Infloor radiant issue

ChrisJ · July 5

So I've got an issue I'm helping a friend with.
He needs to get me more information but here's what I've got so far.

Large room with large windows and in floor radiant under a wooden floor. I think it's also got carpet.

The issue is, the system ends up overheating the room once the sun comes out and then shuts down for too long so the room ends up too cold.

What info do I need to get to solve this issue?

Can an ODR be added to a normal boiler or does it come with a boiler as a system and would it solve this problem?

Apparently the system has no issue keeping up with the actual load, just the control is failing to work correctly.

Danny Scully · July 5

Slab sensor?

ChrisJ · July 5

Danny Scully said:
Slab sensor?

I'm told it has a slab sensor, but I have no idea what it's connected to yet.

pecmsg · July 5

Shades and or Awnings!

What do they have for A/C?

ChrisJ · July 5

pecmsg said:
Shades and or Awnings!

What do they have for A/C?

I'm not sure, why do you ask?
Shades and awnings probably won't cut it, they like the view.

STEVEusaPA · July 5

Location of thermostat, location of slab sensor, and how they’re set up might just be the key.
Or maybe constant circulation with something like this:
https://www.caleffi.com/usa/en-us/catalogue/hydromixertm-injection-pump-mixing-unit-165600a

Tim Potter · July 5

Chris, does this have a conventional atmospheric boiler ie: high temp?
Our house up in the Mountains in Winter Park, CO had an atmospheric boiler connected to infloor pex tubing in concrete for the walkout lower level, & Gyp on the main floor. It grossly overshot temps was an understatement. With help & information from this site, I repiped with a Buffer to make the boiler happy & Injection with constant circulation to make us Happy. It works like a charm. The individual room stats become high limits. The south facing great room has a bunch of windows & solar gain, its way better, but it still overshoots for a few hours in the morning.

Tim

hot_rod · July 5

Concrete slab? That is the toughest radiant method to control, it's a massive flywheel for heat.

Outdoor and indoor feed back would help. Also limiting solar gain, automatically if possible.

Lots of big glass homes in the mountains suffer from this issue.

Jeffery from Steamboat was here recently asking about radiation sensors, I suspect for the same reason, to handle over-shooting issues.

High mass radiant are not a great mix for rapid response, or areas with wide temperature swings. Carpet and pad adds to the problem as they generally run high SWT.

Put a wood panel system over it if it is a slab, like the Viega, Roth or Uponor system

I've been in radiant slab passive solar homes where the AC is running on a cold sunny day.

Tim Potter · July 5

@hot_rod
Amen to the flywheel effect, but the outdoor reset/constant circ helped a bunch. It works very well in the rooms that don't have the big windows facing south. The solar is just too strong at altitude, I've even tried turning the t-stat off for the great room the night before, it still overshoots, no joy, but cracking the slider from 9 to 10 am helps a bunch.
Tim

ChrisJ · July 6

I'm still waiting to hear back from them.

Right now I know it's a wood floor, no concrete.
And he said the temperature is something like 130F if that's even possible?!

hot_rod · July 6

130F SWT, hmmm sounds like a rubber tube staple up

DZoro · July 8

Constant circ, Floor/air combo stat, odr, injection pump and some zoning. Keep all the zones on there own water temps, and pulling from a buffer tank also set up with odr. Lots of fussing with water temps to find the perfect temps. Doable but will take some babysitting. Good to have the HO understand the system and what you are trying to accomplish. That will help with some of the babysitting.
Can get complex with controls...…
D

HomerJSmith · July 11

ODR isn't going to solve your problem.

Staple up, if it's done right (back loss prevention) (low R value padding and carpet) (done with PEX) should be great. Your problem is solar gain, I think.

If you have a single pump pushing all your zones, I might try this.
Put a Taco sentry zone valve or a diverter valve on that part of the circuit input if it is part of other heat emitters and maybe a check valve on the return to prevent ghost flow. I don't know what your circuit layout is. I might put that valve on a timer that shuts that circuit down an hour before the solar gain heats up and turns on that circuit an hour before you loose the solar gain. It all depends on circuit layout as to how I might do it. Make sure you don't have a ghost flow now when that circuit is off that's providing extra heat to that room.

Basically, you need to control the flow and timing to that room. Maybe put the thermostat in the hottest part of the room in direct sunlight.

BirchwoodBill · July 18

I have radiant heat with wood flooring and use a water temp range of 85 to 105 using OTDR. The source for the heat is a Taco heat exchanger coming off the DHW. Control is very simple just use a taco zone valve controller that connects to the heat exchanger.

Voyager · July 18

It is likely impossible to completely solve this problem without turning on AC or opening windows. It is simple physics. When the sun comes through the windows, it adds heat to the room faster than the room can lose the heat emitted by the warm floor. Although, with a wood floor, ODR should help significantly.

Thermal inertia is the biggest downside I have experienced with my heated concrete slab. I have ODR and run low water temps (80-82) most of the winter, but if the slab is warm enough to heat the building when it is 30 outside with no sun, it is way to warm for the building when the sun is out and it warms to 45 outside during the morning. You just can’t make the heat in the slab magically stop being emitted.

