Sorting out this old article. Hopefully this is better... comments welcome
NT
Does the hot water run out too soon? Some ways to increase capacity:
=3D=3D=3DBigger Hot Water Cylinder=3D=3D=3D The obvious option is a bigger cylinder. However this isn't always a good option, eg when renting, or if budget is lacking. There are other options.
=3D=3D=3DHigher Thermostat Temperature=3D=3D=3D The simplest way to increase capacity is to turn the HW [[thermostat]] up. This means the [[Domestic Hot Water|hot water]] is used more slowly, as less of it is needed to bring the shower or bath upto the required temp. Thus the HW lasts longer.
If incoming water is 10C, and HW temps are 55C and 75C before and after adjustment, the capacity increase is (75-10)/(55-10) =3D 1.44 or
44% more.Avoid temperatures that are a burn risk.
A lot of [[Immersion Heaters|electric immersion heaters]] can be set to any desired temperature, even burn risk temperatures such as 95=B0C. Newer immersion heater [[thermostat]]s can not be set to these elevated temperatures.
Gas [[boiler]] water heating works a bit differently, and the cylinder stat should be set to a temp below the primary circuit temp. If its set higher, the circulation [[Pumps|pump]] will run continuously, using power for no gain. Primary temp varies according to system design and setting, but if the [[Pumps|pump]] runs all day, the cylinder stat is set too high.
The possible downsides are the scald risk if too hot, increased [[Limescale|scaling]] in hard [[water]] areas, and increased standing heat loss from the cylinder.
=3D=3D=3DAeration=3D=3D=3D Aeration of shower and taps reduces water use, making a given amount of hot water last longer. Aerators are cheap and easy to fit to showers.
=3D=3D=3DSlower booster pump=3D=3D=3D A [[Pumps|Shower boost pumps]] with no [[Fan Speed Controller|speed adjustment]] can have speed reduced with a [[Fan Speed Controller| series capacitor]], but correct calculation and ratings are required for the capacitor. News:sci.electronics.basics would be a good place to ask if you need to work out what value & voltage capacitor to use, quoting the pump power, VA or [[power factor]] and dc resistance.
=3D=3D=3DDrain Heat Exchanger=3D=3D=3D A lot of heat goes down shower drains. Nearly the entire contents of the hot water cylinder in fact.
A [[Drain Heat Exchanger]] recovers a percentage of this heat, returning it to the shower cold feed. So less [[Domestic Hot Water|hot water]] is needed to bring it upto temp, and the [[Domestic Hot Water| hot water]] lasts longer.
By [[:Category:Energy Efficiency|reducing energy use]], [[Drain Heat Exchanger|these exchangers]] can pay back their cost several times over in some cases. Actual payback depends on system design and use, and only sometimes justifies their use.
=3D=3D=3DMove Thermostat Lower=3D=3D=3D HW cylinder thermostats are typically 2/3 the way down the cylinder on gas heated systems, but are sometimes higher up. If higher up, moving it down can increase HW capacity.
HW cylinders [[:Category:Heating|heat]] up from the top section downwards, and [[water]] below the stat will be at lower temp than the stat setting. Often this cooler water is no more than lukewarm.
Moving the thermostat down increases HW quantity in the cylinder. The implications depend on where the stat is in relation to the heating element or built in exchanger.
- If the stat was high up and is moved to 2/3 down, things will behave normally after moving
- If the stat is moved lower than the [[Immersion Heaters|electric heating element]], the [[water]] may overheat. This needs to be checked for when the stat is moved, and if it occurs the stat needs to be moved back up. Electrically heated hot water must not be left in an overheating condition.
- If the stat is moved lower than the exchanger in a gas powered system, the [[water]] doesn't overheat, but the circulation [[Pumps| pump]] runs continuously. If this occurs, move the stat further up to avoid any [[Save Energy & Money|energy waste]].
=3D=3D=3DSolar Preheater=3D=3D=3D A [[Solar Thermal|solar preheater]] produces a batch of warm water which is fed into the cylinder when [[Domestic Hot Water|hot water]] is used, rather than the HW cylinder drawing cold [[water]]. Whether this increases effective HW capacity depends on the temp of the incoming solar preheated water, and what the HW is used for.
- Hot preheated water increases effective capacity
- Warm preheated water increases effective capacity with baths, but not other uses
There are several designs of [[Solar Thermal|solar preheater]], with performance, cost, payback and ease of fitting varying widely.
With any [[Solar Thermal|solar thermal]] equipment, any proposed system needs proper assessment before construction, as many designs never pay back their cost. Professionally supplied systems are worse than properly designed [[Special:Allpages|DIY]] ones in this respect.
See [[Solar Thermal]]
=3D=3DSee Also=3D=3D
*[[Category:Heating]] [[Category:Plumbing]] [[Category:Fault Finding]]