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Please can you explain how this central heating system works?

(13 Posts)
Moving15 Sat 12-Dec-15 16:13:49

Ok so I'm moving to house with a boiler (don't know what type)/and a hot water tank in the bathroom and a cold water storage tank in the loft. Please can someone explain to me how the system works and what the tanks are for? I currently have a simple combi boiler with temperature adjustment thingys on each radiator. Baffled by the labyrinth of pipes that lies ahead of me.

If you explain to me how it works I would be very grateful. For example, a combination boiler is like a kettle. Is there a similar analogy for this multi tank system??

dementedpixie Sat 12-Dec-15 20:39:07

Sounds like a conventional boiler system. Cold water tank feeds to the toilets and most taps (kitchen tap normally mains fed). Hot water cylinder holds the Hot water until you need it.

We still have this. Seems to work ok. Hot water timer on for a couple of hours a day and gives plenty of water.

PigletJohn Sun 13-Dec-15 09:51:51

The conventional boiler is simpler than a combi.

The boiler has a store of water which it heats up and a pump sends it round the radiators. It is the same water, it does not get used up, it just circulates round.

It is also sent to the cylinder, where it does not mix with the tapwater, but passes through a copper pipe coiled round inside the cylinder and immersed in the tapwater, heat passes from this coil into the hot tapwater in the cylinder.

There is a room thermostat on a wall somewhere that detects the rooms are cold and tells the pump and valve to send heat to the radiators, and a cylinder thermostat that detects the cylinder is cold and tells the pump and valve to send heat to the cylinder. There will be a timer or programmer that tells it what hours you want to heat the house.

For the hot tapwater, it is somewhat more economical to run the boiler for an hour or so morning and evening to fully heat the cylinder, than to let it run for a few minutes every time you run a hot tap, so there is (should be) a timer to allow you to set the timings. Once the cylinder is hot, it contains enough hot water to last all day, but it will be used up if you run a bath, hence time it to be replenished morning and evening. You can set it on all day if you want, the thermostat means that it will still only use gas when it needs to heat the cylinder. The cylinder will keep the airing cupboard warm and dry (if the door is shut) and is a good plafe to out your towels, sheets etc after washing and drying. It is not a drying cabinet so don't put wet stuff in there or it will go mouldy.

It will be capable of filling a hot bath faster than a combi, because the water has been pre-heated, but it is at lower pressure so showers will be weak.

There will probably be an electric immersion heater in the cylinder as well, but leave this turned off unless your boiler breaks down, because energy from electricity is about four times as expensive as energy from gas.

Is it a rented house?

What colour is the cylinder? This is important.

Narp Sun 13-Dec-15 12:37:59


I have this sort of system and I like it - particularly the airing cupboard.

I've got a wireless room thermostat that you can move from room to room, so that if you move into a colder room (in my case the kitchen), you can take the thermostat with you and get the room to the temp you want.

Moving15 Sun 13-Dec-15 14:21:47

Thank you so much for your replies, far more informative than Google offerings.

I am buying this house. I don't know what colour the cylinder is, I will investigate it more fully when we move in. What is the significance of the colour?

We are expecting to have to improve the system as I don't think there are enough radiators in the house and some of the pipework is visible and I want it disappeared.

PigletJohn Sun 13-Dec-15 14:32:19

colour indicates quality of insulation and approximate age, which also indicates speed of reheat time and probable method of installation. It also indicates if the cylinder is unvented (pressurised) or not.

specialsubject Sun 13-Dec-15 16:51:04

the bonus of a tanked system is that if you know a power cut is likely, you can heat your water in advance. This is going to be an issue in the UK, believe me!

make best use of it - don't run lots of little bits of hot water. Use the dishwasher if you have one, do the washing up in chunks once or twice a day.

you need to know the age of the system, if it has anti-corrosion inhibitor in it and when the boiler was last serviced. Especially if it is oil fired.

PettsWoodParadise Sun 13-Dec-15 17:32:05

I love my hot water tank as it means that DH and I can have showers at the same time without them being lukewarm and without worrying if someone flushes the toilet I will get scalded. I also love my water tank as it means I can still flush the toilets if the water is cut off for (which has only happened twice in 15 years!) but do be careful about ensuring your drinking water is from the tap connected to raising main (usually kitchen tap) as water stored in a loft tank may not be quite so fresh. My hot water tank also can act like a giant (but very expensive) kettle of the boiler fails as it has an immersion heater system which will give me hot water without the boiler. I've used it a few times but it isn't something to be recommended on a regular basis more because of the cost of the electric to heat that amount of water.

Downside of hot water tank is you do have to think about how much water you have - our tank allows one deep bath and two showers or one shallow bath and three showers then needs 45 mins to replenish. I prefer that to the lacklustre experiences I have had in the past with combi boilers.

PettsWoodParadise Sun 13-Dec-15 17:35:36

P.s just re-read my post and by saying showers at same time I mean one in main bathroom and one in ensuite. blush

Narp Sun 13-Dec-15 18:42:30

Can I hijack?

PigletJohn (and anyone else)

i have opted for, but not yet fitted an electric shower for our main bathroom, as I don't want to upset the balance of everything in the house, and take water from the hot water tank (we also have an ensuite shower with pump that takes water from the hot and cold water tanks.

The water comes from the Mains, correct? and as such is the pressure likely to be enough? I have bought an 8kW shower as I didn't want to have to replace the electric cable - was told that would need to be upgraded for a 10kw shower.

In summary - is this a good decision?

PigletJohn Sun 13-Dec-15 18:49:10

All electric showers are weedy. Yes, it has to be fed at watermain pressure, not from the tank. Depending on pipe runs, it can probably be connected to the pipe that goes up to feed the cold tank in the loft.

It will be useful if/when your boiler is out of action.

Narp Sun 13-Dec-15 19:06:56


So you think that getting a 10kw one would not make any difference anyway?

PigletJohn Sun 13-Dec-15 19:22:30

it would give you a 25% improvement, but I would still not consider it adequate. It will be especially cool in winter, as the incoming supply is colder.

It can be quite expensive to have a new circuit, with RCD installed, especially if your electrical installation is old.

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