Unvented pressurized system as opposed to thermal stores

[MickBrown]

Why are unvented pressurized systems more popular than thermal stores. They seem to achieve the same end result with higher pressure hot water but thermal stores are easier to install and do not need a special 'ticket' to work on them.

 

[mountainman]

In my experience a thermal store has it's own electronic control system to go wrong. Add that to the boiler electronics and double grief.
Give me an unvented cylinder any day.

 

[MickBrown]

The only one I have worked on did not have any electronics, it was very simple in design.

 

[mountainman]

Not a Gledhill then lol.

 

[mike_s]

I don't think they are as efficient when using with a gas boiler as you always have to keep them at about 76 degrees if you want instantaneous hot water.

The big advantages are not needing a large discharge pipe running to outside which can often make installing unvented cylinders upstairs or in the middle of the house unfeasable.

I think thermal stores are mostly used to combine with wood burner systems and the like which can not be piped up to unvented cylinders.

Most thermal stores are copper, I assume that the likes of the Gledhill boiler mate and the Telford Tristors are stainless steal but don't hold me to it.

I wouldn't hesitate to quote for a thermal store with a gas boiler system if installing an unvented cylinder would be unfeasable as I have seen thermal stores on gas boiler systems that provide amazing pressure on showers as there is no need for a pressure reducing valve. I've seen one do 3 good showers at once.

If you are using a direct thermal store with the system water being pumped around the system for the radiators then be aware of fast heat losses from the store. On the other hand the variants which have 2 coils can be used with sealed systems. Definitely fit scale reducers as you don't want the coil on the domestic side to become limed up.

The best way is to fit an external plate heat exchanger with a thermal store rather than use a coil cylinder. 150kw is not uncommon.

Finally the wiring can become complicated and need multiple pumps but not all of them and it all depends on which you go for, there are many variations.

 

[AWheating]

they have different installation needs so one can sometimes be more suitable then the other. Also i think some times its down to the name........" ive been told unvented are good" is often heard, thermal stores dont seem to have such a brand going for them.

 

[kimbo]

Thermal stores need to be heated to a higher temperature and therefore the heat up time is longer, you will still need a header tank and if it is used on a solid fuel system the header tank will need to be copper which will work out to abpout another £200.00p on top. Some thermal stores have the header tank sitting on top of the store. I always go unvented as first choice unless the location prevents one being installed.

 

[chris watkins]

All I can say is Gledhill gave thermal store a bad name which is most un-justified they are one of the most flexible bits of kit & can be used as a buffer tank for solar & other heat inputs & as Mike say's plates can be very large indeed to give outstanding HW.

 

[mike_s]

How did Gledhill give thermal stores a bad name? I take it their Boiler Mate is an improved version as this seems popular.

My mate who is a joiner built his own house from scratch, they have no gas in the area. He didn't want an LPG or oil tank in the garden so he did a lot of research and opted for a thermal store, heated by a wood burning stove. The thermal store is also backed up by 3 electric immersion heaters on economy 7 cheap rate electricity or similar tarriff. He has 3 pumps on his system, one from the woodburner to the thermal store, one from the thermal store to the radiators and another from the thermal store to the 150kw plate heat exchanger.

They have very good water pressure with a 22mm supply. They were plannning on turning the stop tap down as the shower was too powerful!

A cracking system and he built it all himself, he's not even a plumber! It may be complicated but just shows the versatility of thermal stores. His thermal store is just a cheap copper one from a Scottish manufacturer I hadn't heard of, well I think it cost around 600 quid. A few bottles of inhibitor in it and it should be sound. No coils needed and the header tank is built in.