Boiler replacement advice

[adil]

My boiler is very old IDEAL MAXICO SUPER Conventional Boiler with open vented cylinder in the airing cupboard & water reserve tank in the attic.
My house is a 5 bedroom (Total 18 Radiators), 1 bathroom, 1 shower room, Downstairs & Upstairs WC.

For economical reason i would like to change the inefficient system. I have been advised by a few plumbers:

1 said keep the same conventional system & change the boiler to (Radiant RK50 Conventional/Worcester 40CDI Conventional) change the old cylinder with jacket into a new 210Ltr cylinder & a new control system.

2. system boiler - (Vaillant 637/Worcester 30CDI) with unvented cylinder 210Ltr & new control system.

None suggested the combi boilers.

Can anyone please suggest which is the best option to go for Conventional or System.
Also if anyone has any information or experience with Radiant RK50 boiler.
Thanks

[Razor]

Never seen a RK50 but forget it!

Massively oversized for your needs and if you have a normal gas meter it'll eat the whole output and you won't be able to have any other gas appliances in the place.

They were right not to mention a combi. The choice between conventional system and invented depends on your incoming water pressure and flow rate.

What did they measure these at??

[adil]

They measured about 10l a min,
One guy said Worcester 40cdi can be fitted with unvented cylinder with a expansion vassal, is it a better & economical boiler then 637 vaillant.
Or should get vissmann 200w 35kw system boiler.
thanks,

[Razor]

10lpm? I hope that's a missprint!

If you read the specsheet of any unvented cylinder they all want at least 25 lpm at 2 bar!

Sounds like they were talking about an accumulator, this will ony charge up to whatever your incoming mains pressure is they should've measured that too.

For a house of that size a proper heat loss calculation should be carried out to size the boiler.

[noddy997]

First of all I would like to say if your current boiler is working fine dont change it as there is a huge cost involved.

Stay with a conventional system you would have ideally a immersion heater and possibly a electric shower - so you got access to hot water whereas if you had a combi boiler if it did breakdown you wont have heating or hot water! (Absolute nightmare in UK winters - I HAVE experienced this without heating only!!)

You need a minimum of 40kw if you can get something bigger than that would be better as you have many rads and it is a very big house (The RK50 is 54kw/186,000 btu and depending upon the size of your property you might need that). Dont be fooled into something along the lines of "lower powered boiler is economical go for 16kw or 24kw" or whatever your told). I have had idiots put in 8.8kw, and 16kw boilers in my house and within 5 years they have conked out and I got a 4 bedroom, 11 rads house. I got a 38kw Vailaint ecotec 438 boiler since 2009 had no problems what so ever apart from the condense pipe freezing up which has been lagged now - the house warms up in about 45mins flat out which is what I want.

I'd advise you to get a Vailaint they are solid minimum of 40kw or higher if you can get anything bigger.

[Razor]

As a professional heating guy I'd have to say that just about all the above post is totally incorrect

[thescruff]

As a professional heating guy I'd have to say that just about all the above post is totally incorrect

Not sure what noddys on but it ain't heating thats for sure.

I think the OP needs a few real heating guys/gals to visit with quotes and suggestions. If it's really that big I would be looking at 2 x 24Kw and do the job properly.

Where abouts is the OP, perhaps we can recommend an installer in the area.

[Razor]

Eighteen rads with one and a half bathrooms isn't big in the slightest. It's just a decent sized place.

The odds are that a 26kW or 30kW boiler and unvented cylinder with hot water priority would eat it alive!

Trouble with going for two 24kW boiler it leaves no spare capacity on a U6 for fires/cookers etc

[thescruff]

Could have a U16 already.

[Razor]

You'll be fitting LLH's, weather comp and Ferolli's next

[thescruff]

Nothing wrong with Scodas and LLh, WC and OT are a must if you want real energy efficiency.

[Razor]

But not as good as a nice thick cardy

[noddy997]

What am on about, is from experience. I have idiots come round and put in under powered boilers which packed up within 5 years, the first packed up after 12-18 months whilst the other packed up somewhere between 1 and 4 years. One boiler was a staggering 8.8kw, whilst the other was about 16 or 20kw.

The "experts" as I have seen in my time, sometimes are clueless. They say the new boilers are energy efficient blah blah, but the ultimate truth is, if the boiler doesnt have the "capacity" to heat your home it will conk out very soon. One heating and gas "expert" who I met in my time, was rubbish at fault finding and said he is only good at putting boilers in. Now if the boiler is not going into a new build house, and is going to replace an old boiler, chances are some adjustments need doing which requires a bit of fault finding if things dont work smoothly. But if your "expert" cant do that what good is he?

You do need to pass some exams and have a portfolio to be a gas man, but in all honesty I dont know how some people have done that because they are clueless.

Another example? I have 3 storey house which I let out and the long 30 year lasting glow worm finally gave up, called a few "experts" out and they said a 16 or 20kw would do perfectly fine (which about 50-70k btu). Funny thing is, the old glow worm had its sticker intact which said it was 100,000btu... (in todays terms 30kw). Ran into an old gas/plumber who we used many years ago who moved away and came back, asked his advice and he said you need a minimum of 80k btu for a place that big. So he stuck a 30kw in and since 2007 I have had no issues.

Of course "experts" will want things to go wrong so they can come back and charge you more lol rather than charge more in the first place and do a proper job..

[Dickie]

What am on about, is from experience. I have idiots come round and put in under powered boilers which packed up within 5 years, the first packed up after 12-18 months whilst the other packed up somewhere between 1 and 4 years. One boiler was a staggering 8.8kw, whilst the other was about 16 or 20kw.

The "experts" as I have seen in my time, sometimes are clueless. They say the new boilers are energy efficient blah blah, but the ultimate truth is, if the boiler doesnt have the "capacity" to heat your home it will conk out very soon. One heating and gas "expert" who I met in my time, was rubbish at fault finding and said he is only good at putting boilers in. Now if the boiler is not going into a new build house, and is going to replace an old boiler, chances are some adjustments need doing which requires a bit of fault finding if things dont work smoothly. But if your "expert" cant do that what good is he?

You do need to pass some exams and have a portfolio to be a gas man, but in all honesty I dont know how some people have done that because they are clueless.

Another example? I have 3 storey house which I let out and the long 30 year lasting glow worm finally gave up, called a few "experts" out and they said a 16 or 20kw would do perfectly fine (which about 50-70k btu). Funny thing is, the old glow worm had its sticker intact which said it was 100,000btu... (in todays terms 30kw). Ran into an old gas/plumber who we used many years ago who moved away and came back, asked his advice and he said you need a minimum of 80k btu for a place that big. So he stuck a 30kw in and since 2007 I have had no issues.

Of course "experts" will want things to go wrong so they can come back and charge you more lol rather than charge more in the first place and do a proper job..

As Razor has stated, most guys that know their onions would carry out a complete heatloss calc. You have clearly used the cheapest guy that quoted & ended up with a Lada Heating systems.

You can't advice on the size or type of boiler without knowing or at least having a good idea of, the heat loss of the building. Also a big consideration is the size of family & lifestyle.