Tekmar 260 and thermostats?

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Old 02-24-11, 02:45 PM
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Tekmar 260 and thermostats?

I got my 260 installed, and it's up and running just fine. Thanks for the help guys!

Now, my question is regarding my existing Tstats. I have two zones(and DHW indirect too) one stat is for first floor(zone1), the other stat is second floor(zone2). Remember that I'm using a Taco ZVC too. T stats are simple digital stats set for one constant temp. I haven't picked up a cheap 7 day programmable to do occ/un-occ setback yet, so I'm not doing any setback as of now, but I plan too very soon.

I installed the indoor sensor on the first floor, near the existing stat for z1.

I'm really not sure if I should be letting the stats run the show with the sensor just supplying info about the heat load, or if I should be setting the stats a few degrees higher than the 260 occ temp, and letting the sensor run the show? I'm thinking that the upstairs zone might end up too warm? I guess I should try it both ways, but was just thinking maybe someone here has already tried this, and can offer up their findings or advice?

Thanks.
 
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Old 02-24-11, 02:53 PM
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average the two floors, then it should generate a happy medium.
The stats should be used as a high temp limit, not so much to control the rooms.
With out feedback from the upstairs zone, it may over or under heat depending on the balancing.
 
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Old 02-24-11, 03:05 PM
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Set the room thermostats a degree or two higher than the tekmar setpoint. You might start with 2-3 degrees warmer until you learn what any difference is between the tekmar temp and the room stats (my tekmar reads about a degree higher than my room stats).

In the early going, the system will overheat a bit and the cycling will be weird. Give it a day or two to calm down, then another couple weeks to get dialed in. The key is to not mess with stuff while it accumulates data.

Best also if your stats simply generate a constant call for heat rather than cycles per hour or 'intelligent recovery' and the like. i.e., a call for heat should just close the circuit until the stat is satisfied.
 
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Old 02-24-11, 05:02 PM
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Something that is often overlooked when installing stats... INSIDE a wall, even an interior wall, the temp is always quite a bit cooler... and if this cool air inside the wall leaks out into the t'stat the accuracy will go whack. PLUG THE HOLE that the t'stat wire exits from!
 
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Old 02-24-11, 06:04 PM
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Thanks guys. I went out and picked up a cheapo 7 day tstat for setback use. It's all wired in, and I've set my other stats a few degrees above the occ temp on the 260. I'll give it a few weeks and see how things work out.

If I find I need to add a sensor for zone 2, and knowing that I can't add just one thermistor to get me to 10k, is there any reason that I can't just add another 10k thermistor in series at the sensors, and then parallel both sets to get me back to 10k? The Tekmar sensors are about $30 apiece, but I can get 10k thermistors for about $0.50, and wire them right into the Tekmar housings.

Trooper, I made sure the holes were plugged for the stats and the indoor sensor.

It's 38 degrees out right now, and the boiler target temp is 143. I strapped a 4" type K thermocouple probe to the boiler return line, and put some insulation over it. It didn't take long for the return temp to get over 115. I'm going to keep an eye on it to be sure though.
 
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Old 02-24-11, 06:27 PM
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I don't think you'll need any other sensing. Give it a while and balance using the upstairs stat and closing/foiling heating elements as needed.

The reduced water temperatures alone should keep things moving slowly, space temperature-wise.

Enjoy.
 
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Old 02-24-11, 06:39 PM
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will do....thanks for all the help
 
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Old 02-24-11, 06:39 PM
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is there any reason that I can't just add another 10k thermistor in series at the sensors, and then parallel both sets to get me back to 10k?
No reason at all... but do as Xiphias suggested first... watch and wait for a while.
 
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Old 02-25-11, 10:32 AM
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a 10 k sensor may not be the same as the other 10 k sensor. There are many different curves to the sensors.
If you use the wrong ones, it will confuse the heck out of the control.
 
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Old 02-25-11, 03:47 PM
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I've always thought there was only one curve for thermistor... the "Steinhart-Hart" equations dictate the curve, and it's more or less standard? No?

There are of course different resistance ranges, but I think as long as one uses a 10K NTC thermistor it's same-same...
 
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Old 02-27-11, 03:12 PM
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So it's been a few days now, and things seem to be working pretty well. The indoor sensor is about 2 degrees off from thermostat, and the outdoor sensor is off a few degrees too, and they both seem pretty slow to respond to temp changes.

Both zones are holding to within a degree of one another, so for now, it seems like the one sensor is adequate.

Anybody know if the DHW post purge can be turned off on the 260? It's fine to have it now, but in the summer, when the heating zone valves are closed, the zv for the DHW will close when the aquastat is satisfied, but the 260 will continue to run the pump when all the zone valves are closed. I'm not sure if thats good for the pump?
 
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Old 02-27-11, 05:26 PM
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Anybody know if the DHW post purge can be turned off on the 260?
I don't believe so...

Which schematic did you end up wiring to?

Remember back a way I said that I thought there was some reason that something might not work with one of those schematics? Maybe this was the reason?