ChrisJ · July 18

Voyager said:
It is likely impossible to completely solve this problem without turning on AC or opening windows. It is simple physics. When the sun comes through the windows, it adds heat to the room faster than the room can lose the heat emitted by the warm floor. Although, with a wood floor, ODR should help significantly.

Thermal inertia is the biggest downside I have experienced with my heated concrete slab. I have ODR and run low water temps (80-82) most of the winter, but if the slab is warm enough to heat the building when it is 30 outside with no sun, it is way to warm for the building when the sun is out and it warms to 45 outside during the morning. You just can’t make the heat in the slab magically stop being emitted.

Canpexman · July 18

The dry panel systems that Hot Rod mentioned are good. A better solution is the RAUPANEL system from REHAU. It uses custom extruded aluminum plates that rest on top of the subfloor. It provides a more even heat across the floor, heats up faster, and cools down quicker - all while utilizing a lower water temperature for better response and efficiency. REHAU also offers a plywood version with Aluminum on the bottom (RAUBOARD). From experience, this would be a great solution for your issue.

BradHotNCold · July 18

Homeowner/fan here. What is ODR? (I know it is not “out door rink” or “online dispute resolution”!)

Zman · July 18

Outdoor Reset

Voyager · July 18

ChrisJ said:
I'm still waiting to hear back from them.

Right now I know it's a wood floor, no concrete.

And he said the temperature is something like 130F if that's even possible?!

What is the room size? Square footage of exterior wall? How much of the exterior wall is window area? Single pane? Double pane? Low-E or treatments? Thickness of wood subfloor? Size and length of tubing?

ChrisJ · July 18

Voyager said:

ChrisJ said:
I'm still waiting to hear back from them.

Right now I know it's a wood floor, no concrete.

And he said the temperature is something like 130F if that's even possible?!
What is the room size? Square footage of exterior wall? How much of the exterior wall is window area? Single pane? Double pane? Low-E or treatments? Thickness of wood subfloor? Size and length of tubing?

I'm still waiting to hear back from them..........

Doug_7 · July 18

This is a basically control issue. Your present control system has the heat ON too far long, because it does not anticipate that the sun is out and the day is heating up. Need the heating controlled by outdoor temperature reset, using a Solar outdoor temperature sensor.

I solved a similar problem using two outdoor temperature sensors - one in the shade and one in the sun. The solar sensor picks up that the sun us shining and shuts off the heat early. The shade sensor does its usual thing. Both sensors are connected to a tekmar 152 which controls the heat demand. Works great.

Solar sensor inside a white PVC pipe exposed to the sun may read 12 degrees higher than shade sensor on a sunny day and responds much faster. Grey PVC pipe would would increase response.

Doug

Zman · July 18

This post is highly speculative until the OP returns to the job to get more detail. Could be almost any type of system.
To the original question. Outdoor reset can be added to any boiler. If it a non condensing boiler, condensate protection need to be addressed.

ChrisJ · July 19

> @Zman said:
> This post is highly speculative until the OP returns to the job to get more detail. Could be almost any type of system.
> To the original question. Outdoor reset can be added to any boiler. If it a non condensing boiler, condensate protection need to be addressed.

Agreed.

I'm still waiting to get all of the info. I just wanted to get an idea about odr and other options. Aside from "rip it all out".

pitman44 · July 19

Generally a wood floor radiant system is fairly fast responding. The overshoot may be unrelated to the heating system. Lots of solar gain, not much room loss will provide overshoot regardless of the heating system. Likely not much can be done with that via the heating system.

What I find interesting is the lag once the room cools down, which from the sounds of it, is the primary complaint. Assuming it's controlled by a t-stat, where is the t-stat located? Is it working properly? If the zones are controlled by zone valves, is the end switch for that zone working?

Voyager · July 19

pitman44 said:
Generally a wood floor radiant system is fairly fast responding. The overshoot may be unrelated to the heating system. Lots of solar gain, not much room loss will provide overshoot regardless of the heating system. Likely not much can be done with that via the heating system.

What I find interesting is the lag once the room cools down, which from the sounds of it, is the primary complaint. Assuming it's controlled by a t-stat, where is the t-stat located? Is it working properly? If the zones are controlled by zone valves, is the end switch for that zone working?

Exactly. That is why I wrote earlier that if may well be impossible to prevent this overshoot without the use of AC or ventilation. That is the one advantage of a forced air system that is used for both heat and AC. That system can deal with this scenario if it is really important to avoid significant overshoot. And the reality is that a radiant heat system, unless the radiators are very low mass, will be worse in this regard that other heating systems.

I am waiting for Chris to now add his bologna comment to your post also. LOL.

ChrisJ · July 19

Voyager said:

pitman44 said:
Generally a wood floor radiant system is fairly fast responding. The overshoot may be unrelated to the heating system. Lots of solar gain, not much room loss will provide overshoot regardless of the heating system. Likely not much can be done with that via the heating system.

