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  • FIRST POST
    • mickeyb102
    • By mickeyb102 17th Apr 17, 4:34 PM
    • 3Posts
    • 0Thanks
    mickeyb102
    Love or Hate your Combi Boiler?
    • #1
    • 17th Apr 17, 4:34 PM
    Love or Hate your Combi Boiler? 17th Apr 17 at 4:34 PM
    Hi, I am looking to replace the warm air heating in my home and would appreciate any views. We have a 70's style detached house with 4 bedrooms, single bathroom and downstairs cloakroom. The heating engineer has given us 2 options

    (1) Vailant EcoTec 832 combination bolier
    (2) Vailant ecoTec 630 boiler with a Main unvented hot water cylinder.

    Both would have 11 radiations and we were thinking that we could remove the electric shower over the bath and run this off the new system as well.

    The engineer is trying to push us towards option 2. He said that combi boilers are more complicated and so less reliable. He said, in winter, the water flow will be slow as the mains water will be colder. Is this really the case? We like the idea of the combi and would be most grateful for any advice from anybody who has one of these. Has it been reliable. is the flow ok when say running a sink tap and bath, does it work well with a shower. Thank you very much.
    Last edited by mickeyb102; 17-04-2017 at 4:50 PM.
Page 1
    • Alex1983
    • By Alex1983 17th Apr 17, 5:34 PM
    • 273 Posts
    • 142 Thanks
    Alex1983
    • #2
    • 17th Apr 17, 5:34 PM
    • #2
    • 17th Apr 17, 5:34 PM
    Both boilers are very reliable and will come with good garuntees.
    A combi boiler is generally 1 hot tap operation but as this is a 1 bathroom house it shouldn't cause much issue for you. You will have as much hot water as you need as it will just run constantly until you turn the tap off.
    Winter months will affect you hot water temperature, a combi increases the temperature by a set amount usually about 35-40 degrees but will vary from boiler to boiler. So if your cold water is coming in at 5 deg then you will get around 45 deg hot water. The flow rate also affects the temperature of the water.
    The hot water tank option will give you the same temperature water all year round as it's stored hot water but you will need to heat the tank up everyday.

    I would go with the unvented system but that's just my preference.
    • coffeehound
    • By coffeehound 17th Apr 17, 5:42 PM
    • 974 Posts
    • 1,572 Thanks
    coffeehound
    • #3
    • 17th Apr 17, 5:42 PM
    • #3
    • 17th Apr 17, 5:42 PM
    Worth noting that unvented systems are subject to compulsory annual safety checks.

    Also remember with combis that your heating goes off while water is being drawn, and baths can take longer to run with a combi.

    Personally I've hated combis I've experienced but others love theirs.

    .
    Last edited by coffeehound; 17-04-2017 at 5:44 PM.
    • Ganga
    • By Ganga 17th Apr 17, 6:04 PM
    • 583 Posts
    • 274 Thanks
    Ganga
    • #4
    • 17th Apr 17, 6:04 PM
    • #4
    • 17th Apr 17, 6:04 PM
    Hi, I am looking to replace the warm air heating in my home and would appreciate any views. We have a 70's style detached house with 4 bedrooms, single bathroom and downstairs cloakroom. The heating engineer has given us 2 options

    (1) Vailant EcoTec 832 combination bolier
    (2) Vailant ecoTec 630 boiler with a Main unvented hot water cylinder.

    Both would have 11 radiations and we were thinking that we could remove the electric shower over the bath and run this off the new system as well.



    The engineer is trying to push us towards option 2. He said that combi boilers are more complicated and so less reliable. He said, in winter, the water flow will be slow as the mains water will be colder. Is this really the case? We like the idea of the combi and would be most grateful for any advice from anybody who has one of these. Has it been reliable. is the flow ok when say running a sink tap and bath, does it work well with a shower. Thank you very much.
    Originally posted by mickeyb102
    Cannot comment on the combi option but when we first married 45 years ago we had a council house with ducted warm air heating,hated it with a passion,never got the house hot and made colds and sore throats more common,got a combi now and love it.
    ITS NOT EASY TO GET EVERYTHING WRONG ,I HAVE TO WORK HARD TO DO IT!
    • jack_pott
    • By jack_pott 17th Apr 17, 6:12 PM
    • 3,703 Posts
    • 4,720 Thanks
    jack_pott
    • #5
    • 17th Apr 17, 6:12 PM
    • #5
    • 17th Apr 17, 6:12 PM
    Worth noting that unvented systems are subject to compulsory annual safety checks.
    Originally posted by coffeehound
    Does that apply to heating as well as hot water?
    • jack_pott
    • By jack_pott 17th Apr 17, 6:24 PM
    • 3,703 Posts
    • 4,720 Thanks
    jack_pott
    • #6
    • 17th Apr 17, 6:24 PM
    • #6
    • 17th Apr 17, 6:24 PM
    we were thinking that we could remove the electric shower over the bath and run this off the new system as well.
    Originally posted by mickeyb102
    If you keep the electric shower you will still have some backup hot water when the boiler fails.

