my heating system - can someone explain whats happening?

[dazzammm]

Hi,
I am hoping for a bit of guidance on my central heating system - ive never been able to get the heat out of it I would like and I dont understand the system as a whole.

We have a number of radiators, a timer with 2 switches, one for hot water and one for heating and a gas boiler with a variable output dial.

Can someone explain

1) does it matter which end of a radiator is the lockshield end (when i moved in there was no covers for the taps on the radiators so I dont know which end was which). what should the lock shield end of the radiator be set to (min, max or somewhere in the middle)
2) the timer system switches on the hot water or the heating but the hot water has to be on for the heating to work. If the heating is off (i.e. hot water only) the radiators still heat up. is this normal?
3) Someone told me that there has to be one radiator in the house that must not be adjusted (to ensure the system does not run will all radiators off). is this correct?

thanks

 

[Armo74]

The lockshield is usually on the return side you can tell this by feeling which side heats up first.

The lockshields are there to balance the system so they should be adjusted to maintain a certain design temperature drop from the flow to the return.

The fact that you are getting heating when hot water only is selected will be down to a faulty motorised valve, it sounds like yours is stuck in mid-position.

You do come across a lot of systems that always have one radiator on all the time which is used as a bypass to maintain a certain flowrate through the boilers heat exchanger.

 

[bhm1712]

you have an old pumped central heating and gravity hot water system. The boiler gets its electrical signal to ignite from the hot water switch on the timer. The heating switch supplies the pump with electricity only. The hot water has to be on to ignite the boiler before the pump can pump any hot water around the rads.

If you dont have any thermostatic valves - which i doubt, if you have a system like that - then there doesnt need to be one radiator left un touched. The other radiators will not turn off and restrict the flow.

I was told on this forum years ago, that it doesnt matter which valve is used as the lock shield valve on the radiator. however i prefer to have the lock shields on the return leg as is found on most systems.

Best thing you can do without spending much cash is to bleed the radiators, get the system balanced and flush any crap out with some sentinel or equivalent system cleaner and replenish the water in the system and add inhibitor. This should aid the system.

How hot do you want it? the temperature of a system like yours is controlled by the boiler thermostat. Beware if you turn it up, then the hot water will get hotter and hotter.

Some systems of this type incorporated a motorised valve and cylinder stat for the hot water and so the water temperature at your hot taps may not be affected - however if this was the case i would expect seperate control of central heating and hot water which you do not have.

Armo74 - Old gravity HW and pumped heating systems were wired up to work that way so that the HW had to be on for CH to work. There is usually a switch on the back of the timer to select whether its fully pumped or gravity hot water. Most modern timers still have this option on a dip switch.

 

[twgas]

Seems you need to give us some more info on your system..
First two answers are contradicting one another, either may or may not be correct.
What boiler(make and model)?
Do you have motorised valves?
Is there a thermostat on the side of the hot water tank?