Tekmar Second Stage Heating Problem

Lognut

I have a radiant heating system with 5 floor zones (1st stage) and 3 fancoil zones (2nd stage) on two floors in a log home. The heat is supplied by a WM Ultra 155 (propane) with an indirect DHWH. The radiant heat is an underfloor install with thin plates. Most of the floors are wood with granite kitchen and bath floors. The largest area is the first floor which has 3 radiant  zones and 1 fancoil zone. The whole system is controlled by a Tekmar 422 reset, 2 Tekmar 336 zone controls and a Tekmar 326 expansion module.

The radiant floor heat has worked great from the initial installation, however, the fancoil for the 1st floor takes over all of the heating when connected to the 543 thermostat 2nd stage. I understand that the 543 is a "learning" thermostat and must get to know its operating environment in order to properly control. I have connected the second stage heat and allowed it to run for 3-4 days on several occasions as I tried to get it to work properly without success. When connected to the 543, the fancoil comes on along with the radiant floor heat and runs the entire heat cycle.

I was told by the system designer that this is a known problem with Tekmar controls and that there is no way to adjust the second stage heating control of the 543.

Is there a solution to this situation or should I just disconnect the second stage heat which is only needed when the temps drop blow 20? Thanks!

Ironman

Tekmar

I'd contact Tekmar. They have good tech support.

Eastman

zones

Are you implying that there is a 543 for each radiant floor zone?

Lognut

More Info

The 1st floor area has three RFH zones and 1 air handler with cooling coil for AC and a hot water coil for 2nd stage heating. These 3 zones are controlled by two 543's and one 541. One of the 543's is not connected to the fancoil at this point. The AC for this area is controlled by a separate Bryant Humidistat.



The 2nd floor area has 2 air handlers with cooling and hotwater coils. One of the zones with a fancoil is controlled by a 541 since is does not have RFH. The second zone uses an air handler with cooing and hot water coils is controlled by a 543. The RFH is 1st stage and the fancoil is second stage. The fancoil in this area is not installed at this time so it only uses RFH. I hope that provides enough detail.



One other thing I should mention is that since these Tekmar controls (422/336 and 336/326) were installed, the low voltage output has been just over 30v AC which seems a little high. Is this voltage typical for Tekmar?

Eastman

How is it configured?

What settings are being used for the heat sources on the 543? How is the 422 configured? Are you running two temps?

Lognut

Tekmar System Configuration

To keep life simple I turned off scenes and schedule so there are no setbacks, etc. The 543 heat terminals are set as HRF2 for heat  1terminal and COIL for heat 2. I also have tried CTRL for both as well with the same results. Heat 2 source is set for boiler.  I have the room sensor set to on as well as the pumps for both heat terminals.



The 422 reset is set up for one mix temp for the RFH and boiler temp for the fan coils. Outdoor design = 10 degrees, mix 1 mode = VAR (injection pump), mix 1 indoor = 70, mix 1 design = 140, mix 1 min = off, mix 1 max =150, boiler term = 3, boiler design 160, boiler min = off, boiler max = 180, boiler diff = auto, CYC= AUTO, schedule = off, DHW Mode=2, DHW Exch OCC = 180, setpoint mode = off



I think these are the essential settings for these controls. I do appreciate the help as I have followed The Wall since 2000 and enjoy the helpful attitudes and the information provided by all.

Eastman

mix 1

What is the mix 1 target and actual temps when this happens? Also, are you using a floor sensor with the 543? Could it be you are hitting the max floor temp setting limit?

Lognut

Target vs Actual Temps

Good questions. I just checked the 422. Outdoor = 30, Modulation=18% (minimum for my Ultra), Mix 1 Target= 95, Mix 1 Actual=93, Boiler Target=100, Boiler Actual=101' I will check it again later tonite when the temp drops. Now the unusual thing is that stage 1(RFH) turned off while stage 2 (coil) continued running for at least 15 minutes and finally shut down. A few minutes later, both H1 and H2 came on simultaneously.



