New Vaillant Combi Boiler - Which One?

[Dogger1]

Hello,, I would be grateful for any help you can give please.. My 13 year old Baxi Solo 2 50RS (old style conventional/cylinder/tanks in loft) is on its last legs and needs replacing.It is set to 16.3 mbar and 14.65 kw heat output and has always been adequate for our needs, although of late the gas bills have been extortionate.

We have been recommended by an Engineer to replace it with a Vaillant ecoTec plus 824 Combi boiler which on the face of it (at 24kw) is more powerful than what we currently have but I see on several boiler review forums that at 9 litres/minute it is really only recommended for a flat.. We (3 adults) live in a 3 bed semi with 7 radiators,1 bath and 3 sinks,Dishwasher and Washing Machine plus an Electric shower.

Do you think it is suitable for our CH and DHW needs? Should I go for a more powerful one?

Do you think I should stick with a Cylinder and Tanks in loft system but just change the boiler to a condensing heat only type?. If so which would you recommend?


ps. Decided to consider a Combi initially to free up space in the airing cupboard (no cylinder needed) and loft (no tanks needed).

Thanks RR

Posts: 1
Joined: Sun Nov 09, 2008 12:39 am

 

[Agile]

I think you are taking your "advice" from an installer who is only thinking about his profit and not your needs!

I have no connection with you, your installer or any financial gain! So my advice is that a combi is NOT likely to be the best option and probably the worst solution to your needs!

A Worcester 15Ri would be one simple boiler which would replace your existing boiler with the same power.

Tony

 

[ChrisR]

I'd prefer a GloWorm, with stainless heat exchanger, and cheaper than the imho over-rated Worcesters.
A combi will give you endless showers, and save you space. The power rating is for the benefit of the hot water supply. 24kW is the minimum and most people prefer 28-30kW or more, but if you're used to a widdling 10kW electric shower, then 24kW would be a joy. Combis need a pretty good mains water supply.
All combis now automatically "modulate" down to lower power for the CH, so there's no need to worry about it being too powerful for the house.

With a heat-only boiler you will probably have better reliability, backup in the form of an electric immersion heater, and no interdependance between hot water tap flows. Building regs say you should have a cylinder to the latest spec, but many sane people resist that, depending on what they have already. If you don't have a new cylinder, the heat-only substitution would be a little cheaper than a combi conversion, but not a lot.

 

[Dogger1]

I think you are taking your "advice" from an installer who is only thinking about his profit and not your needs!

I have no connection with you, your installer or any financial gain! So my advice is that a combi is NOT likely to be the best option and probably the worst solution to your needs!

A Worcester 15Ri would be one simple boiler which would replace your existing boiler with the same power.

Tony

Thanks Tony,, could you elaborate a bit on why you are agin modern combi's,I'm on a steep learning curve here...

Also to everybody else, Is Agile's advice the same as your's ?

One thing (amongst many) that I don't understand is why are the modern condensing combi's so much more powerful than the old system boilers?..

thanks again Rob

 

[simond]

They are powerful because they have to heat cold mains water in real time.

To deliver around 9 litres of mains water per minute that is 5C, lifted through to 40C takes around 24Kw.

That is why you have to dance around to get wet in a typical instantaneous electric shower, becuase that is around a third the power (eg: 8Kw) and therefore only heats a third of the water volume (eg: 3 litres per minute).

Since the heat exchanger in a combi has to deliver a minimum of 24Kw to give a usable hot water output, most combis have the ability to deliver that into the radiators as well. However as most new boilers modulate, their output can be regulated to 7-10Kw when CH demand is low.

 

[sambotc]

Hi,

It depends on what YOU want. If you want the extra space, get a combi. The advantages of a combi are, endless hot water, take up less space, cheap to run, no tanks in loft to worry about. Vaillants are about as reliable as you will get for your money. The disadvantages are, they will only supply 1 tap at a time, they have no 'back up' in the event of breakdown and will require some additional work to change over from you existing set up.

If you spoke to your installer i'm sure he would happily install an ecotec 831 for whatever the extra is between appliance price, no other work should be necessery (possibly gas depending on run)

9 ltrs/min is OK, 12ltr/min is better, but we're talking a couple of minutes differance to run a bath, for an extra couple hundred quid.

Choice is yours

Sam

 

[Agile]

Tony

Thanks Tony,, could you elaborate a bit on why you are agin modern combi's,I'm on a steep learning curve here...

thanks again Rob[/quote]

Oh dear!

I have nothing against combis! They are fine for situations where a combi is the best solution and they make up about 80% of the boilers currently being fitted. Also about 95% of the boilers I repair.

However, your situation is completely different! You have a conventional system and the cost of converting that is considerable, I charge £400 for example.

A cylinder fills a bath in 4 minutes whereas a combi at 24 kW about 10-15 minutes. With three people I would usually recommend a conventional system but it does depend on their lifestyle and other factors.

The other major problem is that as a combi only feeds one tap at a time then if either of your other two adults turns on a kitchen hot tap then the one having a shower will get cold!

Tony

 

[Deleted member 105431]

My advice would be get the Vaillant ecotecplus 837 with a magnaclean. It will meet your needs perfectly and be a very good investment long term.

 

[namsag]

What makes you think your existing boiler is on its last legs this boiler should be good for 20 years plus.
The solo 2 rs is a good boiler and parts still readily avialable.

 

[mickyg]

What makes you think your existing boiler is on its last legs this boiler should be good for 20 years plus.
The solo 2 rs is a good boiler and parts still readily avialable.

I agree with this one

best way to save money is don't spend it. A boiler with a cast iron heat exchanger should last 15years minimum if well looked after.

 

[BigBurner]

However, your situation is completely different! You have a conventional system and the cost of converting that is considerable, I charge £400 for example.

£400 to rip out a tank and cylinder?

A cylinder fills a bath in 4 minutes whereas a combi at 24 kW about 10-15 minutes. With three people I would usually recommend a conventional system but it does depend on their lifestyle and other factors.

Then he fits a high flow combi not a 24 kW. The Broag 35C is highly rated using the same parts as a Vaillant but with OpenTherm controls and weather compensation. And cheaper The Glow Worm 38CXI is highly rated and owned by Vaillant too. I would got for the Broag, and fit an OpenTherm timer/controller and an outside weather compensator temperature sensor. You will not regret it.

The other major problem is that as a combi only feeds one tap at a time

High flow combis do more than one tap.

 

[BigBurner]

best way to save money is don't spend it. A boiler with a cast iron heat exchanger should last 15years minimum if well looked after.

It will use far more gas than a modern condensing boiler. If it needs money spending on it it may be best to replace with a state if the art combi and get power showers.

 

[mickyg]

best way to save money is don't spend it. A boiler with a cast iron heat exchanger should last 15years minimum if well looked after.

It will use far more gas than a modern condensing boiler.

far more? not really. Savings qouted by companies with invested interest are very rarely achieved. The cost of installation far out weighs the savings.

 

[mickyg]

The Broag 35C is highly rated using the same parts as a Vaillant

really? which parts are they then?

 

[sambotc]

Just to add another 2 pence.

Personally if you see yourself needing high demand for DHW i would keep your existing system and replace with a new condensing boiler. You then have the option of replacing the cylinder for a fast recovery type or if demand's are high and building control permits you could upgrade to an unvented cylinder, although from what you have said i would think this is OTT.

My opinion is that to get the most out of a high flow combi you will need to have top cold water main flow, bigger gas supply and cold main to boiler and you will probably not see much performance increase from a well installed vented cylinder which you already have!

Sam