Recently had a "combi" Vaillant boiler to replace our old
boiler/tanks/shower pump. I was assured by the plumber that the water
pressure for the shower (upstairs) would be as good as or better than the
pump we had. Needless to say - it isn't! I have read about a system called
Megaflo and I was wondering if this could be added to our combi boiler?
There is no way we could afford to have the combi taken out and new
conventional boiler put back in. Any ideas how to get a better
flow/pressure?(I know I am being imprecise but I hope you understand what I
Thanks for your help.
If you can't afford to replace the boiler again, you can't afford the
Megaflo. However, the Megaflo would be perfectly happy sitting on the combi.
The combi water system could then supply a kitchen tap or something.
On the other hand, we'll need more information about your system to see if
it is working properly. Take a large container of known capacity and time
how long it takes to fill it from the hot taps at various locations to
calculate the flow rate. In particular, test the kitchen hot tap and the
shower head. Make sure you don't turn them on so much that the water goes
cold. What flow rate are you getting?
Also, what boiler do you have? In particular, is there a number somewhere
between about 24 and 35 written on it anywhere?
Can afford Megaflo, but not Megaflo AND new boiler!
I'm not sure I understand what you mean - the combi can be used to "feed"
the Megaflo? I though I would need a non-ombi boiler for that.
The only difference between a combi boiler and a non-combi boiler is the
addition of the instantaneous water heating function. The combi boiler can
do anything a traditional boiler can do, including heating a hot water
cylinder such as a Megaflo.
You should note, however, that the controls may need rejigging. Any built in
programmer will be pretty useless and require setting to 24/7. You will need
an external 2 channel programmer and zone valves, just like a system boiler
installation. These can control the boiler through the room thermostat
wiring and may even need some sort of relay if the boiler requires volt free
contacts and you are not using 2 port zone valves in a Honeywell 'S'
A basic set of controls will cost you under 100 quid, though. You would need
a room thermostat (should already have one), a 2 channel programmer and 2
zone valves (2 port). You can often buy this whole lot as a matched kit for
discounted prices. You may find it more complicated to go for a 3 port valve
version, particularly if your combi wants a simple volt free contact switch
as a thermostat. This is because the 3 port valve doesn't have "call for
heat" microswitches, but must rely on the programmer outputs, which will be
230VAC, rather than simple switches.
Forgive my ignorance of these things - Thanks for all your help.
I wish my plumber was this helpful. He comes highly recommended from a
number of my friends - but he doesn't seem keen to do anything other than
install a standard combi. He persuaded me against installing a condensing
boiler (said he hadn't installed any) which I'm starting to think was also a
Pretty standard for most heating engineers. However, looking around you can
always find one or two that actually keep up with modern technology.
He'll have to look up his condensing boilers soon, though. Non-condensing
ones are effectively being banned soon.
Combis are easier to install than storage systems. Condensing boilers are
more difficult again. I wonder why he wants to install non-condensing
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