Top End Dual Fuel Proposals - Look Good?

[jerryd_2008]

If you continue to try to work with "this HVAC idiot",
you get what The Owner deserves.

if the root cause - windows - is not addressed,
you get what you get
and don't have a fit.

Not a very productive response, Designer Dan. I suppose that you are suggesting that I replace 70'+ of Southern exposure windows or maybe installing $1,000's of film on the windows that kill the beautiful view and may or may not fix the sun load. The true "idiot" in this situation is the original designer that I never met. Placing only one HVAC system in this fairly large, walk-out house and then enclosing all of the duct work in dry wall to prevent any cost-effective duct solutions and then placing the tsat in probably the hottest room in the house. Your smart reply reflects no content that I, a quite accomplished designer in another environment, would attribute to an effective designer. Maybe it's just that it's early and you have a bad day in front of you or, if not, you could just skip reading the posts on this thread.

Now back to Beenthere's comment. Installing additional sensors is a matter of what's cost-effective. This house is fairly large, built in 1994, and each sensor requires a wall penetration and hopefully finding a reasonable wiring path back to the tsat digital control in the garage. The two locations that I think will work are above the return in the highly-used, partially buried, lower level that is naturally cooler and the other is in the first floor master bedroom near the wall vent penetration for when the door is closed and which is away from the hottest room. One sensor is an easy install and the other not so much. These two locations are much more reflective of the true temperature of the rest of the house. During the heating season, the average of these two temperatures will be lower than in the hot room and should cause longer run times to reach the tsat setting. The longer run times should also simulate running just the fan for the hot room causing the air handler to mix the hot air from that room and possibly lowering it there without all of that blowing cool air throughout the house with just the fan. In addition, my HVAC pro feels that too many sensors will solve the problem in no specific location which I kind of agree with as long as the selected locations are indicative of the true house temperature.

So, Beenthere, given that we select appropriate senor locations, do you agree that the proposed two-sensor scenario using the average of the tsat and the new sensor location using the tsat 340 setting is at least technically feasible without any undocumented workarounds for Honeywell's tsat/sensor scenarios?

[beenthere]

Nope. Need two sensors, and the stat is not one of them.

Not any harder to install 2 sensors. Then to install one sensor and move the thermostat to another location.

[catmanacman]

http://www.forwardthinking.honeywell..._products.html might be cheaper and easier in the long run to go wireless thay way you can move the thermostat to your liking

[dan sw fl]

Since, duct changes are probably not feasible.

One should look at SOME window film coverage, with addition of 400 square feet film,
peak load might be reduced nearly one ton.

http://www.windowfilmdepot.com/simulator.html
Prestige 50 or 60 should not change the perceived environment.

+ 20% savings in operating costs
+ 20% equipment life extension likely enables a ROI of < 5 years.
+ significant temperature difference is mitigated.

[jerryd_2008]

Nope. Need two sensors, and the stat is not one of them.

Not any harder to install 2 sensors. Then to install one sensor and move the thermostat to another location.

Beenthere, I have read some technical documentation in my day but I am totally confused by the cross statements between the Honeywell YTH9421C1002/U tsat and the C7189U1005 indoor sensor. The tsat doc says for the 340 setting that you can display average of two indoor temperature sensors and indeed that The temperature sensor in the thermostat is disabled when using remote indoor temperature sensor(s):

340 Indoor Temp Sensor

0 Thermostat location only
1 Remote indoor sensor(s) location(s) only
2 Average between thermostat and sensor locations

Indoor temperature sensors will display the temperature at the sensor location or an average of two indoor temperature sensors, not including the thermostat. The temperature sensor in the thermostat is disabled when using temperature sensor in remote indoor temperature sensor(s).


Then the C7189U1005 indoor sensor doc shows figures on page 3 of legal configurations for 1, 4 and 9 sensors and NOT 2.

- First, why would one even want to "display" the tsat temperature in an average if it is "disabled" by adding an indoor sensor?

- The tsat 340 setting talks about displaying the "average of two indoor temperature sensors" which is an illegal, configuration????

