Viessmann 222-F boiler Tstat wiring Question

NNYSportsman

Hi, I have a Viessmann 222-F Model B2TB 125 Boiler that I had installed in April 2020. It's been a great boiler with no issues. I currently have two circulating pumps, each for an in-floor radiant heat zone and they each have their own thermostat and these are working fine. I recently purchased the AM1 extension module, since I want to add two more circulating pumps for two new in floor radiant heat zones that I want to add.

The manual pages shown below indicate the AM1 would allow two more pumps to be added.

My question is, does anyone know where I can connect two new thermostats, since there are only a total of (3) dry contacts at the boiler DE1, DE2 & DE3 connections and I don’t see a Tstat connection point on the AM1 module itself ? I have emailed Viessmann a few times over the last month asking this question and I haven't been able to get a response yet.

Thanks !

109A_5

Well it seems a bit vague. I think with a multi-zone system (beyond 3 zones), zoned by circulators, for example you need an a external zone controller for each zone type, like radiant or baseboard. The thermostats for each zone would connect to the zone controller for the zone type.

The three inputs DE1, DE2 & DE3 become the boiler's heating temperature characteristic selection for the different zones (radiant, baseboard and DHW). Which may want different temperature characteristics for best heating efficiency. Example DHW would not need outdoor reset, etc.

Thus the three inputs DE1, DE2 & DE3 are no longer direct thermostat inputs for each unique zone. They are boiler temperature characteristics selection controlled by the appropriate zone controller.

The thing that I wonder about is there a temperature selection priority structure so you can't overheat a zone type if multiple zone types are calling for heat at the same time.

GGross

ah yeah so I don't think the AM1 gives you more "heating circuits" or "zone circuits" in the boiler. It just allows for more pumps. so for an installation where you are using up all the pump outputs on the boiler for constant circ "heating circuits" with mixing valve, and domestic you would use the AM1 to gain a few pump outputs for the "zone circuits" which are what viessmann calls the on/off zones controlled with thermostat (or thermostats). DE1,2,3 are the terminals to activate a zone circuit call for heat.

I am typically using 3rd party pump relays for most of that stuff. so for example I can have 6 zone pumps, and 6 thermostats all attached to a caleffi ZSR106 and then use the single dry contact out from that attached to DE1 on the boiler, when any of those 6 zones calls for heat the boiler will fire based on ZC1 heating parameters. I could have a second relay with 6 pumps and zones tied into DE2 to fire at a different temperature based on ZC2 parameters. and the whole time those zones are calling I can have 2 constant circ mix temperature loops running using the boilers controller based on outdoor reset.