Entry # 14
Simon's Supply Co.
Brief overview of the project
Caleffi products used were, a ZSR103 relay, a ZSR101 relay, a combination pressure regulator/backflow, and a SEP4 seperator. The system is fairly simple in design. It is a three zone system that consists of two air handlers, and a panel radiator. It supplies heat to a plumbing showroom and an office space. It is a cold start system using a modulating, condensing boiler, with outdoor reset. The system is composed primarily of copper, but there is some steel, so we felt that magnetic seperation would provide some protection for the ECM pumps. Along with that, we got hydraulic, air, and dirt seperation, all in one. All three zones are equipped with temperature gauges so that we could get the pumps on the correct settings to ensure a good delta T of 20 to 25 degrees. Each zone is isolated with purge valves on both the supply and return. We did this so that we could service either of the air handlers, the panel radiator, or the boiler, without having to drain the whole system. Even though the manufacturer does allow pvc as a venting material, we chose to go with polypropylene because of the higher flue temperatures we might get in the colder months. Condensate is neutralized prior to being gravity drained to the exterior. You'll notice there are two relays. There are a couple of reasons for that, one being that we wanted to take advantage of the versatility of the boiler control, and utilize both of the available reset curves.
The design goal was system efficiency. We wanted to install a system that delivered heat without wasting energy. As the heat emitters were already in place, we just had to make sure we could deliver the heat effectively and efficiently. The project was heating only.
Retrofit. The only real challenge was preventing the small panel radiator from short cycling the boiler. The boiler makes the heat faster than the radiator can release it. When that is the only zone calling for heat, it short cycles the boiler. We solved this problem by using the second relay. The second reset curve allows us to run the radiator at a temperature that is twenty degrees lower than the temperature required by the other zones. We also lengthened the boiler post purge period. This allows the radiator to continue to pump for a period of time without calling the boiler on. For example, if an air handler calls, and the boiler is targeting 180 degrees, once that call is satisfied, the boiler will continue to pump any heat that is leftover back into the system, and the radiator zone will pump until the twenty degree difference between the reset curves, plus the diffierential, is covered. Only then will the boiler fire again.
System performance is what we expected. Plenty of heat and little waste.