    I have a multipoint, not a combi, but they work the same way as the electric shower: the faster you run the water the cooler it gets. I like the flexibility, you can choose between sacrificing time for hotter water or sacrificing temperature to fill the bowl quicker just by adjusting the tap.
    • coffeehound
    • By coffeehound 17th Apr 17, 6:24 PM
    • 974 Posts
    • 1,572 Thanks
    coffeehound
    • #7
    • 17th Apr 17, 6:24 PM
    • #7
    • 17th Apr 17, 6:24 PM
    Does that apply to heating as well as hot water?
    Originally posted by jack_pott
    Hopefully someone in the industry can confirm but I believe it's the hot water cylinder that has the potential to explode if the safety valve doesn't release due to excess temperature/pressure.
    • Doozergirl
    • By Doozergirl 17th Apr 17, 6:27 PM
    • 23,287 Posts
    • 65,310 Thanks
    Doozergirl
    • #8
    • 17th Apr 17, 6:27 PM
    • #8
    • 17th Apr 17, 6:27 PM
    I've had house with combi boilers since forever and have always loved them. The one time we had a hot water cylinder, it didn't matter how many bathrooms it would service at a time when we somehow always managed to run out of hot water. We're a water greedy family. Combi works best for us.
    Everything that is supposed to be in heaven is already here on earth.
    • jack_pott
    • By jack_pott 17th Apr 17, 6:29 PM
    • 3,703 Posts
    • 4,720 Thanks
    jack_pott
    • #9
    • 17th Apr 17, 6:29 PM
    • #9
    • 17th Apr 17, 6:29 PM
    Hopefully someone in the industry can confirm but I believe it's the hot water cylinder that has the potential to explode if the safety valve doesn't release due to excess temperature/pressure.
    Originally posted by coffeehound
    Yes but if the heating is sealed (I thought new systems had done away with the vent pipe and header tank) then they will also explode if there's no working device to limit the temperature/pressure.

    BTW, my multipoint has no safety valve, and it exploded several times when it had a recurring fault that caused the gas valve to jam open when the water tap was turned off.
    Last edited by jack_pott; 17-04-2017 at 6:32 PM.
    • coffeehound
    • By coffeehound 17th Apr 17, 6:36 PM
    • 974 Posts
    • 1,572 Thanks
    coffeehound
    Blimey, what exploded exactly? I'd *guess* that the relative severity of a 200-litre superheated cylinder letting go is worse than the distributed nature of a heating circuit, but I'm not qualified to give the answer.
    • Alex1983
    • By Alex1983 17th Apr 17, 7:03 PM
    • 273 Posts
    • 142 Thanks
    Alex1983
    All sealed system heating systems and unvented hot water have pressure relief vavles and unvented has additional temperature pressure relief. On going maintenance would be visible check, clean filter on cold main, check expansion vessel and operate relief vavles.

    Unvented is dangerous if not installed correctly and additional qualification are required to install and maintain. Search for the myth busters episode when they make one explode. In real terms when installed correctly there is very little that beats main pressure hot water. Also most unvented tanks have 2 electrical immersion heats as for of back up.
    • no1catman
    • By no1catman 17th Apr 17, 9:29 PM
    • 2,462 Posts
    • 1,868 Thanks
    no1catman
    Previous (end of terrace) house, had the traditional boiler replaced -2003 by a combi (but it wasn't a condensing one). It had a bath - no problem, and unlike with the hot water tank, if someone else wanted a bath afterwards - no problem, no need to wait hours for the water to heat up.

    New house (semi), replaced boiler bizarrely sited over the gas cooker in the kitchen, used the same C/H engineer - who this time advised a condenser combi - only have power shower. Curiously, this used to be prone to sudden cool water, when another tap was in use, but since the old shower unit was replaced hardly notice now.
    Still, hot water comes through quickly, and the temperature setting at the boiler can be adjusted.
    I used to work for Tesco - now retired - speciality Clubcard
    • DominicH
    • By DominicH 17th Apr 17, 9:32 PM
    • 272 Posts
    • 199 Thanks
    DominicH
    a combi increases the temperature by a set amount usually about 35-40 degrees but will vary from boiler to boiler. So if your cold water is coming in at 5 deg then you will get around 45 deg hot water. The flow rate also affects the temperature of the water.
    The hot water tank option will give you the same temperature water all year round as it's stored hot water but you will need to heat the tank up everyday.
    Originally posted by Alex1983
    Surely the hot water temperature will depend on whatever you've set it to on the control panel? Yes, a less powerful combi may struggle in winter to raise the temperature of cold water to your desired temperature, and so the flow rate may drop, but not because the combi is refusing to raise the temperature by more than a set amount.
    "Einstein never said most of the things attributed to him" - Mark Twain
    • Annie1960
    • By Annie1960 17th Apr 17, 9:36 PM
    • 2,655 Posts
    • 1,486 Thanks
    Annie1960
    I had a combi fitted in my last house and loved it.

