Smart Thermostats for Radiant Sunroom

Brian

I to have done a few sunrooms and have used the Wirsbo 511 (Tekmar).I haven't used a remote sensor,just the slab sensor.They are a great stat.It does make sense to put your remote away from direct sunlight.I would think the lower location would be better.This is the hook-up I use when using a waterheater as a heat source.

Good Luck

Brian

Unknown

This aproach seem logical to you guys?

A tough room to control. (See Attachment)

I'm working on a 700 Sq/Ft addition that has nearly all southern exposure. Glass. Lots of it. Wall to wall. a high vaulted ceiling and an what I'm expecting to be an extremely slow responding radiant slab.

The only interior wall is facing due south. The rest of the sun room is windows that start about 2 feet from the floor and reach 8 Ft high with transoms above.

SLOW RESPONSE. The floor is 6" of concrete with 2' foam under entire slab. The radiant tubing sits on top of the existing slab on Wirsbo's PEX rail system. (rails work awesome with the Multicor™ PAP). An 1 1/2" of concrete cap is poured over the existing slab. Tile floor and no rugs allowed.

The challenge is to keep the room comfortable at design condition and compensate for the HUGE flywheel effect of solar gain in the daytime vs. BTU vacuum after dark.

I plan on using a Tekmar 510 programmable thermostat. This thermostat seems AWESOME. Amazing what this little thing can do. I'll connect a slab sensor and limit the Min. /Max. slab temperature. I'm thinking 72º Min/87ºMax The thermostat will be placed on the only interior wall and see some direct sunlight. So, I will also have a remote air sensor and place that on the outside adjacent wall farthest away from the stat location. ( just behind me in the photo)This sensor will be about 18" off of the floor. That or above the windows? Not sure yet. Please advise. The radiant supply temperature is fixed via 3 way TMV.
The thermostat will calculate on/off circulator times measured by the temperatures averaged by the sensors about the room. Programing the little bugger is a ****.

This approach seem logical to you guys? Keep in mind this job did have a very tight budget. No varyible speed (sexy vixon;-) injection mixing here. K.I.S.S. with a smart setback thermostat :-) Any reccomendations or criticisms are welcome. I'm still learnin. Never done one like this before.

Gary

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Mike T., Swampeast MO

Some thoughts/ideas. (I enhanced your photo a LOT--love that Photoshop--as it was kind of hard to see. Don't ask my why, it's just sort of fun and I enjoy the practice...)

Not familiar with that t-stat, but something about your placement troubles me. I think it WILL be good to have the main one influenced a bit by the sun--as you should be able to make some intentional compensation in the floor temp. Perhaps you can intentionally vary your slab sensing limits based on this as well?

The remote t-stat location is what would seem to cause a problem. In the placement you suggest it's bound to be influenced by cold air falling down the windows--yes, I know they're good windows, but it still happens. I can imagine a situation where it's really cold but sunny--main t-stat is reading high because of the solar influence with the remote reading low because of convection from the glass. I think it would be extremely difficult to receive much in the way of useful data in this situation.

Your alternative location for the remote t-stat (above the windows) would probably be better. It's a radiantly heated space (even with the solar component added) and we all know that radiant panels don't produce much in the way of warm, rising convective currents

If you could use TWO remote t-stats (one above and one below the windows) you [might] be able to take some useful and predictable action based on the difference between them...again I don't know the level of sophistication of the t-stat.

BUT, I honestly think I would wire for alternative t-stat locations in this space. The wire doesn't cost much to buy or run and any little holes can be filled when you find the best locations and abandon some of the wires.

You might want to suggest automated window coverings to the H/O. They can be extremely expensive (expecially for a segmented layout as you have there) but could well prove HIGHLY useful. Beware however of the lower-cost drape/blind/shade systems. Component quality is lower and, more importantly, their control is proprietary and difficult/impossible to link to any but their built-in control system. In this situation you would likely want the "dumb" systems that connect to line current. The line current can be controlled either directly by some systems or indirectly via relays but YOU get to determine operation.

hr

I'm not convinced

that radiant slabs are the best match for sunspaces! I think a quick responer, maybe panel radiators would be better.

