Tekmar 156

[chuck172]

I installed a tekmar 156 differential controller on my Tarm. Mounted it on the front panel, in-line with the gauges. The unit was very simple to install and does exactly what I needed it to do.
My boiler has become a fill, light and go set-up. No more baby sitting.
The Tekmar squeezes every bit of usable heat out of the boiler and puts it into storage. It will not allow cooler than storage water to circulate into it.
I'm really happy with the efficiency gained from this.

 

[WoodNotOil]

Glad to hear it is a good product and does the job intended. I am still working on homebrew Arduino version of it. Out of curiousity where did you place the two sensors and what do you have the differential set to?

 

[chuck172]

The sensors have a flat machined on them so they can be clamped on the pipe surface. I installed the source sensor on the 1 1/4" boiler supply very close to the boiler tapping.
I installed the storage sensor on the 1 1/4 copper pipe very close to the outlet (return to boiler) of the propane storage tank. The sensors come with their own clamps. I applied heat conductive paste and insulated over the sensors.
The differential default is 5*, I saw no reason to change it.

 

[VeggieFarmer]

Chuck: very glad to hear this is working - I'm ready to try it myself. Does the unit come with the 24V transformer, or did you buy/have one already on hand?

 

[chuck172]

It doesn't come with the transformer, I ordered one, but temporarily used existing 24vac.
Get the controller, you won't be sorry.

 

[Jackpine Savage]

Chuck, thanks for sharing. I'm thinking that this is what I will use on my install as well.

 

[NHFarmer]

Chuck,It you don't mind me asking,how much did the controller run and where did you purchase it.That sounds like something that would be worth the money

 

[chuck172]

Designheating.com has it for 141.83
shipping was about 10.00
That's the best price I could find. Pexsupply has the controller for 149.00 and would match a lower price, but I don't really want to deal with them anymore if possible.
I called designheating.com to verify if they had it in stock and it came in two days.
I think it's definitely worth it.

 

[DenaliChuck]

Thanks for the update Chuck! I've got a 157 to install which does the same thing but controls a variable speed pump at varying speeds depending on the temp diff. Glad to know these work, and also where you installed your sensors.

 

[Rickard]

I just installed my Tekmar 157 and I am finding it lacking the options for the task. I am used to process controllers like Watlow that can do almost anything imaginable. The Tekmar seems to leave a lot to be desired. It seems to only control very specific processes and allows very little variation. For example I had to reverse the storage/source because it won't let me program for a negative differential. So many functions will let me turn a pump on only: or some off only. There are no on/off choices, which I really need. It looks like it might work well for solar heat but the manual says it is also for wood heat. I'm hoping that there is a secret I haven't discovered or that I am just missing something. It is especially frustrating because it is an expensive controller.

How is it working for you DenaliChuck?

Dean

 

[DenaliChuck]

Mine is on the shelf pending boiler install that's been postponed to Feb. All I want the 157 to do is run the pump at a speed that corresponds to the temp diff (higher diff, faster speed) and the turn the pump off when the diff set point is reached.

What doyou want it to do Dean?

 

[WoodNotOil]

For what it is worth, my homebrew version of it is coming along nicely. I just have to place the sensors and wire in the relay. All of the components are working in my test phase. I should have it running the pump by the end of the weekend. I have started documenting it on my web page here (broken link removed to http://woodnotoil.googlepages.com/arduino) . The nice thing about making one is it is very flexible in how you use it. All I have to do is change the formula in the simple code to make it do something else and I can add more sensors later too.

 

[Rickard]

Originally I wanted the 157 to run the charge pump and discharge pump. On startup, discharge pump is on and charge pump is off. When delta T approaches 0 from negative #s then pumps switch.

On cooldown, charge pump is on and discharge is off. When delta T approaches 0 from positive #s then pumps switch.

It seems that it would be very easy to program this controller to do this as it already has two inputs and two outputs. But the 157 has no functions for negative #s and pump 2 doesn't have any delta T fucntions.

I thought I could make use of the 2nd output by making my oil boiler turn on when the storage gets below a certain temp. But because the storage and source need to be reversed I need the "source" (actual storage ) to turn ON the 2nd output (pump 2), which would trigger a relay for me, when the temp goes down to this level. The 157 will only turn OFF a the 2nd output (pump 2) for this situation. It is frustratingly close but no cigar on so many points.

I have it now running only the discharge pump which engages when delta T gets to 2 degrees. This seems to be the best it can do.

It appears to do at least some of what I would need for my future solar heat so I will keep it.

It seems that it was designed only for very specific purposes and unfortunately I am not a one size fits all guy.

