How our heating/hot water system works?

CYPER

So we have this heating system, which I am trying to wrap my head around and understand how it works. Let me describe it:

So it consists of the following parts:

GREENSTAR 30CDi System WALL HUNG RSF GAS-FIRED CONDENSING BOILER on the top floor in a cupboard
Ariston hot water cylinder with an immersion heater
Drayton LP522 programmer - Picture
Honeywell room Thermostat
Radiators with thermostatic radiator valves

Can you please explain to me in layman's terms how this whole system works?

1. I know some households have just a combi gas boiler and get hot water and heating on demand, so what is the point of this hot water cylinder?
2. What is the purpose of the immersion heater if the boiler already sends hot water to the cylinder?
3. What is the room thermostat on the wall controlling the temperature of and how?
4. What is the purpose of the 2 dials on the bottom of the cylinder (3rd picture in the album)
5. How do I find out if the system needs topping up the water or venting the air?
6. The central heating does not work according to the programmer in the bathroom. I've done extensive testing and could not set the system to work properly. For example when the Central heating on the programmer is set to OFF the radiators still work, which leads me to believe that the Hot water programming controls them too. Setting timed mode for the central heating on the programmers makes no difference. I have read the manual of the programmer from top to bottom and I am quite certain something is not quite right.

Thank you.

macman

The immersion will be a backup in case of a boiler malfunction-so that you can still have hot water. The room 'stat controls the temp of the zone in which it's situated. So if the room temp drops below set temp, it calls for heat.
You can bleed the rads with a rad key if necessary just like with a combi sytem.
Looks like you have an unvented cylinder to me, but someone who knows these better will advise.
If the rads are hot when the programmer is set to no heat, then you possibly have a sticking or faulty 3 port valve somewhere in the system-it should offer independent control of CH and DHW.

HappyMJ

CYPER wrote: »

So we have this heating system, which I am trying to wrap my head around and understand how it works. Let me describe it:

So it consists of the following parts:

GREENSTAR 30CDi System WALL HUNG RSF GAS-FIRED CONDENSING BOILER on the top floor in a cupboard
Ariston hot water cylinder with an immersion heater
Drayton LP522 programmer - Picture
Honeywell room Thermostat
Radiators with thermostatic radiator valves

Can you please explain to me in layman's terms how this whole system works?

1. I know some households have just a combi gas boiler and get hot water and heating on demand, so what is the point of this hot water cylinder?
2. What is the purpose of the immersion heater if the boiler already sends hot water to the cylinder?
3. What is the room thermostat on the wall controlling the temperature of and how?
4. What is the purpose of the 2 dials on the bottom of the cylinder (3rd picture in the album)
5. How do I find out if the system needs topping up the water or venting the air?
6. The central heating does not work according to the programmer in the bathroom. I've done extensive testing and could not set the system to work properly. For example when the Central heating on the programmer is set to OFF the radiators still work, which leads me to believe that the Hot water programming controls them too. Setting timed mode for the central heating on the programmers makes no difference. I have read the manual of the programmer from top to bottom and I am quite certain something is not quite right.

Thank you.

Could be a fault with the diverter valve. It's a small box on a T part of the pipework that is supposed to redirect the output from the boiler to the cylinder and/or the radiators. If it's stuck in the wrong position when it's supposed to be heating the cylinder the radiators will get warm too. You could try removing it and see if it is stuck or not.

Cardew

As above.

Generally 'conventional' CH systems with a hot water tank are for larger properties where there are two bathrooms.

Combi's struggle in very cold weather to provide an adequate flow for a single hot shower, and if someone turns on a hot tap elsewhere the shower flow is reduced. Arguments rage on the merits of 'Combi v Conventional on MSE - I am firmly in the latter camp.

As said, immersion is just a back-up.

When your heating is on with the timer, the wall thermostat is set to the temperature you want in that room, it switches the heating on and off to maintain that temperature. when 'off' the pump circulating the water round the radiators stops pumping. The disadvantage of such a system is that other rooms might not be at the temperature you require.

Again as said above, there is a diverter valve that directs the boiler hot water to (a) radiators or (b) hot water tank or (c) both. It is a common fault for this valve to get stuck. There is a lever on some where you can manually move the valve to check. Not normally a big job to replace valve electrical 'motor'.

The large dial on the bottom of hot water cylinder controls the water temperature in the tank(not radiators). No idea about smaller button, could it switch off hot water?

thozza

You have a "standard" central heating system, the Worcester Greenstar 30CDi is not a combination boiler, hence the need for a cylinder. Your layout is likely to be the Sealed central heating system layout (as you have a large expansion vessel above the cylinder) on the attached leaflet from The Association of Plumbing and Heating installers.

APHC leaflet - How Central Heating Works

As HappyMJ says, if the programmer does not seem to affect the operation of the radiators when the boiler is working, you might have a stuck motorised valve, there is some advice here on how to fix them (it is based on a Honeywell, but is applicable to other makes)

http://www.lovekin.net/honeywell-motorised-valve-faults.html

Your questions:
1. You have a standard system, so you need a cylinder for hot water storage
2. Heating hot water if/when the boiler is off
3. Room stat is the main control to turn the heating on/off, when the stat reaches the set temperature, it turns off the heating side of the boiler, it is dependent on where it is sited in the house.
4. Dial is the cylinder stat, controls the temperature of the water in the cylinder when the boiler is operating, the other thing with a slot is probably a reset device.
5. There should be a pressure dial on the system somewhere and a cold water feed, usually the pressure should be set with a red line, if it falls below the line, top up.
6. See above explanation of motorised valve problem.