Need help with Tekmar 260 and Taco SR 503 wiring to boiler

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  #1  
Old 02-04-12, 01:08 PM
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Need help with Tekmar 260 and Taco SR 503 wiring to boiler

I have a Slant Fin Euctectic EC-14 currently running off of a Taco SR 503 with DHW priority. I just picked up a cheap Tekmar 260 boiler control to run the boiler off outdoor reset to hopefully save some fuel costs. I've seen a diagram of this set up with a ZV404 on this site, but can't figure out where all of the wires go with the SR503. I assume that the thermostat wires and DHW indirect thermostat still go to the SR503 and then the X1 & X2 wires to the Tekmar 1 & 2 slots. Then the Tekmar 11 & 12 to the boiler aquastat. Hopefully this is correct, but I am confused about how to wire the DHW priority from the indirect aquastat to the Tekmar or Taco units and in which order. Please help with an explanation or diagram.
 
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Old 02-04-12, 07:30 PM
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I moved you to the boiler section.
 
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Old 02-05-12, 04:46 AM
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If you only have 1 zone other than DHW it would make more sense to wire everything to the tekmar.



If you have multiple heating zones and 1 DHW I would wire it this way.

 

Last edited by hvactechfw; 02-05-12 at 05:32 AM.
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Old 02-05-12, 05:32 AM
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I have 2 heating zones and 1 DHW zone, each with its own circulator coming off the supply header from boiler. Each circulator is activated by the SR503. The aquastat on the boiler is an L7248 if that matters. The thermostats are not 24 volts but honeywell from hardware store. Thank you in advance for your help.
 
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Old 02-05-12, 05:34 AM
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sorry, you just got in before I had changed my previous question. Please see attached diagrams.
 
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Old 02-05-12, 06:13 AM
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Thank You Very Much. Great diagrams. They will also be useful to others. A few questions though.

1) Can I steal the 24v power from the open terminals on the SR503 instead of a new transformer ?

2) I don't think there is a boiler pump inside the Slant Fin Eutectic boiler and I don't see one on the header (just a circulator for each zone attached to the supply header) so I assume I just leave the terminal for the boiler pump on the Tekmar 260 control alone/ empty.

3) It looks as though the DHW circulator runs directly off the Tekmar. Do I disconnect the aquastat wire going to the Zone 1 thermostat connection on the SR503 and disconnect the circulator for the DHW from the SR503 ? And leave the regular heat zone circulators and thermostats connected to the SR503 ?
 
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Old 02-05-12, 06:32 AM
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ahh, yes, there is no circ pump for the boiler, just the zones. I forgot to remove that from the diagram, so yes dont hook anything up there.

If that is a 24V output on the top left of the taco relay then, yes, you can grab it from there, but I think that is an input. I could be wrong though.

The DHW aquastat gets removed from the SR503 and is A1 on the diagram. Wire the DHW pump (P2) as the diagram states as well. Yes, the heat zone pumps and stats stay connected to the SR503
 
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Old 02-05-12, 08:45 AM
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From what I've seen, the older SR (and ZVC) panels did not all have the 24VAC power terminals available. Those are 24VAC outputs and can be used to provide the needed 24VAC.

All of the Tekmar diagrams show "A2" on their indirect wiring, but I don't recall ever seeing an indirect with an auxiliary 'high limit' aquastat such as that. Every one I've seen has the pump wired direct.

Thanks for the diagram hvac!
 
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Old 02-05-12, 09:00 AM
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no problem. My company does A LOT of large boiler work and controls. The diagram was simply modified slightly from the manufacturers. Tekmar's diagram actually had that aux high limit in their diagram.

I leave the boiler threads to you other Pro's most of the time, but I could not resist on this one.
 
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Old 02-05-12, 09:29 AM
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I'm glad ya couldn't resist! saved me some work! Please feel free anytime!

I don't know why Tek includes that on all the drawings? Perhaps some localities require that extra limit? Dunno... cuz it doesn't really make sense to me... I mean, what if the A1 a'stat DOES fail closed? by opening the pump line, sure, yer gonna stop the pump and the tank won't overheat, but why not stop the whole deal? Why not put that extra high limit in series with the operating control and stop the boiler firing also?

OR--- maybe it's intent is to prevent the pump from running if the pump relay contacts in the 260 happen to weld? In that case, the DHW pump would run 24/7 and very likely overheat the tank...

Sometimes it's difficult to second guess Engineers!
 
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Old 02-05-12, 09:38 AM
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I quit trying to figure out why engineers do what they do.
 
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Old 02-05-12, 11:57 AM
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Old 02-17-12, 02:05 PM
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I wired it as you all said and it seems to work properly. Two questions:

1) The jumper on the SR503 between P & ZC was previously removed to make Zone 1 the DHW priority zone. Should a jumper be re-inserted between the two terminals as shown in your provided diagram, or does it matter at all since the Tekmar 260 is now controlling the DHW priority and pump function ?

2) Is there a way to adjust the DHW target of 180 on the Tekmar to 160-170 , or is it a constant ?

Thanks for all your help. I like to know how this all works so I can fix it a 2am if ever necessary.
 
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Old 02-17-12, 02:36 PM
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There are some Tekmar controls that have adjustable setpoint temps.
AFAIK, sadly, the 260 is not one of them.

Peter
 
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Old 02-17-12, 03:46 PM
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Should a jumper be re-inserted between the two terminals as shown in your provided diagram, or does it matter at all since the Tekmar 260 is now controlling the DHW priority and pump function ?
It might not matter. If your DHW was on 'channel 1' and you removed it over to the 260, and channel 1 on the 503 is now open, then there will be no priority calls anyway.

So, it might not be necessary, but it won't hurt either.

You understand the "BOIL MIN" setting on the 260, right? You are aware that setting can't be set so low as to allow the boiler to run too cool... yes?
 
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Old 02-17-12, 04:19 PM
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I have the 260 set to radiator mode which says it goes from 140 to 160 degrees. Is there another setting that i should adjust for the minimum ?
 
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Old 02-17-12, 05:13 PM
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No... that's fine. But I just thought of something...

Doesn't your boiler have a built-in Tekmar controller? or was that an option that didn't come with your boiler?

You can probably drop the BOIL MIN to 130 or so.

Are your radiators all fin tube baseboard?
 
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Old 02-17-12, 05:22 PM
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This is the manual for the optional Tekmar control for your boiler. You could look through this and maybe get some tips on your settings:

http://www.slantfin.com/images/stori...0_sf_10_40.pdf
 
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Old 02-17-12, 06:36 PM
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I have cast iron radiators on my floor and fin tube baseboards in the small apartment above. Would you recommend setting the control for one vs. the other and why ? I have it set for cast iron now
 
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Old 02-18-12, 09:07 AM
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Hmmm... that's a tough call.

It's never a good idea to mix radiation types because 'imbalances' can occur. This is due to the way that each of the types emit their heat.

If they are in separate zones, on different floors, and each has a thermostat, you may be OK though. The worst situation is when they are mixed within the same zone.

I would use the settings recommended in the Slant-Fin brochure as a starting point.
 
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