Nik_huck Posted January 30, 2021 Share Posted January 30, 2021 Hi, I'm looking for recommendations for the type of boiler that suits my requirements based on the my current circumstances. Currently I've combi boiler with 15mm inlet pipe providing water supply for a single shower and kitchen. Pressure drops if taps gets used simultaneously in kitchen and shower. Going through an extension so when it completed I'll have 2 shower, bath and kitchen. What options do I have? One plumber suggested to go for bigger combi and 2 pumps for enough pressure, not sure if it gives enough pressure. Unvented cylinder is of no use due to15mm inlet. Another plumber suggested I can have an unvented cylinder using existing combi as system and one shower directly connecting to combi not best but will work. My though was to go for a bigger pipe 32mm via severn trent, put an application in had survey which will cost £1100 thought to having it done. Here is the twist and nohing was easy since I started my extension, as I live 100 meters close to railway crossing and due to security reason nearby traffic needs manually controlling when severn trent does new connection and that added another £1000 making total bill £2100 just for Water board plus internal digging which will be done by my builder. Can some one please suggest what is the best way forward. Thanks in advance MSN. Link to comment Share on other sites More sharing options...
Temp Posted January 30, 2021 Share Posted January 30, 2021 41 minutes ago, Nik_huck said: One plumber suggested to go for bigger combi and 2 pumps for enough pressure, not sure if it gives enough pressure. Pretty sure you cannot pump the output of a combi boiler! Your first job is to get the supply properly measured. You need to know what pressure and flow rate the incoming main can supply without any restrictions due to the existing boiler etc. Sometimes you can do that at a kitchen cold tap or garden tap or both at once. 54 minutes ago, Nik_huck said: Another plumber suggested I can have an unvented cylinder using existing combi as system and one shower directly connecting to combi not best but will work. If the incoming flow rate is poor some form of variable volume storage tank is needed (A regular unvented tank does not provide this). You would normally use a vented tank in the roof feeding a hot water cylinder and pumped to the showers (or pumped to all hot outlets). The CH side of the existing combi boiler could be used to heat the hot water cylinder and the DHW side could be used for one shower or perhaps the kitchen tap. If the static pressure is ok you might be able to use an accumulator tank to store cold water at mains pressure. Its possible thats what he meant but few plumbers seem to know about them. If you understand electronics they behave a bit like a capacitor in a power supply. 1 Link to comment Share on other sites More sharing options...
Temp Posted January 30, 2021 Share Posted January 30, 2021 I forgot to ask how powerful your combi is? Do your cold taps have significantly better flow than the hot? Link to comment Share on other sites More sharing options...
PeterW Posted January 30, 2021 Share Posted January 30, 2021 Do you really mean you have a 15mm supply pipe or a 15mm meter orifice ..?? Your supply is probably 25mm MDPE from the main - that’s the first thing to check. Upgrading internally once that is confirmed is your best bet, use 22mm Hep2O and look at ensuring you have a decent flow rate too. Link to comment Share on other sites More sharing options...
Nickfromwales Posted January 31, 2021 Share Posted January 31, 2021 22 hours ago, Nik_huck said: One plumber suggested to go for bigger combi and 2 pumps for enough pressure, not sure if it gives enough pressure. Unvented cylinder is of no use due to15mm inlet. Tell him to say "no" to drugs An UVC will have 22mm pipework and will happily connect to a 15mm cold mains. The discipline you need to observe is taking the 22mm cold supply all the way from the UVC multi-block ALL the way back to the 15mm cold stopcock. Reducing the resistance that the cold mains has to suffer before getting to your outlets is the critical thing to observe. You really need a plumber who has done a few ( lots ) of UVC installs, as the difference between plumber 1 and plumber 2 can be night and day. If you wish to retain the existing combi for money saving measures ( as long as it is in A1 serviceable condition ) then just have the hot outlet connected to the kitchen sink, and then use the heating circuit for heating CH and the UVC. That will work just fine. Do NOT connect the combi hot output to a shower, as whilst the shower is running ( the combi is in DHW priority mode ) zero heat will go to either CH or UVC. Flow rate and static pressure of cold mains needs reporting here before ANY advice can be given. You could get away with a Vaillant 938 and an accumulator, but we also need to know how many people living there, when they shower / bath / how often and more. INFO PLEASE! 2 Link to comment Share on other sites More sharing options...
Nik_huck Posted February 2, 2021 Author Share Posted February 2, 2021 On 30/01/2021 at 21:29, PeterW said: Do you really mean you have a 15mm supply pipe or a 15mm meter orifice ..?? Your supply is probably 25mm MDPE from the main - that’s the first thing to check. Upgrading internally once that is confirmed is your best bet, use 22mm Hep2O and look at ensuring you have a decent flow rate too. Yes mate i've15mm supply pipe Link to comment Share on other sites More sharing options...
Nik_huck Posted February 2, 2021 Author Share Posted February 2, 2021 On 30/01/2021 at 20:47, Temp said: I forgot to ask how powerful your combi is? Do your cold taps have significantly better flow than the hot? 28kw Combi boiler, yes mate cold water has got significantly better flow than hot water tap. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now