Line voltage thermostat for radiant?

WesBooth85

So I am a plumber and just venturing into the world of heating. I have a domestic water heater (100k btu Vertex) with space heating loop. I am going to put some heated floors in soon.

My question: Besides having a thermostat with floor sensor, is there any reason not to have line voltage thermostats with a pump dedicated to each thermostat to create separate zones?

The addition of transformers and relays and 24 v thermostats seems excessive and redundant when alls I need to do is power 120v pumps separately. Zone valves are just as expensive if not more than a circulating pump so why not just buy more pumps to creat different zones.

Ironman

Let's go back to design basics: how many gpm are needed for each loop? If one pump can do all the loops, which is quite often the case, why would a circulator on each loop be necessary or even desirable?

To answer your original question, IDK of any line voltage stat that's designed for radiant.

Zman

Is your space heating an open system or closed? If you are planning to deliver an open (bacteria farm) to your customer, please stop reading, you have come to the wrong site.

hot_rod

Sure you can use 120V stats, it requires appropriate wire of course. Look at the stats used for electric radiant mat systems,
they have radiant specific features.

You may find that even the smallest pump available is too large for small zones, so you end up over-pumping and perhaps chocking down flow with balance valves.

Todays ∆P circulators with zone valves is really the way to go. And if flow rates allow a manifold with actuators may work for zoning.

But you need to define the system better, how many zones, GPM and head requirement, single temperature?

A heat exchanger to separate DHW from heating loops is always the preferred method.

WesBooth85

> @hot_rod said:
> Sure you can use 120V stats, it requires appropriate wire of course. Look at the stats used for electric radiant mat systems,
> they have radiant specific features.
>
> You may find that even the smallest pump available is too large for small zones, so you end up over-pumping and perhaps chocking down flow with balance valves.
>
> Todays ∆P circulators with zone valves is really the way to go. And if flow rates allow a manifold with actuators may work for zoning.
>
> But you need to define the system better, how many zones, GPM and head requirement, single temperature?
>
> A heat exchanger to separate DHW from heating loops is always the preferred method.

Hot rod

I think what you said is above my knowledge of the heating.

Itll probably end up being 3 zones. 1 zone to start and 2 added later. Probably same temps. And I'm lost on gpm and head.

Vertex has 3/4 tappings and loop inside so supply heat will get transferred that way. Water Heater is 50 gal 100k BTU. temp is whatever I need.

If you can explain why over pumping is undesirable I would appreciate it.

And what is the circulator you mentioned?

I'm a master plumber and gas fitter and down here boilers are not used as much as forced air so the chance to work on these systems is minimal.

GroundUp

The Vertex does not have space heating taps, it has recirc taps which would require a heat exchanger to separate the radiant from the domestic. Depending on the load for these heat zones, as was mentioned you may wish to run a single circ and zone valves. But in short, any line voltage stat will work to spin a small circ. We use the $20 Honeywell 120v stats all the time for both radiant circulators and hydronic unit heaters (a large portion of my work is pole barns/sheds) so yes it can be done, but may not be practical for your setup.

hot_rod

It takes a few steps to get an exact design for radiant systems.

It starts with a room by room heat load calculation.

That calculation tells you how much heat energy you need to put into a room or space.

Then you look at how much tubing, at what spacing, and what temperature water you need to move that amount of energy from the tank HX to the room.

Then, lastly you select a circulator pump based on how much flow each loop needs to move the right amount of heat into the rooms. If the tube is spaced at 12" on center a typical 250- 300' loop would cover 250- 300 square feet of space. In some cases a small room may only need a single loop.

With 1/2" pex generally around 1/2 gpm per loop. So if the room only needed 1 loop, it would be a very low flow. Look at a pump curve for a common, small circulator and you want to run in the mid 1/3.

Here is a B&G chart showing their small circulator selection, the smallest on lowest speed moves around 6 gpm at mid curve, so you would be flowing far too much in a small single pex loop.

