Should I get a combi?

[tebreak]

Currently I have a Baxi back boiler, about 21 years old now.
It recently had a thermo couple replaced and the plumber said it;s about time I got a combi, before it pacvked up.

He said it would be cost effective, rather than the cost of replacing parts on the back boiler.

Is that generally a better idea than just fixing the old?
the reason being there will be a lot of upheaval in the house, re-arranging furnature and fittings.

 

[stem]

This is asked quite a lot see Click here and scroll down to FAQ 5

Personally I wouldn't have a a combi. You can install a new heat only boiler and keep the hot water system you have, however, others disagree. My reasons are:

Combi's share the normally small diameter main cold water supply with everything else in the house including WC's and it's often not enough to supply hot and cold at the sametime. (heat only boilers use a stored supply for hot water)

The loss of an airing cupboard you can use anytime. (This may be a plus to some if you're desparate for the space occupied by the hot water cylinder)

Often they need a larger diameter gas pipe than existing and it's sometimes run around the outside of your home. Yuk.

They can't heat radiators and supply hot water at the same time.

Combi's are complicated have more internal components and so more items to fail.

Not suitable for DIY work, Non combi's usually have external components (pump, motorised valves, programmer) which can be replaced DIY.

They are slow to get hot water to the taps when started up from cold. (Turn on the hot tap - slight delay - boiler burner lights - delay while heats water in boiler - transfers water to heat exchanger - delay as heat exchanger warms up - Mains cold water starts to pick up heat from heat exchanger - and finally starts to make its way to the taps)

 

[IJWS15]

In addition, I am not a plumber but have had several combi's - currently have hot water tank and it is great

any new boiler you get will be a condensing boiler and the condensate outlet is likely to freeze up at times in winter leaving you with no heating or hot water.

A combi will supply a small amount of hot water or a lot of warm water - unless it is a huge rating (and we have had 28,000 BTU rating combis) you will not get lots of hot water.

Unless it is an enourmous size a combi will not supply two outlets with hot water at once . .

If you have a power cut you lose all hot water, with a tank you can still use the contents.

They are OK for flats with one bathroom, anything else keep the tank.

 

[flameport]

He said it would be cost effective, rather than the cost of replacing parts on the back boiler.

Back boilers have virtually no parts in them, and those that do need replacing are usually very cheap and quick to install.

Even though a new combi boiler would probably use less gas, the savings will never pay for the boiler & installation costs. By the time you have saved enough to pay for the boiler, the boiler will already have had multiple expensive failures and been replaced with another one.

 

[simond]

Back boiler parts are cheap. Gas technicians are not.

Remember when advising people to keep them that they have to pay parts AND labour. A few repairs and you could be well on the way to the cost of a new boiler, combi or otherwise.

Instead, you will have a 25-30 yr old cast iron lump full of sludge. When you sell the house the purchaser will see the old heap and knock you for the price of a replacement.

Sometimes the best advice isn't free.

 

[dcawkwell]

Stick with the back boiler.
My mums is 40 years old so you have got another 19 years to go.
It will probably be going long after any combi you installed
and never need any parts and be as reliable as they come.
It think my mums has needed a thermocouple and thermostat
in 40 years of operation.

PS Get another gas engineer next time it is serviced his advice was
possibly bad. Probably hasn't got much work on.

 

[Phill Peck]

In addition, I am not a plumber but have had several combi's - currently have hot water tank and it is great

any new boiler you get will be a condensing boiler and the condensate outlet is likely to freeze up at times in winter leaving you with no heating or hot water.

A combi will supply a small amount of hot water or a lot of warm water - unless it is a huge rating (and we have had 28,000 BTU rating combis) you will not get lots of hot water.

Unless it is an enourmous size a combi will not supply two outlets with hot water at once . .

If you have a power cut you lose all hot water, with a tank you can still use the contents.

They are OK for flats with one bathroom, anything else keep the tank.

That's interesting you've had a 8.2kw combi no wonder your not impressed

I've installed around 100 combis never had a condense freeze. It's about the quality of boiler and install

A good combi will provide unlimited very hot water not warm

A combi in the right situation is very good. I have one in my house

In reality your back boiler will be more realiable and cheaper to repair
A new combi will be cheaper to run and safer being a room sealed appliance compared to a open flued. This would mean you could do away with the drafty air brick in your living room

 

[kevplumb]

a combi is only as good as the install and the work done beforehand

 

[Dan Robinson]

with a tank you can still use the contents

Unless you have a pump of course .

unless it is a huge rating (and we have had 28,000 BTU rating combis) you will not get lots of hot water.

Twaddle.

the condensate outlet is likely to freeze up

Not if it is installed properly.

