have a thm303m connected to it with 4 wires. I know it sucks but I didn't think it was going to be this bad. It basically turns on and off the furnace like a an old inefficient one. I prefer to keep the fan running for air quality *one of the biggest reasons why I upgraded my furnace*. The most annoying thing is when it gets cold and I want some heat, it takes forever for the furnace to cycle thru plus the fact that the fan keeps running. The house becomes extra cold! ;( I realize now that this is not the furnace's fault but the thermostat...

Can anyone please give me suggestions on what thermostat would let me take full advantage of the features for my furnace? If possible, I don't want to fish more wires. As well, give me options for low, mid and high end ones.

I've done quite a few searches myself and am looking at 3m-50, ct 30, ct 80, visionpro 8000 and prestige iaq. A lot more popped up in my quest like nest (which was my previous choice), ecobee, etc.

It feels like there's some vital info that I'm missing so I can't make a decision and I certainly don't want to be in a point where I would have to upgrade again because I didn't decide properly.

At first I wanted to be fancy and be able to take full control of the thermostat thru wi-fi, phone, etc.. get reports, lots of automated stuff but when you are cold, all that seem fluff.

"I just want to feel comfy!!"

Thank you!
 
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Old 03-31-13, 08:42 AM
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Your furnace is modulating/3 stage, so it can't be used to it's potential even with a two-stage t-stat.

What you need is the manufacturer's communicating t-stat, to not only control output properly but control the continuous fan speed as well.

Do you have the install manual? If yes, see what it says about t-stat.

it takes forever for the furnace to cycle thru
When it's maintaining the setting, the longer the cycles, the better.

It's possible that it wasn't set up properly.
 
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Old 03-31-13, 10:04 AM
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It looks like KeepRite has a custom communicating thermostat that works for your unit. Have you considered that one.....the KeepRite Observer.

KeepRite® Thermostat
 
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Old 03-31-13, 10:12 AM
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I think I have the install manual somewhere but this looks like the online version:

http://icpindexing.toddsit.com/docum...4001420103.pdf

I skimmed thru it and ctrl-F-ed 'thermostat' and here's what I found:

Thermostats and Control Settings
For best results, use a communicating wall control to control
this modulating furnace. A single stage or two−stage heating
and cooling thermostat can be used with the furnace. The
furnace control board CPU will control the furnace and outdoor
unit staging. A two stage heating and cooling thermostat can
also be used to control the staging. However, full modulating
capability will not be available when the furnace staging is
controlled by the thermostat. Furnace staging will be limited to
Minimum and Maximum inputs or Intermediate and Maximum
inputs depending on the configuration of set-up switches
SW1-2 and SW4-2. Refer to typical thermostat wiring diagrams
and the Sequence of Operation section for additional details.
Consult the thermostat installation instructions for specific
information about configuring the thermostat.


To me, it sounds like I can use 1 and 2 stage but as you said, it's not going to maximize full potential of the furnace. It also looks like my thermostat has been wired for a single stage heating. I have not tested cooling since it was installed winter time.

I am somewhat confused by this part here:

"However, full modulating capability will not be available when the furnace staging is controlled by the thermostat."

I have limited understanding on HVAC systems but I thought thermostats is where the control of all output for furnaces happens. With this sentence from that manual, what happens if I install a communicating thermostat?

Does it mean an actual "communication" between furnace and t-stat happens wherein furnace has a say about some things to happen? what kind of scenarios would it be? I figured a 3 stage would be something like a 2 stage but it uses less heat but continuous fan.

It took me a while to find information about the "Observer Wall Control" that is supposed to be the manufacturer's t-stat for the furnace. Probably because I was looking to buy it. I'm dumb. Obviously it's somewhere on the same site I found info about the furnace. lol

Install/Owner's Manual and Specs:

http://icpindexing.toddsit.com/docum...1601101702.pdf
http://icpindexing.toddsit.com/docum...1602101701.pdf
http://icpindexing.toddsit.com/docum...1656100100.pdf

Unfortunately, I have not found any sellers online. Even with using searches for the model number. I guess that means I have to call the installers? Is there no other choice out there that would accomplish the same thing?

As well, how much would I benefit from getting a 2 stage to 3? If I remember correctly, the sales dude mentioned that they are selling the t-stat for 500 dollars but did not discuss it any further. Either he wasn't confident about the product or no one bought it because everybody else is like me. Uninformed and/or cheap.:P
 
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Old 03-31-13, 10:16 AM
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I have! If I have no other choice then I would have to call them and ask for a quote on it. It just makes me frown that it look like there is limited functionality on it apart from being the 'manufacturer's t-stat'. They have a virtual Observer so you can try it out:

http://gokeeprite.com/go/observer/keeprite.html

Edit: limited - I meant to say in comparison to other t-stats that's probably on the same price range.
 
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Old 03-31-13, 12:33 PM
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I read the manual and it turns out that the the use of a communicating t-stat doesn't make such a big difference.

With a single stage t-stat, it runs at a fraction of the rated capacity for the first 19 minutes, then switches to 100% capacity to finish the cycle.