I do not have a floor sensor attached at the moment although I did  try one and it didn't seem to make any difference.



I've attached a pic of the control board for this system. Lots of pumps and probably not the most energy efficient but getting it working as designed is my top priority now.

Zman

543

I think your issue is in the 543. Have you checked the "terminal units" setting for stage 1 and 2?

It would be nice if you could set the differential between the stages. The newer 553 allows it. This would certainly fix the issue.

The install is very pretty. You should send a picture to Grundfos, they would be very pleased.

Have you spoken with tech support?

Best of luck

Carl

Lognut

H1 and H2 Terminals

I'm sure Grundfos would be happy along with my electric utility..........the pumps do work well and are quiet but do use plenty of power.



I have checked the H1/ H2 terminals many times and tried different ones to see if it made any difference in performance which it didn't. It seems strange but if I change the H2 terminal to NONE, the fancoil continues to run (along with the zone pump) as though I had not removed it. The only way to stop it from running is to shut the entire system down and power it back up - almost like a relay is sticking. I also swapped out the 543 with a spare one I have with the same results.

Eastman

stage two

Isn't there an indicator on the screen for stage two? Is the stat actually requesting H2?

Lognut

H2 Indicator

There are definitely H1 and H2indicators on the 543 and I do believe the H2 means the stat is calling for 2nd stage heat. When H2 is showing, the 336 zone control indicator lite for the fancoil comes on, the pump starts, and the  air handler starts. Unfortunately, it comes on way too early and stays on way too long - thus my problem.



I think this was Tekmars first Tn4 2 stage heating thermostat. I wonder if anyone has been able to make it work properly. It looks like the slightly later models (546 and on) have several ways to adjust the 2nd stage heat cycle. I was an early adopter, unfortunately.

Eastman

tn4 BOIL bus

Earlier you mentioned BOIL MIN was off, and the BOIL terminal unit was set for 3 (fan coil) on the 422. The BOIL target/actual temps were about 100. As an experiment, could you set BOIL MIN to 140 and reduce the floor heat Mix 1 max to 130? And finally, although I don't think it should matter, set the Heat 2 terminal on the 543 to control.



Forgot, you'll probably have to reduce your Mix 1 design temp too.

Lognut

Experiment #1

I'll go down and make those changes shortly. What would you suggest as the Mix 1 Design temp? Oh, and just to add a few more variables, I just added a floor sensor., although it is only taped to the top of the hardwood and covered with a pad. I set the floor max at 85 and the min at 65. It is definitely measuring the floor temp. According to the data manual, without a floor sensor, the 543 only calculates how long to run H2. I guess with a sensor, it has feedback to better control H2. We'll see..........



Once it fires up, what temps do you want checked?

Eastman

temps

If you can leave Mix 1 design at 140 that would be best. If not, try 130 or 129. I don't know if the system lets you enter a design temp that is equal to or greater than max.



Keep an eye on targets and actuals. I'm expecting BOIL to be maintained near 140 during an H1 or H2 call, and Mix 1 should really be about the same as it is now. Give the thermostats some time to adjust.

Lognut

Experiment #1

Got tied up this evening with company for dinner. I was able to install the floor sensor and set the floor min temp to 60 and max to 83. Both H1 and H2 both came on for a while. Once the floor temp reached 83, H1 shut down while H2 stayed on. When the room sensor hit the set point, H2 shut down. H1 came back on after the room sensor temp dropped and now H1 and H2 are starting to play better together. I will let it run as is tonite to see if the thermostat can learn its environment. Tomorrow I'll make the changes you suggested and post the actual vs target temps. I must admit that I'm encouraged at this point. Maybe the 543 can work.

