Thermostat recommendations for hydronic staple-up system

kroy2008

I am in the process of installing a hydronic staple-up system. It has 1 zone with 4 loops run off  this manifold , circulated by  this pump , with  this controller. This system is "supplemental" to my forced air HVAC and I'm putting it in because a) despite decent insulation, the hardwood floors are still pretty chilly and b) I'm pretty handy but wanted to learn something new that I had not worked on before - been fun so far!

3 of the 4 loops cover a large L-shaped room (kitchen + breakfast nook + living room) where we spend basically all our non-sleeping time. The 4th loop is in my wife's office - and only needs to be heated when she is working.

Questions:

1. I assume I need 2 programmable thermostats - one for my wife's office, and one for the kitchen/living room?
2. I understand putting thermostats on exterior walls is frowned on - but all the L-shaped room's walls are exterior - so where would you place that 'stat? I guess I could attach on the island under the counter overhang?
3. What thermostat(s) would you folks recommend?

TAG

What's heating the loops ?

You may be better off using a floor thermostat sensor .... the Honeywell unit from Supply House is very nice and works both ways. Room/floor or both

Jamie Hall

Much better off with the floor thermostat sensors. The real trick with what you are planning -- which should be nice and comfortable -- is figuring out how to set the water temperature in the loops so that they can just stay on and circulating most of the time. You don't have to get super fancy (although you can) but it may take some thoughtful control strategies. And I would very much suggest, despite the slight additional complexity, that you pipe the thing as primary/secondary off the boiler, with separate pumps for the two loops and mixing valves on the recirculating lines to allow you control the loop water temperatures differently, as needed.

Big Ed_4

Radiant wood floors . Heating then cooling beats them up .. Radiant is slow to heat and cool . So forget programable . A mixing valve with a outdoor sensor will help flatten the heat curve applied to the wood floor for more of a constant temperature .. A simple thermostat , say Tekmar with a floor sensor and just run on the floor sensor , it would not matter which wall to mount and does not have to be in the room , you can mount them in the boiler room .. Mataining the humidity with a good humidifier will also be needed for comfort and the wood ..

TAG

You also may want to put some plates in for the wife -- pure staple is very slow to respond .... make sure to insulate

HVACNUT

The Tekmar 561 is a nice radiant  thermostat. You can mount it anywhere and use remote floor and button sensors. The internal sensor can be turned off. Lots of room for offsets. It's very forgiving 

kroy2008

HVACNUT said:

The Tekmar 561  

Thanks - that looks really nice - but pretty salty price-wise. All the floor sensors I'm seeing look like that are designed to be embedded in a slab - you have a link to a floor or button sensors you're talking about?

TAG

I use the T6 Honeywell from Supply House 1/2 the price -- comes with the sensor . TH6100AF2004.

They work with wood floors .... stick them in the middle between the tubes .... insulate

Big Ed_4

And I agree with Tag use plates to help distribute the energy

MikeL_2

I reccomend no thermostat.  Constant circulation with an adjustable / programable heating curve based on outdoor reset works well with radiant as a supplemental heat source.... 

hot_rod

Radiant stat have dual functions you can set a not to exceed floor temperature but if the ambient temperature is too warm it will shut down

Any time the floor surface is warmer than ambient heat energy is being added. So a floor sensor only can over heat the space. Chose a stat that has some adjustable logic to get it adjusted to your desire.

epmiller

I’m retrofitting an old house with floor radiant and have learned a lot in the process. I didn’t use plates at the beginning and those rooms

heat much more slowly. Even the inexpensive plates really help. Don’t skimp on the underfloor tubing. I am installing at maximum 8” on center and closer at places. This allows running a lower water temperature. 

I am using inexpensive digital tstats regulating the room from the air temperature only. The trick is to use a correctly set outdoor reset on the boiler and keep the water temperature as low as possible from design temperature up to warm weather shutoff. With my circulator running close to 90% of the time the floors do not feel warm to the touch until the temperature gets down toward design temperature and then not even very warm. You do not want floors too warm or it becomes uncomfortable on your feet. One detail though, don’t even think about using setback thermostats, at the low temperature water I’m running it takes hours to recover from even a modest setback. The nice thing is I’m running well inside condensing temperatures with my mod-con all the time. 

kroy2008

Sorry folks, meant to stay engaged on this discussion but got busy around here!

@TAG and @Big Ed_4 Completely agree on transfer plates and insulation - I've installed both. I looked over the T6 and that looks like it'll do the job. Other folks have mentioned "outdoor reset" but since I'm using a HW heater as the heat source, does the T6 integrate an "outdoor reset"?

@Jamie Hall RE: separate pumps - that would have been a good idea, but I'm too far down the road at this point. I think I'll put an electronic actuator on the office loop and just restrict/close flow to that loop when the room won't be occupied over the weekend.

@MikeL_2 - I probably should have mentioned my heat source in my original post - I'll be using a hot water heater rather than a boiler. I have no experience with boilers - but with a hot water heater, where would I add/program the "programable heating curve" you mentioned?

HVACNUT

kroy2008 said:

@MikeL_2 - I probably should have mentioned my heat source in my original post - I'll be using a hot water heater rather than a boiler. I have no experience with boilers - but with a hot water heater, where would I add/program the "programable heating curve" you mentioned?

Programmable heating curve? You won't get that with a water heater. And yes, you should have mentioned that in your first post. This mistake keeps being made over and over. 

MikeL_2

We use a hydronic mixing block with our radiant installs; Viega & Taco corp make nice units that include a circulator, relay, & outdoor reset. I'm not sure how they'll work with a domestic water heater. Is the water heater oil, gas, or electric?