No-thermostat radiant heat

[Deleted User]

I am living with a heating system that, though provision has been made for zone valves, is currently operating with no zone control whatsover. A brief description: Vitola 200 boiler natural gas. Primary circulation loop connects two residences on a common property; approximately 9000 square feet of living, office, parking space. Two HK1 mixing valve controllers for each building as there is wet and dry system in one res and all wet but only partly occupied in the other. HK1s are OS controlled. We have balanced the occupied areas to comfort with Heatlink manifolds. We have been living here for four years and the system was completed last year so have had a longer time to fine tune than most installers budget. The point is, it can be done.
In retrospect, this could have been done with one mixing valve for each building. Each loop could have been adjusted for comfort as room temperature is a function of the ratio of BTUs lost to BTUs inputted.
Why the complexity? If you got it, flaunt it. ;-)
Cheers.

Baldrick

No-thermostat radiant heat

Howdy,

We are struggling to design a system that would work without room thermostats. The simple reason is that HVAC contractor that did the rough in installation (pex tubing, forced air system) didn't put any thermostat wiring.

Out of 7 zones, only 2 have thermostat wires (only because they have thermostats for central air).

We will use a Trinity Ti100 modulating/condensing boiler in this ~3600sqf house, about 50K BTU/h heat loss. It requires a primary loop without mixing valves.

All loops are <250ft 1/2in PEX home runs to mechanical room.

There are 3 floors:

- 1st on slab, with 5 loops, 1 or 2 zones (depending on controls restrictions - 1st zone would be kitchen/dining - 3 loops, 2nd zone would be 2 bedrooms - 2 loops)

- 2nd under subfloor w/plates 8 loops, 3 zones (5 loops in huge vaulted ceiling room zone, 2 loops in master bed zone, 1 loop in bathrooms zone)

- 3rd under subfloor w/plates 4 loops, 2 zones (2 loops in bedrooms zone, 2 loops in bathroom/loft zone).

This system obviously requires different temperatures for slab and 2 floors.
So far, I consider 2 options:
1. A 3 way or 4 way I-series outdoor reset mixing valves. Mixing temp automatically adjusted and based on supply, boiler return and outdoor temperatures.
2. Variable speed outdoor reset circulators. Output temp will be based on pump speed adjusted by supply, boiler return and outdoor temperatures.

I would appreciate an advice on both options (hey, maybe there's a better one) and controls for these options. All I am finding has thermostat terminals.
Also, any tips on Trinity boilers installs?

Thanks!

Justin Gavin_5

Have you considered Wireless Tstats

Honeywell has them out and I think there are a couple of other manufacturers out there. Is your radiant on a slab or do you have a basement or crawl?

What stage of construction are you in that you can't pull stat wires or install slab sensors??

Norm Harvey

Even without thermostats you will need some kind of input (floor/slab sensor) to let a control know what its doing.

I favor Uponor/Tekmar controls. I would recommend you look into things like the Pro-Mix 311 and that family of controls.

How is the system mixed? Injection, 3 way/4 way valve, etc ?

Why cant you have your electrician snake some thermostat wiring? Is this a log home or something?

GW

options

you're gonna get many different options posted, so hold on to your bippie

Just a foot note: we specify in our contracts that an electrician installs all wiring.

There's two camps out there, the guys who want to see radiant go NON STOP, and the guys who are fine with ON/OFF controls.

So, you're right, you need at least two different temps. First you have to choose your camp you want to reside in.
I'm in the first camp; which has its pros and cons. PRO: tighter temperature band width in the living space. CON: if you want more zones, this can be very expensive, and you need a circ for each mixed zone (more juice).

What are your thoughts so far?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Baldrick

1st floor is slab on grade, lowtemp.
2nd and 3rd floor is under sublfoor stapled, w/ plates, hightemp.

We can't run thermostat wires since it's too late in the game. Everything is painted and trimwork has started.

Which pretty much limits us to above or wireless thermostats (can't find the right stuff though).

Baldrick

The heating system isn't finished yet.
All You can see in the mechanical room are 17 pairs of 1/2" PEX tubing. There is a Trinity Ti-100 sitting right next to it :P

Wiring is done, finished. Owner doesn't even want to hear about hiring electrician to pull wire (it would be a nightmare in this house) and then get the holes patched and painted.