Eastman

floor max

When you get around to trying out the settings, you'll need to adjust the max floor temperature to the highest setting you are willing to allow. Based on the behavior you just described, it certainly sounds like that max floor temp setting is limiting the btu output from H1. And if more btus are needed, they're going to come from H2. However, why is the H2 cycle so long? Since there is no BOIL MIN, I believe it's free to pick the coldest BOIL temp possible in an effort to maintain a continuous heat call on that bus. But that's not really what H2 is desired for.

Lognut

Experiment #1 Results

I made the changes you suggested early this AM. I was able to set Mix1 Target and Mix1 Max both to 140. I set Boil Min to 140 and let it run a few hours to stabilize. H1 and H2 both just came on and the 422 called for 100% boiler mod. Mix1 had a target of 99 and Boiler had a target of 140. Amb. is 36 so I guess that's why Mix1 Target was 99. When the boiler actual hit 140, the  boiler shut down but the Mix 1 Actual went up to 135 vs 99 Target and Boiler Actual went to 165 vs 140 Target. H2 shut down but H1 remained on for a while. The Floor Max is 87 but the Actual never went over 82.



I'm wondering how do I get the floor temp to reach 85 (maximum safe temp for hardwood from everything I've read) to get the most BTU's from the floor before the H2 comes on. It reached 83 last evening but hasn't been over 82 today.  I certainly appreciate the help you are providing.

Eastman

encouraging

"H2 shut down but H1 remained on for a while."



However, I'm disappointed the 422 appears to use the BOIL MIN setting as double duty for both boiler protection and the BOIL bus terminal minimum. Is it possible to set the BOIL bus to Mix 2 along with the second stage heat on the 543? (configuring Mix 2 as necessary) That would allow BOIL MIN to remain off, while Mix 2 MIN could be something much higher. Perhaps it would recognize the lack of the Mix 2 expansion module and generate an error.



"I'm wondering how do I get the floor temp to reach 85 (maximum safe temp for hardwood from everything I've read) to get the most BTU's from the floor before the H2 comes on." Does adjusting floor max (higher) appear to have any affect on the actual surface temp? Perhaps the actual floor temperature is more a function of the 543 favoring the responsiveness of the air source over the floor heat as it attempts to maintain a precise air temperature in an unstable environment. My hope is that reducing the system's control over the air coil supply temperatures will force the 543 to recognize that source as less suitable for precision control than the HRF2 source.

Lognut

Results

As the heating cycles continued, H1 and H2 pretty much cycle together which is not what we want. The 422 only supports two mix temps - Mix1 and Mix2 or Mix1 and Boiler - so I can't have Mix1, Mix2 and Boiler together. I raised the max floor to to 87 last nite and it just stays at 82.



To fully get all the BTU's that the RFH can produce, I need to increase the Mix 1 temp to increase the floor temp. What would happen if I reduced the design temp from 10 to 0 so the 422 shifts the heat curve? Or possibly raise the Mix 1 Indoor temp from 70 to 80. I think these two temps along with ambient to determine the curve that the 422 uses. Another possibility would be to raise the Mix1 Min temp like we did with the Boiler Min. It is set to off now same as the boiler min. I'm thinking if I can get the H1 to do more heating, then H2 won't compete as much. Then I could look for ways to reduce H2 temp curve like lowering Boiler Indoor Temp. What do you think?

Eastman

lots going on there in that comment

First, just to make sure we are on the same page:



"The 422 only supports two mix temps - Mix1 and Mix2 or Mix1 and Boiler - so I can't have Mix1, Mix2 and Boiler together."



In reference to Boiler / Mix 2 functionality, from p19:



"When the control is to operate mix temperature zones, the Boiler / Mix 2 tN4 DIP switch must be set to Mix 2. The Mix 2 Bus uses a second mixing device to maintain a mix 2 water temperature target. The boiler target temperature is determined using Boiler Load Reset, in which the boiler water temperature is maintained at the lowest possible temperature that satisfies the heating load of the two mixing devices."



