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.

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!

Are there zone valves installed on all the zones and wired back to some sort of controller?

You might get wireless thermostats to work.

I am guessing you are past the point of running new wire. You might want to ask an electrician if they can pull thermostat wires for you and what sort of damage is likely to ensue.

alternety said:

Are there zone valves installed on all the zones and wired back to some sort of controller?

You might get wireless thermostats to work.

I am guessing you are past the point of running new wire. You might want to ask an electrician if they can pull thermostat wires for you and what sort of damage is likely to ensue.

Click to expand...

We cannot pull any new wires except for outdoor reset wires.
Any advice on wireless thermostats?

Besides 17 loop pairs sticking out of the slab and ceiling, nothing has been done in mechanical room. Oh, there is Trinity Ti-100 sitting right next to them

How the boiler will be plumbed, pumps, DHW (domestic hot water), heating load, etc. etc..

Are you still talking to the heating contractor that failed to install wiring? Are you going to get another one. This is not a trivial exercise.

I have no brand recommendation for wireless thermostats. It can be iffy. The propagation through out the house is always a try it an see if it works for wireless devices. If you can find one that uses a wireless networking approach where the signal is repeated by other stations it would stand a better chance.

You need smart boiler controller that will talk to the thermostats and outdoor reset. You may well have to adjust water temp because of the various mounting methods. You should probably get some balancing manifolds for connecting things, a good book on radiant heating.

You do not really want the boiler to turn on and off whenever each zone needs water. Particularly with some zones being quite small. A buffer tank may be called for. It is much cheaper to run a single pump (variable based on pressure drop is best) and use valves for the individual pipes/zones. You will need access to a PEX tool compatible with your pipe. Your PEX should have an oxygen barrier in it - if not you will need to do some other things.

If you have a boiler the best way for DHW is an indirect tank fed by the boiler. You would have to look at the BTUs available for this purpose.

There is some serious design and implementation issues for this whole thing.

You could use conventional mechanical thermostats wired to ultra reliable wireless security sensors, using relays at the main panel to control the pumps when the zones call for heat. Ademco/Honeywell has the Vista 40 which will handle 8 programmable relays. The smaller panels handle 4 and some larger panels will handle 16 and up. If you are having an alarm in the house anyway it's a win win. The sensors are now small enough to hide inside the thermostat case, use 5 year lithium batteries, you'd be good to go.

MarkHash said:

You could use conventional mechanical thermostats wired to ultra reliable wireless security sensors, using relays at the main panel to control the pumps when the zones call for heat. Ademco/Honeywell has the Vista 40 which will handle 8 programmable relays. The smaller panels handle 4 and some larger panels will handle 16 and up. If you are having an alarm in the house anyway it's a win win. The sensors are now small enough to hide inside the thermostat case, use 5 year lithium batteries, you'd be good to go.

Click to expand...

The house is not prewired for alarm system, but this option sounds interesting, especially that I priced Honeywell wireless system for 7 zones to be about $2,400, not including Taco hardware.

Due to that fact, I am leaning towards adding some manual (to the point) controls over zoning.

Having 2 hardwired zones (one for slab and one for underfloor), and needing only 1 lower temp for each zone (slab loops: 3x 120F, 2x 110F, underfloor: 8x 155F, 4x 140F), all I would need past the pumps is a manifold with balancing valves and temp gages.

With 10% of wireless zoning hardware (and probably 20% cost) required in this scenario, it's awfully tempting both for me and for the owner.

The question is, how much will comfort suffer?

alternety said:

How the boiler will be plumbed, pumps, DHW (domestic hot water), heating load, etc. etc..

Are you still talking to the heating contractor that failed to install wiring? Are you going to get another one. This is not a trivial exercise.

I have no brand recommendation for wireless thermostats. It can be iffy. The propagation through out the house is always a try it an see if it works for wireless devices. If you can find one that uses a wireless networking approach where the signal is repeated by other stations it would stand a better chance.

You need smart boiler controller that will talk to the thermostats and outdoor reset. You may well have to adjust water temp because of the various mounting methods. You should probably get some balancing manifolds for connecting things, a good book on radiant heating.

You do not really want the boiler to turn on and off whenever each zone needs water. Particularly with some zones being quite small. A buffer tank may be called for. It is much cheaper to run a single pump (variable based on pressure drop is best) and use valves for the individual pipes/zones. You will need access to a PEX tool compatible with your pipe. Your PEX should have an oxygen barrier in it - if not you will need to do some other things.

If you have a boiler the best way for DHW is an indirect tank fed by the boiler. You would have to look at the BTUs available for this purpose.

There is some serious design and implementation issues for this whole thing.

Click to expand...

Trinity Ti100 requires a primary loop, and most likely 009 pump. It will do heating only.

I have started a new thread with new approach to this problem. It includes most recent design schematics.
https://terrylove.com/forums/showthread.php?t=18108

Hell I could fly to your location and install it (alarm system), including the relay interface for less than that. PM me if you are interested, I can get to any major city's airport for just the hassle of it. I would dig working on it since I have my guest quarters all roughed in same as yours. I have the manifolds in, and was looking at the exact ti100 boiler. Hard to believe it will heat 3600 square feet though, you must have some insulation factor! Another thought is that the alarm has the phone interface available also, and gives you status and control of the relays. Might be a green issue for you. A home automation controller could cycle your systems without thermostats at all once you got the timing curves in relation to outside temperature memorized. That's how I do my electric underfloor heat in my bathroom as I got tired of listening to that damn thermostat clicking in and out all night.

MarkHash said:

Hell I could fly to your location and install it (alarm system), including the relay interface for less than that. PM me if you are interested, I can get to any major city's airport for just the hassle of it. I would dig working on it since I have my guest quarters all roughed in same as yours. I have the manifolds in, and was looking at the exact ti100 boiler. Hard to believe it will heat 3600 square feet though, you must have some insulation factor! Another thought is that the alarm has the phone interface available also, and gives you status and control of the relays. Might be a green issue for you. A home automation controller could cycle your systems without thermostats at all once you got the timing curves in relation to outside temperature memorized. That's how I do my electric underfloor heat in my bathroom as I got tired of listening to that damn thermostat clicking in and out all night.

Click to expand...

It's only 50K BTU/hr heat loss, super insulated house.