Tekmar 156 for Domestic hot water controls?

[Piker]

Is anyone using a tekmar 156 difference setpoint control to manage their domestic hot water tank? I will be using a sidearm heater and a circulator on the domestic side and a load circ with a zone valve on the boiler side. Should be able to use the tekmar to control the zone valve, the load circulator, and the domestic circ depending on water temp in the tank. Might have to add a relay or two.

Where do you think the best place to put the sensors would be? It would be nice if hot water tanks had aquastat wells built right into them.

Normally I would just run all the water from the primary loop through the sidearm... but with thermal storage, I want to move water through the system only when necessary to aid in stratification in the tanks... thus the DHW is tied in as a zone.

cheers

 

[stee6043]

When I install my sidearm next year I plan to simply run one of my heat loads through the sidearm "on its way" to the load. I decided it's not worth the cost or the extra plumbing to have a seperate loop just for the DHW. But if money is no object, have at it!

 

[Piker]

Hey, it's only money... they'll just print more if we run out right?

I have my doubts as to whether we would have enough hot water plumbing the DHW "on it's way" ( i like that) to a zone... especially through a sidearm. A plate exchanger might be different, but our water is pretty hard, so I don't want to go that route. Like I said, if it were a system without thermal storage, I would have just put the sidearm in the main loop and called it good.

I have never actually used a tekmar control before... not sure if I have my head totally wrapped around how I would use it.

 

[Piker]

Just thinking... since the tekmar only measures 1 source temperature, this probably won't work how I had envisioned.

ahh well..

cheers

 

[DaveBP]

In case you haven't run into this yet. Tekmar has a library of pdf's on their differents products.

http://www.tekmarcontrols.com/literature.html

I find the application and data sheets doa good job of explaining how they work and various ways to install and use them.

 

[Sting]

I also have my doubts that I piped my DHW make up correctly -- I circulate to all the sinks in the house via the hot supply pipes - return to the boiler via a third "bypass" loop - and send that renewed energized DHW back to the bottom of the 50 gallon NG storage tank. Pumping is controled with a Honeywell strap on aquastat on teh supply pipe - wired to open on temperature rise of 125 - so I never send over temp water out to the load.

Typical use - this is wonderful - I have almost instant 125 degree hot water at the tap and for the most part I have enough of it. Yet under hi or long demand - the storage stratification is lost by the extra pumping and the incursion of the cold street water. I have noted that I have 140 degree water returning from the boiler to the bottom of the storage tank - yet only 95 degree water leaving for the load???

It might be nice if I could divert some of that boiler production to the load supply and keep the tap temp up to code under hi demand -- but at what cost and with what equipment, and how so DHW does not exceed safe code temp?

 

[Piker]

In case you haven't run into this yet. Tekmar has a library of pdf's on their differents products.

http://www.tekmarcontrols.com/literature.html

I find the application and data sheets doa good job of explaining how they work and various ways to install and use them.

Yeah, I have been staring at those for a couple hours now. There really isn't anything taylor made to do exactly what I want to do... but that's ok... I am probably overthinking this.

probably just a close on rise aquastat on the zone somewhere to run the DHW circulator should work well enough. As long as the DHW circulator has a check valve, there shouldn't be a problem preventing the electric tank from thermal syphoning heat back into the boiler if the boiler or the storage gets cold.

Now I just need to figure out the best way to check the temp in the hot water tank... it would be nice if I could tap into the existing thermostat somehow... not sure if I have enough of a knowledge of electronics to do that or not.


cheers