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Viessman any good

Discussion in 'Plumbing and Central Heating' started by rhinosaw, 2 Sep 2021.

  1. Emit

    Emit

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    Seems no one has asked if you have a vented or unvented cylinder, lots of guessing what the installer has seen and jump on there back. Some coils can average 15kw and over and have a good heat up recovery on hot water. The min rate are looking both the same for the 11 and 19kw. I know what I’d recommend.
     
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  3. rhinosaw

    rhinosaw

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    It's a vented cylinder, , he suggested moving to invented which I don't want.
    Does a 19kw use 50% more gas than 11kw, just roughly
     
  4. Emit

    Emit

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    No it can be range rated to your system.
     
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  5. Emit

    Emit

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  6. muggles

    muggles

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    Down to about the 11kw the OP actually needs, maybe? Or they could just buy an appropriately sized boiler in the first place ;)
     
  7. muggles

    muggles

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  9. Emit

    Emit

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    Why is it , please explain. Seems you know the job. You had a look at the job? Personally I haven’t seen the job but giving advice as to why maybe the installer could be specifying what boiler. Yourself are just trying to look like mr big *******s without knowing all the facts.
     
  10. vulcancontinental

    vulcancontinental

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    There were test carried out and published regarding cycling, if the boiler burn time is in excess of 120 -180 seconds the impact on overall efficiency was calculated at around 1.5%. If for example it was a 10 seconds burn time a 12% loss can be anticipated. I'm unconvinced about savings and wear and tear through cycling, the older boilers did cycle in minutes and lasted 20 years plus. Theory is one thing, practical assessment another, use good quality equipment. There are manufacturers out there sayng run the boilers cooler, they will last longer, I prefer a manufacturer that can build a boiler to last whatever temperature it is operated at.

    As long as the modulation ratio is above 1:5, there are many above that without any cost implication, you'll be fine particularly if the boiler is range rated to the true heat load and remember the better boilers will not start at full power, whatever it is range rated to, it will start at a percentage, usually 75% for say the first 15 minutes then ramp up if demand continues.

    Viessmann are OK but nothing special in my mind, only in their own. I put two in 10 years ago, not a huge sample I admit, both had problems with hot spots and blockages on cleaned systems because of the design of the exchanger. Boiler hut and heat geek are both deeply involved with Viessmann.

    A three bedroom semi detached 1930's house with no cavity insulation, 200mm loft insulation and double glazing the heat loss at -5C is around 10kW, it must be a very poorly insulated flat of enormous size to need 19kW in fact I'd put money if I had any on the fact that it doesn't need half that.

    Use Heat engineer software (google it) to do a proper calculation, a proper accurate calculation will cost you a tenner and a couple of hours learning it but it will be correct. There is a free version but if something requires no effort it tends to be less value than something that does.

    A flat loses very little heat so reheat times for a cylinder is of less consequence, buying a big boiler to reheat the cylinder with a high performance coil from cold in ten minutes is a false economy. Occupancy will slow the heat loss and half an hour will not be noticeable but usually the reheat time is far less than that and the walls of the property and surrounding flats will slow heat loss down.

    I work for a manufacturer so feel it not cricket to promote particular product online but if you want to register for a webinar 29th this month, Heating Optimization and Efficiency use this link. https://carrier.zoom.us/webinar/register/2215979244261/WN_T_kjmDt0TAyuMD4xmVw85g
    Most of our webinars are for Gas Safe installers, this one is not.

    If you want to find out a little more about our own, Viessmann and other heat exchangers look here



    and here



    The second video is old now.

    I'm partisan obviously so factor that in.
     
    Last edited: 5 Sep 2021
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  11. Londoner2

    Londoner2

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    Hold on, a 24kw or a 30kw boiler will have the same heating capacity and is usually limited to a certain kw, the higher one deals with better water flow rate to deliver higher number of litres .
     
  12. MeldrewsMate

    MeldrewsMate

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  13. sxturbo

    sxturbo

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    That works if it's a combi.

    If it's a heat only boiler the hot water flow rate isnt a consideration
     
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