tekmar 557 with IBC Boiler

jmiller57

We have a zoned radiant floor system driven by an IBC SL boiler with Tekmar thermostats. The thermostats are all wired using Tekmar 313 wiring centers, which activate the boiler when there is a call for heat. Zone control is handled by thermal actuators on distribution manifolds.

We also have a Mitsubishi heat pump for cooling in the summer and a whole house humidifier.

It seems like the Tekmar 557 should work well for this application as it covers the two stages of cooling that the Mitsubishi third party thermostat interface provides and can control the humidifier.

If we wire up the 557 to the 313 wiring center the only option for the W terminal unit is OTHR and with this set there is no way to configure it to activate the W thermal motor. Instructions say you need a Tekmar System Control connected, but that seems redundant with the controller in the boiler.

With the tekmar 554 thermostat, you can set the W Terminal Unit to OTHR and it still provides the W Thermal Motor configuration option since it is wired to a wiring center.

Anybody run into this sort of problem and is there a reasonable workaround?

Seems like Tekmar is going out of their way to handicap the 557 in this regard relative to the 554 which is odd.

109A_5

Seems you would just connect the AC and/or the humidifier directly to the 557. It seems the 313 and the House Control 400 have no provision for AC and/or humidification. So far I'm not sure if there is any other add on accessories to provide network control of AC and/or humidification.

jmiller57

In the current setup, we don't have a house control module. The IBC Boiler has its own integrated control that handles that functionality.

We have 10x Tekmar thermostats connected to 3x 313 wiring centers. The end switch of the wiring centers are wired up to activate the boiler's reset heating zone.

If we swap out one of our existing 532 thermostats for a 557, we can wire the 557 up to the other equipment just fine as you have in the diagram you show. The problem is that when it calls for heat, the zone valves for that thermostat's zone aren't activated. The boiler turns on but the zone actuators do not.

There are configuration options for the 557 to enable activating thermal motors but those aren't available if it is connected to a 313. Other thermostat models, such as the 554, have those options enabled if they are just connected to a 313.

Just seems like an odd limitation to impose on the 557 for this particular use case, so I am curious if there was something I am missing.

109A_5

I suspect you need the House Control unit to do what you want to do and the zone(s) controlled by the 557 would have to be moved to it. This is just a guess. Some of the documentation seems a bit vague to me. I suspect there is some incompatibility (intentional or not) between the tN2 and the tN4 network command structure or the hardware compatibility. Also seems to me AC and/or humidification control was an after thought to their equipment product line.

If possible I would run your situation by Tekmar Tech support before I spent any money.

And yes there does seem to be control or feature overlap or redundancy between some boilers an aftermarket control equipment.