Header and Header Trench Construction
The purpose of the headers is to provide an ample quantity of secondary coolant to the cooling floor grid in an efficient manner.
If the headers are too small there will be energy robbing pressure drop and the possibility of insufficient flow to meet the system requirements. The headers can be made of Schedule 80 PVC, High density PVC, or Steel.
The Header Trench
The purpose of the header trench is to provide a protected and preferably accessible location for the header to facilitate service. Depending on the design of the building and the installation budget, the trench can be accessible across the end of the ice surface in the viewing area or even buried below the cement slab at any location below the ice surface.
Steel headers have been used for years in ice rinks but fell out of favour due to the tendency to rust on the outside and foul on the inside at the nipples. If the brine is rigorously monitored it will greatly reduce the problems associated with rusting. Steel headers can be used in an open header trench or a buried in the cement if protected from rusting. Due to their strength there is very little chance of breaking or damaging a steel header. They can be provided in straight sections or in curved sections forming the perimeter of the rink to eliminate frosting in the viewing area. As with PVC headers all polyethylene pipes should be double clamped with high quality stainless steel clamps. The cost of Steel headers is quite a bit higher than PVC headers.
If constructed properly PVC headers will provide years of reliable service with no chance of rust and minimum fouling at the nipples. Schedule 80 PVC headers are inexpensive and easy to work with. It is recommended to install PVC headers only in a trench that is accessible. As PVC is breakable, care must be taken not to subject the headers to direct impact. All polyethylene pipes should be double clamped with high quality stainless steel clamps and compatible cement used on all fittings.
High Density PVC Headers
High density PVC headers when properly installed will provide very little chance of leaking due to all of the PVC joints being welded. HDPE headers can be buried in cement or left open in a trench. They can be curved to form the perimeter of the rink, eliminating any chance of frost in the public viewing area. They can be quite expensive to install, but like PVC will not rust or foul over the nipples as readily as steel.
Burried Header Trench
The main reason to install a buried header trench is a cost consideration. With the buried header trench, the time and material to form a trench and the supply of frost protection and trench covers are eliminated. With the elimination of the trench it is easier to make use of viewing area at the end of the ice rink.
The header trench can be positioned at any point along the ice surface, which can reduce piping runs to compressor rooms that are positioned along the side of the facility. The headers can also be placed under the boards at the end of the ice surface.
Brine leaks or blockages can be very expensive to repair, especially if they are in the heating floor. When the headers are buried there is no easy way to block off a leaking heating floor circuit or isolate a leaking cooling floor circuit while repairs are being performed.
Accessible Header Trench
The preferred method of installation is to install a header trench outside the ice surface with removable covers. This permits service procedures to be carried out in the event of leaks or blockages. The addition of a header trench will increase the initial cost of the facility but will pay for itself with the ease of repair of just one problem. When headers are installed in an external trench it is important to provide frost protection in the viewing area to minimize a slip hazard. When PVC headers are installed in an accessible header trench there is approximately a 1% power penalty due to heat gain through the header. To insulate the headers is not usually cost effective. The money would be better spent elsewhere in the system.