Looking for one thermostat to replace two (a twofer)

SteamtoHotWater

I know next to nothing about thermostats. I currently have a Bryant Evolution (SYSTXBBUID01 v16) to control my AC. I don't have a heat pump, or humidifier, or any other accessories connected to it. It only controls the air conditioning. I recently installed underfloor radiant aluminum plates with PEX between my wood floor joists. On the first floor/zone, I have a Tekmar 519 as a thermostat. The second floor hallway, where the Bryant thermostat is located, has shockingly little wall space. It really is like 80% doors and 20% wall. As opposed to installing another Tekmar to control the heating, I thought I'd just use the Bryant. But looking at the manual and wiring, that doesn't look possible, right?
So, is there a thermostat that will control my Bryant AC and my underfloor radiant? The replacement thermostat would need to control a Taco ZVC403, that connects to a Taco Z100P2 zone valve. The whole system is fed by a Laars combi boiler.
I'd greatly prefer the simplest thermostat possible. It doesn't need to be programmable. And I don't want it to have wifi or be connected to the internet. I did some sleuthing before posting this, but my general lack of thermostat knowledge is an impediment.

HVACNUT

The Bryant system is using communicating controls while the Tekmar 519 uses conventional 24 volt switching. So they are not compatible. 

If you're using the slab sensor, and you should, you can mount the thermostat anywhere. Closet, bathroom cabinet, equipment room, etc.

If you're not using the slab sensor, then contact Bryant. I know the Carrier (Bryant's sister) Infinity system offers a hydro coil kit that basically just closes TT to the boiler's heat relay and turns on the Fan. I don't know how you'll get around keeping the fan off during a radiant call though. 

SteamtoHotWater

HVACNUT said:

If you're using the slab sensor, and you should, you can mount the thermostat anywhere.

Why should I use the slab sensor? On the first floor zone, I am - but just because the directions told me to and I thought it would be neat to know the floor temp. How does using the slab sensor allow me to put the thermostat anywhere?

HVACNUT said:

The Bryant system is using communicating controls while the Tekmar 519 uses conventional 24 volt switching. So they are not compatible.

Is there not another thermostat that could do both?

Jamie Hall

Remember that radiant floors work best when they are trying to keep the space at a constant temperature. You don't turn them up and down, you don't turn them off. The best control for them is an outdoor sensor and mixing valve and/or variable speed pumping, trimmed by a slab sensor and, possibly, a space thermostat --which is never changed.

SteamtoHotWater

Jamie Hall said:

Remember that radiant floors work best when they are trying to keep the space at a constant temperature.

Got it.
Still, I'd like one thermostat that can control my AC and heat.

109A_5

Hello @SteamtoHotWater,

This may get you where you want to go. Although your application of it may not be Bryant's intent. I have no experience with it, just looking at the documents.

Bryant® Evolution® Network Interface Module
Item #: SYSTXBBNIM01
MFG: SYSTXBBNIM01
Brand: Bryant®

https://www.peirce.com/bryant-evolution-network-interface-module--2910a56

SteamtoHotWater

Thanks for the recommendation, but I don't think the Bryant NIM is the solution. Which might be a good thing because it seems pretty expensive.

Do people not use third party thermostats with Bryant ACs?

SteamtoHotWater

So, the more I'm researching is there no such thing as an all-in-one communicating and conventional thermostat?

109A_5

Hello @SteamtoHotWater,
I have no idea if other Thermostat manufactures support the Bryant®Evolution ABCD bus interface. You or whoever picked that AC unit may have built you into a proprietary corner you don't like.

You may want to see if the AC unit will use a old school type Thermostat.

SteamtoHotWater

109A_5 said:

You may want to see if the AC unit will use a old school type Thermostat.

That seems like a plan. But how do I know?

I downloaded the datasheet for the Carrier FE4A series Fan Coil, it makes no mention of the thermostat.

109A_5

Hello @SteamtoHotWater,

This may work, I would prove there is a contact closure between R and W of the Fan Coil unit when the user interface calls for heat.



Using a conventional thermostat may get weird.



https://resource.carrierenterprise.com/is/content/Watscocom/carrier_fe4an_ii

Jamie Hall

SteamtoHotWater said:

So, the more I'm researching is there no such thing as an all-in-one communicating and conventional thermostat?

Probably not. Remember that communicating thermostats do marvelous things (when they work and are doing what they are meant for) but each manufacturer's units speaks a different language. There is no common standard for these serial communications (just as there is no common standard for the similar communicating devices in cars, for instance).

The whole concept is completely different from any conventional thermostat -- even such devices as Nests and Ecobees and their friends -- which simply send an on/off signal over a pair of wires.

HVACNUT

SteamtoHotWater said:

Got it. Still, I'd like one thermostat that can control my AC and heat.

Not gonna happen, unless you change the AC system to conventional wiring, which would defeat the purpose of a modulating inverter system. 

SteamtoHotWater

HVACNUT said:

Not gonna happen, unless you change the AC system to conventional wiring, which would defeat the purpose of a modulating inverter system.

Today I learned that there's proprietary thermostats.

Could you explain your earlier comment that a slab sensor would allow me to put a thermostat anywhere? I do have another Tekmar 519 ready to be installed, so I have the slab sensor. But I don't get why monitoring the floor temp allows me to place the thermostat elsewhere.

HVACNUT

SteamtoHotWater said: Could you explain your earlier comment that a slab sensor would allow me to put a thermostat anywhere? I do have another Tekmar 519 ready to be installed, so I have the slab sensor. But I don't get why monitoring the floor temp allows me to place the thermostat elsewhere.

You wouldn't use the built-in room sensor, just the floor sensor. So if just sensing floor temperature, the thermostat can be in Albuquerque. If the wire is long enough. 

SteamtoHotWater

HVACNUT said:

You wouldn't use the built-in room sensor, just the floor sensor. So if just sensing floor temperature, the thermostat can be in Albuquerque. If the wire is long enough.

And what would the disadvantages be of using the floor sensor vs using the room sensor?

HVACNUT

SteamtoHotWater said:

You wouldn't use the built-in room sensor, just the floor sensor. So if just sensing floor temperature, the thermostat can be in Albuquerque. If the wire is long enough.

And what would the disadvantages be of using the floor sensor vs using the room sensor?

As far as I know, none. But I'm not a radiant design expert. I do service. There are others here who could school us both on that subject. @Alan (California Radiant) Forbes ? I do know I service many properties that have all the thermostats in the equipment room. The room sensors are turned off and cycle off of the floor sensors or wall sensors in the case of cooling. 

Have you tried contacting Bryant to see if they offer a Hydro air kit?