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Original poster

Could someone explain my central heating/hot water system to me?

36 replies

MILdesperandum · 16/12/2013 23:09

Just moved to our new house, previously we had a combi boiler and that was it, no cylinder or tank. Boiler had a timer dial for heating and there was a thermostat in the hall.

Now we have a combi boiler, tank in the loft and cylinder in the airing cupboard. I think the cylinder used to have an immersion heater but now the electric supply had been disconnected - the owner described it as obsolete but now I'm not sure if she meant the immersion part or the whole cylinder - would the combi boiler fill the cylinder? How can I tell? Additionally we have a programmable timer which I understand for the heating but we can also program hot water - never had anything like this before, will this be obsolete too or is it somehow controlling when the combi will provide hot water to the taps/cylinder.

So confused or last system was so simple!

OP posts:
5HundredUsernamesLater · 16/12/2013 23:40

Do you have the name of the boiler? Just wondered if it would be worth a try searching Internet for some kind of instruction manual.

PigletJohn · 17/12/2013 00:27

it is unusual, but not impossible, to have a combi with a cylinder. How many bathrooms are there?

how do you know the boiler is a combi?

is the cylinder hot?

when you turn on the hot bath tap, does the boiler immediately fire? Or does it come on after some time, and run for about 20 minutes?

When you turn on the kitchen sink tap, does the boiler immediately fire?

When you run the bath hot tap, does the water get hotter is you turn the tap down, and less hot if you turn it to maximum flow?

Original poster
MILdesperandum · 17/12/2013 06:13

Lots of questions - I will investigate! It's a Worcester boiler and I "know" it's a combi boiler because the survey said so and I'm presuming they did actually look at it. thanks for replies.

Oh we have one upstairs bathroom and one downstairs WC. The airing cupboard is warm and the cylinder feels warmish to touch but I'm not convinced it is because it is full of hot water or just because there's pipes in the cupboard.

OP posts:
Bakingnovice · 17/12/2013 06:22

MIL are you me? Watching with I retest as I posted a similar post a few weeks ago.

Original poster
MILdesperandum · 17/12/2013 06:31

oo - did you work yours out baking novice? I thought when we bought the house it was combi boiler, redundant cylinder but now not so sure, I'm just waiting for the household to wake up so I can play with the taps/dash out to look at the boiler Smile

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Original poster
MILdesperandum · 17/12/2013 08:34

OK the pipe going in to the top of the cylinder is hot so... the cylinder is functional right? Does that mean that the programmer I have is for the hot water in this cylinder? But when the hot water is "off" on the programmer will I still get hot water from the kitchen tap - I suppose there's only one way to find out!

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PigletJohn · 17/12/2013 11:16

the programmer probably controls the times that the boiler is allowed to heat the cylinder and the radiators. It will take (if modern) about 20 minutes to heat the cylinder. The cylinder will then contain about 100 litres of water which will stay hot (if properly insulated) for about 24 hours or until you use it up, even if the boiler is turned off.

What colour is the cylinder?

Original poster
MILdesperandum · 17/12/2013 11:53

Yellow.
OK - that would make a bit of sense. The "hot water" setting has been off for the last few hours but I could get really hot water from the kitchen tap just now (within 30s-1min) and as far as I can tell the boiler didn't fire up. Good to know it only takes 20 mins to heat the hot water tank, do I then need to just put the "hot water" setting on a timer for around 20mins a day?

Thanks

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Original poster
MILdesperandum · 17/12/2013 11:54

Just found the boiler manual Grin it's a Worcester Greenstar CDi conventional. was installed in 2009 I think

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PigletJohn · 17/12/2013 12:01

you do not have a combi.

Perhaps you have a fairly modern condensing boiler and the surveyor is an ignorant buffoon.

A yellow cylinder is about 25 years old and will take more than 20 minutes to heat up. The yellow insulation is quite thin so add a red insulating jacket to it. They are cheapest at Wickes this year. Also add pipe insulation such as Climaflex to all the hot pipes, especially round the boiler and cylinder. Measure the pipes to see if they are 22mm (probably) or 28mm (old) or 15mm (some) so you get the right size. You cut it with a breadknife.

There should be a rectangular thermostat strapped to the side of the cylinder. It will turn off the boiler when the cylinder is up to temp.

Depending on the size of your cylinder (measure its height and width) it probably holds about 100 litres which is about a bath. If you time the boiler to be on before and during your bath, it will reheat while you are splashing about.

Original poster
MILdesperandum · 17/12/2013 15:30

OK just checked the survey and it was me that made the mistake not the surveyor, survey report says "central heating and hot water is provided by the gas fired condensing boiler" Blush in my ignorance I thought that meant combi Blush. Thanks for your replies and advice

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Original poster
MILdesperandum · 17/12/2013 17:03

whilst I'm confessing the cylinder is more green than yellow- is that good bad or makes no difference

OP posts:
PigletJohn · 17/12/2013 17:12

green is better than yellow.

Blue (current spec) is better than green

A red jacket and pipe insulation will reduce heat loss anyway.

Original poster
MILdesperandum · 17/12/2013 17:17

great will get me to wickes Smile

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Original poster
MILdesperandum · 17/12/2013 18:15

Another question (sorry) currently we have no shower, we wanted to fit an ensuite shower and a shower over the bath in the future. As we don't have a combi boiler after all will thermostatic showers be rubbish? Do I need to start looking at electric/power showers?

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PigletJohn · 17/12/2013 18:44

you have probably got a cold water tank in the loft. It is probably only about three metres above the shower outlet, so you will get a weak shower upstairs.

If you have a downstairs shower it will be less weak.

You could fit a shower pump, but it will be noisy and IMO not worth the trouble.

It is vital that the cold water to a mixer shower (or mixer tap) is at the same pressure as the hot, so must also come from the tank.

if you want a good shower you could upgrade to a Megaflo or similar, but you will need a very good incoming mains water flow, which may require new pipes all the way to the pavement£££

Original poster
MILdesperandum · 17/12/2013 18:58

Are all electric showers rubbish then? how good is good in terms of mains water flow?

OP posts:
poocatcherchampion · 17/12/2013 20:30

we got an electric shower in the same situation as you. it's OK. not fab tbh. I'm not sure what we will do when we replace the shower room as I'm sure dh will say he wants more pressure.

PigletJohn · 17/12/2013 20:42

A combi is considered to be adequate if it delivers 12 litres of hot water per minute. Some can do more.

A Megaflo or similar (it is a modern, pressurised hot water cylinder fed at mains pressure, with no cold tank) might deliver 20 litres of hot water per minute.

An electric shower might deliver about 5 litres per minute. In winter the water will not be very hot.

Fill a bucket at the hot tap or under the shower to get an idea of what that feels like.

Original poster
MILdesperandum · 17/12/2013 21:23

will try that out thanks, might need to be a quick decision as the electrician is starting in the house tomorrow and if we want an electric shower I'm presuming we'll need a special electrical supply put in whilst the floors are up.

Might also try to get the price for a Megaflow... so if I want a megaflow my mains water needs to fill a bucket (say 4 litres) in 12 seconds, that sounds incredibly quick! have I got that right? (sorry for stupid questions!)

Thanks for your help

OP posts:
123rd · 17/12/2013 21:47

Hey Mil, remember me from the movers thread. Have we moved to the same house?? We are in the same situation wrt boilers and wanting to change things about. Hope you are settling in ok.

Original poster
MILdesperandum · 17/12/2013 21:51

Hi 123! Yes I remember thinking our houses sounded similar when we were discussing what needed doing, What boiler system have you inherited? Thought we had ours sussed but apparently not!

OP posts:
123rd · 17/12/2013 21:59

A very old creaky looking thing but it works as this house is bloody boiling!!! We have a kingfisher in the kitchen and a big hot water tank in Ds room. But I just went and checked and it looked a bluey colour.
I also thought electric showers were naff so am a but stuck as to what to do when we change the current bathroom into our ensuite. We won't be doing the extension until later but does that mean I won't be able to have a decent shower yet??

Original poster
MILdesperandum · 17/12/2013 22:05

Yes similar dilemma... our boiler isn't too old but I guess you might want to change yours anyway. I'm liking what I hear about megaflow but it sounds like £££ we didn't expect to spend Confused

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TwistedRib · 17/12/2013 22:05

We have a megaflow, but opted for an electric shower because the price of heating oil is so huge. We knew a mains shower would use loads of hot water and cost a fortune. Yes the flow of an electric shower is less but it's fine, and because of the pressurised system the electric shower doesn't run cold when the washing machine is on etc.

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