Balance pressures for thermostatic shower

[Joem]

Hi, I am about to purchase and fit a thermostatic shower mixer valve. I understand that for best performance the cold and hot water pressures should be balanced.
My boiler is a fully modulating combination boiler with a 2.5 bar pressure reducing valve on the cold water supply to the boiler. Is it acceptable to take a cold water connection for the shower, after the pressure reducing valve and before the boiler? I'm worried that with the shower on it may starve the boiler?
Thank You

 

[Puddle]

Well not only should you balance the hot and cold pressures,you should also balance the flow rate to,you will maybe restrict the hot flow rate as in goes through boiler to allow correct hot water temperature at outlets,although you may say both hot and cold flow rate will be reduced at shower head,you have to consider mixing in shower valve and cold could over come hot
You could come off cold supply after pressure reducing valve then stick a separate valve to restrict flow to equal hot and should work Ok,however I would prefer coming off cold mains before pressure reducing valve to boiler and fit separate pressure reducing valve for cold to shower and normal valve to restrict flow as required,this gives you more control as required and will give you a better shower,also gives you adjustment when shower cartridge/capsule loses some of its calibration,increasing its life and the extra cost is minimal

 

[Joem]

Thank you for the advice. Since posting the question I have found installation instruction for my boiler on the internet (how did we manage without it?). For an unvented system, which mine is, the diagram shows the cold feed for the house being taken after the PRV. The cold feed in my house has been taken before the PRV! Should I be concerned?

 

[Puddle]

As said above you can change pipework or fit separate as said,however you have to do one or tuther,do not leave cold with no prv,you will have problems

 

[Joem]

Many thanks for taking to time to help with this, I really do appreciate it. What I'm trying to understand, additional to the shower question is the potential impact of NON of the cold water for the whole house (rather than just the shower) is taken after the PRV. It is all supplied from the mains which is contrary to the boiler installation instructions.

 

[clemda1]

got to this late have you sorted this problem or do you still need help?