Posting a message to the forum will remove the above advertisement
  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. Checkout our Plumbers Insurance area - heavily discounted Public Liability Insurance and Van Insurance specifically designed for plumbers.

Discuss Hot water temperature advice. in the Central Heating Forum area at

  1. Juman islam

    Juman islam Member


    I've got a combi valiant ecotec plus 837 with a control vrc 430 weather compensator controller fitted.

    The picture attached is the mains display of the vrc 430 with both heating and water set to auto.

    1) The only purpose I have used auto is for the heating to kick in when it's in for the heating timer. Is there any other purpose for it to be on auto?

    2) what is the purpose for the hot water to be set to auto if this is a combi boiler. Isn't the purpose of the combi boiler to have hot water on demand? There is currently no timer settings settled for the domestic hot water.

    3) what is the best temperature to have the hot water set on? As from the pic, it's set at 50 C but I've read online and a few sites recommended at 60 C.

    Thanks in advance.

  2. EvilDrPorkChop

    EvilDrPorkChop GSR

    Not come across a VRC430 in a while and certainly haven't programmed one for ages! If it's anything like the Worcester ones, the timer settings for the HW I would imagine are for the 'Comfort' mode. So you can have comfort turned on during set periods so you get HW quicker, but can have it off during the night to save gas and prevent the boiler coming on.

    HW temp can be whatever you want, doesn't matter as it's a combi. I usually recommend 55oc. If you had stored HW like an Unvented cylinder then different matter.
    • Like Like x 1
  3. CBW1982

    CBW1982 GSR Top Contributor!!

    Google it and download instructions if you don’t have them. It can be used to control domestic hot water (dhw) from an additional source. I’m not sure it relates to comfort mode.

    Stored dhw - 60 degrees
    Combi - user preference, but I usually set between 60 and 65.
    • Like Like x 1
  4. SJB060685

    SJB060685 Top Contributor!!

    Hi CBW1982. Sorry to jump in on thread. I work with oil boilers, as you may or may not know oil combi’s have a thermal store or slave tank to aid in HW production. Are there any gas combis that are similar in design or store HW? I’m not trained on gas so wouldn’t know
  5. CBW1982

    CBW1982 GSR Top Contributor!!

    Hi SJB, I'm not to sure tbh, I only ever fit combi's and just those. Perhaps someone else may know?
    • Like Like x 1
  6. SJB060685

    SJB060685 Top Contributor!!

    No worries buddy
    • Like Like x 1
  7. EvilDrPorkChop

    EvilDrPorkChop GSR

    The Vaillant 938 is a storage combi however as far as i'm aware on that model it just uses the comfort setting to keep the store warm rather than timings.

    The only other Storage combis I have come across is the Worcester Highflows which use the timer to keep the store warm as suggested.
    • Like Like x 2
  8. SJB060685

    SJB060685 Top Contributor!!

    Thanks Evil. Oil combis use a store, they use a timer to bring store up to temp to speed up HW production. If the store is cold then that volume of tank needs to be brought up to temp before you get HW at taps. Like I said I’m not trained on gas, what I know about gas is what little we learnt at college and what I’ve studied since. I know the principles behind gas boilers, pipe sizing and everything else you’d expect an engineer to understand but have know experience with gas like I say. My work only consisted of PJ and VS/VP burners
  9. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    will be some kind of hot water pre heat

    60 dc
    • Like Like x 1
  10. SJB060685

    SJB060685 Top Contributor!!

    So Shaun one last question if you don’t mind. These gas storage combi’s. Are all the stores like oil combi’s as in the store is pre heated to supply instant heat to PHX when a tap is opened or are some an actual storage for DHW taps? Sorry if this is a stupid question, I’m just trying to further my understanding of gas boilers.
    • Useful Useful x 1
  11. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Correct but they use the same water eg you take your supply from the tanks until it runs out normally vaillants are around the 15l mark they also have a strat pump moves the hot water to the bottom etc
    • Like Like x 1
    • Useful Useful x 1
  12. SJB060685

    SJB060685 Top Contributor!!

    Got you. As far as I know oil combi’s don’t have a stratification pump. Wether it’s a diverter valve or two pump system the water is pumped through the bottom of oil combi’s storage before coming out the top and going through the PHX to heat DHW.
    • Informative Informative x 1
Similar Threads - water temperature advice Forum Date
Isolator Valve for cold water supply - correct size Valves & Taps Yesterday at 5:34 PM
Main combi 24 he hot water issue Gas Safe Registered Plumbers Only Yesterday at 11:12 AM