You might end up having to install a differential bypass valve... (thinking out loud)
 

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Old 02-27-11, 05:51 PM
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I used the schematic from post #24 in that other thread. I do remember you saying that, and I'll have to see if I can figure out a way to hold the DHW zone valve open for the four minutes that the 260 does its post purge.
 
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Old 02-27-11, 07:33 PM
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You might end up having to install a differential bypass valve... (thinking out loud)
You might not have seen this, I added it after you posted your reply...

It would be nice though to try and come up with a way to leave the valve open... I've got my thinking cap on...

What if:

The DHW zone valve were wired to the 260 (terms 9 & 10)? Just the motor... leave the endswitch wired to the ZVC... let's think about that a bit.

No that won't work... the 260 won't open the valve until it sees a DHW demand, and it won't see the DHW demand until the endswitch makes...
 
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Old 02-27-11, 08:14 PM
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Last thought for the night...

What if:

You remove the DHW zone valve wiring from the ZVC, and replace with a jumper at 3 & 4 on the ZVC DHW channel. The ZVC would think you are running a pump instead of a valve. It would still operate Z4 relay and send demand to the 260.

260 would start boiler, run boiler pump... at same time, 9 & 10 would make... use them to open the zone valve. You would need to run another wire from the ZVC to get the power to open the valve.

You would still dead head the pump for the amount of time that it takes for the valve to open, but that's only a few seconds. And you would gain the post purge into the indirect. Fair trade I think?
 
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Old 02-27-11, 08:30 PM
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I lied... one more idea...

You could always lose the zone valve and go with a pump for the indirect... this of course means a bunch of repiping, but it is an option.
 
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Old 02-28-11, 03:18 AM
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Originally Posted by RedHouse View Post
The indoor sensor is about 2 degrees off from thermostat, and the outdoor sensor is off a few degrees too, and they both seem pretty slow to respond to temp changes.

Both zones are holding to within a degree of one another, so for now, it seems like the one sensor is adequate.
That all sounds fine and within the tolerance of the various sensor types. Let it keep going like that. The bottom line is minimizing space temperature fluctuations. If the house temp is holding steady where you want, it doesn't matter what the sensors say. (FWIW, my outdoor sensor is off by 3-5F compared to a lab-grade thermometer and it's slightly non-linear, too.)
 
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Old 02-28-11, 03:25 AM
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Originally Posted by NJ Trooper View Post
You could always lose the zone valve and go with a pump for the indirect... this of course means a bunch of repiping, but it is an option.
Switches and wires and relays, oh my.... Pump is where I ended up, too. And yes, that's a bunch of work just for that. But probably not any more work than a differential bypass (and would be a better solution than a DPV).

Could also ask tekmar what they think....
 
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Old 02-28-11, 04:40 AM
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Nope a 10k NTC can have different curves.
Seen it all too many times.
Tekmar uses a closer to standard than some, but the uponor 10 K reads quite off once out side the 25 degree C range.
You need to look at the resistance chart for the sensors your thinking about using and compare it to tekmar.
 
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Old 02-28-11, 03:30 PM
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I got the valve working....I wired it up like Trooper suggested above, but with one little change. Terms 9&10 on the 260 are only a NO relay, so you need to provide a 24v source in the circuit to open the valve. No big deal, and it's working like a charm. I may add a 24v indicator lamp to the end switch at DHW valve......just for a confirmation that the valve is actually open.

And TO is correct about the 10k thermistors having different resistance curves. I saw that last week when I was looking at Digikey's website. You would have to match up the resistance to Tekmars thermistor.
 
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Old 02-28-11, 04:14 PM
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so you need to provide a 24v source in the circuit to open the valve.
I did said dat!

260 would start boiler, run boiler pump... at same time, 9 & 10 would make... use them to open the zone valve. You would need to run another wire from the ZVC to get the power to open the valve.
Yes, there are different 'ranges'... i.e. 3K, 5K, 10K, etc at 77F, but looking at DigiKey, or even Omega, I didn't see where there were different 'curves' for a given 10K thermistor. Can someone point to a reference that I may educate myself?
 
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Old 02-28-11, 04:16 PM
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Red, have you noticed by chance that the 260 delays the pump start on a DHW call if the DHW type is set to VALVE ? It sure would make sense to have like a 15-30 second delay built in for the purpose of waiting for the valve to open since there is no feedback from the valve.
 
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Old 02-28-11, 04:21 PM
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Originally Posted by NJ Trooper View Post
I did said dat!




Yes, there are different 'ranges'... i.e. 3K, 5K, 10K, etc at 77F, but looking at DigiKey, or even Omega, I didn't see where there were different 'curves' for a given 10K thermistor. Can someone point to a reference that I may educate myself?

Yeah....I guess you did said that....sorry Trooper. Thanks for the help!


I'll see if I can find the data sheets I was looking at. As I recall, the resistance values weren't radically different for different temps.....like less than an ohm.
 
