Hot water cylinder on CH circuit

[Percyval]

Hello, I am in the process of replacing my 30 year old central heating boiler (Servowarm Elite 50, if anybody has a gas valve, please get in touch).
I would like to keep the existing pipe system as it is, open vent with hot water cylinder.
At the moment the hot water cylinder is on the central heating circuit ie, water flows through the hot water cylinder then to the radiators, there are no diverter valves fitted.
I have been told by an installer, i must have a thermostat on the HW cylinder and also a room thermostat by law, is this true? i would like to keep the system as simple as possible, preferred boiler is a Intergas OV
Thanks in advance

 

[45yearsagasman]

The stats are required and must interlock with the boiler. You don't say what controls you have now, if any. In Summer when no heating is required, how do you turn rads off? A diverter valve would also be required. A bit more info from you would help in making recommendations.

 

[Madrab]

Wld recommend Intergas all day long, excellent design. To comply with Part L of the building regs if you are updating your boiler/heating system then you do need to have a boiler interlock - room stat/cylinder stat and ideally TRV's. Ideally you would also have you space heating and hot water on separate controllable and time controlled circuits to fully comply..

This gives you an idea of the minimum controls and requirements under Part L using a 3 port Y plan setup.

 

[Percyval]

The stats are required and must interlock with the boiler. You don't say what controls you have now, if any. In Summer when no heating is required, how do you turn rads off? A diverter valve would also be required. A bit more info from you would help in making recommendations.

Thanks for replying, the only control we have now is the temperature controller on the boiler. In summer we use an immersion heater, the boiler is not used

 

[Percyval]

Wld recommend Intergas all day long, excellent design. To comply with Part L of the building regs if you are updating your boiler/heating system then you do need to have a boiler interlock - room stat/cylinder stat and ideally TRV's. Ideally you would also have you space heating and hot water on separate controllable and time controlled circuits to fully comply..

This gives you an idea of the minimum controls and requirements under Part L using a 3 port Y plan setup.

Thanks for the diagram, this is precisely what i am trying to avoid, diverter valves!

 

[45yearsagasman]

Madrabs design is about as simple as you would get from an installation and user point of view. Would work perfectly well with you choice of boiler.
Honeywell div valves are the best and I'm afraid you won't be able to avoid using something like that if your system is to comply. Manual valves are soooo last year.

 

[Percyval]

Well its not as simple as the system i have now! but if the government say i must have it then so be it, just one thing, on Madrabs diagram it shows two returns to the boiler, in practise would the return from the HWC be teed into the one return just before the boiler?

 

[Madrab]

I appreciate you want to avoid valves Percy, they can be a pain the a$$. Unfortunately tho, separate circuits and control is the name of the game these days with the regs, and a valve(s) is the way to control them.

Yes, there would normally only be one return, it just shows them as separate in the diagram.

 

[Percyval]

I appreciate you want to avoid valves Percy, they can be a pain the a$$. Unfortunately tho, separate circuits and control is the name of the game these days with the regs, and a valve(s) is the way to control them.

Yes, there would normally only be one return, it just shows them as separate in the diagram.

Thanks Rob and Pete.

 

[mogget]

Just curious, is a by-pass required by law on a y-plan now, even though the rad with the room stat will have no trv?

I'm wondering whether the by-pass in that diagram is there for minimum flow, or regs compliance per se?

 

[Madrab]

If I remember correctly, Part L - building regs now require an automatic bypass to be fitted when required by the boiler. A fixed valve will allow bypass, even when not required (e.g. a rad with no trv) and it cannot regulate to optimise the flow, as required by the boiler, when the TRV's start to close as an autobypass can.

 

[mogget]

Thanks Rob!