combi or conventional boiler?

Canucklehead

silvercar wrote: »

Still no-one voting for a conventional?

Canuckle, you still here?

I need to turn the page on my quotes. Glow worm flexicom CX 30 any good ? better or worse than the Petterton or Baxi ?

Is chemically cleaning with Sentinel X800 OK or is it worth paying for a power flush?

Would you fit a magnaclean or similar?

Good morning: The Glow-worm Ultracom CXi is a better product than the Flexicom or your two The OH always recommends a powerflush and is it standard item in his quotes: the customer has the option of a chemical flush with Sentinel X400...he doesn't use X800. Instead of a Magnaclean he uses a Boiler Buddy or Spirovent and fits a scale inhibitor as recommended by boiler manufacturers for hard water areas eg. the southeast.

After using several manuafacturers over the last 30+ years all he only fits Vaillant, Viessmann and Remeha...all these have stainless steel heat exchangers.

HTH

Canucklehead

silvercar

TheMoneySpider wrote: »

How much do you generally save in terms of fuel bills with a combi bolier?

Depends on the boiler.

Big plus is that you are only heating the hot water you need rather than having a tank full of hot water unused.

As far as boilers go the newer ones are more efficient and will save you more money. For older boilers their individual efficiency may not be that different. I have a 13 year old conventional boiler that is rated as 74% efficient and a 5 year old combi that is 78% efficient. So not much difference in their own efficiency, except that the older one is used more as it heats the water tank.

You can do other things to improve your bills, like fitting a room thermostat and insulating pipes, loft walls and tank.

silvercar

Interesting points Andy. Flow rates is a good one, which is why combis are good in smaller properties.

Metered water is an interesting one. If you have a tank of hot water you get out of the shower when the hot water runs out (if not before). With a combi you can stay in the shower for an hour, or until someone flushes the loo.

AdrianW2

silvercar wrote: »

Interesting points Andy. Flow rates is a good one, which is why combis are good in smaller properties.

You can always put in an unvented cylinder with a conventional boiler and get full mains pressure showers.

Plus you've then got the option of reverting to electrical and/or solar heating if the Russians ever turn our gas off.

silvercar

andrew-b wrote: »

oh and another thing...with a hot water cylinder you have an airing cupboard to air clothes/linen/towels or germinate seeds etc.

Andy

:mad::mad:That is a very, very sore point. I have two boilers and no airing cupboard:mad::mad:

Three viewings before I bought this house and it never crossed my mind that there was no airing cupboard.

Canucklehead

Good evening: an excellent series of guides available from the Bathroom Manufacturers Association explores many of the issues mentioned. I know a few MSErs have posted about the difficulty they have had sourcing taps and shower valves suitable for a gravity system at a cheap price and regreted their decision not to change over to a mains hot and cold supply eg. combi or regular boiler with an unvented cylinder.

Over 70% of the boilers sold in the UK are combis...guess the public are fed up with feeble showers and want to free up space in their properties for a larger bathroom, kitchen etc. A new edition of Part G Building Regs is scheduled to be introduced in October 2009 (long delayed) and it has implications for water efficiency etc.

In terms of maintenance and servicing it is a case of apples and oranges...just as much can and will go wrong with either option.

In the end, a central heating system installed to 'Best Practice' and manufacturer's specifications (especially a proper flush something, again, many MSErs' boilers haven't experienced :eek:) and annual servicing will extend the life of the system.

Silvercar: A one hour shower.....I suspect most working folk wouldn't have that much free time (or the inclination) but you never know.;) Flushing the loo shouldn't be an issue if you have a thermostatic shower mixer.


HTH

Canucklehead

silvercar

Silvercar: A one hour shower.....I suspect most working folk wouldn't have that much free time (or the inclination) but you never know. Flushing the loo shouldn't be an issue if you have a thermostatic shower mixer.

Pressure drops rather than temperature.

Canucklehead

silvercar wrote: »

Pressure drops rather than temperature.

Hi...if the water and gas supply requirements are up to the manufacturer's specs and the RGI does a competent install of a higher output combi ( less than 28 kw will always be disappointing) and the hot and cold supplies to a thermostatic shower valve, a large drop in flow/increase in temperature shouldn't happen.

I've assumed the RGIs have tested the gas pressure and mains water pressure/flow rates at your rental before recommending a combi.

HTH

Canucklehead

silvercar

I'm confusing everyone now, including myself:)

canuckle wrote:

Hi...if the water and gas supply requirements are up to the manufacturer's specs and the RGI does a competent install of a higher output combi ( less than 28 kw will always be disappointing) and the hot and cold supplies to a thermostatic shower valve, a large drop in flow/increase in temperature shouldn't happen.

This is in my home. potterton performa 28i trying to serve a circular shower head 10 inches wide and slowing when the toilet is flushed, struggling when another shower is on.

I assumed that a new bathroom with a mega shower with large showerhead would have the power behind it to deliver. Just as I assumed that there would be an airing cupboard.:rolleyes:

Now back to the rental place:

canuckle wrote:

I've assumed the RGIs have tested the gas pressure and mains water pressure/flow rates at your rental before recommending a combi.

New gas pipe as part of combi spec and he tested the water pressure.:)

Canucklehead

andrew-b wrote: »

So basically your saying that anything less than a whopping 28kW is no good for a combi? (i have an 18kW boiler more than sufficient for our needs) Which means to get a combi that is good requires chucking more cash at it ...which could have been spent on lower powered conventional boiler plus a new shower pump or even an unvented cylinder instead without all the potential problems of combis.

Also you say the boilerperson has to test the flow rate..it's not uncommon for water pressure/flow rates for a street to change...say when a whole new development of houses gets built down the road - plus there can be changes in pressure/flow throughout the day and across seasons. Seems like much more to worry about with a combi.

I've not really heard a good argument for a combi yet other than space saving! Just because everyone else is installing them isn't a valid argument for me! All the weaknesses of conventional condensing boilers are surmountable in other ways like adding pumps or installing an unvented cylinder.

Good evening: The Energy Saving Trust has produced an excellent guide for the specification and installation of gas boilers- it is designed for gas installers but serves as a useful domestic energy primer for the novice and helps dispel the myths.
A good RGI would conduct a site survey, listen to the customer and recommend 'Best Practice' as detailed in the guide but those who pay have the last say.

Any concerns someone might have about water pressure and combis should also have the same issues with an unvented cylinder as its performance is dependent on the water mains pressure/flow: an unvented cylinder is an expensive install and should be inspected every year. Many clients opt for a combi in single bathroom or shower room properties: multiple simultaneous drawoffs of DHW will lead to disappointing performance eg. Silvercar's own property.

Shower pumps can draw high volumes of hot and cold water and will require, in many cases, upsizing the HW cylinder and the cold water storage cistern - these 2 factors as well as the cost implications will deter many from pursuing that option. An excellent alternative is the Aqualisa Quartz but it is not an option for the most price conscious market.

HTH

Canucklehead