Unvented system wiring help

[chappy2000]

Hi, hoping someone can help me out. As part of a rewire I'm connecting up an unvented system and separate boiler for the heating. Boiler, pump and stat for heating all working but I have no experience of unvented cylinders.
I basically have the cylinder, 2 port valve and pump. Looking for a basic understanding and help with terminals. I have 6 terminals on the cylinder ( currently wired with a perm l from a timer switch. The other 3 terminals go to a separate device, thermostat / cut out?
I will attach a picture if possible. Thanks in advance.

 

[Ian1981]

3 terminals are the immersion and the other are for the cylinder stat
You'll need 3 connections for a y plan at the cylinder or if it's an s plan then just 2

 

[davesparks]

The three unused terminals are the C NC and NO connections of the cylinder thermostat. The overheat cutout is usually built in to the thermostata unit in this type of cylinder, but check the manual to confirm.

Connect it as per usual for a hot water cylinder if it is S plan, if it is Y plan the you need to add the two port valve in to the standard circuit so that the DHW demand from the cylinder stat opens the 2 port valve and then the microswitch of that valve fires the boiler.

What is that pump for, It looks like a secondary circulation pump?

 

[Leesparkykent]

As Dave says the yellow pump looks like secondary hot water return and will have either bronze or stainless steel internal components. Usually with a secondary hot water return I put the pump on its own single channel programmer so the customer can time it to come on before they are most likely to be using the hot water.

 

[buzzlightyear]

Domestic Central Heating System Wiring Diagrams; C, W, Y & S Plans - http://timstephenson.me.uk/domestic-central-heating-system-wiring-diagram-c-w-y-s-plan/ their you go print off and keep.

 

[chappy2000]

Hi, thanks for the quick reply.

It's a direct system and the manual was not very descriptive at all, no schematic only a diagram showing 1,2,3 from the valve. Yes I think it's a circulation pump due to the side of the property in guessing.
It's currently temp connected by the plumber so the pump runs continuously and it just have a perm feed on timer. I was hoping the system would come pre wired ready for me to just add a timer & feed.

 

[buzzlightyear]

which company is the cylinder from.

 

[sam400]

Hi you normally have the overheat stat and the standard stat in series as an extra safety precaution. Usually the link is pre wired so timer goes on one stat and valve on the the other.

 

[sam400]

Sorry ignore my post, just had a closer look at stats looks like they have 2 stats in the one unit.

 

[davesparks]

Hi, thanks for the quick reply.

It's a direct system and the manual was not very descriptive at all, no schematic only a diagram showing 1,2,3 from the valve. Yes I think it's a circulation pump due to the side of the property in guessing.
It's currently temp connected by the plumber so the pump runs continuously and it just have a perm feed on timer. I was hoping the system would come pre wired ready for me to just add a timer & feed.

It is not a direct system, it is an indirect system.
A direct system is one where the domestic hot water is heated directly by a source of heat, for example by an immersion heater.
An indirect system is one where the domestic hot water is not directly heated by a source of heat, for example a boiler heats water which is then circulated through a heat exchanger to heat the domestic hot water.

Don't guess with an unvented cylinder, the controls need to be correct as they incorporate a safety system intended to prevent overheating and possible explosion of the cylinder.

 

[davesparks]

which company is the cylinder from.

It looks like a mega-flo unit which is made by Heatrae Sadia

 

[chappy2000]

It is not a direct system, it is an indirect system.
A direct system is one where the domestic hot water is heated directly by a source of heat, for example by an immersion heater.
An indirect system is one where the domestic hot water is not directly heated by a source of heat, for example a boiler heats water which is then circulated through a heat exchanger to heat the domestic hot water.

Don't guess with an unvented cylinder, the controls need to be correct as they incorporate a safety system intended to prevent overheating and possible explosion of the cylinder.

It is not a direct system, it is an indirect system.
A direct system is one where the domestic hot water is heated directly by a source of heat, for example by an immersion heater.
An indirect system is one where the domestic hot water is not directly heated by a source of heat, for example a boiler heats water which is then circulated through a heat exchanger to heat the domestic hot water.

Don't guess with an unvented cylinder, the controls need to be correct as they incorporate a safety system intended to prevent overheating and possible explosion of the cylinder.

Hi, this system is not connected to the boiler, it's stand alone hot water, does that not make it a direct system as the water is heated directly by the source ( element).

 

[Lee42]

Sounds like you need to get someone in who knows what they are doing.

Why is there a two port valve on the system if it's not connected via a boiler?

 

[chappy2000]

Sounds like you need to get someone in who knows what they are doing.

Why is there a two port valve on the system if it's not connected via a boiler?

Every unvented has a 2 port, fail safe / safety device

 

[Lee42]

I thought that was only when connected via a boiler?
You mentioned it is only heated via a immersion which will have its own safety cutout

 

[Leesparkykent]

Lol if it's not connected to a boiler then why have a two port valve? The Plumber can't have his G3 ticket as he has the very basic principals of how the system works wrong.

 

[Taylortwocities]

So, its a direct system with the ONLY source for heating the vessel is from the immersion???

Hi you normally have the overheat stat and the standard stat in series as an extra safety precaution.

Not just normally, this is an absolute requirement. The overheat cylinder control MUST be wired in series with the heat source (the immersion).
They are the things that stop the vessel boiling and squirting super-heated water over everybody should the immersion's temperature controls fail.

Installation of unvented heated water vessels is notifiable to the local authority and you need a G3 qualification to do it.

you need to get someone in who knows what they are doing.

EDIT:
Extract from guidance
The Local Authority Building Control must be notified of the installation of an unvented hot water storage system as they are subject to the legal requirements of Building Regulation G3. The system must be installed by a ‘competent person’ who holds the relevant qualification for the installation of unvented hot water cylinders. The installer must be able to provide a card issued by a body such as the Institute of Plumbing (IoP) or the Construction Industry Training Board (CITB).

 

[Taylortwocities]

So, its a direct system with the ONLY source for heating the vessel is from the immersion???

Hi you normally have the overheat stat and the standard stat in series as an extra safety precaution.

Not just normally, this is an absolute requirement. The overheat cylinder control MUST be wired in series with the heat source (the immersion).
They are the things that stop the vessel boiling and squirting super-heated water over everybody should the immersion's temperature controls fail.

Installation of unvented heated water vessels is notifiable to the local authority and you need a G3 qualification to do it.

you need to get someone in who knows what they are doing.

EDIT:
Extract from guidance
The Local Authority Building Control must be notified of the installation of an unvented hot water storage system as they are subject to the legal requirements of Building Regulation G3. The system must be installed by a ‘competent person’ who holds the relevant qualification for the installation of unvented hot water cylinders. The installer must be able to provide a card issued by a body such as the Institute of Plumbing (IoP) or the Construction Industry Training Board (CITB).

 

[andyb]

Looking at the 2nd picture it would seem that it's plumbed as indirect. The valve is on the flow. You need to wire the tank stat to controll the valve. The immersion will just be a back up and not the primary heating source.

 

[buzzlightyear]

that boys is pullin evolution cylinder .Pullin Evolution Unvented Cylinders - http://www.evolutioncylinders.co.uk/
indirect model he has. I think looking at his pics.