Should I use outdoor temperature reset for 2 different types of heating?

tommygags

Hi all, I have a navien combi 240e boiler that is used for both radiant and forced air heat. Until recently I had the outdoor reset set for the radiant heating and realized that was not good for the forced air. I since installed a mixing valve on the radiant heating side and planned on disabling the outdoor temperature controller reset. I wanted to ask, is that the best option or should I reset the settings on the outdoor temperature controller for the forced air setting?  Thanks!

Zman

What mixing valve did you install? Is the boiler capable of multiple reset curves?

tommygags

Caleffi 3-Way Adjustable Thermostatic and Pressure Balanced Mixing Valve.

No, the boiler can only only have 1 set.

Should I have went with this instead?

 https://www.supplyhouse.com/Taco-I100T4S-1-1-4-Way-Setpoint-I-Series-Mixing-Valve-Threaded

Zman

The 3 way, outdoor reset version of that Taco would be my first choice.
A non-thermostatic mixing valve would actually be the easiest. You would set the boiler outdoor reset to the higher temp and the mixing valve would follow that curve as a parallel line.

tommygags

Thanks @Zman! Did I screw myself by installing a thermostatic mixing valve?

Do you have any other recommendations for an outdoor reset mixing valve or you like that taco one?

Zman

A non-thermostatic one that is the same size as the one you have would be pretty slick. Thermostatic valves are all well and good, by design, you just can't use them with outdoor reset.

tommygags

Would you suggest this?

https://www.supplyhouse.com/Taco-5004-H3-G-1-Press-5004-Mixing-Valve-w-Gauge-Low-Lead

hot_rod

The thermostatic will attempt to maintain the temperature you dial in regardless of the boiler reset temperature.  As long as the hot supply is 10 degrees warmer than the mixed setting.

To have the low temperature reset, either a manual valve that tracks along with reset, or another valve with its own reset.
comfort, and covering the load are paramount, how’s it doing?

tommygags

Thanks @hot_rod, I was under the impression since my thermostatic has numbers and not temperature on the dial it would work, but the numbers match to a temperature - thank you for the explanation!  I just installed it yesterday, haven't had time to mess with it.  Since I'm in the north east, couldn't I just set it to 110-120 degrees for the winter and not worry about it for the radiant heat?

For forced air, would you consider that 'finned tube' on the preset settings? Or should I do a custom setting as I was told it should be around 140-160 degrees? 

Does caleffi make any outdoor reset mixing valves?

Other info, the forced air is ran only at night, the radiant heat all throughout the day. 

Thank you!!

hot_rod

Start with the fan coil setting.

 It can take months or a heating season to get the control dialed in to your “ideal” settings.

Every installer faces the same question, how much control and components to install on a system, and to what end.  KISS or throw the entire tekmar catalog at it😉With reset technology the very best result are often accomplished by a homeowner understanding and tweaking it to their satisfaction

tommygags

Thanks @hot_rod! Being a first time homeowner messing with this stuff and learning, I know exactly what you mean...I want it all!!

Mike_Breault

Mike breault from tekmar here, consider a tn system for boiler control / zone control. the advantage is that the system can be configured. the result is the system controls know what type of system is calling for heat, and can adjust the boiler target accordingly, no hi temp zones calling? lower the temp, keep it there unless a high temp calls.

a side note, I do not think Navien accepts an external input for temps / firing rate, any ODR is good, but hte boiler always runs on worst case scenarion.

a TN is a step up as it uses indoor feedback to fine tune, and adjust your reset curve based on indoor conditions,

ona personal note I am running a hydro air system at 135F water at design temps. coil was sized for whole house heating, replaced a FAF, and is a stop gap as I add the radiant. but is too big even by calc

tommygags

Thanks @Mike_Breault! That is very interesting. Would I only need one boiler controller for all my zones/pumps? Something like the tekmar 260?

Mike_Breault

tommygags said:

Thanks @Mike_Breault! That is very interesting. Would I only need one boiler controller for all my zones/pumps? Something like the tekmar 260?

you could and add zone controls for zone valves / pumps., a house control like the 400 series may be easier (although the box is a tad tight... but would do it

tommygags

Thanks @Mike_Breault! I just spoke with Navien and they it should work with setting the temp, but not adjusting the firing rate. 

Is that an issue? Does that mean I can't use the tekmar 400 or was that in reference to the taco I series?

tommygags

Hi @Zman @hot_rod, curious if you have any thoughts on the tekmar 400 that Mike had suggested.  Or if that taco I series mixing valve is the best option?

Zman

Tekmar is great stuff. You will spend quite a bit more money to get all the different parts required. Tekmar also requires a higher skill level to configure than a simple mixing valve.

tommygags

Thanks @Zman! Think I'll swap out the mixing valve then.

 If navien said, it should work with setting the temp, but not adjusting the firing rate.  Does that mean I can still use the Taco? 

Zman

Tekmar is designed to take over control of the whole show. Once you figure out their products they work quite well.
The Taco I-Series is an inexpensive stand-alone solution. It will send a call for heat to the boiler but nothing else.

tommygags

Thanks @Zman! I think I'm starting to understand now. If my main goal is to reduce the supply temp of the boiler so it doesn't run at 140+, my only option seems to go the tekmar house control route, is that correct?  Or it looks like the boiler has a wifi/app add-on where I can set the water temperature on a schedule, which I could set lower for the day as that's when the forced air doesn't run. 

Or there is not much of a difference in efficiency of 20-30 degrees on the supply and I should be more concerned about return temperature at 80 to keep boiler in condensing mode?

Appreciate your patience!

Zman

If you want the boiler to turn itself down when the low temp is the only thing calling, you probably need to go with Tekmar. Some manufactures like Lochinvar have the ability to change temps when different zones call for heat. I do not believe Navien is one of them.

Mike_Breault

tommygags said:

Thanks @Mike_Breault! I just spoke with Navien and they it should work with setting the temp, but not adjusting the firing rate. 

Is that an issue? Does that mean I can't use the tekmar 400 or was that in reference to the taco I series?

Navien I do believe does not take external inputs, but you couls still use it, we onl tell the boiler to fire