TIME FOR A NEW BOILER - WHAT DO YOU THINK . . . .?

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Hi

The time has come for a new boiler.

I don't want to break any forum rules but are you able to say what make/models
or companies to stay clear off?

We are restricted because it is LPG.

Below are two models that look like they'd fit what we need. I've emailed Vallant to
see if the model below has a conversion kit from Natural gas to LPG.

Any other recommendations would be welcome.

We have a chalet bungalow (ground & first floor), two bathrooms and one en-suite.
But they are never used at the same time.

I gave up yesterday trying to fix an old Alpha CB28 LPG - one of the tests was to see if the
flow was correct, it had to be 2.5 litres in one minute. I got 2 litres in 10 seconds so I'm
hoping that modern boilers do not require more as we do live in a semi rural area and the
pressure is terrible, especially if you wanted to wash the car.

In the end the fault finding chart all pointed to the PCB - it would be throwing money away to
keep this old girl on the wall.

I've read that Worcester Bosch have a good name, but I haven't found much on Vallant apart
from they invented the combi boiler in 1967.

Around 20 years ago I fitted a mains gas Potterton (vented/cylinder) and didn't have a problem
in 10 years, but their website only shows something other than LPG - so it looks like they do
not cover LPG.

What about these three?

1) Vaillant ecoTEC 937

2) Worcester Greenstar 42CDi Classic Combi HE Boiler LPG Gas

3) Worcester Greenstar 38CDi Classic LPG Combi Boiler 38 Cdi

(Worcester names are different, because from different suppliers).

The Worcester 42CDi is too expensive for use, unless I can find it cheaper.

One other point, what is the current rate (south coast) to fit a boiler like above?

Taking in to account this would be a near direct replacement inasmuch as gas, water, flow & return
are already in place and would only require new 'adjusted' pipe work etc, to connect to new boiler.

Many thanks in advance.

Regards

Stephen
 
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May not be as straight forward as you think (depending on gas meter/gas pipe run location)... for bigger kW boilers like the ones you have mentioned, I would say its almost guaranteed you will have to upgrade the size of the whole gas pipe you currently have from meter to boiler.

Another thing maybe worth thinking about, are you dead set on a combi? Have you thought about an hot water storage tank instead, or an unvented if you are getting enough mains pressure 1.5bar?

Some Manufacturers I would stay away from personally would be
Ravenheat, biasi, ferroli (although heard new stuff ok, never seen them myself), sime,

Best to get a few local guys round to quote and they could answer any questions also.

Some manufacturers have installer contact numbers on their websites, this can help with some providing additional warranty.
 
May not be as straight forward as you think (depending on gas meter/gas pipe run location)...

Op has LPG.

Op, what the standing pressure on water main? And running pressure? What the flow per minute? This is the question plumber / heating installer will find out if it is good enough for a combi. You be better off using heat only boiler and unvented cylinder.

Vaillant 400, 600 and 800 series is good for LPG

Daniel.
 
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Why would he go for an unvented cylinder when he has 12 litres per minute? :rolleyes: . You would need a MINIMUM of 20 litres a minute for unvented for it to be worthwhile. I wonder how many people suggesting unvented are actually qualified to install and work on them? ;) (hint: I am).

If you've put up with a 28kw standard efficiency combi for this long already then a new condensing 28kw boiler will still be an upgrade (efficiency has increased so you get more heat into the water for the same 28kw you were putting in before). I can't see any sense in going for a boiler much bigger than say 30kw with that flow rate. You're wasting money and it'll be less efficient than a boiler correctly sized for the load.

All this is assuming you have measured the flow rate correctly (2 litres in 10 seconds X 6 for 60 seconds = 12 litres per minute).
 
brassedoff - I was thinking of a SYSTEM BOILER but I haven't priced it up yet.

If I went for that (that's the sturdy looking cylinder with lots of pipes attached - right?) would the water
pressure for the shower be standard, or forced from boiler pump? or would I have to install a shower pump.

I used to have an Aqualisa 60 foot head that was really good.

Somehow it looks like the system cylinders will be rreally expensive to fit, looks like a lot of work.

I don't fancy going back to vented with cold tank in loft.
 
StOrmer66 - thank you for your reply.

About the flow - I turned the hot tap on (to see if boiler would fire up) hard/full on, and a two litre
jug filled up in 10 seconds, lets say 12 seconds - I said we have rubbish pressure down here.

It makes sense what you say about getting a 30kw boiler - I was under the impression the bigger
the number the more heat it would produce.

In saying that will the following make a difference?

There is a possibility that early next year our chalet bungalow will be converted to a house - that is the roof
will be sliced off, and the height of the walls will increase by around 1.5m to 2 meters, with dormers.