I agree with Mike. A way to control Mother Natures powerful radiation is key. Auto control shading is a great idea, although not for the weak of pocket book.

I use that tekmar control a lot, it will help control, but still not boss around the sun.

We struggled with large glassed rooms a lot in the Utah mountains, everyone needed that large expansive view.

Once we tried a system to recover that solar gain, store it, and move it to north exposure rooms. Lost track of that job after the couple divorced. Took a lot of piping and control work to shuffle stuff (btu's) around.

At the very least a high mounted, quiet, exhaust fan to dump heat quickly if temperatures get out of hand. Let us know how you end up.

Here is a link to "Solar Flares" and article Siggy did on sun spaces. PM Sept 1999 issue if the link doesn't work.


http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,4148,00.html


hot rod

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Mike T., Swampeast MO

Photoshop

I always have a motive...

Your controls have to do the SAME thing that I did with Photoshop--separate the space from the sun...

NOT EASY because the sun can and will overwhelm the ability of the radiant panel to control the temp of the space...

Unknown

Mike, I too have photoshop and,,,

Cheryl knows exactly how to use it;-)

Here's what she did with the photo you manipulated. Thanks for not adding any bodily appendages You did a pritty good job. When I posted,she was asleep and was mad at me for posting it without her going through them first.

Here are a couple more (touched up) shots of the space in question.

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Unknown

Radiant Sun Room = A live-in photon collector.

I just love Siggy’s writing style. “thermal drag racer opposed to a Btu freight train” Here’s what I’ve learned; I sold the freight train. Now I just need to use a better braking/throttle system.

I believe the 511 when used properly can get me really close.

Fin-tube baseboard, thin panel radiators, as well as low mass site-built radiant walls were not a logical option. 2X4 construction prohibited piping runs and the heated air would just pool in the 25’ high cathedral ceiling anyway. That and the budget just wouldn’t allow a second stage low mass high temperature heat emitter at this point. I’ll make provisions for future “ultimate low mass heat emitter” fan coil units under the entrance stairs should they feel they are needed to supplement floor heat output during high load conditions.

I didn’t realize architects won awards based on how many windows they can put in a room;-) This addition is filled with south/south-eastern facing glass. It’s going to be to soaking up LOTS of free solar BTUs by day. However, it may also experience significant overheating and underheating if I’m not EXTREMELY careful.

The wider the day/night outdoor temperature swings, coupled with the the solar heat gains, the worse my overshoot/lag flywheel effect will be. The solar warmed slab by day should releases it’s heat during the day and into the night as the house cools off. However, if the slab is already warm in the morning from operation of the floor circuits at night, its ability to soak up solar energy will be negligible. Heat input to the floor will cease. (Some basic yet interesting thermodynamic food for thought.)

Lets say; if I start the heating process at 5 a.m. on a February morning when the outdoor temperature is at it’s lowest for the day; (perhaps it's even below zero here in New England) the dual air sensing thermostats which control the floor circuits circulator will be sensing this situation and heat will be injected into the core of the concrete slab at design load rates. Little does that Tekmar 511 control know that in about 4 hours, bountiful quantities of sunlight will be streaming in through east and southeast facing windows unless I command the Tekmar 511 to wait a while to see (sense) if the sun is coming out today. How long should I make it wait is the real question here.
Even though my tubing is located relatively shallow in the concrete cap poured over a 4- to 6-inch thick slab. It may take me SEVERAL hours for the hydronic heat surge to drive up the air temperature in the room. I’m afraid that just as the solar heat gains are coming on strong, the heat wave injected during the early morning hours reaches the surface of the slab to worsen an already heated situation.

How will I accurately calibrate the Tekmar 511 with it’s sensors placed in the slab’ sun and shade to the solar heat gain characteristics of the sun room?

Thanks for all that you Wallies do.

Gary
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GMcD

Time lag - Enertia

What you need to do is heat the slab up in the wee hours and turn it off before daylight during sunny days, and maybe have a low setpoint during cloudy warm days and slightly higher setpoint for cold overcast days. Concrete slabs respond at anywhere from 1 to 2 hours per inch of concrete. You need to model and set up the room dynamics based on seasonal and daily transient loads, very hard to model and predict. Laws of physics are hard to change by willpower and hope. The controls being used are based on "air temperature" which is not the same as the mean radiant temperature. Maybe you should see if you can find a good radiant temperature sensor ( http://www.yamatake.com/products/innovative/radiant/index.html ) which can be coupled into the controls.

Mike T., Swampeast MO

Dynamics

You got it 100% in my book.

"How will I accurately calibrate the Tekmar 511 with it’s sensors placed in the slab’ sun and shade to the solar heat gain characteristics of the sun room?"

Computers can play chess very well, but they still can't tell a Ford from a Chevy...

Mike T., Swampeast MO

Architects

They really don't win awards based upon how many windows but they do win them upon how they relate the windows to the surroundings.

hr

That 511 thermostat

is a very good choice. A couple notes. Homeowners struggle with the adjustments, it borders on being overwhelming. And the tekmar instructions are not real "end user" friendly.

On the last install I had my partner go over the adjustments with thee lady of the home, as she was much more receptive to learning.

Scott had her then show him how to make the adjustments and jump to different menus. To assure she understood the features and functions. She really appreciated this schooling and called the next morning to thank us, again! Now she can dial it in to her exact liking. i think she likes the stat more than the warm floors

Spend the time training the owners on all the features, or you will be going back. A LOT! Be sure to lock them out of the programing they don't need.

It's a powerful control and when set to their liking it will be a big plus on that job.

It is available as a Wirsbo item also. Better price in my area under the Wirsbo badge. Still they need to hire a homeowner to write the operating instructions

I wish it were easier to wire. You need to balance the thing in your hand while making connections on those minute terminals, ala tekmar. Use stranded wire!

A larger, American sizes 2 X 4 size that would cover a flush mounted electrical box would help a ton. As would a sub base to wire first. It's nice to have a junction box behind, thats a lot of wires to deal with, especially if you leave some spares.

You can buy a larger backing plate, they barely cover a box, still. Looks like an after thought and costs 17 bucks!

hot rod

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hydronicsmike

What about this?

Gary,

My feedback would be that there may not be too much you will be able to do about the overheating that occurs during exposure to thermal heat gain (sun light), unless you add cooling.

I like what Hot Rod suggested about the fast responding heat emitters that may be better suited for those kind of applications. However, even those will not limit or eliminate overheating caused by thermal heat gain. They can reduce the amount of underheating you experience when the temperature drops below desired room temperature in the evening, due to a much shorter pick-up time. But you can get similar results when you maintain a Slab Minimum and raise the surface temperature from there.

I come across radiant applications like this fairly often and usually deal with the overheating with cooling. If cooling is not possible in this case, there is nothing we can do to stop overheating. The only thing that I can see that you can do, is to have the 511 thermostat programmed for setback in and around of the time when the thermal heat gain starts. In other words, if you know the sun comes up strong at 10AM and you would like to maintain an indoor air temperature of 70°F, have the thermostat set for 65°F about half an hour to an hour before 10AM to slow and minimize the overheating as it occurs. This would be a preprogrammed time affected by a setback schedule and would cause the thermostat to stop calling for heat before the sun picks up the room temperature and elevates it above the desired setpoint.

In the evening, the problem with radiant floors usually is underheating, because of the large mass of the floor. If the floor has been turned off all day long, it will take a fair amount of time before the mass of the slab is heated up and before it can produce heat. That time delay usually causes the underheating. Now since you have a 511 thermostat with a slab sensor that can be programmed to maintain a minimum slab temperature at your desired times, you can use it to help minimize the undershooting problem. In other words, when you know the sun goes down at 6PM, you can have the thermostat programmed to maintain a slab minimum of about 70-72°F half an hour to an hour before then. Once the air temperature in the space drops below the desired air temperature setpoint, the thermostat simply has to elevate the slab surface temperature from the minimum to react and satisfy the air temperature requirement. Basically, it will minimize the time it takes to have the slab surface at a temperature that is sufficient to add heat into the space. The beauty about radiant (or any kind of heat) is that as long as the surface temperature of a heat emitter is lower than the air temperature, no heat is being transferred. At least not to the space.

Next problem being the sunrise and sunset times that change constantly. We’ll have longer days within a couple of weeks time.

