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Dual Temp Hydronic System



1 Story Hydronic Dual Temp System

1 Chiller--1964 Worthington

1 Boiler-1964

1 Dual Temp Pump

1 Expansion Tank

1 Diverting Valve-to distribute Water flow through Boiler or Chiller.

1 Mixing Valve for Hot Water Reset on Outside Air

1 Safety-Chiller--Must be below 90 Degrees on Loop to Run

1 Safety-Boiler--Must be above 65 Degrees to have Boiler Run

1 Changeover SWitch--Changes at 58 Degrees--Above -Cooling-Below-Heat.


1. What is the Proper way to Drain and Refill a Expansion Tank--I have always been taught to Valve Expansion Tank off fvrom System--Run a Hose to a Drain--Loosen the bottom of the Airtrol and allow all Water to Drain out--Close Drain--Open Tank to system--Keep Airtrol Loose until you see Water come out then Tighten and allow to complete Fill--Should be Air Gap in Sightglass when Finished.

Question 2:

If Dual Temp System has been Over Pressurized by a Defective PRV-Would you Bleed the Air from the Top of the Expansion Tank to Lower Pressure--Would this let your Air Pocket Out??

Would it be ok to raise the RElief Arm to get Pressure to Normal after installing new PRV--any more Ideas??

Question #3:

When dealing with a Dual Temp system--Should the Boiler-Water Pressure be the same as the Dual Temp Pump Pressure--in Heat-We are varying about 6 PSIG between the Pump Pressures and the Boiler Pressure??

The Expansion Tank we have is:




125 PSI at 650 Degrees

Stonesteel Brand

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