Burnham V9A manual

i.If minimum return water temperature can be maintained at 135°F and temperature differential across the system is at 40°F or less, refer to Figure 26 or 27 for recommended minimum boiler piping details.

ii.If minimum return water temperature cannot be maintained at 135°F or the temperature differential across the system varies, a blend pump is recommended as a minimum to help protect the boiler from flue gas condensation and/or thermal shock. See piping details in Figure 28. Primary secondary piping with a by-pass is an alternate to the blend pump method and is shown in Figure 29.

d.If conditions exist where the boiler is subjected to prolonged periods of operating conditions below 135°F, other mixing methods such as three or four way valves or variable speed injection should be used. Burnham Commercial offers an RTC Return Temperature Control kit to protect the boiler. See separate RTC manual.

e.Multiple Boilers - Recommended minimum multiple boiler piping is shown in Figure 30 as primary secondary with a by-pass. The boiler circulator will maintain a constant flow through the boiler during every heat demand while the by-pass diverts a portion of hot water back to the return. Alternate minimum multiple boiler piping is shown in Figure 31. The blend pump

will maintain constant flow through the boiler during every heat demand and provide a hot water blend back to the return.

f.Glycol Antifreeze Solutions - Many systems today use ethylene or propylene glycol antifreeze solutions as a measure for freeze protection, as well as a pump lubricator and corrosion inhibitor. The properties of the glycol mixture have an impact on valve and pump sizing. All glycol solutions have a lower specific heat than water.

This means that the glycol solution cannot transfer heat as well as pure water, resulting in the need for higher flow rates. In addition, the viscosity of the glycol solution is usually higher than water, requiring a higher pump head for the same given flow. Consult factory for specific applications, pump selection and flow rate.

WARNING

A properly constructed Hartford Loop must be installed on all gravity return steam systems. Hartford Loop is not required on pumped return systems.

2.STEAM HEATING, consult I=B=R Installation and Piping Guide No. 200. For piping details, see Figure 32. Figure 33 shows a typical pumped return/boiler feed unit arrangement. Figure 34 illustrates the required elevations for McDonnell and

Miller 150 and 63 float low water cut-offs.

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