Boiler replacement - advice please

[freebooter99]

Hi - thanks for reading

I am about to replace my Baxi System boiler with a Worcester 30cdi system boiler retaining the current Megaflow water tank in the sealed system.

There is currently no CH system thermostat although all rads have thermostatic valves. The system is currently controlled using a wired programmer near the Megaflow which allows me to select CH or just Water if i need to boost the tank. I am not sure but think that the controller is currently activating a (three way ?) value near the Megaflow which is closing the CH circuit when Water only is selected

Q1 - do I need to change the current controller or just have it wired into the Worcester ?

Q2 - what would be the benefits of fitting the Worcester divertor kit ?

Many Thanks


B

 

[Tibbot]

You can keep your current controls. Even if they needed replacing, you don't need Worcester's own. You must have a dedicated 2 port zone valve for the Megaflo even if a 3 port Y-plan is installed. A roomstat will also be required.

 

[freebooter99]

Hi Tibbot and thanks.


I have just checked the pipework leading to the megaflow - there is a single 22mm feed from the boiler which the splits with one 22 mm goging to the mega and the other presumably feeding the CH system.

Both feed pipes have Honeywell (presumably motorised) valves - one either side ot the "T"

When you say I need a roomstat - is that to comply with current regs or is it best practice ?

The problem here is that I don't see how I introduce the room stat to the existing programmer arrangement.

The Megaflow itself has a thermostat which is wired into the circuit somehow (sorry but I haven't checked out precisely how). This will be limiting the amount of boiler output which is hitting the Megaflow.

House temperatures are maintained by the setting of each rads thermostatic value so that rooms I use most are kept comfortable whilst guest bedrooms etc are just kept warm enough. I am quite happy with the current setup unless I need to change it to comply with regs.

 

[Whitespirit66]

When you say I need a roomstat - is that to comply with current regs or is it best practice ?

Building regs.

The TRVs close individual rads down when the room they are in reaches temperature, but you need a room stat to turn the boiler off when the house is up to temperature. It's a no-cost item, as it will pay for itself in energy savings over a few years.

It's basically a thermostatically controlled switch, between the programmer and heating valve and boiler. It cuts the power from the controller to valve/boiler if heating demand is satisfied. Simples!

 

[freebooter99]

Thanks for that.

So my best bet might be to replace my existing controller with a two channel (HW and CH) programmer with an RF roomstat - something like a Honeywell Sundial RF2 Pack 2 since I dont want to run additional wires for the room stat to the programmer ?

 

[D_Hailsham]

So my best bet might be to replace my existing controller with a two channel (HW and CH) programmer with an RF roomstat - something like a Honeywell Sundial RF2 Pack 2

A cheaper option is to retain the existing programmer for the hot water and use a Honeywell CM927 wireless 7-day programmable thermostat for the central heating. The only disadvantage is that you can't control the CH and HW times from the same place; but as HW times are rarely changed, this is not really important.