so your saying that if I bring the outdoor design temp down that it will bring the supply temps down? I will take pics of my system later to show you what I have.
radiant temp
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Floydian
Feeling the Heat
Ha, having no master thermostat probably wouldn't fly just about anywhere
. I do plan on adding a bang bang thermostat that's only real function will be to shut off the pump/ivalve at times when I have enough solar gain that the TRV's stop all flow. Overshooting for me is only due to solar gain or lots of occupants, never the radiant floors-the TRV's make sure of this.As far a system like mine waaay up north? Sure it can work, and well with proper designing. Rob at http://nrtradiant.com/index.html is a top notch guy in the biz and helped me immensely with the distribution side of my system. He's designed constant circ, ODR systems like mine all over the place, including Maine, where he lives.
Noah
Floydian
Feeling the Heat
cpeltier
Member
Yes, but that's assuming this control modulates the temperature of the radiant loop. A system description or pictures would help. Are you changing the design temp directly on the boiler or on a boiler/mixing control such as a Tekmar or other brand?
The idea is by lowering the design temperature (in your case to what it should be) you will lower the system temperature for a given outdoor temperature. The design temperature is one of 4 values used to calculate the reset ratio which is described nicely above by Noah.
So im gonna assume going from a design temp of 0 to -15 should help. Its a tekmar 356 outdoor reset. it mixes the water temp going into the radiant manifold. I wish there was a calculator or something on there website to see what my curve would look like. I will take pictures when I get home to give you guys an idea of my set up
cpeltier
Member
I know those units well. Your running a variable speed injection pump to control the radiant loop temperature. It's a sophisticated little unit and uses a characterized heating curve instead of a straight linear line as most simpler products do. It attempts to accommodate for the non-linear performance of the radiant floor and the heat loss of the structure. It's impossible to calculate what it's doing as it proprietary to Tekmar.
The concept is still the same. Lowering the design temperature will shift the curve downward providing the desired effect. After you have done that the next step if necessary is to adjust the mix design temperature (a setting in the menu) up or down a few degrees. These units are so easy to program on the fly!
cpeltier
Member
I see the Tekmar next to the Taco zone control. The injection pump is to the left of the Webstone primary/secondary purge tee and out of sight. It looks like a nice setup.All of your zones are running off of one mixing temperature. If they don't all have the same heat loss or floor coverings then expect some heating variation in the zones. It looks like you have another remote manifold. i can see why you don't want to swap out thermostats as you must have a bunch!
These systems always need adjustment after turn-up and you usually have to go through a heating season to get them tuned just right. Most HVAC contractors don't have the price of all those truck rolls figured in for that.
cpeltier
Member
If the system was setup properly based on an accurate heat loss calculation then you should expect the contractor settings to work for all outdoor temperatures. I'm skeptical based on the design temperature being set to 0 however.
You can lower the room temperature on the Tekmar and it will cause a parallel shift of the heating curve downward in temperature. This will lower the mixing supply temperature for a given outdoor temperature and may give you the desired effect.
Write the numbers down before you change them. It's easy to go back.
If it were my system then I would setup the design temperature properly and I would set the room temperature for what I expect the room to be (IE 70). Then I would play with the mixing design temperature.
I also have my warm weather shutdown set to 55 since my house holds heat well and mixing maximum should be set to the mixing design temperature or a little hotter if you want for the colder then design periods.
I guess im just frustrated because I really think that this system could run a lot better. I hate that it heats the slab pretty much once a day, it allows for slab cooling when I would rather it stay consistent. I burn about 18-19 bags a week. I really do think it could run better and make the house more comfortable.
cpeltier
Member
Adjusting it as suggested will make it more efficient and keep in mind that it has been a very cold winter and a record for February. February's AVERAGE temperature in Caribou was 2.5F!
That's over 11 degrees colder then average.
That's over 11 degrees colder then average.
cpeltier
Member
Without changing the thermostats to a PWM capable version I would try and adjust the Characterized heating curve of the Tekmar to exactly match my building. This will lower the water temperature entering your floors to the point where they are just warm enough to heat the house at the desired indoor temperature. This will cause the radiant circulation pump(s) to run most of the time. Your thermostats would always be just below the setpoint and would keep the zone valves open and calling for a mix demand. This way you would not have heat swings assuming passive solar doesn't interfere and it also assumes that your outdoor sensor is in a shaded location outside away from any heat sources.
Usually it's impossible to achieve this perfectly without careful engineering but you can try. If you can't get it close enough with this technique then replacing with PWM thermostats (or maybe just in the hot rooms) will make it work.
I've described it already in the preceding posts but to summarize:
1)Lower the design temperature in the Tekmar mixing control to -18F or so (this should be set to your normally experienced low temperature).
2)Adjust the mix design temperature in the Tekmar to the desired radiant water temperature at this outdoor design temperature. Without knowing your current values it would be hard to guess but since your running hot now I would leave it at the current setting since the previous adjustment (1) will lower your floor temperatures.
3)Set the Room Temperature in the Tekmar to either 68-70 or what you set your thermostats for on average for comfort.
Run it for at least 24 hours and see what happens. If it's too warm adjust step 2 above lower, if it's too cold make it warmer. Make sure you give it sufficient time to adjust. It can take a day or two to stabilize.
Adjusting just the Room setting in the Tekmar as your contractor suggested I consider a hack, but it may work. The fact that the outdoor design temperature is no where close to what is experienced tells me the system isn't set up correctly.
Current Values
room temp 67
outdoor design -15
min ind. 70
design mix 120
mix max 120
boil min 100
wwsd 85
actual indoor temp is 1-2 degrees higher then the setpoint of 70dg on the thermostat this morning
I really think i'll try the wirsbo thermostat in my biggest room (living, kitchen) it is always off by a couple degrees in the day. another question is what sitting doing you think my variable speed pump should be on?
cpeltier
Member
From what I can see you need at least 4GPM for the manifold shown. There is another remote manifold so I would guess at speed 2 or 3 for the B&G pump.
Did you set the Outdoor Design to -15 from 0? Are all of the rooms hot or just the living room/kitchen? My next adjustment would be to lower the "design mix" to 115 and not change anything else.
If only the living room/kitchen is warm then I would add the PWM thermostat.
pretty warm in all the rooms. my daughters room is 73 right now. I will bring the design mix down to 115
Gonna have three wirsbos in the mail today. All I have to do is hook up the two wires correct ? No other changes?
cpeltier
Member
Correct. They "steal" power from the two wire circuit and will work with the modern Taco Zone controllers which you have, If it doesn't power up after you hook up the two wires let us know.
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