To keep it the simplest and give the customer the best you can do with what he has, I would locate the thermostat on an Indoor Wall (maybe the one you’re facing on the picture?) and run a slab sensor half way between the pipes about 1” below surface. Set your desired Room Air Temperature of 70°F and a Slab MIN at 68-70°F and Slab MAX at 82-84°F.

Just another idea. Either way, please let me know what you ended up doing and how it served you.

Mike

hydronicsmike

Backing Plate

Would a 007 Plate be enough, or would you like to see one made bigger than that? It covers the 2x4 electrical boxes.
I often wodered if they shouldn't be a little bigger than they are.

Mike

Unknown

HydronicsMike=Tekmar. Pro. Way Cool!!!

Finding a Brother in the dark is always a pleasure.

"Maintain the Slab Minimum and raise the surface temperature from there." OK.

For instance, if we know the sun comes up strong at 10AM and you would like to maintain an indoor air temperature of 70°F, have the thermostat set for 65°F about half an hour to an hour before 10AM to slow and minimize the overheating as it occurs. This would be a preprogrammed time affected by a setback schedule and would cause the thermostat to stop calling for heat before the sun picks up the room temperature and elevates it above the desired set point. Hmmmmmm??? Slow cranial absorbsion rate.

Now since I’ve got the511 thermostat with a slab sensor that can be programmed to maintain a minimum slab temperature at your desired times, you can use it to help minimize the undershooting problem. In other words, when you know the sun goes down at 6PM, you can have the thermostat programmed to maintain a slab minimum of about 70-72°F half an hour to an hour before then. Once the air temperature in the space drops below the desired air temperature set point, the thermostat simply has to elevate the slab surface temperature from the minimum to react and satisfy the air temperature requirement. Basically, it will minimize the time it takes to have the slab surface at a temperature that is sufficient to add heat into the space.

The beauty about radiant (or any kind of heat) is that as long as the surface temperature of a heat emitter is lower than the air temperature, no heat is being transferred. At least not to the space.

I really need to find out what the response time will be before I will know for sure. Might have to wait till next winter:-(

GMcD

Radiant heating physics

Your note: "The beauty about radiant (or any kind of heat) is that as long as the surface temperature of a heat emitter is lower than the air temperature, no heat is being transferred. At least not to the space." is not quite correct. Radiant heat transfer occurs between objects in a space. Air is essentially transparent to radiant energy. What happens is that the radiant emitter (the floor) will always be transferring heat to colder objects in the space- primarily windows, walls, ceilings, etc. The fundamental problem you will still have is that the solar transients are fast acting big loads that the radiant slab can't react to. What you need to do is use the slab as a warm floor for comfort (just hold the floor temperature at a comfortable temperature) and then use an additional faster reacting heater/cooler in the room to keep it relatively stable. If there are conditions where the slab picks up and absorbs solar gains, then you may have conditions where the space can overheat unless you have a slab temperature override to shut of the heating water, and maybe quickly switch to cool water supply into the slab loops to draw off the solar gains. Basically just have some kind of control setup to keep the slab at a steady state temperature. The temperature you are going to sense in a radiant space is the "resultant temperature" which is a combination of the mean radiant temperature and the air temperature. One of Bjarne Olesen's papers states that in very low air velocity spaces, the resultant temperature is the average of the air temperature and the mean radiant temperature. For example, in a radiant heating environment, with a radiant floor or ceiling surface temperature of say 80F, and an air temperature of 65F, the resultant temperature would be (80+65)/2= 72.5F (assuming high performance windows are in place so the mean radiant temperature isn't affected by the radiant cooling panel effect of the cold windows). The resultant temperature is what the human body feels. Using air temperature sensors to control resultant temperature is always problematical, and requires a great deal of dynamic fine tuning to get anywhere near close while ma nature keeps playing with clouds, sun, and outdoor temperatures. The real key to getting any kind of sun room to work properly is to use high performance glass to reduce the heat losses to a minimum and then control the solar loads to get the natural daylight without the heat gains.

Unknown

Geoff,,,Please continue,,,

"The real key to getting any kind of sun room to work properly is to use high performance glass to reduce the heat losses to a minimum and then control the solar loads to get the natural daylight without the heat gains."

