Central Heating Hot Water

5 HOT WATER

Please note: book illustrations are omitted to save download time.

THE CYLINDER ....................................................................................... 20

PROBLEMS .............................................................................................. 21

POSSIBLE CAUSES ................................................................................. 21

REMEDIAL ACTIONS ........................................................................... 22

Causes for Air Lock .................................................................................. 23

Removing of Air Lock ................................................................................ 24

Leak ............................................................................................................. 26

REPLACING THE CYLINDER ................................................................ 26

Electric Immersion Heater .......................................................................... 29

Refilling the cylinder .................................................................................. 31

DRAINING OF SYSTEM WATER .......................................................... 30

HOT WATER FAULT DIAGNOSTIC CHART .................................. 33

Hot water cylinders are made of copper. They vary in size and shape but normally have capacity about 36 gallons. Their function is to store hot water for the taps.

The water for the hot water taps is heated by a heat exchanger (a coiled pipe) within the hot water cylinder. The heated water from the boiler is circulated through the heat exchanger. Where it progressively loses its heat to the cooler water in the water cylinder, but, most importantly does not mix with it. The cooled water returned to the boiler and heated again hence the term "indirect."

The boiler- heat exchanger circuit is called "Primary circuit." A fixed amount of water recycles round the primary circuit. This heating process is continually repeated.

Gravity or Thermo syphoning (old types) system, it makes use of the fact, the water heated become less dense and rise above and the cooled water moves down. Hence by arranging the boiler at a lower position to hot water cylinder, it is possible to circulate the heated water through the hot water cylinder. It should be noted that a good circulation depends on the height between the boiler and cylinder.

The modern system uses a circulating pump in the primary circuit. Now it is common to use a circulating pump and a diverter valve, so that the hot water from the boiler is circulated through the primary circuit and also through the radiator circuit as and when required. For more details please read diverter valve section.

PROBLEMS

1. No hot water

2. Leak on the cylinder

3. Takes longer to warm up

POSSIBLE CAUSES

1 No hot water

1.1 Boiler faulty

1.2 Pump failure

1.3 Diverter Valve faulty

1.4 Cylinder stat faulty

1.5 Programmer faulty

1.6 Air lock

2 Leak on the cylinder

2.1 Electrolitic corrosion

2.2 Damaged

3 Takes longer to warm up

3.1 Boiler thermostat faulty

3.2 Pump running slow

3.3 Scale

REMEDIAL ACTIONS

Try and eliminate each possible cause from the list.

1. No hot water

1.1 Boiler faulty. Check and eliminate boiler from the list. Refer Boiler section.

If the radiators are warming up then the boiler is functioning correctly.

1.2 Pump: Again if the radiators are warming up the pump is working well.

1.3 Go to diverter and zone valves sections

1.4 Go to cylinder stat section

1.5 Go to programmer section

1.6 Air lock: Symptom: Water in the cylinder but it couldn't be drawn to the tap.

CAUSES FOR AIR LOCK

A properly plumbed system should not trap air in the pipe work that can cause air lock. Normally, the air won't get into the system, unless for some reason the main water storage tank become empty and the air is sucked in by the hot water cylinder feed pipe.

The reasons may be; the Water authority may have shut down supply for few hours, the Ball valve is faulty on the tank. In winter Frozen pipe/valve.

Note: If your system has frequent air lock suggest the fault is on the cold storage tank either is small and is struggling to cope with the demands of the family or water supply rate is low. The solution is either to increase supply, by put in a high capacity tank or fitting two ball valves to supply more water when demanded.

Alternatively, regulate the water demand. Example, when filling the bath open only one tap, try not to use more than one tap at same time. This will give enough time the for the ball valve to replenish as the water is been drawn out from the tank.

The diagram illustrates increased storage (without using a large tank, which may be difficult in some cases) by putting an extra tank.

You must join the tanks in the middle or low level, alternatively join the draw off pipe to get the same effect.

The supply also can be doubled by fitting and additional Ball Valve to the existing tank or to the added tank.

REMOVING OF AIR LOCK

IMPORTANT: The idea is to drive the locking air back to the tank where it can escape.

The rising main or Cold mains from street can be used because it has high pressure, which is enough to push the air back along the pipes. If this is not possible a pressure pump may be used.