- Beenthere says that it is "Not any harder to install 2 sensors" which is an illegal Honeywell configuration????

- Beenthere said in the past that there is an "undocumented work around" for two indoor sensors but I can't find any documentation to provide my HVAC pro.???

- Is it just time for me to say forget it, because I cannot resolve the communication path between Honeywell/this forum/my HVAC pro??? I have no idea what to order for him nor does he and has little interest in researching it.

The close-to-the-vest format on this forum is just pure frustration for a home owner trying to solve a real HVAC problem. I appreciate the concern over do-it-youselfers but I am NOT one and it would be a cold day in .... before I start running wire in my house. The change in focus of this forum a while back is hard for a home owner to navigate.

PS: thank you, catmanacman, for the suggestion, but it sounds like I would have to scrap all of my tsat equipment and start over to do wireless.

[beenthere]

No idea why anyone would want to display an average temp but not use it to control temp.
Averaging of one remote and the stat is useless.
Its not an "illegal" configuration. Honeywell the support that you talked to is residential, not commercial, so they probably don't even know they make the 20,000 ohm sensors.
Thats up to you. To me its simple. Get the 20,000 ohm sensors and install them.

The install manuals are not written by engineers. They are written by people that went to school to learn how to write technical documents. They don't really know how whatever they are writting about works. they just transcribe notes on operation from the engineers. And those notes aren't always clear, so the writer will sometimes adlib it.

[jerryd_2008]

No idea why anyone would want to display an average temp but not use it to control temp.
Averaging of one remote and the stat is useless.
Its not an "illegal" configuration. Honeywell the support that you talked to is residential, not commercial, so they probably don't even know they make the 20,000 ohm sensors.
Thats up to you. To me its simple. Get the 20,000 ohm sensors and install them.

The install manuals are not written by engineers. They are written by people that went to school to learn how to write technical documents. They don't really know how whatever they are writting about works. they just transcribe notes on operation from the engineers. And those notes aren't always clear, so the writer will sometimes adlib it.

Beenthere, I think this is getting through my HVAC thick skull. I have been proceeding along assuming that you were recommending that a very specific 20,000 ohm electrical component was needed along with 2 Honeywell C7189U1005 indoor sensors and that they are to be wired in some undocumented electrical circuit which I couldn't understand why you couldn't describe that circuit for my HVAC pro. I finally located the TR21 wall mounted sensor assembly and think I know what you really meant. Please verify this scenario:

- Buy 2 TR21 indoor sensors with the following description (from Amazon):
Product Description: The Honeywell TR21 wall mount temperature sensor is a 20k sensor that replaces the T7770a1006 sensor

- Install these 2 sensors per the instructions (I hope) in the literature in place of the 4 Honeywell C7189U1005 indoor sensor scenario.

- PS: I assume that I would then set my tsat 340 setting to: 1 Remote indoor sensor(s) location(s) only

If this is what you meant, I still wish to retain my HVAC non-wannabe and HVAC Idiot titles on this forum.

[beenthere]

Now you got it.

[jerryd_2008]

Thank you, Beenthere. I am running on light sleep so I can get testy at times, especially when I go down dumb paths.

[jerryd_2008]

We have had the two 20k remote temperature sensors installed for a cooling and big part of heating season. I was a bit disturbed when the installers didn't seem to know that these two sensors needed to be hooked up in parallel versus serial in order to get an effective 10k circuit. Whereas I know little to nothing about how to wire real-world circuits, I waded in based on circuit theory and insisted that they needed to wire them in this way. Now I am trying to figure out why temps in the three locations and the furnace tstat seem to disagree. I would appreciate any guidance that seems needed.

We set the tstat at 69 during the day. I note that three thermometers in different locations, two close or in the same room as a sensor, do not agree with this setting. Most of the time the temps measured are 2 or more degrees higher than that registered on the tstat. As I understand, if wired and set correctly, the tstat should show the average temp for the two sensors. I also understand from the literature that the sensors may vary up to 1 1/2 degrees. I also understand that the proximity of a vent could effect these readings.

