Taco wiring diagrams??

Joe Mattiello

Glenn H

SR-501-2

Take a look at the attachment which shows 2 diagrams with the same date(June 2006). The one on the left came from inside the Sr-501-2 relay I just installed. The one on the right is one I downloaded from Taco's website. See the difference? Left one has ZR(starting the boiler) being fed by jumper from H. Right one has ZR being fed by ZC from the boiler.

What do you think happens when you try to start a burner motor thru a 5 amp fuse as is the case with the left diagram?

Taco obviously found the problem since they changed their diagram but why continue to send out the incorrect diagrams with their relays. addendums? service bulletins??

Is this another case of the bean counters winning?

Unknown

I see your point,

no pun intended but I think someone was asleep at the switch. Sure would tick me off!

Dave

Joe Mattiello

SR501

You’re correct the SR501 was recently modified, adding a 5 amp fuse to fuse protect the board. The reason we fuse protected the board was to eliminate the possibility of any detriment to the board if the amp draw exceeded the maximum rated amps. Both drawings could possibly cause the fuse to blow when firing the burner directly through the ZR terminal. There was an oversight by engineering when adding the fuses, and because of your vigilance, engineering is revisiting this. Thank you for your support.

Joe Mattiello

safty notice

I thought this document that dates back to 12-08-05 would help explain why the wiring diagram was changed in the first place. No need to rewrite it;

We have issued a clarification on wiring diagrams contained in the product instruction sheets for the single and multi-zone Switching Relays when used with oil-fired boilers.

The clarification concerns technician safety when using switching relay controls (not just Taco's) in conjunction with an oil-fired boiler with a tankless coil. A potential safety hazard exists if two separate sources of power are connected to an oil boiler's aquastat control. When servicing the boiler a technician may think that he has shut off all power to the boiler at the service switch, when in fact a secondary source of power may be wired directly to the aquastat through the Switching Relay. Under this scenario, if a zone calls for heat, sending power from the switching relay directly to the boiler, the technician could be injured.

This potential hazard only exists on oil-fired boilers with a tankless coil because they require a line voltage demand signal to turn-on.

Whenever servicing an oil boiler, technicians should always check for two power sources by determining (1) if power from the circuit breaker is wired directly to the Switching Relay and (2) determining if line voltage supplied by the Switching Relay is wired directly to the boiler Aquastat.

Taco has changed its wiring diagrams and added warnings on its instruction sheets to alert technicians to this potential hazard. The warning will read:

"Warning: Wiring instructions must be followed so power originates from the boiler aquastat. Failure to follow these wiring instructions may result in a secondary source of power being connected to the boiler that may activate it under certain circumstances, causing injury or death."


What You Need to Do:
Order the Safety Notice (copy attached) from prisho@taco-hvac.com. It needs to be distributed to all wholesalers and posted at or near their trade counters. For those wholesalers who have customers that service or install oil-fired boilers, the Safety Notice is available in larger quantities for use as bill stuffers or a direct mail piece.


Remember, this is a safety notice published as an industry service by Taco. The dual power source wiring could happen with any style control by any manufacturer. A version of this Safety notice will also appear in some popular industry magazines as an industry education notice.

We are also offering free updated Zone Control Wiring Guides by logging onto www.taco-hvac.com/wiring. Besides the updated instructions as noted above the new wiring guide will also include select Radiant Mixing Block, X-Pump Block, iSeries Mixing Valves, and Electric Water feeder wiring schematics.

Glenn H

Thanks Joe
In the case you mentioned I have already put a double pole switch in for the burner service switch and switched the power to the boiler *and* the line to the burner from a secondary source.

You make some great products but if you cant increase the rating of the relay to handle the burner motor I'm afraid I have to go back to honeywells r845a relay.

Joe Mattiello

You're welcome; Give us an opportunity to look at this more closely and make the neccessary corrections. Thanks for the plug on great products!! Taco products are great because we're in touch with our customers, and listen when you're talking.