Thermostat location and how many? Opinions wanted

ChrisJ

So,

I've kind of run into one of those situations where I have too many options and just can't make up my mind.
The wife wasn't helpful, though I can't blame her, she's got a lot going on right now but her response was "I don't care, either way will work for me"

I'm hoping for some opinions, thoughts etc.

Basically the scenario is this. I have two VisionPro 8000's, a basic TH8110 and the top TH8321. Both are the older, green display models. I bought the 8321 to control the 2 stage air conditioning.

My assumption right now is that for air conditioning I'm going to do better having my thermostat on the second floor under the return which will primarily be serving the first floor via the stair well. I kind of wonder if T-STAT A could do both fine, but the diffuser above it concerns me as does the fact the hot floor typically runs warmer.

The two best options I've come up with are either two separate thermostats, one for my heat and one for the air conditioning. Or, two mount the 8321 on the first floor using a relay to control the boiler as the 8321 lacks the RC terminal and using an external sensor on the second floor in the summer but disabling it in the winter.

Both scenarios require some attention between seasons. The first one, just using two thermostats is probably the simplest and cheapest as I won't need a relay or an external sensor. But, it does seem nicer to have one thermostat for everything.

I don't know? I'm torn.

What does everyone think?
The reason I'm putting a lot of thought into it is it's going to be fairly easy to run wires right now but will be an absolute nightmare once I run my duct work through the closet.


I've attached a drawing showing location of vents, radiators etc. T-STAT A is what I'm currently using for heat and have been for a few years. It works well.


Please excuse the crudity of this model. I didn't have time to build it to scale or paint it.

Jamie Hall

Being fundamentally lazy -- and no less often slightly confused -- may I suggest that you run the extra wires you might need while you can do it easily? They're cheap, and if you don't need them you can forget them (for some other poor chap to wonder about) and if you do decide you need them, you have them...

ChrisJ

Jamie Hall said:

Being fundamentally lazy -- and no less often slightly confused -- may I suggest that you run the extra wires you might need while you can do it easily? They're cheap, and if you don't need them you can forget them (for some other poor chap to wonder about) and if you do decide you need them, you have them...

The problem is it's not as simple as running extra wires.
It's, where am I going to run the wires.

If it was your house, would you expect, and want two separate thermostats for the systems or would you rather one thermostat with a switchable?

Where would you want the sensor for cooling, the first, or second floor?

This is an unzoned system.

gschallert

ChrisJ said:

If it was your house, would you expect, and want two separate thermostats for the systems or would you rather one thermostat with a switchable?

As a homeowner I would probably prefer one stat for an unzoned system. I don't understand much of what you said but if the gist is that by having a remote sensor on the second floor for AC wired to the first floor stat you could get away with just the one on the first floor, that's what I would want. I would think the AC sensor would be more important wherever you sleep and spend the most hours in the house during cooling season. Which is the second floor right?

ratio

That model of thermostat supports a hard-wired sensor on S1 & S2. IDR if you can average the remote with the stat sensor or it's one or the other, but you can have a number of them. They offer a 10k & a 20k model, so you can do odd numbers of sensors.

SWEI

You can series-parallel four 10k thermistors to create an average. If you decide to go that route, PM me. I have far more packaging options available, generally at about half the price.

I'd be suspicious of the 20k curves actually matching, but it might work.

ratio

If we operated close to the extremes, I'd have to take a hard look at the curves, but ±10° around the sweet spot? There's a good chance that consumer-grade tolerances will occlude any error.

Also, the new model (white backlight) can use up to IIRC 6 RedLINK wireless indoor stats, along with the onboard sensor, for averaging.

Keep in mind that the average of 60 and 80 is 70. Adding an averaging sensor may make that location feel better, but at a cost to the rest of the space. Whether or not that's a good trade is hard to determine ahead of time.

ChrisJ

So,

Here's my concern with one thermostat located on the first floor. I really am not sure how this will work.

According to what I understand about diffusers, it should cause an updraft past the thermostat, which is of course awesome for cooling.

My concern is, leakage out of the back of the diffuser and down the wall, shutting the system down prematurely.


The red X's show a soffit that will be removed if all goes as planned. Best we can tell it's cosmetic only, but I won't know until I actually pull some sheetrock off of it.

The thermostat in the picture is well, the thermostat.