And earlier on that page: "The boiler / Mix 2 bus is connected to a Zone manager via terminals 59 and 60."



And that zone manager would need a 440 mix expansion module dropped into it to actually interface with the additional mix hardware. Here's a simple example of where such an arrangement would come into play: Suppose you had a simple on/off cast iron boiler that could only run in a range from 140 and up. With Mix 1 being used for a medium temp application, and Mix 2 for another medium temp zone. The 422 controls the boiler temp supply as needed for DHW, Mix 1, or Mix 2 --whichever demand requires the highest temp, that's what the 422 fires the boiler to. But the BOIL bus settings enforce limits on these demands, even when the bus is set for Mix 2. If we can shift our temp requirements to Mix 2, then we are free to leave the boiler minimum off.



"As the heating cycles continued, H1 and H2 pretty much cycle together which is not what we want. " They are back to being on together roughly the same amount of time?

Eastman

just reading through the manual

At a minimum, it looks like there would be some sensor errors if you enabled Mix 2 without a 440 mix expansion module on the bus. Frustrating.

Lognut

422 with Mix2

I think we're on the same page with the Mix2 situation. Before I came to The Wall for help from the experts, I did try flipping the Mix2 switch and got multiple error codes. Then I read the manual to see what additional hardware and wiring changes would be needed to use this feature and decided to try and work with my current controls. I already have a 336 Zone Manager attached to the 422 with two zones pumps and a 480 user switch attached. And yes, it was frustrating.......to say the least.



Since my last post, I reduced the design temp from 10 to 0 and the H1 temps went up (110-120) along with the floor temp (up to 85). I checked the floor surface temp with my FieldPiece and it's right on 85 so I guess I have maxed out the RFH BTU output. I am letting it run longer to see what else happens as result of this change.



Do you have any thoughts on my other possible changes like raising the Mix1 Indoor temp from 70 to 80 to further raise Mix1. I think the 422 uses this

temp along with Design Temp and ambient to determine the heat curve for Mix1. Or what about reducing the Boiler indoor temp from 70 to 60 to reduce the heating curve for the Boiler?

Eastman

design temps and more

With indoor feedback, I kinda expect small adjustments to the design temps to have very little impact. The feedback loop is there to correct errors in the ODR curve, and I think it would eventually override your adjustments. But try it and see what happens.



If you adjust the mix 1 minimum higher, my fear is that the 543 will have less control over the floor. I suspect it may recognize this and reduce the rooms dependence on the HFR2 heat source resulting in more hot air and an on average cooler floor. Basically the opposite of what was wanted. But try that too and see what happens.

Lognut

Design Temps

So far the reduction in Mix1 Indoor Design temp has raised the floor temp and although H2 cycles on and off, H1 seems to be staying on to maintain the floor temps. I guess it could take some time for the 543 to learn it's new environment so I can really see what this one change makes. I think I'll leave it as is for a day or so and then try raising the Boiler Indoor Design Temp if H2 is still over-riding H1. Thanks for the help. I'll be back.........

Eastman

What exactly did you change?

Outdoor Design, or the Mix 1 Design, or Mix 1 Indoor? That's the typical coldest day temp, the expected water temp on coldest day for mix 1, and the typical desired indoor air temp.

Lognut

Changes

So far I only changed the outdoor design temp from 10 to 0. Im going to let it run all nite and then see how it acts in the morning. I'll post the temps, targets, etc.

Lognut

Experiment #2 Results

After changing the Outdoor design temp from 10 to 0 last evening the floor temp increased to the max of 85 and H1 cycled to maintain the room temp of 66. H1 and H2 both cycled on and off but H1 would cycle off on reaching the floor temp max. H2 seemed to be much more independent of H1.



I checked the 422 temps this morning during a heat cycle. Amb. is 23, Mix1 Targ was 124, Mix1 Act. overshot to 140 before the boiler shut down. Boiler Targ was 141 and Act reached 147 before shutdown. Floor Temp stayed at 85. I noticed that the Mix1 injection pump was running wide open the entire cycle.



