BadgerBoilerMN
Hydronic Heating Designer
Buffer tanks are an indicator of a lazy mind, present company excepted.
I used to use a lot of Polaris water heater for combi service. But as you point out, they do not modulate, nor is there an option to change hysteresis. Not even a differential adjustment. Inexcusable. If you really want to see a water heater cycle, buy the Polaris in a 34 gallon and heat a two story SIP home with it! Still working great but the noise and the cycling doesn't add value.
Still, the built-in buffering is an invaluable bonus and the standing water a must for the filling of large tubs or other hi-demand peak loads.
The Phoenix will modulate and if matched up with the Taco XPB will not short-cycle.
Running the Polaris at 120°F is not considered safe by the Legionella scare crowd. But depending on the design temperature you will not have to worry much about condensing.
With old cast iron radiators a properly sized ModCon with an indirect fired water heater is really the only viable solution if NG is available.
NTI makes one of the best and import a great indirect and IBC, also Canadian, makes another boiler with a 10-1 turn-down. It is hard to short-cycle ModCon boilers driving cast iron radiators unless you ignore the EDR and heat loads altogether.
I used to use a lot of Polaris water heater for combi service. But as you point out, they do not modulate, nor is there an option to change hysteresis. Not even a differential adjustment. Inexcusable. If you really want to see a water heater cycle, buy the Polaris in a 34 gallon and heat a two story SIP home with it! Still working great but the noise and the cycling doesn't add value.
Still, the built-in buffering is an invaluable bonus and the standing water a must for the filling of large tubs or other hi-demand peak loads.
The Phoenix will modulate and if matched up with the Taco XPB will not short-cycle.
Running the Polaris at 120°F is not considered safe by the Legionella scare crowd. But depending on the design temperature you will not have to worry much about condensing.
With old cast iron radiators a properly sized ModCon with an indirect fired water heater is really the only viable solution if NG is available.
NTI makes one of the best and import a great indirect and IBC, also Canadian, makes another boiler with a 10-1 turn-down. It is hard to short-cycle ModCon boilers driving cast iron radiators unless you ignore the EDR and heat loads altogether.