Method 1

1. Start by closing hot & cold taps on the kitchen sink.

2. Use a small hose pipe & clips, connect tightly and securely the open ends to the taps using the hose clips.

If it is a mixer tap fold and tie up one end so that the water will not leak when the taps open.

3. Fully open HOT tap & then slowly open COLD tap.

The water from the COLD tap will now slowly force the air in the HOT pipe work back into the open over the storage tank.

4. When the water begins to come through the vent, first close the COLD tap.

5. Then close HOT tap and remove the hose pipe.

Method 2

1. If the problem didn't go away by the method 1 or that method is not possible, then you need a long hose pipe.

2. Take care of any water spillage and use hose clips to secure

the connections.

3. Tightly connect one end to the hot water cylinder drain cock

4. And tightly connect other end to kitchen sink cold main tap.

5. Unscrew the drain plug on the cylinder

6. And then slowly the cold main tap.

The water from the mains will now force the air back into the storage tank.

7. Have someone to watch for Air bubbles through the feed pipe at the bottom of the tank. Then the water level will rise. Take care of any over flow that may happen.

8. First the cold mains and then the plug should be closed. Rarely you have to repeat the procedure.

NOTE: You can use this technique to remove the bath cold water tap AIR LOCK. You need to connect the involved tap to the rising cold water mains normally the kitchen sink cold tap.

2 LEAK

If LEAK develops there are no alternatives, but to replace the cylinder. If you are lucky an identical make and model may be available, which make the job lot easier.

You are advised to buy cylinder that complying with revised building regulations (1995). The aim of the regulations is to save energy hence save money and environment. It also ensures that the heat exchanger is sufficiently large to quickly transfer the heat from the heated water from the boiler to the contents in the cylinder. These cylinders come with factory insulated to a superior standard to minimise the heat loss from the cylinder.

REPLACING THE CYLINDER

1 Turn OFF boiler and let it cool.

2 Remove the terminal covers of the cylinder stat and the immersion heater.

3 Note it down all electrical connections.

The colour of the wire to the letter or number on each terminal.

Then loosen screws and remove the cables.

4 Shut down the water supply by closing the gate valve on the cold feed pipe. If there is no gate valve, you'll have to tie up the ball valve arm in the cold storage tank, above, so that it closes the valve.

5 Open the hot water and cold water taps to drain the water. This will not empty the cylinder

6 The cylinder is still full of water to empty locate the drain cock on its side near bottom.

7 Connect securely one end of a long hose (Garden hose) to the drain cock. take the other end to sink or drain. Now, open the drain plug the water will run out and the cylinder will empty itself.

8 If there is no drain cock, then you will have to siphon the water out from the cylinder.

(a) Undo and slightly move the pipe connection at the top of the cylinder.

(b) Find a long hose pipe which could pass through this orifice

(c) Fill it completely with water; close one end so that no water leaks out and secure it in the sink or near drain must be at lower level than the cylinder. Put your thumb firmly on the other end.

(d) Take this end to the cylinder. release the thumb and push deeply into the bottom of the cylinder through the connection hole at the top of the cylinder.

(e) Now go down to the other end of the hose and let the water to flow. The water will flow out and the cylinder will empty itself.

DRAINING THE SYSTEM WATER

CAUTION: Don't try to drain the hot water, allow the system to cool.

TIP: If there is no drain cock or unable to use the existing drain cock, then you could make one! The SELF-CUTTING TAP or CLAMP-ON stop cocks sold for quick plumbing of washing machines is very useful to make a drain cock. You could get them from DIY and plumbing merchants. They are designed for plumb-in to existing pipe work without draining the water.

Do read the manufacturer's instructions to fit them water tight.

Clamp on the device on to the piping and screw in the control knob. It will automatically tap on (make a hole) to the clamped piping. Further tighten it securely you have the instant stop cock! Now, water in the pipe hot or cold can be drawn to feed the washing machine.

An alternative use for this device is to make an instant drain cock. First, find a lower most convenient point on the heating pipes and clamp on the stop cock device. Then it can be used to drain the system water.

Method

1. Tie up the float arm of the ball valve in the Feed & Expansion tank.

2 Find the drain cock, You may be lucky and have a system drain cock fitted at a low point in the system pipe work. Otherwise you will have to make one as detailed above.