Should I be concerned that H1 overshot the target? It does seem that lowering the Outdoor Design Temp had a significant effect.

Zman

553

It think that the 543 is not going to get you there. It seems like it was somewhat of a mistake on tekmar's part

I would buy a 553 and set the differential as you see fit.

Your 543 is not considering the slow response time of h1 and is turning on h2 too quickly.

Carl

Lognut

553

I expect you are correct about the 543. Anyone want to buy 4 slightly used 543's? You would think Tekmar is aware of this design issue and would let me trade up to the 553. 

Zman

Worth a try?

I would talk to Tekmar about it. You might start with your local rep.

Even if they just give you a partial credit, it would be worth your effort.

Carl

Eastman

results

This is with Boil Min set back to off?

SWEI

Tekmar site

says the 543 has been replaced by the 553

Lognut

Replace 543?

I looked on the Tekmar site and they just introduced  the 521 which has two stages of heat or one each of heating and cooling. Since I don't want to combine my heating and cooling controls, maybe the 521 would do what I want. The 553 has two stages of heat and one stage of cooling.I think I will compare the features of both and talk with my local Tekmar Rep about them before moving forward. Thanks for the advice.

Eastman

floor max

If you're at floor max, I can't see things changing too much for the current weather.

Lognut

Boiler Min

Yes, I set the boiler Min to off as it was originally set. Mix1 Design and Mix1 Max are both set at 140. The floors are staying right at 85 and H1 is on by itself to keep them at that temp. H2 is cycling occasionally to maintain the room temp at 66. Maybe this is the best it can do without a more direct control of H2. It ceratinly better than it has been since the initial install.

Lognut

Floor Max

Good point. It will be interesting to see how it behaves at a significantly lower or higher ambient temp. 

Eastman

temperature spikes

"I checked the 422 temps this morning during a heat cycle. Amb. is 23, Mix1 Targ was 124, Mix1 Act. overshot to 140 before the boiler shut down. Boiler Targ was 141 and Act reached 147 before shutdown. Floor Temp stayed at 85. I noticed that the Mix1 injection pump was running wide open the entire cycle."



It looked like the radiant zones are down stream of the air zones on the primary loop. Perhaps the tempered supply during a simultaneous H2 call is enough to force this injection pump to 100%. But that doesn't really jive if you are getting actuals higher than target.



When you say Mix 1 over shoots, does it spike right before/after boiler shut down, or spike after an H2 end, or does it climb over the cycle irregardless of the status of anything else?



Regarding the boiler temp target overshoot, that just sounds like the boiler differential.

Harvey Ramer

On that

85° degree floor temp. I believe it is an 85° max surface temp. That is quite different from what the floor sensor would see. Verify that with the type of hardwood you have, of course.



Harvey

Lognut

Temp Spikes

I've checked the temps during several heat cycles now and Mix1 consistently overshoots but  the boiler temp is always much closer to target when the boiler shuts down. Makes me think that the 422 is actually controlling only the boiler temp and Mix1 is just along for the ride. Temps from the most recent cycle -  OD temp is 26, floor temp is 86 (H1 shut down on max), Mix1 Act is 100, Mix1 Targ is 79, Boiler Act is 128, and Boiler Targ is 126. Again, the injection pump was running wide open. The overshoot only seems to occur right when the boiler is shutting down.



I've never really looked at the system temps this closely before. I would think the 422 would only let the injection pump limp along since the Mix1 target is so much lower than the Boiler target. Maybe my circulator pumps are set at the wrong speeds since that's the only way the secondary loop can get rid of heat. I'll have to check them vs the design. How can I test the function of the injection pump control?

Eastman

weird

Mix 1 target is 79? (not 97?) And overshoots to 100 right when the boiler shuts down?