View Single Post
  #17   Report Post  
Posted to uk.d-i-y
John Rumm John Rumm is offline
external usenet poster
 
Posts: 25,191
Default how hot do you run you CH boiler

On 11/01/2019 23:48, Harry Bloomfield wrote:
tim... pretended :
I had a new Combi fitted today (in the to-be-moved-to house).

Fitters told me that I should run this at 74 degrees.

Which I thought far too high, as


I have an opened vented system, with stored HW and the house is heated
by the one boiler, installed new last March. A Vailant ECOfit Pure 418.
We like the stored water to be good and hot, the boiler only has one
temperature setting available for its output temperature - so I have it
set at its max, of 75C, in order to meet our HW needs. The house heating
would be satisfied by a lower boiler temperature around 60C and it would
be more gas efficient, but unless I manually manage the temperature
setting I am stuck with the less efficient 75C.

I even tried to find a way to fool the boiler into working at a lower
output temperature, by adding a separate bi-metal stat on the boiler
output pipe to CH only, set at 60C, to shut it down at that temperature
- as heating satisfied. That was a miserable failure, in that the boiler
constantly cycled on/off via the stat, whilst ever the room stat
indicated a demand, rather than modulating its output down - as it would
on its own as it neared its 75C setting.

If anyone knows a workaround, to allow split boiler output temperatures
on this boiler - do let me know please.


IME many of the Vaillant boilers do support split temperature operation,
but it does depends on what controls you have them paired with.

The 400 series Vaillant I did (probably previous model range, since this
was = 12 years ago), actually had separate knobs on the front for CH
and DHW flow temperatures. Although that was retrofitted into system
with traditional controls that could not distinguish between the source
of the call for heat - hence the DHW control never came into play and it
ran like your system does.

The blurb on their web site:

https://www.vaillant.co.uk/for-insta...ler-26116.html

Seems to suggest its compatible with the VRC 700 weather compensating
controls, so that ought to allow split temperature as well.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/