Learning so much since this job started. Haven't even met with the cooling guy yet and I'm done for the most part sadly. This can not stand. I must confer with AC guy.

Do you guys know how wonderfull you are?

A word- (words) CAN'T explain how much this helps me. I'm buying another brick.

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GMcD

Glazing performance

From the architect's point of view, the sun room wants to be a bright sunny space for whatever one wants to do in a sun room. From a mechanical heating and ventilating perspective, sunrooms are a challenge. Various types of heating and cooling terminal systems for the North American HVAC market are designed for fast response and are based on "air temperature control". Nobody does anything about radiant comfort and mean radiant temperature. Conventional double glazing, even with thermally broken frames are still poor performers in more extreme climates in my opinion. In winter, they become radiant cooling panels, and the more glass you got, the worse this is. Sunroom - lots of glass.....So, the first thing you do is work on controlling the heating and cooling loads passively- use high performance glazing with very high thermal performance- R-5 or better, think Heat Mirror quad or Visionwall 4 element. That will stop the glass from becoming radiant cooling panels in the winter and radiant heating panels in the summer. This also keeps the heat loss transients to a long duration seasonal low level transient, very easy to treat with a slow response heating system like a radiant slab. Now, the heat losses and the heating system can become a fairly easy exercise. Now, what to do about solar loads and heat gains from direct sunlight: what most architects don't take into account is that too much direct sunlight is too much light and glare for most people. Nice for plants, but not real good for people. I am going to assume that the sun room function in your case is for allowing a bright sunny space during the winter, which is a good thing. In order to reduce the passive solar gains to the slab, the glazing has to be designed and selected to match your radiant slab performance and heat reaction dynamics. You can tint the windows to various degrees- still get the natural light, but reduce the infrared solar gains down to tolerable levels, or provide overhangs to shade the windows to prevent high azimuth sunlight from hitting the slab, but still allow low azimuth sunlight to penetrate the room without hitting much of the floor area. There is a local building where four-element Visionwall was used with a very heavy tint- looks like those southern sherriff mirrored sunglasses from the outside - and the visible light transmittance is "only" 9%. Sounds low right? The building manager has had to add interior sheers to the offices because there was still too much glare and direct bright sunlight coming in and making it hard to see computer screens. Slightly different occupancy compared to a sunroom, but the point is that even with heavy tints on the glass to reduce the infrared solar gains, you can still get lots of direct sunlight into the space to get the bright "sun room" effect, without overheating the slab or the space. Why add all kinds of fancy controls and air conditioning stuff to deal with a passive set of windows that could be designed to do the right job in the first place? Lot less energy use and maintenance on windows over the life of the house compared to a bunch of A/C and heating stuff. I'm a firm believer in the concept that windows and glass ought to be part of the mechanical HVAC system design as well as part of the electrical lighting design package. They are integral to a properly functioning comfort system.

Mike T., Swampeast MO

High Performance Glazing

Hey Geoff,

Are there yet any good add-on products for older (historic) structures where the LAST thing we can do is change our original windows?

I have an original sleeping porch high above grade with North and West exposures. Large double-hung windows (eight) with new triple-track storms. Very pleasant place to be/work/sleep. Summer solar gain is pretty easy to control with shades on west windows (three). Comfortable in the winter as well with the BIG TRV'd rad but I would like to be able to reduce the heat loss somewhat while keeping the natural light.

GMcD

Retro fits

I've had similar challenges while trying to rebuild Heritage Buildings here in town- picture this: we have a City Energy Bylaw we have to meet (minimum ASHRAE 90.1 type) in order to get a building permit, and the Heritage Committee won't let us replace the old single glazed windows with up to date glazing....so we can't meet the energy bylaw, and have to have special dispensation to get a building permit without meeting the energy bylaw, while satisfying the Heritage Committee. Dumb. If one was willing to spend a bit of time (and yes it will cost a bit of $$) you could retro-fit some high performance glazing into the existing window openings, depending on the heritage nature of the existing frames. Likely you'd be into something custom built though. Is there a possibility that you could have an add-on interior windows for use during the winter? A maintenance chore in October and late March, but at least the exterior windows remain untouched while you improve the interior conditions for winter... I know the Heat Mirror products come as plain sealed window units without a frame, that can be installed in whatever framing system you had, while the Visionwall product has integral framing, mainly commercial type aluminum extrusions. Visionwall makes the whole sealed window with the frame, since their design for the suspended film glazing uses a different mylar film suspension clamping system than Heat Mirror. The only other alternative would be to look at some argon filled double glazing sealed windows or triple glazing. The problem with triple glazing is that their weight is 1.5 times double glazing, so if you retro-fit it into double hung windows you have to rebuild the counterbalances etc....