The amount of heat the furnace puts out over the first 19 minutes is determined by the board, based on the length of the previous few cycles.

With a two stage stat, it works the same way except the furnace can switch to 100% capacity right away when there's a call for high heat.

With the communicating t-stat, it works the same way but the firing rate (first 19 minutes only) is determined by the thermostat rather than the board.



Continuous operation at the correct level of heat output (40-100% capacity) is not possible with your furnace. Most better modulating or 3 stage furnaces don't switch to high after a fixed time delay when used with the right t-stat.

There are other ways to set up the vc97:

1. Two stage t-stat -> operates at 40% capacity when there's a call for low heat, 100% capacity when there's a call for high heat

2. Two stage t-stat -> operates at 60-70% capacity on low, 100% on high. Just like a normal two stage furnace.

---------------------
What problems are you experiencing with your system?

Perhaps the problem can be solved without purchasing a two stage or communicating t-stat.
 
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Old 03-31-13, 03:17 PM
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Hi again Muggle,

Thank you for taking the time to reply!

I felt somewhat disappointed at first when I read your post cause it sounded like the furnace isn't as good as I had hoped it to be. I had started to reply when I decided to try and find the info you are saying here.

What I found out was most interesting! Now, I just need to be able to understand HOW the most comfort is attained with the communicating t-stat and how bad/good is it compared with a single staged + modulating heating operation as well as the other modes. At the end of the day, I would still be purchasing a new thermostat because I really want to have a better set of features, only this time I'm not tied to the manufacturer preferred one.

The problem that I am experiencing with the t-stat is that it really takes a while to fire up. I would say 10 minutes but thinking back and reading this, 19 minutes would actually make sense. It always felt longer, I just did not time it. Reading all this info, it looks like this is normal operation?

Can I get a simpler set of instructions on how I can verify this? There seems to be a few ways to set up single stage:

1. ON/OFF - modulates thru the program on the furnace and calculates based on the history of heating cycles (This is the part where it really interests me! Where does it get the information, is it stored somewhere where I can grab it or can I somehow get my own samples? It didn't expound too much on how the furnace does this and I don't think it referenced any other sheet).

Huumm, I'd like to stop here. I keep re-reading the explanation on the this mode but it just keeps on confusing me. Why the hell did they have to describe the 2-stage operation on the single stage! Now I am not sure if the Min heat switch and the intermediate heat switch matters to activate different modes on the a single stage t-stat.

Please explain.

I think I should explain the problem more now - apart from it taking longer to start there isn't much that I noticed except for the fact that the house "cools" because I want the fan set to 'on' all the time. As I've mentioned, this is one of the major reasons I upgraded in the first place. I partially blocked the closest vent which is across the t-stat (~5-7 ft). I read somewhere that you can tweak the heating process by managing the vents opening in term of how close/far it is from the t-stat. Should I have not done this? From time to time, I notice that the fan is blowing a little bit and there is heat that comes with it. After all this info read, is that the 'minimum' heat? I always thought that it's just the vents are still heated because I can swear right now that minimum heat is sometimes cold! lol.
 
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Old 03-31-13, 04:40 PM
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Re: heat balancing...

The registers should be adjusted so that the room where the t-stat is located is the same temperature as the rest of the house. Partially close dampers only in rooms that are too warm relative to the room where the t-stat is.

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re: heat output...

My understanding is based on the description service manual. The manual says that the communicating t-stat works just like a normal two stage one, but determines the initial (19 minute) firing rate based on the room temperature.

Why manufacturer would program the board to automatically shift to high after a per-determined delay is beyond me, considering that the t-stat can monitor rate of temperature change. So, there's a chance that it wasn't described correctly.

--------------
re: time it takes to warm up

You can tell if the furnace is burning gas by checking the exhaust pipe if the furnace isn't vented through the roof. (there are other ways too - ie take cover off)

If you don't like the fact that the house doesn't warm up quickly after increasing the setpoint, a two stage t-stat is the fix.

If the house seems comfortable but there isn't much heat coming out of the vents - don't worry about it, it's normal. The majority of the time, it will be operating at 40-50% capacity.

The airflow in continuous fan mode should be similar to when it's running at 40% capacity.

Unless your ductwork is in a crawlspace or attic, running the fan continuously shouldn't make it cold, but the air coming out of the vents may seem cool.
 
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Old 03-31-13, 05:08 PM
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Re: heat balancing...

I actually think that I am failing to balance it properly. The other rooms are warmer compared to the room where the t-stat is! I may have another problem/question about that.

re: heat output...

