Unvented system to replace immersion heater?

andyfff

Hi

Got a 30 year old one bedroom 2nd (top) floor flat with a storage heater (great info on this site about them!) in living room and convection heater in the bedroom.
its double glazed, cavity walls done and i'll be looking to top up the loft from 75 mm to 300 mm. Again from this site - insulate insulate insulate! Flats on economy 7

Cupboard has a immersion heater and something has fallen from the large water tank above it and blocked the immersion heater.
Plumber advised replace system with an unvented one (thanks for info on this site about what that is) for £700. I'm in west of Scotland.
There is no gas on site but I've chased up a quote from the gas supplier for the 60 flats and it would be about £2000 for each flat plus some individual costs e.g. higher up ones etc. and minimum of 19 flats would need to take it up for them to start work. i'm forwarding this quote to the managing agent for site.
i know gas is much cheaper, but not too keen getting gas in a flat. Guess I would be heading towards 4000+ for that. Probably need to go the whole hog and replace the storage heaters as well.

Take it I should go unvented (after getting another two quotes) or is there something better that I could do?

Thanks,
Andyfff

System

An unvented system DOES NOT replace an immersion heater. If you have no gas, then an immersion heater will still be required to heat your hot water cylinder. Vented or unvented will make little difference to your actual hot water heating costs.

Forgive me, I am not sure that you have understood what the actual problem is, and I confess that if I had been given the explanation in your post I would be sitting here scratching my head. Put simply, to get hot water through a system there has to be pressure. An unvented or sealed system uses cold water pressure to force hot water through your taps. Alongside the unvented/sealed cylinder will be a 3 bar pressure reducing valve. It follows that your hot water will be controlled to 3 bar. There will still be a dual thermostat in the cylinder to heat the hot water during peak and off peak times.

Finally, if you have any thermostatic showers is it is important to check that your installer proposes to use the other port on the pressure reducing valve as the cold water source for the shower. If not, you could find yourself with 5 bars of cold water on one side of your shower alongside 3 bars of hot: in such circumstances, you might only get warm showers.

Edit:

A further thought. If you were to go for the gas option, not only would you get cheaper energy ( I pay 3.5p/kWh for gas and 13.65p/kWh for electricity) but you wouldn't need to buy a cylinder of any type. The best option would be to go for a combi boiler which provides heat and on demand hot water. You need to factor this into your sums.

AndyPK

The advantage of an unvented system is that you have mains pressure hot water. And you don't need the old cold tank.(although you may like to keep it supplying toilet if you have water outages in your area)


Unvented tanks are expensive, don't last very long (15 years), requires special training to maintain/install.


Unless you would benefit from main pressure hot water, I think I would avoid!

andyfff

Thanks for the reply and apologies for my lack of clarity.

Think i'm with you Hengus, so i'd possibly replacing my old vented a new to unvented (plumbers suggestion and he sent me a picture of it, which fits your description but not what i typed!)
So i'll check out the gas in more detail as well and look at vented options as well (as i think Andy PK hints).

Thanks to both of you!