How can I run two showers at the same time

porky22

Hi,
please help I have an Vailllant ecotect plus 624 and Vaillant unistor 210 cylinder installed last year.Have a new loft bathroom with a shower.The shower works fine but now i have installed the same shower unit downstairs,both are trevi thermostate controled valves,when i turn loft shower on pressure is fine but if i try and turn downstairs shower on that works fine but the loft shower drops to a dribble.Is there anyway to solve this problem or have I paid £2000 for the wrong boiler system,my mains water preesure is good.Please help.

Porky

Be Lucky

robv_3

You have an unvented hot water cylinder which is about as good as it gets (along with thermal stores / heatbanks). They normally deliver 20+ litres per minute of hot water making them suitable for multiple showers. The documents for your cylinder show it can do 40+ l/m if the incoming main is up to it. (page 3)

http://www.vaillant.co.uk/stepone2/data/downloads/c9/42/00/uniSTOR.pdf

Showers can use anywhere from 10 l/m to 30 l/m for a full multi jet system. About 50% of this will be hot water and 50% cold so hot water tank only needs to supply half.

My 'guess' is your water main is not up to the job. What static pressure and flow was recorded before the cylinder was installed? Normally the manufactures recommend at least 20 l/s / 3 bar which would power two showers, just.

robv_3

Although it does not affect you, a work of warning. If you have multiple bathrooms/showers do not install a combi as it is unlikely they will be suitable.

The combi manufactures measure the flow rate based on a 35 degree rise with most suppling between 10 and 15 l/m of hot water. Expect most water main temperatures are ~5 degree this time of year so at full bore you will only see 40 degree water where most other system will provide hot water at around 60 degrees which is a 50% higher.

So to run a shower a combi will require 75% hot 25% cold rather than 50%:50% of your system. 20 l/m shower will use the full capacity of the best of combi's.

KimYeovil

Develop a closer relationship with the other users?

TomsMom

I've got a Vailant boiler (not the same as you, it's a combi) in the house we're renovating. There's a thermostic shower in the main bathroom to be run off the boiler and there's going to be an electric shower in the en-suite although I doubt they'll both be on at the same time anyway.