This location was chosen due to how it should cool the areas, as well as the location of the ductwork within a closet no one will care about losing some space in.








The specific diffuser will be a Hart & Cooley 12x12 2 way corner diffuser running at approximately 170 CFM on low, 250 CFM on high.






So, the million dollar question.
Will the diffuser tend to pull an updraft past the thermostat working for me. Or will it tend to shut the system down constantly and make me hate life?

Fred

I'm guessing you will find that soffit is hiding a support beam but you'll find out soon enough. If it were me, I'd relocate the thermostat somewhere as close to the stairwell as I could get it. I think that's where your warm air updraft will be greatest. JMHO

hvacfreak2

From an operating standpoint you would want the cooling stat upstairs. It would also be wise to run a wire from the AHU to the boiler and energize a relay anytime the heating stat is enabled
( using the O or B terminal ). This will prevent simultaneous heating / cooling operation. ( edit : fail to heating )

njtommy

I would install a t-stat on each floor and zone the duct work. Just saying if your doing all your home work and duct design what's an extra few hundred for two zone dampers, panel and t-stat.

ChrisJ

Fred said:

I'm guessing you will find that soffit is hiding a support beam but you'll find out soon enough. If it were me, I'd relocate the thermostat somewhere as close to the stairwell as I could get it. I think that's where your warm air updraft will be greatest. JMHO

In this house, anything is possible.
However, the joists are running in the same direction as that soffit on both sides and there's absolutely nothing there to support the thermostat side of it in the wall that I saw when we tore the chimney down. I have pictures and nothing goes past the thermostat. Best case scenario, there's a 2x4 going down to the floor, but what's supporting that in the basement?

98% chance it's cosmetic.

2% chance I'm going to be saying "W T F".

ChrisJ

njtommy said:

I would install a t-stat on each floor and zone the duct work. Just saying if your doing all your home work and duct design what's an extra few hundred for two zone dampers, panel and t-stat.

You and your mini-splits and zoning.

Fred

ChrisJ said:

Fred said:

I'm guessing you will find that soffit is hiding a support beam but you'll find out soon enough. If it were me, I'd relocate the thermostat somewhere as close to the stairwell as I could get it. I think that's where your warm air updraft will be greatest. JMHO

In this house, anything is possible.
However, the joists are running in the same direction as that soffit on both sides and there's absolutely nothing there to support the thermostat side of it in the wall that I saw when we tore the chimney down. I have pictures and nothing goes past the thermostat. Best case scenario, there's a 2x4 going down to the floor, but what's supporting that in the basement?

98% chance it's cosmetic.

2% chance I'm going to be saying "W T F".

When they opened that wall up, who thought that they needed to support it all the way down to the basement with a footer?
If the joists are running parallel to that wall. you may be lucky. From the looks of that room, I would have guessed the second floor joists run perpendicular to that header and rests on it. They typically ran the joists the shortest distance.

ChrisJ

Fred said:

ChrisJ said:

Fred said:

I'm guessing you will find that soffit is hiding a support beam but you'll find out soon enough. If it were me, I'd relocate the thermostat somewhere as close to the stairwell as I could get it. I think that's where your warm air updraft will be greatest. JMHO

In this house, anything is possible.
However, the joists are running in the same direction as that soffit on both sides and there's absolutely nothing there to support the thermostat side of it in the wall that I saw when we tore the chimney down. I have pictures and nothing goes past the thermostat. Best case scenario, there's a 2x4 going down to the floor, but what's supporting that in the basement?

98% chance it's cosmetic.

2% chance I'm going to be saying "W T F".

When they opened that wall up, who thought that they needed to support it all the way down to the basement with a footer?
If the joists are running parallel to that wall. you may be lucky. From the looks of that room, I would have guessed the second floor joists run perpendicular to that header and rests on it. They typically ran the joists the shortest distance.

Yes,
However being there's nothing in the basement supporting anything other than the foundation, the shortest span is in the other direction.

In theory of course.
It's not that I'm lucky, it's that I a long time looking at everything, including the nails in the ceilings to figure out what direction I felt the joists went. I know which way they go in the basement obviously.

Oddly enough, in the kitchen the ones in the second floor ceiling go in the opposite direction of the first floor. Found that out by knocking on the ceiling and looking for nails. But, this is because the cistern makes the span half as far as it would in the second floor.

