Gotta get wired with storage for 2nd year.

[MrEd]

Brief recap, installed the tarm last year w/out storage using pretty much the "simplified pressure system" layout, (though my oil boiler is actually powered off with no plans to use). Ran mostly in "manual" mode where I switched on circs as needed and shut them off when not...this year everything is getting wired up (by me), including my storage tank. Was good to get a real "feel" for the demands of the heat etc, but don't want to continue to run this way forever.

Tank is in place, mostly plumbed and now need to complete the wiring and control aspect of my system...
What I am thinking is that whenever the boiler is running, and the temp gets above 140 (or so), the circ on the back of the back of the tarm should run. If any of my 6 zones are calling for heat, my secondary circ will also be running. As soon as all the zones are satisfied, circ 2 shuts off, and water automatically directs to the storage tank.

Question comes to mind is how do I get my circ to come on at 140 , but only run as long as the fire is burning? With all the excess heat redirect to the tank, if I wait for the 140 to get passed on the way down, it'll mean I just sucked out all the heat from my tank.. Is there any alternative to a timer? I'd like to avoid as many manual operations as possible...I remember this coming up before, but didn't pay attention to the answer at the time...

BTW: Is the L4006B the right aquastat to use to turn the circ on at above 140 and off below 140? I have one of those, a L4006B, L4006A and 3-4 other used ones that I could potentially use.

 

[chuck172]

Look at the Tekmar 156 Ed.
http://www.tekmarcontrols.com/prod/156.shtml

 

[hayrack]

A simple aquastat will start your circ pump at 140 or whatever temp you want to set it at. You can set the differential on the aquastat so it shuts off when temperature drops.

If you ran through your supply manifold on the way to your tank your zones would be satisfied and tank charged at the same time.

 

[MrEd]

Look at the Tekmar 156 Ed. http://www.tekmarcontrols.com/prod/156.shtml

Is that what you used to solve the problem? or are you plumbed differently than me?

 

[chuck172]

That is what I used, works great.

 

[MrEd]

That is what I used, works great.

Trying to understand how it works…what I *think* I need to happen is to have the circ pump heat into the tank as long as I am actually generating heat in the tarm, I could envision that if the tank is upto 180 and my fire is burning out, that it will continue to circulate hotwater thru the tarm(now with the fire out), and the circ would stay running because I am actually taking heat out of the tank and keeping the tarm over 140 by using the tank's heat and it will continue until the temp of the entire 550 gallons drop below 140…how does the techmar avoid that scenario?

 

[chuck172]

The tekmar has two sensors, one for the tarm boiler temp and the other for the storage tank. The control turns on the tarm circ. at lets say 160*, as long as the tank temp. is below the boiler temp., the circ. will run. When the tank heats up to the boiler temp, the circ. shuts off.
Thats a very simple explanation of what it does.

 

[RobC]

Does the Tekmar have 2 differential set points ? For example = Set pump ON at +8 degrees Dif and pump OFF at -4 degrees Dif. The colder water coming back from the tanks will drop the Tarm temp quickly with no fire.
Have you adjusted the low fan limit switch inside the cover behind control panel ? There are some subtle set up changes in the stove when using storage. Alternate Instructions.....
A second Tekmar would also work well to turn on your oil boiler automatically if there was no heat from storage.

 

[kabbott]

Couple ways to do it
#1 TIMER (YUCKKKKK)
#2 differential controller. This is what the tekmar chuck172 is I believe. prolly the easiest.
#3 something geeky like the nofossil control system. ultimate in control but a bit of a learning curve.

You are correct in your assumption that it will drain heat from your storage with just a setpoint control.

 

[jebatty]

Question comes to mind is how do I get my circ to come on at 140 , but only run as long as the fire is burning? With all the excess heat redirect to the tank, if I wait for the 140 to get passed on the way down, it’ll mean I just sucked out all the heat from my tank

Some more thoughts. When you say you want the circ to come on at 140, what are you using for boiler return water protection? Do you have the Termovar or similar? Generally, you want return water protection of 140, certainly as a minimum, although something higher (150-160) may be preferable. If you do have the Termovar, it may act to substantially limit any circulation to the system at 140. In my system, with the boiler circ on, there is virtually no circulation to the system until boiler output is 150+, assuring return water protection of approximately 150 (although may be lower if return water is very low temp).

As to having the boiler circ run only when there is boiler heat, there is an option with the Tarm involving the low limit control and wiring. This is the control and probe inserted into the firebox well. It shuts the draft fan down when firebox temperature reaches the low limit (Tarm recommends 60C without storage and 90C with storage). Using 90C (194F) as an example, when the firebox cools to 90C, the low limit control turns the draft fan off. You can wire the low limit so as not only to shut off the drat fan, but also to shut off the boiler circ. I did this on my Tarm, using the low limit wiring to power the coil on a relay, and then wiring the circ (actually, a couple of circ) to the contacts so that the circ system is "on" when the Tarm is "on," but when the low limit shuts down the Tarm, the boiler circ also is shut down. Thus, the circ runs only when there is boiler heat.

As to how to do this, a post on this forum many moons ago provided the info. This is what I did, based on that post.

I wired a 110vac relay coil in series from lug #11 on the Tarm Strip, to the aquastat that controls the circulator. I played with the settings and found 90* works well enough. I don’t have the problem of my storage tank discharging back into the boiler anymore. The low limit shuts off the circ as the fire dies out.

 

[MrEd]

Actually, 140 was just an arbitrary number, and you are right 150-160 would be better. I do have a termovar and it works fine. I'll need to dig somemore into that lug#11 solution, don't remember seeing that - is the procedure better documented someplace? i.e. part numbers and a wiring diagram so I don't have to reinvent the wheel? Love to gets this aspect wrapped up in the next couple days.

 

[jebatty]

Your Tarm manual has the wiring diagram -- not much to it though. You might call it an "off-label" use. I used the relay to ensure that the Tarm circuitry could not be overloaded, and leave an option to hook more up to it, if desired. I used a SPDT relay.

 

[MrEd]

Anyone knows what the original intent of the pump switch and wires 8-13 were for on the panel? Seems odd they would build them in and then scratch them out of the manual...did they not work as advertised? or did they find a better solution.