Cylinder Advice - Vented or Unvented

[jaydub]

Just about to get a new boiler and cylinder installed.  The house is a four bedroom house with four adults living in it.

We have two bathrooms, both with 3 bar power showers in (although never run at full blast!)

We had two quotes for the boiler / cylinder replacement and both quotes quoted for a system boiler, but one of them proposed an unvented cylinder. The other was proposing replacing the existing vented with a larger one, principally based on the fact that our mains feed and all internal piping is 15mm.

We have had some flow and pressure measurements taken one evening and we get 4 bar pressure dropping to 3.1 bar with 4 taps open (including two downstair sinks, the downstairs loo and the bath) and a flow rate of over 22 l/min measured at the kitchen sink, dropping to 14 l/min with the above four taps running.

We are going with the plumber who quoted the vented cylinder originally, but asking him to install a unvented cylinder.  He is still being cautious about reduced water flow through the showers if both are being used.

How big a concern should this be?<br><br>I'm also interested in people's views about whether a Nest thermostat is worth fitting or not.

Many thanks for your assistance.

 

[macackau]

What were the flow rates at the different outlets when they were open? I prefer Hive to Nest, similar in how they work but I just have a preference for it. Have one on my own home.

 

[jtsplumbing]

I think with those flow rates & pressure I would stay with the system you have , Just install a larger capacity cylinder, Unvented would be ok but a lot more work and expense you may even have to upgrade your water main

 

[jaydub]

Only checked the flow at the downstairs kitchen sync, but 14l/min when that and three other taps open.

The plumber I'm using is a registered Nest installer, so a bit limited in choice. More of a question about whether intelligent thermostats are worth the extra expense.

 

[jaydub]

I think with those flow rates & pressure I would stay with the system you have , Just install a larger capacity cylinder, Unvented would be ok but a lot more work and expense you may even have to upgrade your water main

Appreciate the advice. Existing boiler is a 29 year old Glowworm Hideaway rated at 26.5 kw and the current cylinder is only a 140/150 l cylinder, so both due an upgrade to get us to something more suitable for a 4 bed house with 4 adults in it.

Cost of the unvented option is not that much more, but if I am likely to be compromised by the 15mm feed into and throughout the house, then you are probably correct that I would be better sticking with the current vented set up. Upgrading the feed in the house would be a disruptive option as it would mean pulling up the bathroom flooring and possibly removing tiles from the bath surround, neither which I really want to consider. And I really don't want to think about upgrading the water main with the associated cost.

 

[ShaunCorbs]

Appreciate the advice. Existing boiler is a 29 year old Glowworm Hideaway rated at 26.5 kw and the current cylinder is only a 140/150 l cylinder, so both due an upgrade to get us to something more suitable for a 4 bed house with 4 adults in it.

Cost of the unvented option is not that much more, but if I am likely to be compromised by the 15mm feed into and throughout the house, then you are probably correct that I would be better sticking with the current vented set up. Upgrading the feed in the house would be a disruptive option as it would mean pulling up the bathroom flooring and possibly removing tiles from the bath surround, neither which I really want to consider. And I really don't want to think about upgrading the water main with the associated cost.

if your happy with the flow and pressure / showers you have now i wouldnt bother

 

[macackau]

Just because your installer is a Nest registered installer doesn't mean you have to have Nest. Your the customer and its your choice.