Boiler to SR502 to HZ301 to First Company AH to thermostat

lookloan

Hi - New system. Viessmann boiler - (propane) connected to a Taco SR502 with 2 zones so 2 water pumps. There are two First Company air handlers, so each hot water pump circulates hot water to either First Company AH 1 or AH2 depending which of 2 thermostats calls for heat.

 Here is where it gets confusing. Each air handler has a newly Honeywell HZ301 damper control added. So a HZ301 for AH1 and a HZ301 for AH2.  Each air handler has two dampers so each air handler has two zones for a total of 4 zones. There are 2 thermostats for each air handler for a total of 4 thermostats to control the dampers.  

Each damper is wired to it’s appropriate HZ301 board, so each HZ301 has two zones. Each HZ301 board has a spot  for zone 1 and zone 2 thermostat wiring. 

This is where I am confused. My guess is the 4 thermostats get wired to their respective HZ301 boards on each air handler.  The problem is the Taco ST502 wants thermostats wired for zone 1 for AH 1 and zone 2 for AH 2 to turn on the pumps to their respective AH.  

Can someone explain how I can make the hz301 and the st502 both happy if I only have one set of wires from the thermostat? There are only two spots on the Taco st502 which is ok since it looks at the air handlers as two zones. Thank you in advance.  

HVACNUT

From "EQUIPMENT" on the Honeywell zone panel, those wires go into their respective air handler. 
You need to install (in or at the air handler) an isolation relay to close the circuit R-W in the SR502.
So W and C from EQUIPMENT will power the isolation relay on a heat demand, and close a set of Normally Open contacts to R-W on the Taco SR502. 

P.S. Did you use  separate transformers to power the zone panels? 

lookloan

Hi HVACN - thank you for the reply 
is the isolated relay something that normally is part of the air handler (these are newly purchased) or something I should buy - not sure what specifically to buy or where to buy the relay.  Yes I bought 2 Honeywell 24v transformers, one at each air handler to power HZ301. My electrician did the preliminary wiring so we had heat last winter and is going to look at the wiring next week. Do you think the specific isolated relay is very common and he will know about it?  

The dampers are spring open and power close. Can you offer any advice on how to wire them so when Zone 1 calls, then Zone 2 closes? My HVAC guy did a nice job on the boiler, but doesn’t do wiring. Thank you again for any help you can offer

ratio

The TrueZONE panels should manage the dampers & air handlers, with an additional (supplied by you) isolation relay to send the heat call to the SR502, which will manage the boiler & whatever pumps & valves you have. Just take it one step at a time & it'll come together for you!

HVACNUT

lookloan said:

Hi HVACN - thank you for the reply 
is the isolated relay something that normally is part of the air handler (these are newly purchased) or something I should buy - not sure what specifically to buy or where to buy the relay.

These relays are usually purchased separately. Some air handlers have boiler contacts in their circuit  board. Not sure about yours.

Yes I bought 2 Honeywell 24v transformers, one at each air handler to power HZ301. My electrician did the preliminary wiring so we had heat last winter and is going to look at the wiring next week. Do you think the specific isolated relay is very common and he will know about it?  

Your electrician should be very familiar with this simple relay and how to wire it.

The dampers are spring open and power close. Can you offer any advice on how to wire them so when Zone 1 calls, then Zone 2 closes?

If the zone panel  is wired correctly, then the opening and closing of dampers is automatic. 

My HVAC guy did a nice job on the boiler, but doesn’t do wiring. Thank you again for any help you can offer