Tekmar 256 Honeywell L8148E Circulator

I added a Tekmar 256 to my Crown Boiler, currently controlled by a Honeywell L8148E Aquastat but am having trouble understanding how the outdoor control is wired in to the L8148E. I have it wired as instructed and it turns the burner on according to a call from the thermostat. However, when the temperature of the furnace reaches that required by the tekmar, it shuts down the burner and that shuts down the circulator. How do I bypass the aquastat to keep the circulator running when the burner cuts out until the upstairs thermostat is satisfied?

 

The tekmar 256 should be wired in the burner circuit that has all the safeties in a series circuit, that way the call for heat is not broken shutting down circ. This would be similar to splicing in a low water cutoff or high temp limit.

 

Break B1 through terminals 5&6. They are rated up to 240v.

 

What if I bypass the aquastat to run the circulator? I'm considering just putting in an on/off switch and letting the circulator run constantly through the entire heating season.

 

You would have to be really close on your reset curve and you would use more electric for constant run pump. Oh-oh I'm starting to sound like others worried about pump electric but in this case it makes sense. Your comfort is already increased dramatically with ODR no need to run the pump constantly. If we think back to the days of constant running pumps you had one zone, the thermostat only operated the fire and the fuel savings was about 20 - 25%. This was before ODR. My OPINION is I would not run the pump continuously especially if you have more than one zone.

 

I have only one zone, so I'll give it a try this year and see how it affects my electric usage. The electric company has the monthly differential on each bill, last year vs. this year. If that proves to be more expensive I guess that I'll go to a fall back position and get a switching relay. Thanx for the info.

 

Jag, you don't need another relay... read back to rbeck's post where he said to use the relay contacts in the 256 to control ONLY the burner. ZL said essentially the same thing.

B1 is the hot wire to the burner.

I just looked at the drawings and specs... the relay in the 256 is rated for 5 Amps... I don't think the burner draws that much, but it might exceed that on start-up, momentarily. Maybe not enough to damage the relay contacts, but worth considering. Maybe another relay is not such a bad idea?

 

NJT, I just finished wiring an on/off switch into the system and it seems to work just fine. It may even save me some more money hooked up this way because I have an inline space heater hooked up in my shop. It used to run constantly whenever there was a call for heat. Now, I have installed a separate on off switch in the line for the circulator, so I can turn the heater fan on only when I'm in the shop. We'll see how well this all works out this winter. It's a lot less expensive than putting in a new relay.

 

What is the main circ motor ?
There are timers that will shut the motor off after "x" minutes of post purge.

This would be the idea situation.
Be very aware of what running a 1/3 HP motor 24/7 will cost you.

The capital cost of a relay will be WAY less.

 

A RIB relay is $12-$15 but you won't need it. the burner is using about 2.5 amps. Just wire like suggested above. Wire the circulator to the C1 & C2 so it cycles with the boiler.

 

It was attached to C1 & C2. The tekmar reached its cutoff after only two minutes, which also cut off the circulator and the hot water never even left the basement. I needed the circulator to run long enough to allow the heated water to leave the immediate area of the furnace. Without that happening, the living space never received any heated water from the furnace. Normally, the circulator runs almost all of the time in the winter, so putting in constant run ability through my switch is no big deal.

 

The whole problem is this not the proper control for your needs. How many zones do you have? Do you have a multi-zone relay? As long as there is a demand on T&T the pump will continue to run until the call for heat ends.
Wire the thermostat (If you have only 1) to T & T on aquastat to start the pump and maybe the burner if the boiler temp is down.
Break B1 through terminal 5 & 6 on Tekmar. Wire a 24v transformer to Tekmar terminals 8 & 9. Do not use Tekmar terminal 7.
Before you do this check the amp rating on your burner motor and let us know. If this is a Beckett AFG the amp rating is higher than some of the others. If it is a Beckett AFG you will need a relay for the burner motor.

 

Re: "The whole problem is this not the proper control for your needs."

 

I would have wired as stated and installed a thermostat with a heat/off subbase so everything was automatic and the circulator would have operated with the control as designed.

 

I already have a double setback thermostat in the living area of my home. It was the aquastat that was causing my problem with premature circulator cutoff.

 

I have a similar situation. I also just installed a Tekmar 256, but connected to a Honeywell L8124A controller, also a 3-stage Aquastat as jag's, running a Peerless boiler that is only used for heating, not DHW. I have three zones. I noticed the same thing, the circulator now only runs when the boiler is firing, and hot water never makes the full trip back to the boiler before it cuts out. I contacted the distributor, who suggested disconnecting and capping the lo limit control (red wire). I tried that and it didn't do the trick.

Looking at rbeck's post about breaking B1, I checked the current rating on the burner plus igniter, and it totals over 7 amps, which I don't think the Tekmar was designed for, so I would need a relay.

My real questions are, assuming I do not break B1, what exactly is the effect of removing the red wire from the lo limit control, and what should the hi and lo (if I reconnect it) settings be with respect to the Tekmar settings? Thanks.

 

I wired an on/off switch into the system and it seems to work just fine. It used to run constantly whenever there was a call for heat. Now, I have installed a separate on off switch in the line for the circulator, so I can turn it off after the heating season. So far. it has worked just fine. We'll see how well this all works out this winter. It's a lot less expensive than putting in a new relay.