This is because next door have knocked down their small bungalow and built a totally out of proportion
huge property (due to possible flooding from sea all living space has to be on first floor).

This has made our property look like the runt of the litter.

Council have been round and agreed in principle that we can increase wall height - but will have to
wait until plans have been submitted to see if we get planning permission.

Because this would not be a new build, we would keep the ground floor for living.

I mention all this because although there are radiators up stairs by changing it to a house this will
increase the amount of rooms and sizes by quite a lot.

I have to say the Alpha CB28 for central heating has always been excellent - it is the hot water, in
the en-suite or bathroom that is a real pain, you can wait a couple of minutes for hot water to arrive,
the boiler is in the kitchen so the sink tap is not too bad. I have a feeling it is the way the pipe work has
been laid out, but never had the time to correct this, and we just put up with it.

So could you confirm that it is the flow amount per minute that dictates what "kw" boiler you should go for.

I know you have to work how many radiators the property has, and room sizes come into the equation - but
from what you are pointing out the bottom line is, if the flow rate is not powerful enough it makes no difference.

And would I be right in saying that unless you have every radiator fitted WITHOUT TVR's and full on - it would
only be then that you would notice a difference in the heat from the radiators, but even then if the
circulating pump speed was set in middle position the return would take a tad longer to reach boiler before
being heated again, so it wouldn't be that noticeable.

Of course that's a layman's thinking.

Sorry for long reply.
 
It makes sense what you say about getting a 30kw boiler - I was under the impression the bigger the number the more heat it would produce.

a boiler can only give out as much heat as the load, all radiators have a designed heat output. For example a 600x1000 single convector rad has around 1kw of heat output, so in order for the boiler to give out 30kw's of heat it would need 30- 600wx1000h single convector radiators attached to the system. That is a lot of radiators!

combi boilers have a capped heating output which is usually smaller than the hot water output, for example a 42cdi has a maximum load of 30kw's for heating and 42kw for hot water. This is because it takes a lot of power to heat up the mains in such a short period of time.

The higher the kw rating of a combi the faster it can heat the mains so the higher the flow rate, but its no good putting in a combi capable of 16lpm if you only have 12lpm coming in as the boiler will never be able to give more than its input (12lpm comes in so 12lpm has to come out).
 
Thanks dean7445 - it is all making sense now. I never knew that is how combi's work and what the actual KW stood for.

I will probably end up buying the Greenstar 29CDi i.e. 29kw.

They don't make a 28kw.

I needed some answers as it's getting cold now.


THANK YOU TO EVERYONE WHO HAS HELPED.
 
:)


Hi

First chance to get back and wrap this post up.

Just thought I'd add what the final outcome is going to be for those
that have followed other posts connected to this one - purely to help
anyone else who might find themselves in a similar situation.

I have included this post to the others posts connected.

I looked in to other boilers that others recommended.

I also checked other web sites with Boiler Installers recommendations
who on balance rated Worcester Bosch Greenstar **CDi Classic
as the boiler to go with.

Briefly a while back I did a flow rate test - 10 seconds gave me two litres.

So this equated to 12 litres per minute.

The boiler to be replaced was an Alpha 28CB.
The 12 litres per minute would have matched the Alpha.

I nearly went for Greenstar 29CDi Classic LPG - because that was the nearest
to the Alpha . . . . BUT I thought I best double check flow rate again.

This time I did a FULL 60 SECONDS and this resulted in exactly 14 litres per minute.

I really don't understand this discrepancy, (12 vs 14) but this is what it came out as.

So I phoned Worcester Bosch main help line - the woman didn't have a clue what I was asking
about and put me through to Technical dept.

The guy said the two boilers that I thought would be okay the
Greenstar 34CDi Classic OR Greenstar 38CDi Classic were both okay with 14/lpm

He said he'd go for the "38CDi" because it delivers 14 litres per minutes at 40 degrees.

And because it's not more than around £150 I'm going to go for the Greenstar 38CDi Classic LPG

I asked about an installer, he said if you use a local Gas Safe guy I wouldn't receive 7 years
(8 with fitted filter) parts & labour guarantee BUT I would get 5 years parts & labour guarantee.


For those interested Greenstar info;

Greenstar 34CDi Classic

Central heating output: 30kW
Domestic hot water flow rate: 14.3 litres per minute at 35 degree temperature rise
(provided adequate mains pressure is available)
Designed operational flow rate 12 litres per minutes at 40 degree temperature rise.


Greenstar 38CDi Classic

Central heating output: 30kW
Domestic hot water flow rate: 16.4 litres per minute at 35 degree temperature rise
(provided adequate mains pressure is available)
Designed operational flow rate 14 litres per minutes at 40 degree temperature rise.

Many thanks again - I couldn't have got here eventually without helpful snippets here and there.

Stephen
 

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