Lochinvar KBH285 Space Thermostats and respective Zone Pumps

dori

The boiler provides for 3 switched thermostats to be connected to the low voltage terminals per page 55 of the installation manual.

How do I wire the zone circulators for these 3? I am thinking of running the thermostats first to a Taco zone relay controller SR506, similarly to the other thermostats in the facility. Then wire a line voltage SPST NO relay in parallel with the circulator, and run its contacts to the thermostat inputs on the boiler. Sound like an ugly solution. Anyone with a cleaner solution?

Ironman

No, the three t'sat inputs are for different Supply Water Temperatures with three different reset curves. Use the SR503 Taco to control the zones and their pump(s).

dori

Hi Ironman, thanks for the fast response.

It is this feature of the boiler that I wish to explore. Even though the Taco will control the pumps, the source temperature (from the boiler) will allow adjusting the reset curve for each circuit IF the higher setpoint circuit is not in demand.

For example, the kitchen floor heating, which runs through a mixing valve, does not demand the high output temperature that the 2nd floor cast iron radiators do. While the 2nd floor is not demanding, I will be able to lower the boiler output.

I figured a better way to have the 'stats drive both the Boiler and the Taco zone controller. I will make sure that all thermostats in the house have the Common grounded and that the Rh is only fed from the Taco Zone controller, rather than from the boiler or separate 24VAC transformers that have been added over the years. This will eliminate phase issues with the Rh and the C and allow me to connect the thermostat directly to both control inputs.

Am I wrong?

Ironman

If you want three separate SWTs then use three SE501 with the end switch from each going to a different “TT” on the Loch’s board. The down side is that you will need to install a thermostatic mixing valve on each of the two lower SWT zones to prevent the hotter SWT that the boiler will supply when the higher temp zone(s) are calling.

Either that, or use the accessory module that Loch has, but then, you’ll also need three motorized mixing valves.

Ironman

Also, if all three zones can operate with a SWT that’s within 15* of each other, then there should be no need to create three different SWT zones. KISS.

dori

I like KISS. Thanks for the good advice(s).