2nd Stage Heating issue


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Old 03-09-08, 03:19 AM
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2nd Stage Heating issue

Help...

I have a Keeprite VS90 Dueal Stage, Variable speed furnace tied to a Rogers 2 stage thermostat.

I use the t-stat to control the time till 2nd stage (it allows 5 min increments). I have it set to a 10 minute delay. I have noticed that the t-stat will kick in 2nd stage and within a minute the house is warm enough that the t-stat will stop the call for heat.

Am i better off setting the setting to a 15minute delay or using the 2nd stage for a short while. As well, what is the "normal" cycling temperature. the t-stat allows me to set when it will call for heat (after the temp. spread is greater than x degree).

I am located in Toronto, Canada - we hover around 27-35F

Thanks.
 
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Old 03-09-08, 07:13 AM
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A true 2-stage t-stat should automatically switchover from stage-1 to stage-2 as the house heating needs call for it...and switch back to stage-1 once the house starts warming-up. It should not keep the furnace running on its 2nd stage and the turn it off on stage-2.

Would you please post the full M/N of this t-stat?
You say is a Rogers. I suppose you mean White Rodgers.
 
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Old 03-09-08, 08:44 AM
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T-Stat Correction

Pflor, the correct info for the T-stat is:


Robertshaw 9815i

From what I can tell the T-stat calls for 2nd stage under either of the following conditions:

1. Current temperature of the house and the set temperature are greater than x degrees (x is user definable)
2. When the t-stat calls for heat for longer than x minutes (x is user definable, in 5 minute increments)

Thanks,
 
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Old 03-09-08, 03:49 PM
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I don't know that brand of stat, but if you got a timer, shut it off. Only allow the stat temp to cycle 2nd stage as needed.
 
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Old 03-09-08, 06:59 PM
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Hi...
please clarify:
I see from Robershaw that they have the following,
--> a 9825i2 t-stat, and a
--> a 9915i t-stat

But I don't see the 9815i you mention.
Please tell me which one of the two above is yours?
 
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Old 03-09-08, 07:51 PM
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T-Stat

Pflor - it is definetly a Robertshaw 9815i - I am looking at the manual that it came with. There are other 98xx models, but they are for heat pump units.


Jay11J - I am ok with killing the timer mode for 2nd stage, but based on history that would never activate 2nd stage - ever. The t-stat has an EER (Energy Efficient Recovery) mode - similar to a Honeywell adaptive reccovery. When EER is set to on, as it is, it holds 1st stage when returning to a warmer setting. therefore, house is 65 empty days, 70 occupied evenings - going from 65 to 70 would be held in 1st stage. turning off EER would force 2nd stage immediately upon activation of revory to 70, but albeit at a less efficient fuel usage than staying in 1st stage - or so Robertshaw says.

The current limit settings are 1degree for 1st stage and 2degree for 2nd stage to kick in


To be clear, I am in Canada - i have a Single Stage A/C, with the Keeprite 125,000 BTU furnace. The furnace is over-sized, as the I was told the typical for a 3500sq ft house (main and 2nd level - full basement not included in the sq. ft) is a 100,000btu unit.
 
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Old 03-09-08, 07:56 PM
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T-stat link

Here is the link to the Robertshaw catalogue showing the 9815i

http://www.robertshawtstats.com/imag.../150-1410K.pdf
 
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Old 03-10-08, 02:44 AM
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You sure seem to know what you're doing here, and you most certainly have done your homework and know your t-stat too...

Telling us that you are aware of your unit being oversized (for the size of your home) explains why would the t-stat stay on 1st stage at all times.
 
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Old 03-10-08, 03:23 AM
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As knowledable as I seem (thanks to the internet, and sites like this) I am still concerned about the whole 2nd stage thing. Although I paid cost (had a very good connection for the parts) I probably could have gotten a 1 stage 125btu unit.

seeing that i have what i have, is it ok to have the t-stat on a 1 degree setting or should it be at 1.5 prior to calling for heat

i had it at 1.5 and that is when i hit the 15min mark and had 2nd stage for all of 2 minutes - it didnt seem "good" to have it on for such a short time. at 1degree the unit cycles on and off more often but 2nd stage does not kick in.

So, which is better - 2nd stage kicking in for a few minutes each time, or 1st stage cycling more often?

Thanks in advance.
 
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Old 03-10-08, 05:36 AM
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For comfort, let the 1st stage run a long time, and as we said, just turn off the time, and let the stat itself cycle 2nd stage as needed.. I'd do 2˚ on 2nd stage, and 1˚ for 1st stage..
 
 

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