rolls royce system advice pls....

[Beerlover]

Rolls Royce system? Hmmm...

Here is how it normally works:-

You specify what you need the system to do, ie showers with body jets and 12" rain head? How many people to use them? Peak periods of usage?, will all occupants of the six bedrooms be showering at the same time in the morning?

Buliding construction; oak framed timber building with pegged tiles and no roof felt? Modern highly insulated with triple glazing?

Water supply pressures and flow rates (dynamic) to the property?

Spare space; to accomodate a breaker tank, pressurisation pumps, accumulator arrays and heating circuit accumulators (if using biomass boilers as well as renewables)

The list goes on and is what we robbing heating engineers and plumbers have learnt, and paid for, over the years.


And the final most important point; what really is your budget? A 20 year old Roller can be bought for less than a grand, while the new, all singing and all dancing one is around £200,000. How big is your wallet really? as big as your dreams or as thin as your promises.

I've been knocked by more 'millionaires' than pensioners

 

[africanplumber]

You need to fit Barron boiler they're made in Africa you know. I can fit it for the £100

 

[roguetrader]

bit of a hijack, Mysteryman- is there a stand off kit for the 200 series??

 

[mysteryman]

No, there isn't a standoff kit for a Vitodens 200.

What is the purpose of a thermal store? It is crazy to add thermal mass - it just reduces controllability.

 

[carlsquires]

Not sure if this helps but it may give you a few ideas. A company I used to work for installed a system on a large house, 6 bedroom, 5 bathroom, 2 kitchen with very poor incoming water pressure. So we installed a very large CWS tank in the basement which was rigged up to a large booster pump feeding the system consisting of Vaillant system boiler, unistore, vaillant solar panels, weather compensation and HW circulation pump (was a few years ago so don't remember exact model No.s etc). The system as a whole works a treat and as I said this was a few years ago and the customers haven't had any issues.

 

[ChrisR]

If you rely on mains pressure for 3 shower/bath outlets you're asking for trouble.
The suppliers are cutting the pressures in the interests of reducing leaks. It can vary a great deal depending on time of day.
If you have a shower two floors above a bath, the realities of plumbing mean the showerer will suffer large supply fluctuations.
Accumulators help with flow, but are limited by their size and you're still reliant on unpredictable mains pressure.
The only way you can guarantee the pressure, and keep it independent of flow, is to pump the water, which means using a large break tank.

Even 51kW is in practice not OK for 3 showers even if the supply pressure does hold up, unless you install miserly shower heads. Users used to a good shower using about 30kW will complain when it gets cut by other users. That means you have to store hot water.
Thermal stores, whether you happen to like them or not, represent a small percentage of installed systems. If something goes wrong, with sludge/scale/pumps/mixing valves, there's a correspondingly smaller number of people used to them, and faults can come from a combination of the above so take time to resolve. They're also harder to get right in the first place.

Whatever you use, you have to confident that it's going to work. That confidence can be harder to achieve than you might think. If you wife complains, telling her that some bloke on an internet forum reckons she doesn't have a problem, could be suboptimal.

 

[simond]

As keen as I am on accumulators, I have to agree with ChrisR regarding their application.

This Johnsville correspondent sounds like the latest incarnation of the presumably banned Water Systems, George Bamford, Dr Drivel, Big Burner etc. You just can't keep a good man down.

 

[BlueMoonMole]

Well, since you asked, and noone has suggested it, you'd better look at a Viessmann Vitodens 200-W system boiler with weather compensation plus a Vitocell 300-V 300 or 500 litre cyl. Everything that matters in these is the best stainless steel, all made in their own factories. All control wiring is low voltage and is simplicity itself.

Aside from going down the Vaillant route, this is probably the best advice you've been given on here smurf.

Vaillant are brilliant. I have just installed one myself (EcoTec Exclusive) and I must say I really am impressed.

I repair boilers, and I rarely come across Vaillants or ATAG, but the reason I don't see the latter is more to do with a distinct lack of them in this country.

Veissman would be your best option on such a scale.
Vaillant if, as previously mentioned, your wallet is not as big as your dreams.

