Help with unoc timer for tekmar 256

albandjann1725849

Hi

Yeah, I see what he is doing now... It wasn't to clear on this end how he was going to hook it up on quick read of the first post. Actually that's a pretty cheap and elegant work-around for the 031 or 032 timer.

mike yozell

Help with unoc timer for tekmar 256

Folks,
I've just installed a tekmar 256 on a basic boiler set up with trv's . the system works great and the wife is well pleased. My question is, Can I temporarily use a normal setback type thermostat as a substitute for the tekmar 032 timer? I've ordered the tekmar timer but it will be a few days till it gets here. I assume that if i use a regular thermostat I would set it as a "call for heat" to start the unoccupied time period.
Anybody ever done this?

thank you
mike

The Wire Nut

Glad to make Contact...

Mike,

Any type of "dry" (non-powered) contact will work. You can use a t-stat, a light switch, or just a jumper wire. Just make sure you wire it to terminals 3 and 4 as if it was the timer contacts.

Come to think of it, you could use a programmable t-stat and set the temperature up high for the onocc period.

In either case just make sure that the t-stat is setup to provide a "dry" contact. This usually requires removing a jumper from between the R and Rh terminals. The Rh and W then go to the onoc terminals on the 256.

Alex

mike yozell

thank you Alex,
By ¨set back type I meant programmable. Your answer confirmed what i thought.

albandjann1725849

unoccupied building

I'm not sure how you are doing this? A setback thermostat doesn't do the same thing as the unoccupied input on the Tekmar. The unoccupied input recalculates a lower setting on the Tekmar's operating curve for the target temperature for the boiler. If you're using the setback thermometer to lower the thermostat setting, it won't be as efficient as the timer, IMO.

Pete

JohnNY

Actually,

It's not a matter of opinion. It's a matter of closing terminals and energizing a circuit.

The Tekmar clock is nothing more than a set of terminals being opened and closed by the hour of day.

A programmable thermostat will do the same thing while incorporating a room temperature activated switch into the circuit.

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albandjann1725849

how do you??

Hi John

I'm still a bit confused on how this is done.

How do you separate the clock contacts from the thermostat contacts?

?

Or, am I reading too much into the post?? Is he using a regular stat for the room temperature, and a SECOND programmable stat for the unoccupied timer contacts?

Pete

The Wire Nut

He's not trying to use the thermostat to control the tekmar, but rather to use the t-stat to switch the unit into unoccupied mode.

Think of it this way. A thermostat, stripped to its basic function, is a switch. When the temperature is above the preset, the switch opens, when it's below, the switch closes (eg:to start the boiler).

If you strip a set-back or programmable t-stat to it's basic functionality, it's a timer that changes the thermostat settings at selected times. For example at 7 am the timer sets the t-stat 70, at 9 am to 65, then at 4:30 to 68 and at 9 pm to 63. So, at 7 am, if the ambient temperature is below 70, the contacts will close, at 9 am they'll surely open as the temp will be at or above 70, at 4:30 they'll close again and at 9 pm they open (until the temp falls below 63).

In Mike's case, the tekmar is what regulates the interior temperature by using outdoor reset and the boiler temperature.

We use the set-back t-stat as follows. At your desired unoccupied time, say 9 am, set the t-stat to a really high temperature, say 100 deg. At the desired occupied time, say 5 pm, set the t-stat to some really low temperature, say 50 deg.

So, at 9 am the t-stat closes it's contacts as the room temp will surly be below 100 deg. The tekmar doesn't know or care that the contacts are on a t-stat, it's just a set of contacts. At 5pm the t-stat switches to 50 deg and since the room is certainly above that temperature, the contacts open and the tekmar goes into occupied mode.

Hope that adds clarity rather than confusion...