3 Connect securely a hose pipe leave it into a drain. Open the drain plug and drain the system.

4 Once the system is drained. You could undo all the connection pipe links to the cylinder. Always use two spanners one to take the strain and the other to undo the union nuts.

5 Before standing the new cylinder in place, make sure all the fittings are fitted (you may even use the fittings from the old cylinder) Use PTFE taps in the threads to make it water tight. DO NOT USE joining compounds.

6 Stand the cylinder in place tentatively fit all connecting linkup pipes.

It's quite likely that you'll have to adjust the pipe work.

7 The way is to cut back a short length of the linking pipes that are not lining up and insert new sections. Bend to fit in the required position. You can buy & use flexible sections, they can save you a lot of time and effort.

8 Use PTFE taps on and tighten all joints to the cylinder.

ELECTRIC IMMERSION HEATER

9 Fit the electric Immersion heater on the boss (2" hole) or fit its plug

Some are reluctant to fit electric immersion heater. When they replace the cylinder, because they think it is expensive to run. Remember, it is an ideal back up for hot water during boiler breakdown. But, you need a special spanner to fit the immersion heater

10 If the old cylinder had an immersion heater, then you already have a suitable, nearby electricity supply to connect into. However, if you are considering for the first time, you must have a radial circuit from the consumer unit to a 20A fused double pole switch with neon indicator.

WARNING: Do not connect to the ring main the 3KW immersion heater will overload the ring. This will cause problem, when you have the boiler breakdown. You happily turned on the immersion heater after few hours will end up both electricity and the boiler breakdown!

11 Refit the cylinder thermostat. About 1/4 to 1/3 up from the bottom of the cylinder. When mounted on form lagged cylinder, sufficient area of insulation to the depth of the metal surface must be removed (take care not to damage the cylinder), to allow the thermostat to be in contact with the metal of the cylinder.

12 Now, fill the system. In order to prevent any air locks, it is best to fill bottom-up.

Refilling the Central Heating System Bottom-Up Method

13 Connect one end of the hose pipe to the kitchen sink cold tap and the other to drain cock on the boiler. First, unscrew the drain plug and turn on the cold tap. Make sure the water is flowing slowly.

14 The water entering will force the air back through the system and then will begin to fill the feed & expansion tank through the feed pipe at or near the bottom of the tank.

15 Turn OFF tap and then close the drain plug.

Refilling the System Top Down Method (Easy but not always work!)

Release the float arm and let the ball valve in the F&E tank to fill the rest of the tank.

16 You will have to check each radiator (one at a time) by opening the bleed valve and close them as the water begins to flow from them.

Refilling the Cylinder

18 Refill the cylinder by connecting the hose pipe from the kitchen cold tap to the drain cock on the cylinder.

19 First unscrew the drain plug and then slowly turn on tap. The water will force the air back through the cylinder.

20 When the water begin to flow with air bubbles through the feed pipe at near bottom of the storage tank.

21 Close the cold tap and then tighten the drain plug.

22 Release the ball valve float arm and let it fill the rest of the tank.

23 Check for water leak on each joints.

When you're happy that all in order turn ON electricity and start the boiler. The expansion of pipes caused by hot water flowing through them may weaken the joints, so check again for leaks.

Why not Save Energy, Save Gas,

Save Money and the Environment?

Nearly half of your heating bill is for hot water. So using hot water economically will save you money. A shower takes only two fifth of the amount of hot water needed for a bath.

If the water is heated to a scalding temperature, turn down the cylinder thermostat. For most people about 60C or 140F is quite adequate.

This will also reduce the scale formation in the cylinder and taps, therefore the repair or replace cost of the above. And because the rate of heat loss at high temperature is very much higher than that at lower temperature (Newton’s law on Cooling), there will be a saving made on your heating bill.

In a day, a dripping hot water tap can waste hot water that is enough to fill a bath, so fix it quickly.

FAULT	REASONS	REMEDY
NO (hot) WATER	Air Lock	Remove air lock
NO water Heating	Faulty; Motorised valve, Pump, Cylinder thermostat, Boiler	Check each component.
Water too Hot	Cylinder thermostat; setting highloose, fallen or fitted over insulation	Check and reset or refit
Takes long to heat up	Scaled cylinder, Boiler or Boiler, Cylinder thermostat setting low	Reset, Replace Cylinder, Boiler
Leak	Corrosion or Damage	Replace Cylinder