 

[stem]

A good combi will provide unlimited very hot water not warm

The quantity of hot water is limited by the cold mains supply to the property. The hot water supply will drop off rapidly if someone flushes a WC or the washing machine starts filling etc., etc.,

 

[tangowaggon]

If there's just one or two of you in the house then a combi is ok but they're rubbish in a family home when more than one hot water outlet is likely to be turned on, I've had two combis, the last was a 35kw w'bosch, the shower would stop altogether if anyone turned another hot tap on and it took ages to fill a bath, especially in the winter.

Condensing boilers condensate outlets only freeze up if they have been badly installed.

Go for a system boiler and the existing tank or better still a system boiler and unvented tank.

just the cost of a failed circuit board in a modern boiler will cover the cost of numerous repairs to your back boiler, comparing the repair costs of our modern boilers to the running and repair costs of Mum & Dads ancient old potterton, there's not much between them

 

[Mikefromlondon]

I would go for the combi boiler any time, despite its only disadvantage being that it cannot supply hot water to an upstairs bathroom as well as if someone had wide opened thye kitchen hot water tap.

2nd disadvantage is rare but can often happen when the mains incoming pressure is too low during certain times, but most modern boilers will heat water on flow rates as low as 3 litres per minute.

on the other hand, storage heaters soon run out of hot water after a couple of family memebers have taken a bath one after the other! there isn't enough time for the tank to heat up fully, but main advantage that it does not run out of water,

other disadvantages of storage water heaters:

1. pipes everywhere in your bedroom cupboard.
2. Controls everywhere,
3. external pump!
3. external control valves,
4. Loft filling and venting tanks, gets contaminated with dust, and other debri, the hot water is not suitable for drinking thus.
5. very messy when it goes wrong, water could potentially leak upstairs and cause flooding and water gets in your ceiling, and electrical wiring.

 

[stem]

I don't know anyone with a fully pumped system that complains that their hot water cylinder runs out of hot water. They can be reheated in the time it takes a person to have a bath. However, the older gravity hot water systems suffered from this as they were slow to reheat the cylinder.

1. pipes everywhere in your bedroom cupboard.

With a combi extra pipes will be required in the kitchen (or wherever the combi is) instead of hidden in a airing cupboard. A non system heat only boiler can have has as few as three neat discreet pipes and a condensate drain. A combi will have those plus a cold water supply pipe, hot water supply to the taps plus isolation valves, filling loop and possibly a larger gas supply pipe.

2. Controls everywhere

Hypebole? There won't be controls everywhere. The user controls are a timeswitch and room thermostat the same as a combi. There will be a motorised valve & cylinder thermostat but having them outside of the boiler can be an advantage. See below.

3. external pump!

Easily accessible for DIY replacement with readily available standard parts.

3. external control valves,

No need to call a Gas Safe engineer to open up the boiler if they fail, so great for DIY repairs using standard parts readily available from local plumbers merchant or DIY shed if it's a Sunday. With a combi, the comparable items (plus a quite a few extra) are inside, so it's a wait for the Gas Safe engineer to come with specialised manufacturers parts.

4. Loft filling and venting tanks gets contaminated with dust, and other debri, the hot water is not suitable for drinking

Not a problem with properly installed tanks with Water Bylaw 30 kit. Also keeps system topped up no need to repressurise the boiler at regular intervals or after bleeding or removing a radiator. Also easy to introduce corrosion inhibitor into the system.

5. very messy when it goes wrong, water could potentially leak upstairs and cause flooding and water gets in your ceiling, and electrical wiring.

Any system can leak. There's still a lot of water in a combi when it's connected to seven or eight radiators.

I'm not anti combi, they do have some advantages. They provide mains pressure hot water, they free up space a hot water cylinder would require (although you loose the immersion heater as a back up) and they are easier to install as part of a new system. Engineers like them as they don't need to employ the services of an electrician as most of the wiring is inside.

 

[Mikefromlondon]

Stem, you are right, you are absolutely right, and you are quite right, and you are dead right, and you are truely right, and best of all I like your point where you can nip down to your local Wickes and get any standard heating parts and fix your own heating without having to call registerd gas safe engineers, who not only would be charging you double for Sunday work, but also you are at their mercy. Right now I have got my balls in their hands, if I say someting, it gets squashed a little at a time, one ball in the hands of HSE and the other in the hands of you know. Aah changing subject slightly, talking about saving lives, those poor 6 children who died in a Derbishire house fire, can we ask HSE to make a new rule that all parents with kids are responsible to have smoke detectros fitted in their house by Law. Someting new to delve on HSE. and make sure that only qualified Fire Alarm engineers can service and install these alarms, as they frequire maticulous planning where they should be fitted and how some people remove batteries because theu become nuisance when you burn a toast they go off!

 

[tangowaggon]

Bottom line is that both sytems have advantages and disadvantages, the right system will depend upon the design of the building, who is using it and their lifestyle