Quick question: what are the best make of thermal stores to go for (indirect type) but open vented. And are the connections to the flow and return and the hot water and cold connections the same size as a normal hot water cylinder, ie 22mm / (3/4 inch) - or are they larger??
May have one installed, depending on what the job involves, ie pipe changes, etc.
Any advice would be useful, thanks all for your time.
Take no notice of the bathroom changers.
Get a heat bank, one with a plate heat exchanger. They do not loose heat as they are insulated like any other cylinder. No complex safety and pressure reducers, etc.
zero-risk of explosion
Get a heat bank not a thermal store. A heat bank has an external plate heat exchanger.
Get an integrated CH/DHW heat bank/thermal store. They are not equivalents to an unvented cylinder they offer, far, far more. Also look at Range and their plate heat exchanger versions:
http://www.rangecylinders.co.uk/products/fortic/
Also:
http://www.advanceappliances.co.uk/gas_or_oil_thermal_store_systems.html
Who do bespoke stainless steel, and will supply the plate heat Exchanger, flow switch and you assemble. Get one with two cylinder stat probe pockets to eliminate boiler cycling.
Have the CH off it, with a Magnaclean filter on the CH return to the cylinder. Use a Smart pump on the CH with TRVs all around and no central wall stat. Using a plate heat exchanger the pressure can be up to 10 bar, so no pressure reducers needed.
Definition:
Thermal Store - has an internal DHW take-off coil
Heat Bank - has a DHW plate heat exchanger and pump.
People get them mixed up.
An integrated heat bank, CH & DHW, is very different to an unvented cylinder. It is not a direct replacement, although there are DHW only heat banks/thermal stores. It offers so much more. In most cases it is foolish not to use an integrated heat bank/thermal store.
Thermal Stores/Heat Banks are far superior to unvented cylinders - and safer. Read below....
Advantages of Thermal Stores/Heat-Banks
- Instant high pressure hot water - When the store has reached temperature, or just the top of the store in a heat bank, water is delivered instantly at the taps.
- High mains water pressures - At up to 10 bar using a heat bank plate heat exchanger, compared to 3.5 bar maximum with most unvented cylinders.
- Very high water flow-rate - The high-end heat-banks have a flow-rate up to 45 litres/min.
- Long efficient boiler burn - Eliminates boiler on-off cycling increasing efficiency and boiler longevity.
- Maintains a Low Return Temperature Promoting Condensing Efficiency - using high efficient plate heat exchangers the return temperature from the plate s guaranteed to be very low. The bottom of the cylinder get very cool while the top can be 70C to 75C. Even is the store is set to 80C, 80% plus of re-heat time the boiler is condensing.
- Boiler Operates in the Ideal Hydraulic Environment – Using a blending valve the flow/return of the boiler can be kept to the ideal heat exchanger temperature differential. This maintains greater efficiencies. The boiler operates at optimum performance in the ideal hydraulic environment.
- May combine the output of the stored water and the boiler - The boiler and energy in the store may be combined to increase output. This in effect makes the cylinder larger.
- Superb Neutral Point For Combining Different Heat Sources - Provides for linking a variety of directly connected heat sources providing a brilliant neutral point: boiler, wood stoves, electric immersion, solar panels, heat pumps, etc, can all be connected to the one cylinder.
- Cylinder may be smaller for a similar performance - smaller cylinders than unvented cylinders.
- Cylinder at low pressure - Unlike an unvented cylinder vented stores do not store water at high pressures. Even pressurised heat banks operate at 1 bar cold, and rarely get above 2 bar.
- Fast cylinder recovery rate - When the boiler is connected directly to the heat-bank, and not via an indirect coil, the recovery rate is rapid. Although in some cases a boiler may heat the heat-bank via an indirect coil, reducing the recovery rate.
- Legionella bacteria virtually eliminated - The Legionella bacteria cannot survive in the high temperature sealed conditions of a heat-bank.
- No scale build-up in heat-bank – Containing primary and not secondary fresh water, there is no scale build-up inside the heat-bank cylinder.
- Cold water storage eliminated - No need for cold water storage tanks.
- No G3 certification to fit – Unvented cylinders require an approved fitter to install. Heat banks, pressurised and vented, require none and can be DIYed. Also vented thermal stores required no G3.
- Solar heating storage - Water heated via solar panels may be stored in the heat-bank via a solar coil.
- Easy maintenance - If an external plate heat exchanger requires cleaning or replacing it is a matter of draining down the heat-bank, or closing isolating vales, and unscrewing the plate heat-exchanger. In some rare instances plate heat-exchangers are fitted directly inside the heat-bank preventing on-site maintenance.
- Easy to improve hot water flowrates – By simply adding additional plate heat-exchangers in parallel, hot water flow rates may be improved. Retrofit additions are possible if extra bathrooms or showers are installed. This is impossible with unvented cylinders.
- Stored water vessel need not be cylindrical – As no internal coil is used for hot water heat transfer the stored water vessel may be any shape, as opposed to a thermal store which has to be cylindrical for maximum efficiency. This has advantages where space is limited.
- No Annual Service Charge – Unvented cylinders require an annual service of between £60-£100. Thermal stores and Heat Banks are service free.
- Thermostatic Radiator Valves can be on all Rads - No wall thermostat required and TRVs on all rads when the CH circuit is taken off the store cylinder and an auto modulating speed Grundfos Alpha pump used.
- Cheaper, Smaller, Simpler Boilers May Be Used – The large buffer of stored water means that a boiler sized for average use, not peak use, can be fitted.
- Larger Boilers may Be Used Without Fear of Boiler Cycling – A larger boiler can be used to reduce the cylinder size or give rapid heat recovery rates or both.
- Full Electric Backup of CH and DHW – An immersion Heater(s) can be fitted in the cylinder that will give CH and DHW backup very cheaply.
- Vented Thermal Stores/Heat Bank Eliminate Explosion risk – Unvented cylinders have an explosion risk. This is not a problem with vented thermal stores/heat banks.
http://www.masterplumbers.com/plumbnews/2001/dec/avon.asp
http://seattlepi.nwsource.com/local/33094_boom28.shtml
http://www2.canada.com/edmonton/edm....html?id=02acabcc-e7c4-43e4-8fe0-5c298527e2d5
http://www.abc15.com/news/local/sto...orth-Phoenix-home/7p8jpeMzcU664FSrKb_osA.cspx
http://i43.tinypic.com/2d3s6v.jpg http://i43.tinypic.com/ehg7l0.jpg
http://au.youtube.com/watch?v=pu3FwgIHsQA
http://au.youtube.com/watch?v=GF_Wrm-Ns0I
- Pressurised Heat Banks Don't Need Annual Service - No G3 unvented certification for fitting or annual service is required if a heat bank is pressurised and uses a plate heat exchanger.
Disadvantages of Thermal Stores Heat-Banks
- The store needs be near full temperature to supply baths - Before any hot water is drawn off, the store must be near up to temperature. Many later versions use a blending valve on the return to the boiler to ensure only up to temperature water is pumped into the store by the boiler. This prevents agitation of the stored water, and aiding heat stratification within the store giving useful hot water at the top of the store within a short time. The water is heated only in one pass through the boiler.
- Needs more inhibitor - A minor added cost.
Advantages overwhelmingly to thermal stores/heat banks. 