Mark Eatherton1

Need for intelligent logic...

Someone (I don't care who) needs to listen to what I've been saying for the last few years. It is entirely possible to predict when the sun will rise, based on time of year, and latitude location. These are all real easy parameters to plug into a controller.

In addition to this basic methodology, the control manufacturer needs to develop a night sky re-radiation sensor. This is REAL simple. I've already done it and tested it. It's a simple stagnated shielded sensor in an airtight, clear cover. It also has an ambient sensor that doesn't see any sunshine.

When it is clear outside at night, the shielded stagnated sensor will get noticeably cooler than the ambient air/ With this point of reference, and knowing that solar gain is soon to follow, a person could have a modified PID+ control logic that would shunt a call for heat in a south facing room. This would allow the room temp to drift lower, allowing for solar charging without the double jeopardy of dual incident gain issues.

One of these days, one of these control manufacturers is going to get it, and they'll be rich, and I'll be standing around saying "See!, I told you so..."

I hope they're listening...

ME

jerry scharf

Sensing the sun

Mark,

You're right. It's not about what's happening now, it's about predicting what's going to happen in 3 hours. If the room had low mass radiant panels on the ceiling, you would be in great shape. These can react in minutes to changes and provide a similar level of comfort. Looking at the tubes, it's probably a little late for that!

I had a different thought on how to do the controls for this. I think direct sensing would have problems with providing both reasonable predictions and control stability.

Here's my swag. Find the nearest local airport that has an AWOS (automated weather observation system). You will be able to get hourly updated information on current cloud coverage from that over the internet. Then you want to take the daily solar track and angular radiation density, also from the inernet. You need to then reduce it by the shadowing of external obstructions, and come up with a predicted direct radiation gain over the day. You then take all that and the system lag to choose the current water temperature.

With this and some tweaking, you stand some chance of actually being ahead of the curve where you want to be. It would be a fun control project, but not one I would give to an average homeowner. It's for a home automation person or a heating technology lover.

jerry

hydronicsmike

I think...

...that this may be the future. But how long, I don't know.

Like you said, for the average residence, this would be
overkill. There will be a price attached that most everyone won't want to or can't afford. "Controls are already too expensive". Technology costs money.

I am convinced that one day we can anticipate weather changes better than we can today. But we are not yet near it. I can't even trust my weather guy on TV when he tells me what the weather is supposed to be tomorrow. "Mixture of sun and clouds and a 40% chance of showers" simply ain't cutting it for me when it comes to making Control Systems around it.

jerry scharf

long term is hard, short term not so bad

check out http://adds.aviationweather.noaa.gov/, it's the finest experimental weather site out there. Their RAC weather forcasting model is experimental, but the best I've ever seen. Even so, I wouldn't give it much credit for anything past 24 hours. If we're talking about a 3 hour lag from the slab, the current cloud cover updated hourly should be enough.

The cost difference for an internet connection is going to depend mostly on whether the house has broadband and whether the boiler room has wiring. On the other hand, you could give the homeowner some really cool monitoring tools that would make them feel like they are getting something for their money.

IMO, the biggest pain about what I proposed is figuring out how to input the local shading characteristics. Since we are working three hour predictive, you are really need to understand exactly how much solar energy is going to be available, and local shading is critical to that. Stereo photo synthesis with leaf coverage prediction?? Ouch!

IMO, we're getting to the point where the amount of control capability will vastly exceed what is reasonable using local sensors and a PID controller. The internet could change things completely if we can figure a way to exploit it well.

just my random thoughts

jerry