Radiant control questions

nickybotz

Hi everybody hope you can help I'm electrician my good friend is a plumber we just finished installing the radiant throughout my house the house is 3 floors basement is radiant in slab first floor is radiant in slab and the second floor is radiant under the subfloor in between joist base insulated with the aluminum foil insulation and an r12 almost my question is what is the best way to zone and control the radiant in the joist bays do I put it all on one thermostat and a floor sensor or one thermostat and room sensor or do I put each loop/room on an individual thermostat with floor sensor or air temperature

Ironman

First, you need extruded aluminum heat transfer plates under the joist or else you're not gonna get more than 7 btus per sq. ft. output. With plates, it's about 3 times that. Foil backed insulation does nothing to transfer heat; you need plates to conduct it to the floor. And not the cheap beer can type.

What is your heat source?

The wood floor will need warmer water than the slab, and if you don't use and ODR control on the slab, it will overheat the area.

Here's a current link to another thread where this is explained. If you try to micro zone the system (not recommended), then you may need a buffer tank as shown in the link.

https://forum.heatinghelp.com/discussion/167469/installing-htp-utf-80#latest

nickybotz

I installed the heat transfer plates , so you suggest just one theremostat to turn on and off from air temp rather then floor temp

nickybotz

Heat sources hot water and a half inch PEX every 8 inches with heat transfer plates very well insulated spray foam house, and also if using a thermostat for the whole floor/ rooms where would you think is best to put the thermostat in the biggest room the smallest room farthest room from the manifold excetera, and do you recommend the same type of thermostat for in slab heating

Ironman

No, you'll need different water temps and controls for the slab(s) than for the wood floor.
You'll need to grasp the concept of outdoor reset and why it's critical in controlling a high mass emitter like a concrete slab.

Here's a link to an article that should help:

http://www.tekmarcontrols.com/images/_literature/e0003_06.pdf?lbisphpreq=1

Gordy

I think we need to back up to the heat load calculation if done. This determines the water temp, and flow rates for each room, zone, and differing radiant panel assemblies.

What @Ironman is trying to convey is you will need a higher supply temp for the under floor panel because it takes more btus to push through the less conductive would, and what ever finish floor material is on top of that.

So the slabs may need 100, or less, and the under floor maybe 120, or more. However this is all wag until a heat loss calculation is produced

nickybotz

I get the point that you need to have different water temperatures for the slab and for the wood floor my question is right now for running wire purposes where do I put the thermostats and what kind of thermostats do I use for each heating zone

DZoro

If it were mine I would do slab/floor sensing thermostat. Those will react quickly which is what you want with a radiant system. Tekmar 519 is a suitable stat.

Gordy

As for zoning you don’t want zone loads smaller than the minimum modulation of the boiler. Micro zones will short cycle, and kill efficiency.

Back to the heat load calculation for that.

How you zone depends on personal preferences in the rooms. Some prefer control in bedrooms for cooler sleeping temps. Some like a toasty bathroom floor.

nickybotz

So you would use floor sensors for both the slab and under subfloor installations if so where do you put the sensor in this slab ?in the middle as, far as you can with the lead provided? and for the under subfloor system does it go in between the joists bays or notched in the subfloor underneath the wood and also where would you put the sensor in the subfloor at a central location closer or further away from the manifold is there a rule of thumb I should follow

Eastman

Tekmar has a lot of interesting controls for radiant. Their thermostats can provide zone synchronization and water temperature correction ("indoor feedback") if you connect them to their full boiler control system.

Here's one of their thermostats that provide air and floor temperature control:
http://www.tekmarcontrols.com/products/zoning/552.html

Gordy

I would put the sensor where it will get a true reading of the panel. In other words not close to tubing, and middle of the zone as far as the sensor wire will allow. Run the sensor in some conduit for future ability to change out if it goes bad.

For the under floor in the top portion sub floor. It’s not as much mass.