Thermal store advice

[sirocosm]

I am looking to install a thermal store to replace my current vented cylinder. My current boiler is also vented, so I guess I would need a stainless or copper cylinder. All of the ones I have found seem to have quite small heat exchangers for the the hot water, so I am thinking to use an external plate exchanger.

So I am really looking for a plain SS tank (no internal coils) with a variety of connections, at least 2 at the top and bottom, a place for a cylinder stat, and a connection for a backup immersion heater.

So far the Gledhill Flexible Buffer store (PLU300MB) seems like it could work. Any one know of anything similar from other manufacturers?

 

[flameport]

I am looking to install a thermal store to replace my current vented cylinder.

Why?

 

[sirocosm]

Because I want mains pressure hot water and the ability to have heat flowing to the radiators whether or not the boiler is running.

 

[bernardgreen]

so I am thinking to use an external plate exchanger.

Which will require a pump and an electrical suppley and control for that pump.

(no internal coils)

using an internal coil for heating hot water will (1) provide hot water without the need for a pump and (2) keep hot water ( for taps ) separate from the hot water that will be flowing through radiators and boiler.

 

[sirocosm]

The stores available in the UK seem to have the internal DHW coils undersized, hence the myth that thermal stores need to run at 80C. I plan to run mine at 60C.

I would use a mild steel tank with a large stainless coil (300l version has a 4.1m^3 coil) like this:
http://plumbingsupplies24.co.uk/hygienic-buffer-storage-tank-vertical/

However, a steel tank needs to be sealed or corrosion will be a problem, and in the UK people are generally scared of sealed systems, and they are thus over-regulated. This makes a vented system for the primary water more attractive here.

 

[ianmcd]

the ability to have heat flowing to the radiators whether or not the boiler is running.

boiler will still have to run to maintain the store temperature

 

[sirocosm]

boiler will still have to run to maintain the store temperature

Sure, but not all the time. A buffer between the boiler and the rads is a great way to prevent cycling, and eliminates the need for a modulating boiler. It also means the boiler can be oversized, in case your demand varies a lot.

 

[JimCrow]

https://www.mcdonaldwaterstorage.com/products/thermal-store

 

[sirocosm]

https://www.mcdonaldwaterstorage.com/products/thermal-store

From what I can see they don't really make plain tanks. All their thermal stores come with an integral DHW coil, which is likely too small for a 60C store. I could not find the surface area of their DHW coils in their brochure, but most are around 2 sq. m. or less.

 

[ianmcd]

They will make to any spec you want

 

[sirocosm]

They will make to any spec you want

Thanks, I will draw up what I would like and contact them for a quote.

 

[ianmcd]

Thanks, I will draw up what I would like and contact them for a quote.

They will give you all the free design advice you want , they offer excellent service

 

[Ryler]

I am looking to install a thermal store to replace my current vented cylinder. My current boiler is also vented, so I guess I would need a stainless or copper cylinder. All of the ones I have found seem to have quite small heat exchangers for the the hot water, so I am thinking to use an external plate exchanger.

So I am really looking for a plain SS tank (no internal coils) with a variety of connections, at least 2 at the top and bottom, a place for a cylinder stat, and a connection for a backup immersion heater.

So far the Gledhill Flexible Buffer store (PLU300MB) seems like it could work. Any one know of anything similar from other manufacturers?

Fit an unvented cylinder instead. Far better system.

 

[sirocosm]

Fit an unvented cylinder instead. Far better system.

An unvented cylinder is IMHO an inferior choice. I will do fine for hot water, but does not solve the inherent problems of an unbuffered heating system.

With a thermal store you don't need a house stat, instead you can use a modulating pump and TRVs all around. The rads are always warm and do not cycle on and off with the boiler. Each room can be set as warm/cold as you like, and it does not require fiddly balancing, which can be a huge pain (or impossible) if some of your rads are over/under sized. You also don't need a modulating boiler, and you eliminate boiler cycling. Buffering also allows a larger boiler to run efficiently, which can be handy if your demand is highly variable.

Not too mention that an unvented cylinder is not really a DIY option in the UK, as people here seem scared of pressurized hot water tanks (hence the hot-cold tap phenomenon unique to the UK), and thus there are a lot of hoops to jump through for a DIY unvented.

 

[bernardgreen]

Fit an unvented cylinder instead. Far better system.

For some life styles a vented cylinder is a better option.