Bigger size Combi Boiler or Megaflow System?

[Optimiser1981]

Hi All,

Firstly Happy New Year to everyone! New to the forum and was after some advice please.

I am having renovation work done to my property starting next week. As part of the renovation work I am having two additional bedrooms in the loft (dormer). The property currently is a 3 bedroom property.

I currently have one bathroom downstairs with an electrical shower. I have a Wocester Bosch Greenstart CDI 30kw Combi Boiler. Once the work has been completed I will have a total of 5 bedrooms and two bathrooms.

With the current bathroom downstairs is someone is having a shower and someone turns the tap on in the kitchen, the pressure is lost from the shower.

I have been advised by my builder that the boiler will need to move from where it currently is in order to be able to incorporate the stairs that will lead to the loft. The boiler has been installed since 2012 and have had the odd minor issue. What I am trying to understand is where I will need to move the boiler, do I look at upgrading the boiler to a bigger sized on (to help with the pressure loss when having a shower) OR do I look at investing in a Megaflow system? My main concern is that if I stick with the same boiler and once I will eventually have two bathrooms, the amount of pressure loss would be significant hence why looking at a Megaflow system.

Also when it comes to choosing showers I believe I only have the option of a mixture shower OR an electric shower, is this correct?

Thanks all. If you need any further information please let me know. Apologies if I have missed out any key information.

Thanks

Nadeem

 

[steadyon]

Before yo do anything you need to know, for your incoming mains cold water supply:
1. The static pressure. This is the pressure measured at a cold tap attached to the mains (e.g. kitchen tap or outside tap normally) with no other taps or outlet running.
2. The dynamic pressure. This is the pressure measured at a cold tap attached to the mains (e.g. kitchen tap or outside tap normally) with another mains attached tap running. Typically measured at an out side tap or washing machine tap with the kitchen tap running.
3. The flow rate (in litres per minute (lpm)) of the incoming mains. This should be measured at an outlet as close as possible to the incoming mains with no restrictions such as isolation valves or half closed stop cocks.
4. The measurements can be made:
4a. Pressure requires a special gauge, such as Screwfix item 82412.
4b. Flow can be measured by timing how long the fully open outlet takes to fill a 10 litre bucket. From that the flow in lpm can be easily calculated.
5. For a combi, you need to be looking at a minimum dynamic pressure of 1.5 bar and a flow rate of 15 to 20 lpm.
6. For an unvented cylinder you need to be looking at a dynamic pressure of 1.5 to 2.0 bar, and flow rate of 20 to 30 lpm.
7. If you can't achieve these figures, there are ways round it, but all are quite costly.
8. You can't pump the output of a combi or unvented hot water cylinder, which does restrict your shower choices to electric or mixer. Essentially you can't have a separate shower pump or a power shower with its own pump inside.

If it is the electric shower which loses pressure when the kitchen tap is turned on, I would suspect your current set up will not meet the criteria set out above.