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Old 02-28-11, 04:21 PM
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just for a confirmation that the valve is actually open.
What if:

On the unused channel on your ZVC, you wired the endswitch of the DHW valve to the TT terminals of that channel?

Should light that channel thermostat LED, but not interfere with any operation because there is no valve connected to that channel.
 
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Old 02-28-11, 04:26 PM
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That should work....I tried something similar, where I used the terms on the unused zone valve connector to light up the end switch LED on the unused zone, but when it made contact, it acted like another call for heat. Your method will give just the stat light, and no call for heat.
 
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Old 02-28-11, 04:36 PM
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I didn't think that an endswitch closure in the absence of the associated TT closure would generate a demand signal?

Even so, if it did, it shouldn't matter, because that valve would only be open during DHW, and DHW is on priority in the ZVC... so the ZVC would ignore it, and the 260 would never know.

I sure wish Taco would publish the schematics for their controls... it would save me having to 'reverse engineer' one... (on my to-do list now for a few years!)
 
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Old 02-28-11, 04:41 PM
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When the valve and endswitch opened, the relay and zone 3 endswitch indicator stayed on....I had to actually remove power from the ZVC to turn it off. I didn't pursue it much past that.....it was time to feed the dogs, and they aren't all that patient.
 
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Old 02-28-11, 05:01 PM
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When the valve and endswitch opened, the relay and zone 3 endswitch indicator stayed on
That's bizzaro!

it was time to feed the dogs, and they aren't all that patient.
I must be part dog then! ... bacon ... bacon ... bacon ... maybe even ALL dog!
 
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Old 02-28-11, 05:25 PM
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It seems to be working fine on the TT terms.....thing is, it only needs one wire from the zv endswitch(term 3 on the taco valve) to one of the terms on the TT connector to make the light come on......
 
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Old 02-28-11, 05:48 PM
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OHHHHHHHHHHHHHHHHH.... You have Taco valves! That actually explains it...

You shoulda yelt at me when I kept drawing the 4 wire Honeywell type on the schematic!

You need to be careful which terminal you hook that too, it's possible to short out the transformer in the ZVC panel!
 
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Old 02-28-11, 06:03 PM
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Sorry for not clearing that up....it seems to be working just fine now....thanks for your help!

xiphias.....are you doing any setback with your 260? Like I mentioned earlier, the indoor sensor is kinda slow to respond, so the house ends up getting overheated when coming out of setback. I was trying a 5 degree setback, but I might try just setting back a couple of degrees. Other than that, when the system has stabilized at the setpoint, the house is very comfortable.

Does making any changes to the occ or unocc setpoints wipe out the existing curve that the 260 has already learned?
 
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Old 02-28-11, 06:06 PM
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Originally Posted by NJ Trooper View Post
Red, have you noticed by chance that the 260 delays the pump start on a DHW call if the DHW type is set to VALVE ? It sure would make sense to have like a 15-30 second delay built in for the purpose of waiting for the valve to open since there is no feedback from the valve.
I don't think there is any delay...but I'll check it out.
 
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Old 02-28-11, 06:51 PM
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Originally Posted by RedHouse View Post
xiphias.....are you doing any setback with your 260? Like I mentioned earlier, the indoor sensor is kinda slow to respond, so the house ends up getting overheated when coming out of setback. I was trying a 5 degree setback, but I might try just setting back a couple of degrees. Other than that, when the system has stabilized at the setpoint, the house is very comfortable.

Does making any changes to the occ or unocc setpoints wipe out the existing curve that the 260 has already learned?
I used to do a 5F setback. Then went to 2F. Then a couple years ago went to no setback. Mostly because the whole system just seemed happier (and used less fuel) without setback. But I did see some overheating coming out of setback, consistent with your experience. Nothing bad, just a degree or two for an hour or so.

Changing setpoints won't hurt the accumulated data.
 
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Old 03-02-11, 06:14 PM
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Thanks for the input xiphias. I think I've got some decent settings now, so I'll just have to wait and see how it adjusts itself.

Any thoughts on turning off the DHW during setback periods? Can't seem to find much data to see if it saves fuel or not. I'll do it for sure during the summer....it helps to keep the basement cooler.
 
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Old 03-02-11, 06:27 PM
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I don't do setback anymore, so use occ/unocc to regulate times of DHW production. I give it a couple hour window in the morning so it's hot for morning shower and can recharge for any day use, then it stays off until another couple hour window in early evening so it's ready for dishwashing, shower, etc.

Not sure if that saves any fuel, but it does make sure the tank is topped off and ready to go during the principal periods of use. And avoids random DHW calls when it might be 8-10 hours before hot water is even needed.

April-October is full solar hot water season, so don't know whether timing DHW helps with basement temps in summer.
 
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Old 03-02-11, 06:38 PM
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I figured I would try shutting it off during unocc periods. We are seeing if we like having no setback on house temps...so I figured why have the DHW heating up when we don't need it.

Last summer, we would just turn the boiler off during the day, but there was a few times when we forgot to turn it back on....I don't enjoy cold showers when I'm not expecting one.....so the timer will be nice for that.
 
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