Can you please explain it further? in a more specific scenario perhaps? I can't seem to put them together. As well, maybe I did not read it properly but I can't find the part where you are referencing it to be compared to a 2 stage t-stat. I read where it says it operates like a 1 stage except for modulation - let me quote:

Communicating Control and Modulating Heating
(Adaptive Mode)
Best comfort will be attained when a communicating wall
control is used with this product. Wiring and setup instructions
are provided with the communicating control. See the furnace
data sheet accessory section for help in selecting the
appropriate communicating control for this furnace.
When a communicating control is used, the furnace will
modulate through its full operation range, or can be limited via
the minimum and maximum CFM capacity configurations.
Operation of the furnace at the beginning and end of each
heating cycle will be the same as detailed below in the
Single-Stage Thermostat section, EXCEPT that the
communicating control will send modulating rate command
signals through the communication bus rather than energizing
the 24−V thermostat terminals. Note that the R to W/W1 circuit
signal will be controlled by the COMMR relay on the furnace
control. See the wiring diagram in Figure 15.



re: time it takes to warm up

1. I will try to verify if the furnace is running when I thought it wasn't. I guess I'll have to shovel my way through! lol (It's in a side of the house that's not easily accessible because of snow). Come to think of it... I don't think the snow became THAT high... damn! Why did I not think of that.

2. If you don't like the fact that the house doesn't warm up quickly after increasing the setpoint, a two stage t-stat is the fix.

You mentioned increasing the setpoint here, how do I determine the set 'setpoint'?

Also at this point, can I actually assume that you suggest that I just choose one of the 2-stage t-stats? I ask because, I saw some that are 3-stage/modulating as per their claim. Those things wouldn't do me any better?

I have actually experienced that. Air is coming out of the vents but very minimal but the air is heated. As for the last paragraph, I apologize for the exaggeration, no it was not cold, it's close to cool more like but to be clear it's not the same as the heated minimal air that I just mentioned. What does this mean?! As for the ductwork, this is gonna sound stupid again... My basement is in a conditioned space - when I say this, I mean that there is insulation, windows are all good, as well as rim joists are taken cared of BUT I barely go there. I decided to close down the vents coming to the basement so it is definitely colder there. The difference in temperature is probably around 5-8 degrees from the room above it. Was this a mistake? Although, I recently just closed it, ~3-4 months and the cool/minimal heated air has been noticed longer than that. So I don't know....


EDIT: Also, is it supposed to actually turn OFF? If the fan is off, it would turn off. Only with the fan on can I get minimum about or something? Right now, it's definitely OFF. :/
 
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Old 03-31-13, 05:37 PM
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By setpoint, I meant the setting.

With the single stage stat, if you raise the setting, it won't hit high heat for 19 minutes.

With a two stage stat, when you raise the setting, it will jump to high heat almost right away.

----------------------
A single stage normal non-communicating thermostat work like a single light switch. (ie, only signals the furnace when to turn on and off, nothing more)


The circuit board determines the firing rate based on the length of the previous few cycles.


Even when a single stage t-stat is used, your furnace still technically modulates the output, but not in an optimal way.

Using a two stage stat in your case is like have two light switches -> the first one tells the furnace when to turn on/off, and second one to tells the furnace when it's not keeping up or the room temperature is far below the setting.

When only switch #1 is on, the furnace goes through it's normal cycle. (lower output for 19 minutes, high output after that until cycle ends)

When switch #2 comes on, the furnace jumps to 100% capacity right away instead of going through it's normal cycle.

Re: communicating t-stat, the manual is vague, but rather than relying on the length of the last few cycles to determine the firing rate, the t-stat controls the firing rate directly. I think it switches to high after 19 minutes even with the communicating t-stat, but not 100% sure.
 
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Old 03-31-13, 05:41 PM
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Also at this point, can I actually assume that you suggest that I just choose one of the 2-stage t-stats? I ask because, I saw some that are 3-stage/modulating as per their claim. Those things wouldn't do me any better?
Your furnace isn't equipped to use a conventional 3-stage/modulating t-stat. (there's no physical connection for it)

T-stat types that will work:

1. Single stage
2. Two stage
3. Observer communicating, modulating
 
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Old 04-01-13, 12:29 PM
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Thank you very much for all the answers and inputs Muggle. Much appreciated!

I played around with the switches inside the furnace and increased min heat airflow. Unfortunately it didn't make much of a difference. There's a lot more steps to find out what's up but ultimately the manual says, the furnace should be capable of delivering proper CFM as long as the resistance isn't far off and all other factors are normal.

So back to basics:
1. I gotta get my ducts cleaned. 4 years I've been in this house and have not done it. Who knows if previous owners did any as well. Some repairs are needed too.

2. Airseal and Insulate. I'll update insulation in my upstairs bedroom which is also the attic (1 1/2 storey house).

For now:

I am looking into getting 3M-50. My colleague has one and mentioned a lot of good things about it. But before that I am looking to get a cheap 2 stage heat t-stat and test the difference before fully getting a full featured (not very cheap) thermostat (I am even considering getting the observer if it's really worth it). I already saw one at kijiji selling for 20 bucks! hehe.

Thanks again!
 
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Old 04-01-13, 05:33 PM
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The honeywell stuff is excellent -> NEST is overpriced/limited, 3M I'm not sure about.

-------------
As for airflow settings, variable speed blowers compensate for ductwork/filter resistance and maintain proper airflow.

It's pre-set from the factory for optimal performance.

I don't recommend changing the airflow settings unless you really know what you're doing.

The t-stat dip switch settings are safe to change though -> just follow manufacturer's instructions.
 
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