Unvented system quote

[Welly75]

Hello all,

I've just had a quote to change my current vented system to an unvented system. The work involves installing a thermostat cut out to my existing boiler so it's compatible with a sealed system. Supplying the cylinder and marrying up excisting pipe work.

What I'm not sure about is they say I need a pump plus two zone valves for my central heating to run off the sealed system. I was under the understanding that the mains pressure does away with the need for any pumps?

The plumber said there was no issues with the flow/pressure of the water coming in however he never measured either.

Cheers

 

[twgas]

Are you changing your vented cylinder to unvented (mains hot water) or your heating system from open to sealed?

 

[Welly75]

Both but could get by keeping the heating unvented

 

[twgas]

Get another plumber, the pressure and flow rate need to be checked before you have an unvented cylinder fitted.
What boiler and system type do you currently have?

 

[doitall]

As above, what is the boiler make, model.

You need the flow rate and pressure at peak times or you could be wasting a lot of money

 

[Welly75]

In his defence I did tell him that I measured the flow to be 25 l/min

Currently have an old ideal classic rs50 boiler running a vented system with hot water tank on 1st floor and cold water tank in loft.

Is it normal practice when running central heating on sealed system to install a pump, is the incoming water pressure not adequate to distribute it around the house (including loft)

Cheers

 

[Fluffster]

You are mixing up an unvented hot water storage cylinder which distributes the hot water to all outlets with mains pressure. The heating system is pumped around a dedicated circuit by a pump (which can be sealed or vented) unless it is very old and works on a gravity system.

Pete

 

[twgas]

According to MIs your boiler must be vented. I could find no mention of an overheat thermostat to make it convertable to a sealed system. This would not, however, prevent you from having an unvented cylinder.

 

[Agile]

I would also doubt that boiler should be converted to an unvented heating system. But...


However, as I always have to say the open pipe water flow is of no great significance!

its the dynamic flow rate that matters and so few either understand or measure that.

To get reasonable performance from an unvented cylinder a minimum of 22 li/min dynamic flow at 1 bar is needed.

Tony

 

[Welly75]

http://idealparts.com/docs/116771_6.PDF

 

[Agile]

That is the link to the MIs which DOES say that an sealed system kit can be fitted:-

The boilers are suitable, as standard, for connection to open
vented systems ONLY.

An Overheat Thermostat Kit is available to allow the boiler to
be used on sealed water systems.

A complete Sealed System Module, which fits on top of the
appliance, is also available as an optional extra.


Whilst thinking about it I have seen one of these with the maker's kit fitted on top.

Unless clearing the loft is the objective I done see much point in converting it though.

The energy efficiency does say that it increases the efficiency by 2%-3%. But that comes at the risk of leaking rad valves and then need to top up manually.

Tony

 

[twgas]

I stand corrected on the sealing of these boilers

 

[Welly75]

My reason behind this is that I'm currently having loft converted and will be putting in en suite with shower therefore would require either sealed system or putting in negative head pump.

Space isn't so much an issue as I can move the water tanks to void in the loft.

I'm now starting to lean towards putting in a good quality electric shower and lift the tank so it will be slightly higher than the hot water tap in the loft.

Will there be an issue putting rads up there and if so will it be a case of upgrading the current CH pump?

 

[Agile]

The Ch pump will be fine.

BUT you will need the F&E tank to be 1m higher than the top of the highest rad !

If that's possible then that is what I would do.

But converting to a sealed heating system would also be a solution. Possibly a more expensive one!

An electric shower may be better and that would save the cost of an unvented cylinder which is about £1000+

Tony Glazier

 

[Fluffster]

You would have to convert to a sealed heating circuit for a rad in the loft. A standard 5m head pump on full speed should suffice, however it all depends on the existing load, your installer will be able to advise.

If you are going for an unvented cylinder then the loft shower should be fine if you have the correct flow and pressure initialy.

Pete