[Continuation from last week’s MMM] Let’s assume we have a SIX story health care building and the heating system is 90 feet high with a 180 degree supply temperature. The pump and boilers are on the first floor. The BRYAN boilers selected come with 125 PSIG relief valves. Let’s also assume that the pump has a capacity of 800 GPM at 100 feet at design.
Maximum pressure in a hydronic system depends on a number of variables. Last week we used an example to introduce the maximum pressure at the expansion tank. Let’s look at a couple more examples. EXAMPLE TWO: Figure 1 shows a one line diagram of a heating system with a boiler and pumping system.
Cold fill pressure is defined as the initial pressure required to lift water from the point of the gauge readout to the top of the system plus 4 PSIG for positive venting. This statement holds true for systems from chilled water to heating systems up to 220°F. From 220°F to 250°F, consult the Bell and Gossett Air Management training manual, available from R L Deppmann Company, serving Michigan and Ohio, or from your local B&G representative for other parts of the globe.
In part 2 of the R L Deppmann Monday Morning Minutes we determined the initial and final temperatures of the hydronic system in order to calculate the expansion tank selection. When we heat the water in a hydronic system, the water expands. This expansion is expressed as Ew in the formula: Ew – Ep = The expansion of the water minus the expansion of the pipe.
Last week the Monday Morning Minute introduced the expansion and compression tank formula. We described the numerator as the tank acceptance. The formula is (Ef – Ep) X Vs where Vs is the system volume and (Ef – Ep) is the expansion of the fluid minus the expansion of pipe. Let’s review some of the required data.
We could entitle the next dozen weeks as: TANKS-A-LOT. (Sorry). Over the next few months, the Monday Morning Minutes blog will examine expansion and compression tank sizing. We will also tackle some more advanced issues in the selection and troubleshooting of closed system expansion tanks. Tanks are often selected using software programs such as the Bell and Gossett ESP-Plus™ selection program.
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