Lesson One Direct ColdWater System Direct ColdWater System

Lesson One

Direct Cold-Water System

Direct Cold-Water System Advantages Ø Ø Economical on pipework Only needs a small storage cistren. Disadvantages Ø Ø If the supply is cut off even for a short period, there is no water available. When the supply is cut off, back syphonage could occur which could contaminate the mains.

Direct Hot Water System n n n The water is heated in the boiler. The boiler water is fed by the water in the cylinder The cylinder is fed by the storage tank in the attic.

Boiler and cylinder placed close together to minise heat loss.

Direct hot water cylinder 1. 2. 3. 4. 5. 6. 7. 8. Drain Cock Incoming cold feed Main tank immersion Top up immersion Expansion pipe Hot pipe to fed taps Cold feed out Cold feed in

Storage tank

Hard water disadavntages n n n Hard water can cause water heaters to run up to 60 percent less efficiently than with softened water. Clothes washed in hard water tend to wear out 15 percent faster than those washed in soft water. The American Water Works Association has found that washing machines that use hard water can wear out up to 30 percent faster than those that use soft water. Hard water can leave an unsightly film build-up on glasses and dishes. Hard water requires much more soap, shampoo, or detergent than soft water, Hard water leads to furring of pipe work therefore hot water travelling through these pipes does not effectively heat the house: more fuel is burned in heating the house

Pipes Carrying Hard Water, Clogged with Scale

Homework Assignment Outline the main differences between direct and indirect (hot and cold) water systems, and the effectsthey have on both domestic costs and environment 200 -250 words Points to be dicussed: • Installation costs • Domestic costs. • Their use of fuel • Their effectiveness of tranmitting heat. • The effects of water properties on each system.

Lesson Two

Indirect Cold water System

Advantages of the indirect cold water system n n provides a reserve of cold water. Reduces the risk of contamination to the mains by back syphonage. Since all sanitary appliances are fed from the cistren there is generally less pressure on taps and valves and therefore less wear. This system also prevents pressure drop at peak demand periods

Indirect hot water system v v v The large storage tank supplies water to the cylinder. The small storage tank supplies water to the boiler This system is broking down in to two parts. 1. Primary System 2. Secondary system

Primary system n n n The water in the boiler mixes with the water in the cylinder. The water in the boiler is onlt subject to fresh water after it is filled, when you need to replace any water loss due to evapouration. This system requires a second expansion pipe due to its seperation from the secondary system.

Secondary system n n n Requires a larger tank due to it been the water which supplies the hot water to the taps. The water is heatd in a closed loop circuit (coil). Cold water exiting the coil returns to the boiler to be reheated, not the water in the cylinder.

Indirect Cylinder 1) 2) 3) 4) 5) 6) 7) 8) Drain cock Incoming cold feed Return to boiler Flow to boiler Heat exchanger Immersion Hot feed to tap Expansion pipe

Primatic Cylinder n n n This cylinder was developed to elimanate the need for a primary cold water system and its feed and expansion pipes. As the cylinder is filled so to is the primary system, creating an air seal in the primatic unit. The expansion which takes place when the water is heated displaces some of the air in the upper seal. Any excess air is atumatically vented through the secondary system.

Lesson Three

One Pipe System. Advantage n n Ease od installation Low cost Diadvantage n The temperature of the water entering each successive radiator is gradually reduced therefore the last radiator would not be as warm as the first.

Two pipe System Advantages n The cold water exiting the radiators is returned to the boiler to be reheated therefore all radiators are receiving water at a high temperature. Disadvantages n Costly due the extra pipe work.

Standard Radiator

Vented and Unvented Heating Systems The direct and indirect heating systems are called "vented" systems. Because they both contain a vent pipe (expansion pipe) to the atmosphere (tank in the attic). They are open to atmospheric pressure and operate as "low pressure" systems. They both call for cold water from a cold tank stored, generally, in the roof space. Because they are low pressure, sometimes the flow from the taps etc is not as great as one might like and pumps can be introduced, both for the domestic hot water and the heating, to give greater flow. An unvented system does not contain a vent pipe to the atmosphere due to the lack of storage tanks.

Safety devices of an unvented heating system. • Pressure reducing valve • Check valve • Expansion vessel • Expansion valve • Temperatire relief valv. E • Tundish

Lesson four.

Pressure Reducing Valve n n n Reduces mains presure to a suitable level for supply directly to the storage cylinder Overcomes the fluctuations in ressure from the mains Supplys water to the cylinder at a constant pressure.

Check Valve Ø Ø 1) 2) 3) 4) 5) 6) Permits flow in one direction only. Water running in the opposite direction to the flow will force the disc O ring down to close off the pipe. Back syphonage therefore cannot occur. The mains would be contanianted. Parts. Spider Unit Spring Disc and stem Body “O” Rings Clamp Disc “O” Ring

Expansion Vessel n n n Acts the same as an expansion pipe in that it accommodates thermal expansion of the water. As the water expands the diaphragm gives way as the nitrogen is compressed in the chamber Instaled in the cooler returen pipe which is the negative side of the pump to reduce wear. Adjusted to provide min water pressure of 10 Pa @ highest point. Need to ensure that no water is contained in the vessels during instalation.

Expansion Valve Ø Ø Used to releif pressure is the expansion vessel should fail. Should be capable of withstanging 1. 5 times the maximum pressure to which thay are exposed to.

Temperature Release Valve n These components are set to open at 95°C max and to discharge to waste. The sensing element is submerged in the water

Tundish n n A funnel to catch overflow/expansion water from the safety valves. The funnel is lead out through the cavity wall and into the gulley.

Advantages of an unvented heating system n n n n n Balanced hot and cold water pressures Improved shower performance Less pipework and no storage cistren Reduced risk of frost damage to system Saving n installation time and cost High resistance to corrosion Excellent heat transfer capability Allows the use of a wider range of moderen tap fittings and showers High efficiency insulation

Unvented System 13. Pressure vessel Expansion relief valve Cold water inlet Temperature relief valve Hot water outlet Immersion heater Visual overflow Non-return valve Cold to taps Pressure limiter Strainer Stopcock Mains 14. Discharge pipe. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Unvented heating system