When I mentally average the measured temperatures at the two sensors, it seems never to agree with the tstat "averaged" temperature. Can you verify that should these sensors have been wired incorrectly, in series say, that the tstat would be way off due to an effective 20k circuit when it is calibrated to a 10k circuit? Also, does the temperature variances between three locations and the averaged tstat temperature sound good enough?

[beenthere]

If 2 20,000 ohm remote sensor whee wired in series, the stat would think it is -46°f inside the house when it was actually 77.

Put the 3 thermometers side by side in a room and see if they read the same temp as each other.

[ga-hvac-tech]

If 2 20,000 ohm remote sensor whee wired in series, the stat would think it is -46°f inside the house when it was actually 77.

Put the 3 thermometers side by side in a room and see if they read the same temp as each other.

I cannot count the number of times this has happened:

HO buys a VERY expensive thermostat, then puts his $5 WalMart thermometer in the same room (not the same place, the same room)... and says the couple hundred $$$ t-stat is bad. Amazing logic there...

[jerryd_2008]

I cannot count the number of times this has happened:

HO buys a VERY expensive thermostat, then puts his $5 WalMart thermometer in the same room (not the same place, the same room)... and says the couple hundred $$$ t-stat is bad. Amazing logic there...

Actually, the thermometer is a digital one from Harbor Freight & Tools. Second point which you probably missed is that the very expensive thermostat (Yes it was!) does NOT measure the temperature in this configuration. As I understand, it only shows the AVERAGE temperature of the two remote temperature sensors. Further, this digital thermometer agrees exactly with at least one of the other thermometers in one of the sensor rooms. But thanks for the reply.

[jerryd_2008]

Beenthere, thank you for the reply. You confirmed what I figured - the average temp at the tstat would have been very weird if they incorrectly wired the sensors in series.

I have done a bit of comparison with two of the thermometers and they seem to agree. Perhaps, I need to be more systematic with all three. Since two of the thermometers are indoor/outdoor displays associated with an outdoor sensor that has limited range, I may not be able to put them close to the actual tstat sensors. I'll have to see if they will still report an accurate indoor temp when out-of-range of their associated outdoor sensor.

[beenthere]

The sensors in the remotes, are very small. They will tend to indicate the air temp fairly accurately, and the air temp at the wall won't always be the same as the wall itself, or any other area. So your thermometers must be next to the remotes to check the remotes.

Thermostat wire length and gauge from the remote to the thermostat can also have a slight effect. For highest accuracy, the wire is suppose to be shielded wire.

[ga-hvac-tech]

Actually, the thermometer is a digital one from Harbor Freight & Tools. Second point which you probably missed is that the very expensive thermostat (Yes it was!) does NOT measure the temperature in this configuration. As I understand, it only shows the AVERAGE temperature of the two remote temperature sensors. Further, this digital thermometer agrees exactly with at least one of the other thermometers in one of the sensor rooms. But thanks for the reply.

Here is a story about this:

In our industry, we have a variety of digital thermometers.... some of them are only air, some will do liquid also. Most of them read in 1/10 of a F*.

If one takes a dozen or so, lays them out on a table side by side... I can guarantee you they will not say the same thing. Usually, the range will not be more than 1-1/5* F... however I have never seen this done where any two read exactly the same to a 1/10th.

[tedkidd]

Had the York dual fuel HP with Honeywell IAQ thermostat installed in the summer of 2009.

Both units work well and I have never seen a thermostat that maintains the temperature setting so accurately as this Honeywell unit does.

Here is my problem. We have a total southern exposure on the back of the house and the thermostat is located on the wall over the only first floor return in the living room in that area with a lot of windows. In the winter, the sun heat load frequently raises that room temperature beyond the setting while the rest of the house remains 2-6 degrees lower than the setting (70 degrees in the winter) and beyond our comfort level. We just had our youngest son with young children move into a back bedroom and it gets too cool for them as well as us in another bedroom and in the lower walkout area where I spend a lot of time.

