Trade.Information

Product Name: Heating Products

Product Description

Sealed Systems: - The Sealed System is the Primary System or Heating System. It is concerned with providing the heat for the building and, in some cases, the heat for the hot water. Filling the System: - The main method used to fill a sealed system is a temporary connection to the main water supply. The temporary connection is made by a filling loop made up from three components - A means for controlling the incoming water A short length of pipe that can be easily disconnected A WRc listed double check valve 1. Controlling the incoming water can be done in two basic ways a) Manually using a screwdriver operated ball valve or a screw down stop valve. b) Automatically using a pressure reducing valve. The pressure reducing function can also be combined with shut off valves, check valves and gauge points to form a control group. 2. Connection to the system is always via a flexible hose with connections that can be made and broken by hand. 3. A WRc listed double check valve. Accommodation of Expansion (Expansion Vessel): - Once the system is full of water, if heat is then applied to the system the water will expand and pressure will rise quickly so a method of accommodating this expansion must be used. The simplest method is the expansion vessel. The size of expansion vessel used is dependent on the system volume and the pressure it is to work at. This can be related to heat input (normally 12lt per 4,000 BTU) but in systems using convertor radiators for instance this method will over size the expansion vessel. The following table can be used for conventional systems.The static head refers to the charge pressure of the vessel which must be at least two meters higher than the actual static height of the system. A maximum system pressure of 3 bar has been used for the above table. This is not the design running pressure. The maximum running pressure should be a minimum of 0.5 bar below the setting of the system pressure relief.For systems that fall outside the above table either in pressure or volume the expansion vessel size would have to be calculated by use of the standard formula. Safety Valve: - As the expansion vessel requires servicing for it to maintain its correct function a Safety Valve has to be incorporated into the system. For conventional systems this is set at 3 bar. This valve is sized against the heat input to the system and will function as an expansion valve (unless no control is exercised when filling the system) or for a short time as a steam relief valve. Pressure Gauge This is an essential part of the system as it shows what the working pressure of the system is. It is also used when manually filling the system to show the pressure at which the system is being filled. Air Vent There must be fitted into the system at the high(est) point(s) a method of releasing air from the system. Air will cause a variety of problems in the system from stopping it working completely to stopping individual radiators from working. Additional Valves There are other controls which can be used to make the system suit particular requirements. These valves are :- Line Strainers A line strainer fitted before the circulating pump can save a great deal of money. Most pumps removed, as being defective, from a new system were not defective when installed. Most instructions include the immortal phrase "flush pipe work before connecting". This very often can not be done on a system without installing most (if not all) of the fittings that can be damaged by dirt in the system. A line strainer fitted before the circulating pump (with service valves either integral within the strainer or fore and aft so that the strainer element can be cleaned) will take out the dirt as the system circulates. Differential By Pass Valves With the almost universal use of thermostatic radiator valves and the increasing use of zone valves pump pressure and system flow rate alter as each part of the circuit switches in or out. A Differential Pressure Regulator is used to stabilise the circulation flow rate and pump pressure in pumped central heating systems. Air Separators These are used on the flow of larger systems to help separate the air which is naturally trapped in the water. They perform most of their function in the first hours of operation in a new system. They are normally fitted with or have integral within their construction an automatic air vent.