Tekmar RoomResponse or Outdoor Reset Modulation

Stoli

I am looking for some insight on the best way to set up my heating system, specificallyhow to modulate my boiler. I realize that there are many variables and no definitive answers but I was hoping to get some professional opinions. My question is, should I use the Tekmar 306P to modulate my Laars Mascot LX boiler using their RoomResponse technology, or should I let the boiler modulate itself using the outdoor reset?


Location: NH
3200 sq ft house
Very tight (spray foam insulated)
HRV in use
Radiant floor heat throughout (4 zones)
Heated Garage slab
Indirect DHW on priority zone
Tekmar 306P switching relay
Laars Mascot LX 175K
Grundfos Alpha2 circ pumps

Zman

I am very skeptical of a boiler modulating controller that does not read the temp of the water, especially with a slow reacting system like in floor.

Let the boiler control itself with a finely tuned outdoor reset curve.

SuperJ

I agree with @Zman , but the controls geek in me sees some value in the room response strategy in some situations.

The room response not intended to directly control the firing rate of the boiler without reading the temperature. It is intending to the give the boiler a discharge temperature setpoint. The boiler should then run at whatever firing rate necessary to maintain temperature at the setpoint.

Some boilers (Lochinvar) offers a setpoint optimization/boost option that seems kind of similar. You basically setup your OA reset to keep the temperatures on the low side, and the boiler can increase it's setpoint slowly if the run cycle goes too long.

I could see it working ok sometimes, but on higher mass systems I would predict the room response might start raising the setpoint prematurely when you don't really need warmer water, you just need to wait for the concrete to warm up. OA Reset is tried and true and would be my go to. I would see room response control as an arrow for special situations. In houses with a high solar gain, it might be a nice thing to keep you system temps down when the sun is shining but it's cold out. Your OA reset doesn't know how sunny, windy, if your wood stove is on too or not.

The instructions call for setting up the room response signal to match the boiler setpoint. The boiler must have the ability to accept a 0-10v/4-20mA remote setpoint (not firing rate) for this to work.

Stoli

Thanks guys. That is extremely helpful info. Like SuperJ, I have some controls geek in me so I initially set up the system to use RoomResponse with a low boiler output of 80° and a high of 130° and the MaxMod set at 65%. But I am now thinking that I should go with the Outdoor Reset and set my points at 80° for an outside temp of 65° and 130° for an outside temp of 10°. Maybe I'll experiment with the RR further down the road. The side of the house that faces WSW has a lot of glass on it, so there is a solar gain on sunny afternoons.

Now I need to figure out the Alpha2 circs. Initially thought I'd try out the AutoAdapt but after reading a thread on this forum, I'm rethinking that and maybe a constant pressure would be better for my situation.

Thanks again.

Robert O'Brien

I have to ask, why a 175K boiler in a house with a heat load probably 1/3rd of that?

Harvey Ramer

How about room response and outdoor reset together. In my experience, that has produced stellar results.

The only problem with an indoor sensor is, you really need one for every zone.

I really wish the industry would shift to thermostats that provide temperature feedback to the boiler. It would obviously have to be set up to work across multiple zones.

I see no reason room response cannot work with both high mass and low mass, given the right software programming. If the temperture is split up in 100th of degrees, and the control not only measures the deviation from set point but also the acceleration of change, it should be able to accruately control any system regardless of response times or weather conditions.

ODR is great but in real life it falls short of achieving the results that could be achieved with real time room response. Also, I can't tell you how many times I run into systems that have incorrectly set ODR curves or none at all. That's not efficient and could easily be solved with room response. Hydronic technology is at least 20 years behind what's possible and available.


I'll shut up now.

Stoli

Robert O : The "oversized" boiler is for garage slab and ice melt for the front entry.

tuffcalc

Stoli - any commentary on the room response?

I’m setting up a large 20 zone system using tekmar 306v, 561 thermostats and a Lochnivar Knight boiler. Planning on using room response instead of outdoor reset.

Did room response do a good job of finding a reasonable boiler Setpoint?

Call me crazy but room response makes way more sense to me - using direct indoor feedback and never having to fiddle with an outdoor curve.