I suspect that the advanced variable speed air handler and very accurate thermostat may also be contributing to the problem because of lower air flow speed and shorter run times.

Sorry, I'm a little confused here. 5-6 degree delta between rooms. So one room is 70, and the other is 64. What do you think temperature averaging will accomplish that changing your thermostat set point to 73 won't do? Maybe this comment was missed:

Averaging is nice, but doens't solve the eproblem, it mostly will just "average it out". Meaning it will overheat one area to heat hte others.

Sounds like oversized equipment, and your first post indicating replacement of 80k 80% that heated sufficiently with 100k 95% seems to confirm this. I don't know York, but if that's a communicating furnace (like Carrier Infinity), there is a good possibility that getting the communicating stat will run that furnace better.

"maintains the temperature setting so accurately" indicates, particularly with oversized equipment, that you probably have very short cycling. This will exacerbate temperature imbalance caused by solar load. One other possibility is increase deadband from .5° to 2° for longer cycles. Again, already suggested by others:

Something to consider: longer run times tend to lower temp differences within a structure.

Also... might set the fan to run continuously in the winter... and auto in the summer.

[jerryd_2008]

Here is a story about this:

In our industry, we have a variety of digital thermometers.... some of them are only air, some will do liquid also. Most of them read in 1/10 of a F*.

If one takes a dozen or so, lays them out on a table side by side... I can guarantee you they will not say the same thing. Usually, the range will not be more than 1-1/5* F... however I have never seen this done where any two read exactly the same to a 1/10th.

The thermometers I am using are certainly not accurate to anything like 1/10 degree. They are all digital and read temps to tenths. I have done a few more experiments using all three close to each other. In only one case did they all agree within .4 degrees and also the tstat read the same temp without the tenths the thermometers provide (it truncates the reading - more on this later). Even the new digital changes temp when switched from indoor sensor to outdoor sensor that is just a wire with a sensor on the end. The difference can be close to a degree but then the outdoor sensor is hanging lower by about a foot.

The bits of wisdom I take away from this discussion and my experiments with all three thermometers:

- No set of thermometers read the same, including the indoor and outdoor sensors of the new digital thermometer.
- There seems to be a significant difference in thermometers and tstat that is worse when heat is on.
- The tstat averaged temp is almost always LOWER than the three thermometers by over one degree (remember, the tstat only shows whole degrees).
- To answer Beenthere's comment about using shielded wire. Don't know. It is covered and seems to have 3 wires, one unused. My confidence that the 2 guys doing the work makes me question whether they would even know that. Whereas, I admit to no practical knowledge about wiring, I did check to see if they had used the same color wire on the same connection on both remote sensors.

To tedkidd's concerns over the original temp variations before the addition of the remote sensors, The variance seems much better now. I haven't actually checked the thread posts way back, but the large temp variance was due to the high end tstat being located in a room away from these variances and subject to a lot of sun load, I believe. This in my mind made the tstat think it was great in the house when it was significantly different in the two other locations I chose to place the remote sensors. I was specifically looking for an averaging in 2 locations far from the sun load tstat sensor.

Back to my comment about the high-end Honeywell YTH9421C1002/U tstat. This may be getting down deep in the mud, but can anybody tell me how the tstat measures temp? Since it shows only full degrees, does it truncate the actually temp reading or does it round up or down above or below .5 readings?

[second opinion]

They read in tenths of a degree.
You will not see this. It is part of the PI algorythem that determines the staging and rate of recovery based on distance from set point and how fast it is recovering.

[tedkidd]

the large temp variance was due to the high end tstat being located in a room away from these variances and subject to a lot of sun load, I believe. This in my mind made the tstat think it was great in the house when it was significantly different in the two other locations I chose to place the remote sensors.

I was specifically looking for an averaging in 2 locations far from the sun load tstat sensor.

Aha! Bad thermostat location (passive solar making the rest of the house all screwed up), except it's a convenient place to have it.

That makes great sense as does your solution.