Probably find a small domestic water recirculation pump for those real low flow applications. I use a recirc pump like shown below when I have a single or two loop system, but they are a bit $$.

Of course plenty of folks just buy some tube, install it 12" on center, buy a pump at Menards and hope for the best. I've done that in my early days . Hydronics is a very forgiving technology, many un, or poorly designed systems, on the flow side of things work to the owners satisfaction.

The group here tends to want you to do the steps to get it right without guessing so you end up with an efficient, quiet, comfortable system.

WesBooth85

> @GroundUp said:
> The Vertex does not have space heating taps, it has recirc taps which would require a heat exchanger to separate the radiant from the domestic. Depending on the load for these heat zones, as was mentioned you may wish to run a single circ and zone valves. But in short, any line voltage stat will work to spin a small circ. We use the $20 Honeywell 120v stats all the time for both radiant circulators and hydronic unit heaters (a large portion of my work is pole barns/sheds) so yes it can be done, but may not be practical for your setup.

Omg!!!! You are correct! I was always under the assumption that those taps were a separate coil inside the tank. I never found definitive paperwork stating that and I never actually took out the taps. I always thought it would not be smart for AO Smith to combine space heating and DHW in one tank without separation. If that makes sense

WesBooth85

> @hot_rod said:
> It takes a few steps to get an exact design for radiant systems.
>
> It starts with a room by room heat load calculation.
>
> That calculation tells you how much heat energy you need to put into a room or space.
>
> Then you look at how much tubing, at what spacing, and what temperature water you need to move that amount of energy from the tank HX to the room.
>
> Then, lastly you select a circulator pump based on how much flow each loop needs to move the right amount of heat into the rooms. If the tube is spaced at 12" on center a typical 250- 300' loop would cover 250- 300 square feet of space. In some cases a small room may only need a single loop.
>
> With 1/2" pex generally around 1/2 gpm per loop. So if the room only needed 1 loop, it would be a very low flow. Look at a pump curve for a common, small circulator and you want to run in the mid 1/3.
>
> Here is a B&G chart showing their small circulator selection, the smallest on lowest speed moves around 6 gpm at mid curve, so you would be flowing far too much in a small single pex loop.
>
> Probably find a small domestic water recirculation pump for those real low flow applications. I use a recirc pump like shown below when I have a single or two loop system, but they are a bit $$.
>
> Of course plenty of folks just buy some tube, install it 12" on center, buy a pump at Menards and hope for the best. I've done that in my early days . Hydronics is a very forgiving technology, many un, or poorly designed systems, on the flow side of things work to the owners satisfaction.
>
> The group here tends to want you to do the steps to get it right without guessing so you end up with an efficient, quiet, comfortable system.

Honestly I would do the same. Install according to manufacture specs and tweak it if it doesnt act right.

The problem is I love hydronics but it's so hard to find training/schooling for it. If you know of any training I can take please let me know. I pretty good on the basics but beyond that its trial and error

ratio

I can't believe no one has mentioned Caleffi's hydronics magazine, Idronics, yet! It's well worth the time to read, & will advance you far in the right direction.

SuperTech

Yes! Idronics is exactly what you need to help learn. The great folks at Caleffi do a fantastic job.

Zman

SuperTech said:

Yes! Idronics is exactly what you need to help learn. The great folks at Caleffi do a fantastic job.

The coffee with callefi videos are great.
Also check out Taco's flow pro university and the offerings of heatspring.com

Ironman

In addition to the excellent materials from Caleffi, I'd recommend these 4 books available from the store on this site:

https://heatinghelp.com/store/detail/hydronic-radiant-heating-a-practical-guide-for-the-nonengineer-installer

Erin Holohan Haskell

@DanHolohan's online seminars: https://heatinghelp.pivotshare.com/home

SuperTech

Classic Hydronics and Pumping Away by Dan Holohan really helped explain to me how things were, how things are and how things should be with hydronic heating. And this site is a valuable resource for learning about problem solving with all things related to heating.