Would love some feedback if you have any.

nicholas bonham-carter

I wonder how that works with 20 zones, if there are different exposures-sunlight-shade-etc.

tuffcalc

> @nicholas bonham-carter said:
> I wonder how that works with 20 zones, if there are different exposures-sunlight-shade-etc.


It picks the highest load zone for boiler setpoint.

Zman

tuffcalc said:

Stoli - any commentary on the room response?



I’m setting up a large 20 zone system using tekmar 306v, 561 thermostats and a Lochnivar Knight boiler. Planning on using room response instead of outdoor reset.



Did room response do a good job of finding a reasonable boiler Setpoint?



Call me crazy but room response makes way more sense to me - using direct indoor feedback and never having to fiddle with an outdoor curve.



Would love some feedback if you have any.

Your Crazy
Do room response and outdoor reset. You will get the efficiency benefits of lower return water temps. Sending the correct water temp to the zones will help reduce over/undershoots. Outdoor rest really doesn't take much fiddling and is well worth the effort.

tuffcalc

> @Zman said:
> Stoli - any commentary on the room response?
>
>
>
> I’m setting up a large 20 zone system using tekmar 306v, 561 thermostats and a Lochnivar Knight boiler. Planning on using room response instead of outdoor reset.
>
>
>
> Did room response do a good job of finding a reasonable boiler Setpoint?
>
>
>
> Call me crazy but room response makes way more sense to me - using direct indoor feedback and never having to fiddle with an outdoor curve.
>
>
>
> Would love some feedback if you have any.
>
> Your Crazy
> Do room response and outdoor reset. > You will get the efficiency benefits of >lower return water temps. Sending the >correct water temp to the zones will >help reduce over/undershoots. Outdoor >rest really doesn't take much fiddling >and is well worth the effort.

I don’t think it’s possible to do both. Room response sends a setpoint temperature to the lochinvar knight based on the on/off cycle of the thermostats (long off periods results in lower setpoint temp). Outdoor reset would do the same thing based on a different input.

... unless I have this wrong?

Zman

Sorry,
I was thinking of TN4 systems which run outdoor reset and PWM for the zones based on indoor feedback.
I would just do outdoor rest if those are your options.

tuffcalc

Apologize if this is a double post - was trying to quote and something went wrong.

@Zman - I don’t think I can do both outdoor reset and roomresponse. Room response changes the setpoint boiler temp based on the on/off time cycles of the connected thermostats (more on time results in higher setpoint).

I’m thinking indoor feedback (roomresponse) would provide truer feedback and better boiler setpoint.

Anyone out there with any experience using tekmar 304 or 306 controllers with room response?

tuffcalc

... so my system is in and I have it setup with room response (as thought, you can only do room response or outdoor reset, not both).

I have to say, room response is really impressing me and dare I say better than outdoor reset because it uses actual conditions in the home to set boiler setpoint. I know this is tekmar’s lower line, but it works really really well based on some pretty simple concepts. Essentially it figures out the on/off times of the thermostats based on a 10 minute cycle, and based on that calculates a boiler setpoint (more on, higher setpoint). Within a few hours it is able to find a steady state setpoint and is always recalculating. If it can’t meet setpoint it jacks up the water temp to the high limit you program, forces thermostat off, and restarts calculating downward.

I’ve paired it with a lochinvar knight. On the knight I can select the lower and higher boiler bands - so on the low end I have it set at 70f, and on the high band 120f supply water temps - I have the mod dial set to 100% on the 306 so it can modulate it’s fully range.

It’s fairly mild here in Ontario (about 10c). The boiler is humming along with long cycles with supply water temp at 73f.

I think because of the large amount of zones I have tit works extremely well because there is always a zone or two calling, so boiler rarely turns off (I also properly sized - it’s modulated down to 20% right now and has been running for a good while).

I’ve paired my system with tekmar 561 thermostats set for radiant/pulse width modulation. If you have one big zone I’m not sure how this would work as it would pulse at setpoint.

In any event I really wanted Wi-Fi thermostats with a simple controlling app, so I built around the tekmar 561’s which meant I could only use their classic range 306 zone valve controllers.

This seems to be working amazing. Outdoor reset curves are thing in the past for me, now!