Can I have a new combi boiler and keep my hot water cylinder

[ianniann]

Weather compensation is the best and simplest form of control you can get.

 

[ajstoneservices]

I believe that the OP is planning far too complex a job

The OP

 

[mehran]

agile you can put your electronics kit away

the only extra component you need to make a weather comp'ed combi run in a y/s plan is a relay. (at least for intergas boilers)

 

[Agile]

With an Intergas or some Viessmann perhaps but not a Worcs or Biasi or Heatline!

Tony

 

[Agile]

With an Intergas or some Viessmann perhaps but not a Worcs or Biasi or Heatline!

Tony

 

[blondebier]

I don't know without knowing the type of house [rad sizes, insulation].

It's a 4 bedroom house. We've got one bathroom with a shower over the bath. 3 rads downstairs, 6 upstairs. Cavity wall insulation and loads of rockwool in the loft space. If you need to know any more let me know.

I believe that the OP is planning far too complex a job.

We want a backup for hot water if the boiler breaks down...

Not wanting a storage tank in the loft may have narrowed my options, but I think the thermal heat store is a fairly neat solution.

I like the look of the Vitodens 200-W boiler. I'd get the system boiler version of this and attach it to something like a Telford thermal store. This would have a built in immersion heater, so that if the boiler were to have a problem, we can still have hot water.
The boiler would also do our radiators.

What's complex about it?

I'm all ears if you have simpler solution?

 

[Agile]

Be VERY careful with thermal stores.

They are only good with non con boilers because they need to be heated to 85 degrees.

At 65 degrees they have far less than half the capacity!

Tony

 

[blondebier]

Good point.

That pretty much rules out Viessmann as all their system boilers are condensing.

 

[picasso]

I know you want belt and braces but why not go for a top quality combi properly installed and have it repaired if and when it breaks down, combis normally give some signs they are going wrong, just dont ignore the warnings

 

[JohnD]

two other things to reconsider:

a new, well insulated cold water cistern in the loft (will enable you to have a conventional cylinder, very good flow for filling the bath, and with a backup electric immersion heater), also means you can safely run a bath or shower at the same time as someone else is running a tap, without losing flow on hot or cold in the bathroom (this is the method I went for, but I like belt and braces, and can put up with plumbers sneering at me for being old-fashioned). I have a Viessmann Vitodens 100 Compact, the latest model seems to be very good, but I would have gone for a 200 if I wanted Combi ability as well as (or instead of) the cylinder.

an electric shower, especially if you have a separate shower room - will be fully independent of gas boiler. Not as powerful a shower, but will relieve the problem, if you get a combi, when it breaks down

 

[blondebier]

Thanks Guys.

There's certainly lots to think about.

I appreciate your time and suggestions.

Cheers,

Blondebier

 

[ajstoneservices]

blondebier,
Just to add to your woes
Have a look at the link below you may find that heat bank/thermal store coupled to a condensing boiler can work. As I said before several cylinder manufacturers make thermal stores that do work with condensing boilers.
The DPS site is probably the most informative with regards thermal stores you will find on the net.

The GXV Heat Bank thermal store, designed by DPS for local authority use, effectively demonstrates how direct heating of the store can produce some quite spectacular results with regard to efficiency, recovery and performance. Not only will the store prevent boiler cycling during recovery, it also keeps condensing boilers operating in condensing mode for a longer period. It allows the full output of both the boiler and thermal store to be directed to hot water outlets, providing over 150 litres of hot water from a system employing an 80 litre store which fits under a kitchen worktop. Hot water can be drawn from taps within three minutes of a cold start, with flow rates in excess of 30 litres per minute, and mains supply pressures up to 6 bar. This kind of specification is simply not achievable by any other type of domestic system, and may explain why the GXV is the only hot water cylinder to ever reach the finals of the Institute of Plumbing Challenge, which has quickly been recognised as a true mark of excellence for innovation in the plumbing industry.

From here http://www.heatweb.com/editorials/heatbanks/compare2.htm

 

[Axel]

HOLD UP! REWIND A BIT!

16 litres per minute - is that at the mains coming into the property or at the taps?

Considering the costs being proposed for this project, the first thing to do is surely crack into the mains as it comes into the building and see what the max flow rate potentially available is. Wouldn't cost much to run it in 22 direct to an unvented if there was enough coming in, in which case a system boiler plus unvented would be the answer, with the immersion heater providing DHW backup in case of boiler failure.

Far easier, simpler, cheaper and more reliable.

 

[blondebier]

Have a look at the link below you may find that heat bank/thermal store coupled to a condensing boiler can work. As I said before several cylinder manufacturers make thermal stores that do work with condensing boilers.

Thinking outside the box! I like that. Thanks for the link. I'm a bit knackered now, but will give the article a good read and digest.

Cheers!

 

[mysteryman]

Good luck with that. Try to keep your system simple but well controlled. I honestly think you should stick with a combi or a system boiler plus cylinder. Look at you mains flow rate when selecting vented or unvented.

I live in a 2003 built house that had a Powermax boiler, which was basically a thermal store with integral boiler. I have replaced this with a good condensing combi with weather comp, and my hot water performance is no worse than it was.