"Marv" wrote in message
A conventional systems in the loft is difficult, and probably not
achievable, and will entail a lot of upheaval. You would be better
having a
new larger bore plastic water main from in from the street.
Depending on the cold mains pressure/flow. If this is fine and the
combi is
not man enough for its intended hot water use. The best solution may be
to
install another combi. Yes, another combi. Combi's are cheap. Have
one do
downstairs heating, one upstairs, on two different time clocks. This
means
upstairs can be off while downstairs is on, or vice versa. Then split
the
hot water taps between the two combi's (have two showers on two
different
combi's). A new gas supply will have to be run from the combi back to
the
meter.
Thanks for the feed back, that makes sense.
Must be a poor cold water mains that I have.
The model I have here is a Microgenus.
This model operates on low water pressure, a reason why it may have been
chosen. It is also small and reliable.
I have
since visited the new house and the water is 10 times more powerful
than I have, thats restored my confidence in Combi's. The idea of 2
combi boilers one for upstairs and one for downstairs is also very
interesting, especially when the washing machine/dishwasher is on.
Just a thought here and before you say I'm daft I work in computers
, I was wondering if it were possible to join the 2 systems together
on some sort of switch, for example if the 2 systems were joined but
shutoff from each other in the event of one breaking down would it be
possible to open the switch to make them one system ?
Yes. But! "most" makers don't like you to combine the outputs, as they don't
want their technical depts answering queries all day from poor
installations. Technically there is no reason why you can't using
non-return valves.
One combi can serve a section of taps and the other another section to
spread the load independently and provide backup if one fails. But you may
need both combi's outputs to say provide a good flow to fill a bath and/or
shower.
Say you have two bathrooms and a shower in each. One combi does one
bathroom the other the other bathroom. Simple. After the washbasin and
before the bath and shower draw-offs of each bathroom join the pipes using a
few tees. "Before" the tee offs and after the basin draw-offs in each
bathroom, fit spring loaded non-return valves.
The way it operates is that the taps before the non-return valves operate
off separate combi's. Obvious. When any of the two baths or showers are
opened "both" combi's operate giving high flow.
If one combi fails then at least heating is available on another floor. One
bathroom will work off the remaining combi. This way is foolproof and
requires no user intervention.
For backup heating joining the two combi's heating circuits and using full
bore valves to open one and close the other is the way. But you need to
know what valves to open and close.
You could have both boilers on the heating circuit and split the circuit to
upstairs and down using zone two 2-port zone valves. A single pole double
throw wall switch (like a light switch)can have either boiler on run and the
other off. One drops out, press the switch and other operates. This gives
full backup, but the expensive of two extra zone valves.
In your case, adding a combi is not a great expense or upheaval. Just make
sure you do not exceed the meter loading. You are allowed 212 cu foot per
hour. divide the BTU/h of the combi by 1000 to get the cu ft/hour. A
80,000 BTU/h combi consumes 80 cu foot, so two is 160. Give enough for your
gas hob too.
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