    I considered getting an unvented system in my current house, but when I looked into it the advantage of an unvented system is that it is good if you have 3 or more bathrooms.

    If you go for a combi, I think it would be a good idea to also have an electric shower as a back-up.
    • Alex1983
    • By Alex1983 17th Apr 17, 9:53 PM
    • 273 Posts
    • 142 Thanks
    Alex1983
    Surely the hot water temperature will depend on whatever you've set it to on the control panel? Yes, a less powerful combi may struggle in winter to raise the temperature of cold water to your desired temperature, and so the flow rate may drop, but not because the combi is refusing to raise the temperature by more than a set amount.
    Originally posted by DominicH
    All combis increase cold water main by a set figure at a specific flow rate.

    I fitted a 300 litre gledhill that recovered from cold in 29 mins. A lot of modern unventeds around 200 litres recover from cold in around 20mins when connected to a correctly sized boiler
    • d0nkeyk0ng
    • By d0nkeyk0ng 17th Apr 17, 10:55 PM
    • 388 Posts
    • 142 Thanks
    d0nkeyk0ng
    We had a hot water cylinder in our parents' house. I don't recall much about because we were quite young then. They upgraded to a vaillant that lasted around 22-23 years. I don't recall it ever being serviced. When that broke down, I replaced it with another vaillant - the same model as your first choice - 832. Parental home a terraced house but each of the three bedrooms are double sized. Total of 9 rads, 3 sinks, 2 toilets, 1 bathtub and 1 shower. No problems with heating or hot water.

    Our marital home has a combi too but an electric shower. The pressure and temperature aren't that great compared to a mixed shower fed by combi but because it had a cold water feed only, it would work fine even if the boiler were to break down.

    I would love to have a power shower but have been told this has to be via hot water cylinder system as a combi cannot supply water fast enough.
    • thescouselander
    • By thescouselander 17th Apr 17, 11:05 PM
    • 5,119 Posts
    • 4,623 Thanks
    thescouselander
    Our combi is great. We've got a Worcester 36CDI which can heat the water as fast as it comes into the house at any time of year.

    We considered going for an unvented cylinder instead but they do need a bit of extra maintenance and finding a heating engineer with the correct certificates for unvented systems can be problematic.
    • jack_pott
    • By jack_pott 18th Apr 17, 11:37 PM
    • 3,703 Posts
    • 4,720 Thanks
    jack_pott
    Blimey, what exploded exactly?
    Originally posted by coffeehound
    Fortunately it used to reach the melting point of solder before the pressure was sufficient to rupture the heat exchanger, so it usually failed by slipping one of the joints. Nevertheless, it was still a big bang followed by a kitchen full of scalding steam then a flood of water.

    When the problem first started there was no non-return valve on the rising main, so the pressure could never exceed mains pressure. In those days if the gas valve jammed you could hear knocking in the pipes as the water boiled, and save an explosion by quickly turning the water tap back on while you go and shut off the gas. (Remembering to stand back as the steam and solder droplets come out of the hot tap.)

    After the water main was renewed with a non-return valve on it things were very different. There was no way for the pressure to vent back into the main, so failure was almost instant, with no more than a second or two warning. That's when the explosions started.

    It took about sixteen years to get the gas board to fix it. At first they sold us a new water heater on the pretext that would solve it, but that was just the same from the day it was new. Repair men used to keep coming round and unjamming the valve, but then shrug their shoulders as if it was all a big puzzle and they'd never seen a problem like it before.

    It turns out that there was a modification available to fix it, but nobody told me until they hurriedly fitted it two days after I wrote a letter threatening legal action. That was over 20 years ago now, and it's been fine ever since.
    • Kernel Sanders
    • By Kernel Sanders 19th Apr 17, 2:45 PM
    • 3,047 Posts
    • 1,269 Thanks
    Kernel Sanders
    Nobody seems to have mentioned the Achilles' Heel that unvented systems have; namely, what happens when the water is turned off by the supplier? Whether that be for repairs in the street, contamination or the overdue 1976-style drought, you'll be able to flush your toilet just the once, have no hot water to wash your hands afterwards and no cold even to heat some.
    Last edited by Kernel Sanders; 20-04-2017 at 1:16 PM.
    #JeSuisCharlie
    • prosaver
    • By prosaver 19th Apr 17, 2:48 PM
    • 6,457 Posts
    • 5,002 Thanks
    prosaver
    a plumber told me combi dont last as long as the other, too many parts or something
    “Life isn't about finding yourself. Life is about creating yourself.”
    ― George Bernard Shaw
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