Anyone got any experience of a Viessmann Vitodens 111-W storage combination boiler? Do they really deliver hot water at the rate they claim?
Other than the increased cost, is there any downside to installing a
35kW rather than a 26kW?
Not personally
The storage combi's contain a small unvented cylinder - so they should be able to deliver at whatever flow rate the cold main can manage - for a period of time anyway.
The only downside will be a slightly higher maximum gas rate (probably ~
3m^3/hr), which may require a fatter gas supply pipe depending on distance from the meter. Generally, where a combi in involved larger is usually better, but it will matter less with a storage combi.
On the whole large boilers modulate down to a higher heat output than a small boiler, which can result in HW cutting out unless excessive water is used in showering. Whether that's an issue varies, I've certainly encountered a need to use excessive water & thus gas.
NT
Thanks.
The boiler would be within 1M of the gas meter so, hopefully, the supply would be adequate.
I'm not a fan of combi boilers but the Viessmann looks like a reasonable compromise and would free up space in the house by removing the current HW cylinder and get rid of the storage tanks in the loft.
I'm just wary of Management complaining that the hot water goes cold when she uses the bath...
Thanks. I'm probably being thick but I'm not sure why the hot water might cut out unless 'excessive water is used in showering'.
If your boiler only modulates down to twice your usual shower water consumption, it gets too hot & cuts out unless you double your shower water & therefore gas consumption.
NT
Can't see that being relevant here. This is a storage combi. It will supply DHW from its integrated cylinder, and then run the boiler flat out in whatever duty cycle is required to maintain the store.
It won't go cold as such, although you may find the flow rate reduces once you have depleted the store. (it has a 46L store built in, which it appears to use via PHX like a mini heat bank).
Being a combi, it can produce DHW indefinitely.
The 111 has a 1:6 modulation range. So minimum output is 6kW
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