What I find interesting is the lag once the room cools down, which from the sounds of it, is the primary complaint. Assuming it's controlled by a t-stat, where is the t-stat located? Is it working properly? If the zones are controlled by zone valves, is the end switch for that zone working?
Exactly. That is why I wrote earlier that if may well be impossible to prevent this overshoot without the use of AC or ventilation. That is the one advantage of a forced air system that is used for both heat and AC. That system can deal with this scenario if it is really important to avoid significant overshoot. And the reality is that a radiant heat system, unless the radiators are very low mass, will be worse in this regard that other heating systems.

I am waiting for Chris to now add his bologna comment to your post also. LOL.

Chris won't be because pitman44's comment as quite a bit different.

He never said anything even similar to "It is likely impossible to completely solve this problem without turning on AC or opening windows. It is simple physics."

Paul Pollets · July 19

ODR should be used with every boiler. It just makes sense to control the boiler's temperature output. I've dealt with large thermal gain in several home projects with extensive walls of glass exposed to 6-12 hrs of sun. In one case, the living room and dining areas had 100ft of 9ft glass facing the western exposure. The floors were limestone tile. The solution was to install slot diffusers over the window wall and a 2 stage thermostat. The thermostat turned on the A/C zone and turned off the radiant pump, as required. Setpoint temps stayed within 2 degrees. This was designed before the home was built. When we commissioned the system, the overshoot (without A/C) was 18 degrees with outdoor temps at 70. Even with Low E windows.

ChrisJ · July 19

Paul Pollets said:
ODR should be used with every boiler. It just makes sense to control the boiler's temperature output. I've dealt with large thermal gain in several home projects with extensive walls of glass exposed to 6-12 hrs of sun. In one case, the living room and dining areas had 100ft of 9ft glass facing the western exposure. The floors were limestone tile. The solution was to install slot diffusers over the window wall and a 2 stage thermostat. The thermostat turned on the A/C zone and turned off the radiant pump, as required. Setpoint temps stayed within 2 degrees. This was designed before the home was built. When we commissioned the system, the overshoot (without A/C) was 18 degrees with outdoor temps at 70. Even with Low E windows.

It sounds like you're agreeing with @Voyager s thoughts.

I can admit if I was wrong......and it's looking like I may have been wrong and owe @Voyager an apology.

I'm curious, why run A\C and not just bring in fresh air?

Paul Pollets · July 19

Because make up air would not drop the indoor temperature due to the flywheel effect to noticeably make a difference

ChrisJ · July 19

Paul Pollets said:
Because make up air would not drop the indoor temperature due to the flywheel effect to noticeably make a difference

I just noticed you said 70 degrees.

I didn't know anyone ran their heat when it's 70 degrees out? Mine gets locked out at 65 because it's about where my house breaks even and will maintain it self on most days. Actual, 62-63.

Paul Pollets · July 19

a glass wall with so much exposure is like a magnifying glass. The heat doesn't have to be on for the room to exceed 90 degrees. When the heat is on, and setpoint exceeds 75, the A/C will start cooling (and the RFH pump turns off).

pitman44 · July 19

Paul Pollets said:
Because make up air would not drop the indoor temperature due to the flywheel effect to noticeably make a difference

In my experience I haven't seen the "flywheel effect" when a slab wasn't involved. The OP said it was a wood floor. I'm assuming it's a wood structure only. If it's wood over concrete, I'd agree with you 100%.

pitman44 · July 19

ChrisJ said:
The issue is, the system ends up overheating the room once the sun comes out and then shuts down for too long so the room ends up too cold.

What info do I need to get to solve this issue?

Chris, is the primary problem the overshoot or the room getting cold after? I think they're two separate issues.

Voyager · July 19

ChrisJ said:

Chris won't be because pitman44's comment as quite a bit different.

He never said anything even similar to "It is likely impossible to completely solve this problem without turning on AC or opening windows. It is simple physics."

This is virtually saying the same thing. “Lots of solar gain, not much room loss will provide overshoot regardless of the heating system. Likely not much can be done with that via the heating system.”

Saying that it is likely that not much can be done vita the heating system, means you need to use something else like a cooling system or opening the windows, which is exactly what I said.

Voyager · July 19

ChrisJ said:

...
I'm curious, why run A\C and not just bring in fresh air?

It depends on the degree of thermal mass, the extent of the overshoot and the OAT. If the thermal mass is not huge, as is likely the case with a 3/4 to 1-1/4” wood subfloor, and if the solar gain is not huge and if the outdoor temp is at least 20 degrees below the target indoor temp, then a purely ventilation solution may well work.

However, if there is large thermal mass, high solar gain and the OAT is close to the IAT, then you may need the power that only AC can provide.

It all depends on the circumstances. That is why I asked all of the questions earlier, you really need to know things like the temperature differences, the area of the windows as a percent of the total wall area, the thickness of the floor to estimate thermal mass, the R value of the wall and windows to know how much heat is being lost compared to what is being added to the room, etc.

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