Justin Gavin_5

My suggestion

Well with that said I think your best bet is to run a 3 or 4 way mixing valve. I like ESBE because you can set everything up and make modifications to the curve real easily and it has a digital readout. It comes with the wire for outdoor reset and supply line to your supply piping. Pipe it primary/secondary and let the pump run cont. during heating season. Put them in series with a summer winter switch for ease of installation or you could tie them to turn off when your boiler shuts off the heating circuit do to wwsd but that would require addtional relays and or controls. If you are concerned with the pumps running too ofter you can cyle them on/off with a timer.

Good luck.

Baldrick

This system has to run efficiently, with as much zoning controls as possible. It sucks to fix someone else's mistakes but it has to be done.

First option I mentioned, includes mixing valves to regulate each zone:


Second, variable speed pumps:
http://www.taco-hvac.com/en/products/Variable Speed Outdoor Reset "00"^&#174; Circulator/products.html?current_category=192

In both cases, there would be temp sensors in 3 places: supply, boiler return and outdoor. I can't work out the controls/boiler connections.

That Trinity boiler has pretty nice modulation ration, 15K-100K BTU and it does require a primary loop w/ proper circulator (I figured Taco 009 because of nice flat curve and good middle 1/3 efficiency).

Restriction head loss is 7' at 6gpm (or 12' at 8gpm).
Can't find a boiler water capacity for expansion tank sizing, but I assume that 30-size would work.
All 17 loops are ~250' 1/2" PEX.

Baldrick

Thanks!

1. Do You have any more info about wireless thermostats. The only one I could find was 1 receiver - 4 sender combo but it didn't allow for zoning, just 4 locations to change heat source temp.

2. With mixing valves, how would You place circulators (and how many). Obviously 7 3-way valves and 7 circulators (working on 7 zones) will be expensive plumbing nightmare. Not mentioning the wiring.

bovide_4

how about

two Taco radiant mixing blocks, one for the slab, and one for the plates? And ask Bill @Honeywell for wireless tstat model numbers?

Baldrick

I will do more research about thermostats (calling) on Monday.

With 1 mixing block for 2nd and 3rd floor, is it possible to do some further zoning?

It looks like mixing block operates on 15ft head max. It might be not enough for 2nd or 3rd story (it's all home runs).

bovide_4

the mixing block

needs a "secondary loop" to deliver the goods to the other floors. Go to the Taco website and download the piping diagrams. I think this is what you are looking for.

Baldrick

Looks like I have the same problem everywhere I look.

RMB diagrams require a switching relay (or zone valve control) and it has thermostat terminals.

Without thermostat present, how do I complete the wiring?

joel_19

tstat

the theremostat you want is from honeywell it is a Chronotherm model I Believe the model number begins 8665. Should be able to find at Grainger if no where else. You need a reciever to go with it in basement

Derheatmeister

In 2004 i used a wireless Thermostat system from Danfoss:For the transmitter:TP 75 RF ; WP 75 RF; for the receiver:RX-1 ;RX-2;RX-3.Not sure if it is still available!

Paul Rohrs_7

Waiting to see the Dan Foley Job

with a viessman boiler with no t-stats. It sounds like the Big-V has an indoor sensor that will regulate the constant flow reset temp and ramp the firing rate of the boiler up/down.

Has anyone ever tied a "Temporary Construction" T-stat to the TT of their boiler? It is a sensor bulb type that can be purchased at a fixed 60°F setting. (Or different temps)

I would love to try a constant flow target temp system. I have retro-fitted an older boiler/radiator system with a Tekmar 260 that is constant flow when the outdoor temp falls below WWSD, but I haven't tried a mod/con boiler setup running soley off of indoor feedback.

Paul

Rich L.

T'stat wiring with no stat

"RMB diagrams require a switching relay (or zone valve control) and it has thermostat terminals.
Without thermostat present, how do I complete the wiring?"

If you're going constant circulation just jump out the t'stat terminals. If you want to get just a bit nicer wire it through a light switch and that can be your summer winter switch for the pumps.