 

[Beerlover]

For BlueMoonMole,

I too have an exclusive 838, although I'm very pleased with mine, a coupe of tips for you and the future.

When the pump goes, and it will, get Vaillant to do their field fix, pump housing from a 35 kw Turbomax + the pump body from the Ecomax 835. This will give you full modulation of the pump but it will be Grunfos not a carpy Laing pump.

NEVER touch the service valves they will leak and cost around £50 each.

The hose will block after around 4-5 years, no big hassle to replace, but often misdiagnosed as pump, plate heat exchanger or even main heat exchanger.

And finally they work brilliantly with the VRT392f or even the VRT430f.

Now you know it's weak points I hope you are as happy with yours as I am with mine 15l/min hot water waytogo

 

[sweet]

Ideal, check their website...

 

[SimonH2]

If you rely on mains pressure for 3 shower/bath outlets you're asking for trouble.
The suppliers are cutting the pressures in the interests of reducing leaks. It can vary a great deal depending on time of day.
If you have a shower two floors above a bath, the realities of plumbing mean the showerer will suffer large supply fluctuations.
Accumulators help with flow, but are limited by their size and you're still reliant on unpredictable mains pressure.
The only way you can guarantee the pressure, and keep it independent of flow, is to pump the water, which means using a large break tank.

Even 51kW is in practice not OK for 3 showers even if the supply pressure does hold up, unless you install miserly shower heads. Users used to a good shower using about 30kW will complain when it gets cut by other users. That means you have to store hot water.
Thermal stores, whether you happen to like them or not, represent a small percentage of installed systems. If something goes wrong, with sludge/scale/pumps/mixing valves, there's a correspondingly smaller number of people used to them, and faults can come from a combination of the above so take time to resolve. They're also harder to get right in the first place.

Whatever you use, you have to confident that it's going to work. That confidence can be harder to achieve than you might think. If you wife complains, telling her that some bloke on an internet forum reckons she doesn't have a problem, could be suboptimal.

That has to be the most sensible and considered answer in the whole thread - though carlsquires and Beerlover also make some good points.. I really cannot believe so many people (some of them I believe claiming to be "professionals") are happy to just say something like "you need <model x>" when in reality they know b***er all about the installation.

What is the purpose of a thermal store? It is crazy to add thermal mass - it just reduces controllability.

Keep it simple and spend a tiny bit extra on something useful - weather compensation.

What complete rubbish. The purpose of a thermal store, apart from storing heat, is to decouple the vastly different and in some ways conflicting elements of the system.
What's a typical central heating load, especially if you fit TRVs all round ? Highly variable flow rate, which is very low in warmer weather. How many boilers really like running at very low water flow rates ? Not many - most will either kettle or shut down.
What's the typical heating demand relative to peak DHW demand ? Usually a tiny fraction.
So having a store allows you to run the heating loop at a flow rate that's optimal for that - fully TRV and modulating pump gives an incredibly quiet system. You can draw off the DHW at whatever rate is required*. You can run the boiler at a flow rate and heating input that it's happy with.
And for a bonus, you can have an immersion heater so you aren't left completely without heat or hot water when the boiler does break down - which it will do less often by not being a combi.
* Yes, there is a practical draw off limit for a thermal store or heat bank, but if specced correctly it's considerably in excess of that from a combi that isn't grossly oversized for the heating.

The main downside is as ChrisR states - there aren't that many people who understand them and there's a good chance that the next plumber along will have a biiiiig suck through his teeth and suggest you rip it out and replace with a combi. I think that says more about the industry and the people in it than the technology.

Must go, I have a feeling I'd be needing my flameproof overalls quite quickly

 

[mysteryman]

A good modern modulating boiler is at its best thermal efficiency at about 30% of full output. Weather compensation keeps it modulating and condensing as much of the time as possible, and a really good boiler with a modulating pump [compulsory from 2012] will look after the flowrate. Modern boilers - properly installed - are very reliable. There is no point in increasing the thermal mass of a domestic system by adding a thermal store. They are not recommended anywhere other than by their manufacturers. They do have their place, such as in relatively uncontrollable systems, such as heat pumps feeding a low thermal mass underfloor layout.