4 questions on my in-floor heat

Users who are viewing this thread

birchlake

Member
Messages
32
Reaction score
0
Points
6
Location
Melrose, MN
First, some background. Not that experienced with in-floor heat, so bear with my novice questions.

I have a 1008 sq. ft. home, concrete slab on grade, built in central Minnesota in 2011. Radiant heat provided by an Electro Industries 9KW electric mini-boiler, model EMB-H-9. I also have a Mitsubishi mini-split and a fireplace for additional heat sources. My in-floor system is controlled by a Tekmar 552 one stage heat thermostat using both the air sensor in combination with a floor sensor. No zoning; one loop.

#1. I have read from a few online threads that my "maximum floor heat" should not exceed 85 degrees. I have my maximum floor heat set-point on the thermostat set to 88 degrees. In the very cold weather that we have every winter in Minnesota, reducing this set-point from 88 degrees to 85 degrees becomes problematic in achieving my room air setpoint of 70. Is it a problem to be running with a maxiumum floor heat setpoint of 88 degrees? My floor coverings are a mix of carpet and sheet vinyl, with no hardwood flooring. The floor does not seem overly hot, even to bare feet, with the 88 degree setpoint. Is the primary reason for recommending 85 degrees to protect floor coverings, or does it have something to do with the concrete itself?

#2. I have my boiler temp set to 114 degrees farenheit during the colder winter months of December through February. In the spring and fall with more moderate outdoor temperatures, I can get by with a reduced boiler setpoint of 102 degrees farenheit. Is the 114 degree boiler temperature reasonable? It seems to keep up at this temp except for a few exceptionally cold days, where during load control (I'm on a dual-fuel program from the local cooperative), the power can be cut from my radiant system for 3-4 hours. The next higher temperature on the boiler is 126 degrees. So my question here is could I consider using the 126 degree boiler set-point for situations like this? Or would it be best just to leave it at 114 degrees and allow it to catch up?

#3. My system is operating at around 8-10 psi, according to the pressure gauge on the side of the boiler. While there are no issues with the operation of the system, I seem to remember it operating at a higher pressure when the system was first installed 5 years ago. Is my current pressure of 8-10 psi of any concern? What would be a reason to see a pressure drop over time? Would adding some water to the system increase my pressure and would there be any benefit to that? I have not added any water to my system since it was installed in 2011.

#4. I am considering spending part of the winter in a warmer climate. I understand that Tekmar has recently introduced a Wi-Fi thermostat, Model 561 (one stage heat unit) which could replace my Tekmar 552 and I wouldn't need to purchase the additional internet hub unit. This would give me peace of mind by allowing me to monitor the temperature in my house while I am away. Does anybody have any experience with these new Tekmar Wi-Fi thermostats for my type of application?

Thanks for any input/insight!
 

Jadnashua

Retired Defense Industry Engineer xxx
Messages
32,770
Reaction score
1,190
Points
113
Location
New England
1. Some electric in-floor radiant heating systems allow up to a 92-degree floor surface...I don't think you'd have an issue if you raised it slightly, but I would not go higher. Depending on where the in-floor sensor is, if you go too high, and say you were measuring at the end of the loop, you could have excessive temps at the beginning. I think some of it comes from wanting to limit the temperature extremes...pex itself will expand and contract with temperature changes.
2. Often, the heating runs start at the perimeter and wind their way towards the interior. This puts the hottest water closest to the typically coldest section of the slab. You'd have to try it and after things have been running for awhile, use a thermometer in various areas (put a rug over it and let it sit for awhile) to see what the ultimate temperature is. You could use a thermal imaging camera, but you'd have to spend the money to buy one (the FLIR One is neat and they have versions for both Android and iOS systems), and that would give you an idea. You'd need to adjust the setting for the reflectivity of the flooring material, but once done, it can be quite accurate.
3. If the system is all on a single floor, that pressure should be fine. The most you'd want to raise it to would be around 14-16psi if you did. Just like in a car's radiator, the pressure is to ensure things don't boil and flash to steam if the control circuits fail and the water keeps getting hotter and hotter...a steam explosion can be very damaging.
4. There are lots of WiFi enabled thermostats out there. Most of them can be configured for the type of heating system you have (which is critical to minimize overshoot and comfort levels). It doesn't have to be Tecmar. I have one made by Nest that works well for me.

If your boiler has the ability to use an outdoor reset module, you might consider adding one on. This would adjust the boiler's temperature to the outside temp to help maintain the desired heat output. IOW, on a really cold day, it would raise the boiler's water setpoint, and on a warm day, lower it.
 

birchlake

Member
Messages
32
Reaction score
0
Points
6
Location
Melrose, MN
Thank you Jadnashua for your comments!

I'm learning more about my radiant heat system every year. Unfortunately, my Electro Industries Mini-Boiler does not have a capability for adding an outdoor reset module. I sure wish it did! From what you have said, I think I am pretty close on having the correct boiler temp set-points, pressure etc. I think I will stay with my current settings. As I have found out that my system is not optimally designed, understanding how to get the most out of it under all conditions is pretty important to me as the true coldest temps of the Minnesota winter are on our doorstep.

The reason I like Tekmar thermostats is because they use a combination of both air temperature and a floor sensor to control. I like having the additional controls for min/max settings on floor temperature and the like. Switching to my current Tekmar thermostat has been a big improvement over the original thermostat that my contractor installed. Also, by staying with Tekmar, I have verified that their new Wi-Fi thermostat will mate right up to the current Tekmar floor sensor I have installed. So I think I'm probably going to try their new Wi-Fi stat. I have had very good luck with Tekmar thus far and their customer service has been excellent.

That FLIR phone gizmo for thermal imaging that you mentioned is very cool! It seems like it does a decent job for a pretty low price point, just over $200 online. I have been using my infrared point and shoot thermometer for getting some data, but that of course doesn't give all of the benefits of true thermal imaging.

After reading through the manual for my Tekmar thermostat though, I do have one question. It is regarding the setting of W CYCLES PER HOUR. Currently, I have left mine at the default setting of SYNC which synchronizes thermostat to a 20 minute cycle. Options for this setting are AUTO which does automatic cycles per hour to minimum temperature swings and I can also manually set this anywhere from 2-12. Is there any reason for me to consider a setting other than DEFAULT for W CYCLES PER HOUR?

Appreciate the comments, folks.......
 
Last edited by a moderator:
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks