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Combi, system or regular boiler?

Postby reggieroo » Sat Aug 29, 2009 8:19 pm

Right I'm in need of a new boiler as I have been without one since Xmas.

I have a few questions I need answering so I can make the right decision on which type of boiler to go for & what set up to have.

I'll start with my house info so to give an idea of what might be best for me & my new family ( a new baby on the way in 6 weeks )

3 bed detached bungalow, nine radiators, one bathroom & a toilet/cloakroom. Also an open fire in the lounge with a back boiler ( currently disconnected). The system I have in place at the moment is a regular boiler with the hot water tank in the airing cupboard & water cistern in the loft. Also we run on LPG gas bottles as we have no mains gas in the village.

The boiler I have at the moment is around 15 years old & gave up the goose last Xmas, leaving us with no central heating as we couldn't afford a new boiler. I've still had hot water as I have just used electric to heat the tank when needed. I bought some cheap oil filled radiators & had a coal/log fire every night to get us through the Winter. Now Summer's coming to an end & a new baby on the way I need central heating again.

I've been thinking about hooking the back boiler back up with a neutraliser to a new regular boiler to save on LPG costs. I had a chap out the other day & told me that the back boiler will only heat the water as it's not that big & to work out if it will make me any savings over the year. I have a coal/log fire nearly every night in Winter so thought it would be wise to use the back boiler so I'm not just wasting the energy.

I was then thinking doesn't your hot water heat up anyway when your central heating is on, which would be on most of the Winter anyway?
So is it worth the extra expense of hooking up the back boiler as the water would already be hot wouldn't it?

So this is the dilema I having & I'm not sure what to do as I've had a few people out & have all told me different things. I bascicly want to keep fuel bills down to a minumum as we will stuggle more than ever now with a new baby on the way.

Do I go for a combi boiler for their effeciency (so i'm told) or system boiler( I like the thought of still having hot water in the event of a boiler breakdown), or hook up the back boiler (at extra cost) with a regular boiler to try & keep LPG bills down?

Bit of a long post I know but wanted to give as much info to people in order to get the right advise.[b][/b][b][i][/i][/b][b][/b]
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Postby plumbbob » Thu Sep 03, 2009 6:50 pm

I think any answer could be even longer.

My first thought is a question to you really about what you believe is a "regular boiler"? There are in fact only two types of boiler. A combination boiler that instantly heats both water to the taps and central heating water or a system boiler that does the central heating whilst warming a store of hot water for the taps in the traditional way.

Maybe you are confusing the new condensing boilers and the old fashioned style boiler which are no longer available as they can't legally be installed any more.

I don't see why you can't fit a new system boiler into your existing circuit and incorporate the back boiler too. Is the back boiler connected now?

How much you might save using the back boiler is anybodies guess. Maybe nothing! It is partly going to depend on how much hot water is used, when and how big the fire is and when it's lit.

Se the back boiler aside, and I can say for certain a new combi boiler is the most cost effective way of heating. Instant water heating with no waste combined with the efficiency of the new condensing mechanics is a real money saver.

Unfortunately you have one down side and it is a pretty big one. LPG has to be the most expensive fuel to buy. Well at one time it was - whether that is still so, I am not sure.
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Postby Perry525 » Thu Sep 03, 2009 7:09 pm

Lets start with Propane gas - this is the most expensive type of heating there is.
But it is capable of clever control, even being turned on and off by telephone.

The back boiler, the cost of running one of these, is but part of the issue.
If you can find cheap wood and have the storage space and the strength, and you are there all the time to keep it going - then this can be your best and cheapest bet.
However, no all back boilers can produce enough heat to keep all those radiators and your hot water going at the same time.
But, spiting your home into zones, where the hot water is directed where you want it to go, when you want it will work. This just requires two room thermostats, a tank stat. And three motorized valves. And a simple segment timer, if you must turn the heating on and off.
Keep in mind the future, when you want to sell and move on, try not to have a heating system that will put people off, as its too difficult to maintain and run. Older people like gas as its easy and does not require any storage space, or road access.
Combi boilers, if you live by yourself, or only have one other person to live with and you know where each other are all the time. Then a combi can work.
If you want to be able to use several taps at the same time then a combi is useless.
If the water pressure in your area drops during the morning and evening when people are using lots of water its useless.
A modern boiler is built to the same standard as a combi and it is much more efficient, in as much as, it does not have to run at maximum output to heat cold water. A normal boiler, merely turns on when the thermostat calls for heat and the hot water tank will supply several taps with hot water at the same time and rush hour means nothing.
Your existing boiler, why not have it repaired?
If you search on the net, you will find there are lots of spares for all makes and types of boiler.
Find an engineer who is familiar with your type of boiler and ask him how much to repair, do not accept that it is past repair or that spares are difficult to find.
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Postby reggieroo » Sat Sep 05, 2009 10:55 am


The three different boiler types I was refering to was the regular(open vented), system(sealed) & combi.

At the moment I have the open vented regular boiler, which is in fact 25 years old & I won't be repairing that. We had an agreement between me & the fiancee that we would replace it with a new condensing boiler once it had given up the goose. She wanted it replaced ages ago while it was still working to improve our efficiency but I said wait till it goes wrong.

The back boiler is not currently connected & I believe it hasn't been since the boiler was fitted around 25 years ago.

We had a couple of engineers around who have told us that the back boiler is only big enough to heat the hot water & not the radiators & will need to be tested before any reconection takes place as it could be corroded by now.

At the moment a combi seems to be the best option as we have looked at how much hot water we use & its not a lot at the moment but that will change a little when the baby arrives. The engineers still think a combi would be best as we have an electric shower, dish washer so only really need it to wash hands & a very small amount of washing up.
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Postby plumbbob » Sat Sep 05, 2009 8:42 pm

You are probably right in the circumstances to opt for a combi boiler as they are by far the most efficient.

Just to clarify about the types of boiler available. A system boiler can be either open vented or pressurised (sealed). The description "system boiler" simply means it is part of a heating system and not a stand alone item such as a combi. All "regular" boilers are system boilers.

It is possible to combine your back boiler (assuming it is not faulty) with a new system boiler provided it is an open system. Extra considerations have to be given to safety and it will cost more to install, but it could be worth considering especially if the fire is lit constantly.
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