Which boiler: Combi or system

[lala15]

Hi,
I NEED HELP.
I'm going to have a new boiler installed. That much I know, the rest is a mystery to me. I am considering Vaillant EcoTec Plus 937HE storage combi.
I'll have a loft extention built in summer 2009. When that's finished I'll have 4 bedrooms and 2 bathrooms over 3 floors.
My builder tells me that there's going to be a loss of pressure to 3rd floor bathroom. He suggested I get Vaillant EcoTec Plus 618 system boiler and either Megaflo unvented cylinder or a vaillant uniStor one.
I'm not very keen on having a cylinder but if there's no choice I'll have to have one.
Please, please can you advise which system would suit best
Thank you in anticipation

 

[bengasman]

your builder is a builder, not a plumber. most builders don't know jack about heating and hot water, best to ignore him.

easily the best way to go about; find a good heating engineer, tell him what you want and put your faith with him.

and don't trust anyone who recommends to use a glowworm or ideal.

 

[ctp]

check out wostcester 440/550 combi boiler it is floor standing but worth a look and could satisfy your requirements

 

[gas4you]

Why does your builder think that a megaflo won't be affected by the pressure drop on the 3rd floor?

It works off the same mains pressure.

 

[swbjackson]

A high flow combi will do the trick if all the outlets are reasonably close together. If there is a long distance between outlets and the boiler you will be disappointed.

As bengasman states it is best to get someone in to give you advice and a price for doing the work. Make sure you specify what you want from the system and a reputable tradesman will be able to help.

Mike

 

[BigBurner]

A high flow combi will do the trick if all the outlets are reasonably close together. If there is a long distance between outlets and the boiler you will be disappointed.

Dead-leg pipe. That will be the same if the cylinder is far from the taps too.

Consider the Ethos 54C high flow combi.
http://www.ethosboilers.co.uk/products_54c.php

It can have a secondary circulation kit fitted. This forms a pipe loop from combi and back again, with taps off it giving instant DHW at the taps. It also has integrated outside weather compensation that gives excellent economy, so buy the outside temperature sensor.

Check the mains pipe. What is the pressure in bar? Also time from the kitchen tap how long it takes to fill a bucket in litres per minute.

Replace the maintap with a full-bore tap and have a dedicated 22mm cold feed to the combi.

 

[Tipper]

I've just had a Vaillant 937 installed in my 3 storey town house. The boiler has been re-located to the basement garage and there are 3 living floors above and HW is fine on the top floor with good pressure.

I think it's a great setup and the boiler appears to be well engineered and well thought out. The HW response to the top floor is constrained by the time taken to travel the distance but it would have been anyway if we had gone for the unvented cylinder/system boiler instead. We also gained a cupboard in the kitchen, a very large linen cupboard and removed 3 tanks from the loft which gave us more storage space and removed all pipework likely to freeze.

Overall an excellent upgrade and cheaper than boiler + unvented cylinder.

 

[lala15]

Hi Guys,

Thanks a lot for all your comments - very useful!
I'm especially grateful to Tipper.
Your reply helped me make my mind up.
I, too, will go for Vaillant ecoTec plus 937, which was my intention in the first place, until the builder put a spanner in the works and confused me with all the technical info. Apart from being a cheaper option (always welcome), I'll save on space by not having the cylinder.
Thanks again for taking the time and responding to my question.
lala15

 

[BigBurner]

Think hard, you have two bathrooms. The 937 has a poor flowrate. The high flow is only when the small 15 litre water store is hot. Then it reverts to a lower flowrate of around 15 litres/min. This will not do two bathrooms and is really only suitable for one bathroom.

I mentioned the Ethos 54C because it has a flowrate of around 24 litres/min - much higher. And a better OpenTherm control system with DHW secondary circulation which may be essential in your place.

 

[gas4you]

Before you make any decision, one assumes you have had the incoming cold mains pressure and flow rate professionally checked?

You will need at last 25 l/m and hopefully around 3 Bar for any of these systems to work at their design spec.

You will need around 30 l/min cold to let drivels Ethos deliver its 24l/min, allowing for losses in the pipe work etc.

What readings have you got?

 

[simond]

Any good installer will ask you what you want the system to do eg: whether you want to run two showers at the same time.

Then they will measure the incoming flow rate and the water pressure to ascertain suitability for the solution.

The ecoTEC937 will give the same performance as an unvented up to 20 litres per minute, if you want more hot water than this then you could look at a floorstanding Worcester Hifghflow 550 (this gives 25l/m) and after that an unvented is the common option.

The Ethos boiler is a basic unit with almost no market penetration in the UK and very little installer/customer feedback.

In contrast Vaillant and Worcester Bosch have been around for years and their products have earned a reputation, most here (myself included) would say a good one.

But getting back to square one, it's what you want from the system and what the water suppliers actually delivers in terms of performance that will dictate the ideal solution. And a builder is normally the last person to entrust this type of work to.

 

[BigBurner]

Before you make any decision, one assumes you have had the incoming cold mains pressure and flow rate professionally checked?

You will need at last 25 l/m and hopefully around 3 Bar for any of these systems to work at their design spec.

You made that up. Best read the Ethos instructions.

You will need around 30 l/min cold to let drivels Ethos deliver its 24l/min, allowing for losses in the pipe work etc.

I don't known about drivels, but have been spouting some drivel.

 

[gas4you]

You are showing your ignorance again drivel.

Why answer the first quoted part of my post with reference to the Ethos, it was not aimed at this.

The Ethos is rated at 25l/min at 40C not a 35C temp rise as per standard combi meausurement of hot water delivery, so in comparison to a 'properly' rated combi it will produce less than this.

You can't change the laws of physics, the same amount of heat into any boiler will produce the same amount of HW delivery.

Like wise how is the Ethos going to produce the specced flow rates if the cold mains is a lot less than the 25l/min.

We know you have delusions of grandeur, but you're not f**king Jesus parting the water

Even you're googling drivel cannot change this Dr Drivel.

The Ethos also quotes initial water pressures as 2 Bar to obatin its specified outputs, yet again you choose to ignore this, or perhaps it was time for your afternoon nap and fell asleep before reading any useful info from the Ethos website, as per usual.

You really do show your non existence of real world knowledge the more you post

 

[Doctor Drivel]

We know you have delusions of grandeur, but you're not f**king Jesus parting the water

I am Dr Drivel, or am I Spartacus?