Unit 316 Session 5 Instantaneous multi-point hot water

​Instantaneous multi-point hot water heaters

​Electric

​Gas

​Gas fired instantaneous multi-point hot water heaters

​Electric instantaneous multi-point hot water heaters

​With these types of hot water heater, cold water is taken from the water undertaker’s main and heated in a heat exchanger as demand requires before being distributed to the outlets.


As long as the tap is running, hot water will be delivered to the taps.
There is no limit to the amount of hot water that can be delivered.

There is no storage capacity.

Open Ended

As we are aware, water expands when heated, how do you think we allow for expansion in an instantaneous multi-point hot water heater ?

​Expansion of water due to being heated is normally accommodated by back pressure within the cold water main.
However, if this is not adequate or the cold water system contains pressure reducing valves or check valves, then an expansion vessel must be fitted.

​Combi boilers are dual function appliances.

They provide instantaneous hot water and central heating within the same appliance.

​Gas or oil fired combination boilers

​In normal working mode, combination boilers are central heating appliances, supplying a proportion of their available heat capacity to heat the central heating water.

When a hot tap is opened, a diverter valve diverts the boiler water around a second heat exchanger, which heats cold water from the water undertaker’s cold water mains to supply instantaneous hot water at the hot taps.

​Thermal stores

​Sometimes called water jacketed tube heaters, thermal stores work by passing mains cold water through two heat exchangers which are encased in a large storage vessel of primary hot water fed from a boiler.

Multiple Choice

What is the main characteristic of instantaneous multi-point hot water heaters?

• Less storage capacity

• Limitless hot water delivery

• Slow heating process

• Low energy consumption

Multiple Choice

What is the primary function of combi boilers?

• Only central heating

• Only hot water supply

• Both central heating and hot water supply

• Cooling system

Multiple Choice

Which name is also used to describe "water jacketed tube heaters"?

• Instantaneous multi-point heaters

• Combi boilers

• Thermal stores

• Expansion vessels

Multiple Choice

What is the role of the diverter valve in combination boilers?

• Reducing pressure

• Supplying central heating water

• Cooling the system

• Diverting boiler water for hot water supply

Multiple Choice

What must be fitted if the cold water system contains pressure reducing valves or check valves for instantaneous heaters?

• Combi boilers

• Expansion vessel

• Diverter valves

• Electric heating element

Multiple Choice

How do thermal stores work in supplying hot water?

• Passing cold water through heat exchangers in a storage vessel

• Using a storage tank

• Diverter valve operation

• Limiting hot water delivery