Which boiler to use with Megalfow?

[lynnm]

Can anyone shed some light on this matter, I have had two different answers already from two different plumbers.

Can I use a combi boiler with a megaflow so that the megaflow serves my bathroom with shower and ensuite and the combi serves the heating and utilites and is there a specific king of combi to use?

I'm starting to build an extension this weekend and I'm still non the wiser, I don't want to end up fitting something that either doesn't work or is inefficent....can anyone help please.

Regards

Lynn

 

[blahblah]

Presuming you've checked mains pressure , flow rate, and discharge pipe requirements to ensure that you can have an unvented cylinder, and have it fitted by a certified person (after notifying building control), then there's no reason not to heat it with a combi. I shall be doing the same in my extension next year.
Boiler choice a bit like choosing cars, but generally you get what you pay for. Vaillant would be my choice.

 

[oilman]

There's a very good reason for not using a combi. It's unnecessarily complex. Pipe the hot water from the Megaflo to all the hot taps, and you don't need a combi. The Megaflo will be expensive to maintain anyway, don't add more maintenance expence by having a combi. A standard boiler will work fine, and be more reliable.

Do I have an axe to grind? I make good money from both unvented cylinders and combies, but there are lower cost ways of keeping warm.

 

[blahblah]

Sorry oilman I have to disagree. Nothing complex about it. Gives extra options especially in a larger dwelling, ie. the benefits of unvented multi-usage and still have combi 'instant and always' in selected area(s). Horses for courses as they say.

 

[oilman]

blahblah, Are you telling me a combi boiler is no more complex than a conventional boiler?

If you have a cylinder of any sort you have stored hot water. Why would you NEED instant hot water from a combi?

Do we know yet whether lynne's boiler is gas or oil? Not that it should make much difference except that the combi oil burner is huge just to give the hot water, when it has too much capacity for the heating side.

Even boiler manufacturers steer away from combi boilers in the wrong circumstances, how can you justify one on such limited information?

One more thing, where in the country do you work, as I know from manufacturers there are particular problems in Scotland because of the water characteristics (not to mention bad installers). With these difficulties, simple is best, not an expensive high tech "modern" solution.

 

[blahblah]

No Oilman, of course the actual boiler is more complex but when you said, 'It's unnecessarily complex', I thought you were referring to the system principle.
As for 'Already have stored water why need combi'? Well here's an example.
I have a decent combi but suffer with flow problems with more than one tap open. I'm putting in a bigger main. I'm having a new (much better flow rate) combi and unvented cylinder. Main bathroom will be from unvented. Other (occasional) shower room from combi, kitchen and utility split. Because we often have usage at odd times we are covered when the cylinder is cold and still have an immersion for breakdowns. It's what I want and I wouldn't want an installer presuming to tell me I don't want or need it.

 

[oilman]

It's what I want and I wouldn't want an installer presuming to tell me I don't want or need it.

Anybody can have whatever they want, that's their choice. You know enough to weigh the options and make your choice. People who do not have this knowledge frequently get half a story, and take on something they were SOLD rather than something they BOUGHT. (We get this all the time, blasted merchants who sell us what they want us to have, rather than what we want). There are advantages with unvented cylinders, but they don't come cheap, either purchase or maintenance costs, but most people are never told this.

As for your not wanting an installer telling you you don't need something, exactly the opposite is done by installers all the time to people who don't know anywhere as much as you, in telling them they NEED a combi or they NEED an unvented cylinder.

 

[blahblah]

Oilman, these discussions get so drawn out by their 'ping pong' nature. I'm away now for the weekend so I must opt out. I suspect that over a beer we'd find ourselves agreeing more than not.

 

[ChrisR]

Neither of you is "wrong" I'd say, but on balance I'd not use the combi.

I accept that a combi can provide unlimited showers in sequence (with the heating off!), but a good unvented cylinder like a Megaflo has a very high (~25kW ) heat transfer so the thing will reheat in as little as 20 minutes from cold. Very unlikely to run it out if it's properly sized.

You're still likely to get flow problems from the combi if you're using the hot from the Megaflo plus cold mains to mix it with, all at the same time. Depends on the mains of course.