Anyone play around with 2 input/2 output PIDs?

Dean

 

[steam man]

Originally I wanted the 157 to run the charge pump and discharge pump. On startup, discharge pump is on and charge pump is off. When delta T approaches 0 from negative #s then pumps switch.

On cooldown, charge pump is on and discharge is off. When delta T approaches 0 from positive #s then pumps switch.

It seems that it would be very easy to program this controller to do this as it already has two inputs and two outputs. But the 157 has no functions for negative #s and pump 2 doesn't have any delta T fucntions.

I thought I could make use of the 2nd output by making my oil boiler turn on when the storage gets below a certain temp. But because the storage and source need to be reversed I need the "source" (actual storage ) to turn ON the 2nd output (pump 2), which would trigger a relay for me, when the temp goes down to this level. The 157 will only turn OFF a the 2nd output (pump 2) for this situation. It is frustratingly close but no cigar on so many points.

I have it now running only the discharge pump which engages when delta T gets to 2 degrees. This seems to be the best it can do.

It appears to do at least some of what I would need for my future solar heat so I will keep it.

It seems that it was designed only for very specific purposes and unfortunately I am not a one size fits all guy.

Anyone play around with 2 input/2 output PIDs?

Dean

Dean, remind me of this when you call. I am a little confused on what you want to accomplish but think I may have a scheme that will do what you want to do.

Mike

 

[WoodNotOil]

Originally I wanted the 157 to run the charge pump and discharge pump. On startup, discharge pump is on and charge pump is off. When delta T approaches 0 from negative #s then pumps switch.

On cooldown, charge pump is on and discharge is off. When delta T approaches 0 from positive #s then pumps switch.

It seems that it would be very easy to program this controller to do this as it already has two inputs and two outputs. But the 157 has no functions for negative #s and pump 2 doesn't have any delta T fucntions.

I thought I could make use of the 2nd output by making my oil boiler turn on when the storage gets below a certain temp. But because the storage and source need to be reversed I need the "source" (actual storage ) to turn ON the 2nd output (pump 2), which would trigger a relay for me, when the temp goes down to this level. The 157 will only turn OFF a the 2nd output (pump 2) for this situation. It is frustratingly close but no cigar on so many points.

I have it now running only the discharge pump which engages when delta T gets to 2 degrees. This seems to be the best it can do.

It appears to do at least some of what I would need for my future solar heat so I will keep it.

It seems that it was designed only for very specific purposes and unfortunately I am not a one size fits all guy.

Anyone play around with 2 input/2 output PIDs?

Dean

It may work for you to put the charge and discharge pumps on a DPDT relay and have the Tekmar charge the coil. That way one pump is on until the differential is met and then the the coil would be charged and the other pump would come on instead. Not sure if I fully understand what you want but I think by adding a few relays in you could get what you want in the end.

 

[Rickard]

After overthinking and overwiring I finally settled on simple with a triggered normally closed relay on the wood boiler and charge circulators and it is working great. Thanks Woodnotoil and Mike.


There are still a few things that I would have liked to see the Tekmar 157 do that it is not able to do.
One is for the functions of the 'storage' and 'source' to be switchable. It is annoying to have to see my storage tanks called source and my wood boiler called storage.

I would also like to have seen the 2nd output have some kind of delta T functions. This seems like a large oversight.

Also temperature reading on both sensors reads 6 degrees F below the actual temp. I've tried different wires and thermal paste to help correct but the best I could get is within 6 F. I am using a watlow PID and a laser thermometer as well as the temp reading on my wood boiler as the standards (they are all within one degree of each other). Because both sensors misread the same, the system works but it is still annoying.

Dean

 

[WoodNotOil]

One is for the functions of the 'storage' and 'source' to be switchable. It is annoying to have to see my storage tanks called source and my wood boiler called storage.

How about masking tape and a Sharpy? ;-)

Also temperature reading on both sensors reads 6 degrees F below the actual temp. I've tried different wires and thermal paste to help correct but the best I could get is within 6 F. I am using a watlow PID and a laser thermometer as well as the temp reading on my wood boiler as the standards (they are all within one degree of each other). Because both sensors misread the same, the system works but it is still annoying.

I have found that even the DS18S20 sensors I am using are reading about 5* low when used as a strap on. I have it foil wrapped several times and well insulated. The sensor I have in a well however reads right on. I wrote a +5* correction into my software to compensate. It would be nice if they offered you some sort of calibration method for accuracy on the Tekmar.

 

[Rickard]

Unfortunately the masking tape approach won't work because it is a digital readout but I've never been shy about messing up the pretty silk screen with my labels.

Dean