Normal unvented indirect tank or high gain unvented indirect tank

[roobaru]

Hi,

Trying to decide which cylinder to go for?

I am renovating my house which will end up having four bathrooms and a wc. I am planning to go for a 300l unvented indirect cylinder as currently I have a vented cylinder with a cold water tank in the loft and face issues with hot water pressure.

One of the things I am trying to decide is whether to go for a telford tempest, telford tornado or a Joule cyclone tank?

The other is that while speaking with the telford technical team, they told me about a high gain variant but I can't find any details online. I plan to use the cylinder with my vaillant eco fit 430 gas boiler. Will this support a high gain cylinder or am i better off with a standard unvented indirect cylinder?

Thanks

 

[SJB060685]

Before deciding you want to go for a mains pressure unvented cylinder have you first had your incoming main pressure and flow rates checked? If your incoming supply isn’t up to meeting your demands it changes the design of such a system drastically and could mean one of several approaches.

 

[ShaunCorbs]

Also why not go with vaillant controls and make it priority hot water then you won’t need a high gain as most will do 20-25kw coils ?

 

[roobaru]

Before deciding you want to go for a mains pressure unvented cylinder have you first had your incoming main pressure and flow rates checked? If your incoming supply isn’t up to meeting your demands it changes the design of such a system drastically and could mean one of several approaches.

I haven't checked, I called the water company and they said that they only guarantee 1 bar pressure. I have put in an application to change the supply pipe into my home as the existing one is a lead pipe as per my builder and that I should have at least a 22mm pipe. Is there an easy way to find the pressure and flow rate?

 

[roobaru]

Also why not go with vaillant controls and make it priority hot water then you won’t need a high gain as most will do 20-25kw coils ?

Can you provide a bit more details as to what you mean by vaillant controls and priority hot water?

 

[SJB060685]

If you had a pressure gauge and a flow cup you could measure static and dynamic pressure and the flow rates. Getting the incoming mains upgraded is usually the first step to ensure adequate flow and seeing as your current supply pipe is lead then it needs to be done for that reason as well.
PDHW or priority hot water is where the boiler and controls system priorities heating the cylinder before central heating. You won’t have both at the same time. If the heating is on and there’s a demand at the cylinder the boiler will transfer energy to the cylinder and then revert back to central heating. Very common procedure these days.

 

[roobaru]

If you had a pressure gauge and a flow cup you could measure static and dynamic pressure and the flow rates. Getting the incoming mains upgraded is usually the first step to ensure adequate flow and seeing as your current supply pipe is lead then it needs to be done for that reason as well.
PDHW or priority hot water is where the boiler and controls system priorities heating the cylinder before central heating. You won’t have both at the same time. If the heating is on and there’s a demand at the cylinder the boiler will transfer energy to the cylinder and then revert back to central heating. Very common procedure these days.

Thanks for explaining PDHW, I thought that was the standard for any boilers these days. Do I need to do something specific in case of using an unvented tank? and do I need to go for Vaillant unistor tanks for this or can use any?

 

[SJB060685]

Anything specific in what sense? Any cylinder can be used but might change the controls needed if not a Vaillant cylinder. I’m an oil boiler technician not a gas engineer so I will leave it to @ShaunCorbs to guide you in that area

 

[ShaunCorbs]

If you email vaillant with your chosen boiler and vaillant cylinder and your need eg 2 zones etc and they will email you back what you need

Or @EvilDrPorkChop @king of pipes

Can advise

 

[EvilDrPorkChop]

Thanks for explaining PDHW, I thought that was the standard for any boilers these days. Do I need to do something specific in case of using an unvented tank? and do I need to go for Vaillant unistor tanks for this or can use any?

You can use it with any tank, providing you use the Vaillant sensor and keep the cylinder High Limit stat wired in series with the motorised valve. Should the Vaillant VR10 sensor fail the MV would cut out the flow to the cylinder.

I've done a few systems with PDHW with Vaillant controls and other control systems. It works well providing you know how the system works, it's configured correctly and the timings are set correctly. The Vaillant boiler will allow you to set your coil ratings and Flow temperatures through the D. settings.

I have PDHW on my own system using a Main, an older MegaFlo. On a 170L system my hot water recovers in about 10 minutes with a what i'd say is a 50/60% draw off.