My guess is that soffit is there because they used to use one of the areas as a dining room as now we use the entire thing as a livingroom.

But, I'll know for sure in the spring when I go to open it up. I've learned to never be 100% sure of anything on this house. A lot of weird things have taken place over the past 150+ years.

Canucker

ChrisJ said:

Fred said:

ChrisJ said:

Fred said:

I'm guessing you will find that soffit is hiding a support beam but you'll find out soon enough. If it were me, I'd relocate the thermostat somewhere as close to the stairwell as I could get it. I think that's where your warm air updraft will be greatest. JMHO

In this house, anything is possible.
However, the joists are running in the same direction as that soffit on both sides and there's absolutely nothing there to support the thermostat side of it in the wall that I saw when we tore the chimney down. I have pictures and nothing goes past the thermostat. Best case scenario, there's a 2x4 going down to the floor, but what's supporting that in the basement?

98% chance it's cosmetic.

2% chance I'm going to be saying "W T F".

But, I'll know for sure in the spring when I go to open it up. I've learned to never be 100% sure of anything on this house. A lot of weird things have taken place over the past 150+ years.

I'm hoping for your sake that it isn't a **** moment when you open it up. I've owned a few old houses and always had at least a few of them. I know the previous owner of the house I live in had zero respect for the building trade and the engineering principles the codes are based on. Apparently in my house joists can be any length you want, loading be damned and walls can be moved anywhere you like because, point load, pfft, like what's that? Haha

ChrisJ

Canucker said:

ChrisJ said:

Fred said:

ChrisJ said:

Fred said:

I'm guessing you will find that soffit is hiding a support beam but you'll find out soon enough. If it were me, I'd relocate the thermostat somewhere as close to the stairwell as I could get it. I think that's where your warm air updraft will be greatest. JMHO

In this house, anything is possible.
However, the joists are running in the same direction as that soffit on both sides and there's absolutely nothing there to support the thermostat side of it in the wall that I saw when we tore the chimney down. I have pictures and nothing goes past the thermostat. Best case scenario, there's a 2x4 going down to the floor, but what's supporting that in the basement?

98% chance it's cosmetic.

2% chance I'm going to be saying "W T F".

But, I'll know for sure in the spring when I go to open it up. I've learned to never be 100% sure of anything on this house. A lot of weird things have taken place over the past 150+ years.

I'm hoping for your sake that it isn't a **** moment when you open it up. I've owned a few old houses and always had at least a few of them. I know the previous owner of the house I live in had zero respect for the building trade and the engineering principles the codes are based on. Apparently in my house joists can be any length you want, loading be damned and walls can be moved anywhere you like because, point load, pfft, like what's that? Haha

This is a balloon framed house built in the 1860s. Balloon framing started sometime around the 1950s, so it was all very new at the time. No ridge board, no diagonal sheathing or subflooring. I've got 2x8 joists running a 15' span on 24" centers.

But, it's still here.

If it is a **** moment, I'll have to figure out something else to do with my diffuser. Hopefully not though.

JUGHNE

We did a small movie theater here. There are 3 HVAC systems.
I put remote sensors in the return duct right at each AH/furnace. We have variable speed blower motors and have them run constantly. The 3 HW 8000 T-stats are located in one place and we can see the RA temp at a glance.

Disadvantage is that the humidity sensor is in the actual T-stat body. So adjusting for RH% correction by over cooling is somewhat a guess.

(My wife will allow me to make such decisions also, at my own risk.....any issue of course is solely my fault......the point system: Husband gains 1 point if the temp is comfortable but loses 5 points if any discomfort is experienced. Then there is an age later in life that may have you going from AC to heating several times in one September day)

ratio

@JUGHNE, the RedLINK indoor sensor reports both temp & humidity, at the cost of replacing batteries from time to time.

JUGHNE

Ratio, if the sensor was in the RA at AH could it tap 24 VAC from that power supply? Batteries are always a nuisance.
Just asking concerning ChrisJ's situation.

njtommy

I have a RedLink zone sensor in every room. Really does a nice job balancing out the house and keeping an even temp. I have ranch/ single story home 1800sqft.

ratio

The RedLINK sensor runs on two AAA batteries IIRC. I'm sure something could be hacked together, but they're not intended to run on external power