Megaflow or Combi Boiler

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In need of help

Since Thames Water reduced the water pressure my the shower and bath have struggled to get sufficient water pressure, with fluctuations in temperature (which in the shower i believe to be the safety mechanism when it gets too hot) and in the bath simply due to insufficient pressure

I had a plumber come round today recommending the Megaflow system as i have 2 bathrooms. Think my water pressure is just above 1 bar

However i have British Gas coming tomorrow whom i am sure will recommend a Combi boiler as i do not think they install Megaflow unvented systems

1) Which would be better for my flat? Megaflow or Combi?
2) Can central heating be installed with a megaflow unvented system?
3) Do companies like British Gas & Servowarm install these systems or just individual plumbers?
 
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BG do install unvented systems now.

You need to concentrate on the flow rate of water into the property, because without an accumulator or some other form of improvement it sounds like a mains pressure system may be unsuitable.

I would respectfully suggest that you should discount anybody who comes round that doesn't measure the flow rate and static pressure. They will be a chancer.
 
Which one did you go with and how did it work out. We have the same decision to make and are getting contradictory advice. thanks
 
Some "plumbers" dont give very good advice!

The simple fact is that no standard combi will feed two showers at the same time ( unless they are only about 6 li/min flow rate ).

Neither unvented or combi will give more flow than the mains supply will provide.

A supply pressure of 1 Bar static is unlikely to give enough pressure to operate an unvented very well. Probably marginal for a combi too!

Tony


Cue Simond : accumulator
 
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Some "plumbers" dont give very good advice!

You got that right!

The simple fact is that no standard combi will feed two showers at the same time ( unless they are only about 6 li/min flow rate ).#

A Glow Worm 38CXi and W-Bosch 42kW will. They are standard.

If the mains static pressure is OK and the flow poor, a high flow combi and cold water accumulator is the way. The accumulator will be no bigger than an unvented cylinder (megaflow) - and not have the qualities of TNT.
 
Thank you both.

I had not heard of an accumulator before, good suggestion. very helpful idea
 
Great, these links are very useful and easy to understand. Now all is need to do is to find a good plumber to make it happen. Much appreciated
 
Great, these links are very useful and easy to understand. Now all is need to do is to find a good plumber to make it happen. Much appreciated

Accumulators are simple and simple to fit. a check valve and after a tee to the accumulator in 22mm. Simple. Sizing is, the water content is about half the capacity they state. 200 litres stores 100 litres of water.

However, you may only need the accumulator for the showers to give high pressure and flow. So a small accumulator can be fitted for the showers only, and the rest off the mains. If a combi then all of DHW in the house and the showers cold feeds off the accumulator. The toilets and kitchen tap can be directly off the mains before the accumulator check valve.

I have fitted some in the attics of garages. Just put a cylinder jacket around them if in the garage to prevent frost. If a water outage you have a reserve of water too :)
 
I have fitted some in the attics of garages. Just put a cylinder jacket around them if in the garage to prevent frost. If a water outage you have a reserve of water too :)

I am disappointed that a graduate design engineer would be so hard up that they would have to do a lowly plumbers job to make ends meet.
 
If you have a static pressure of about 1 bar you will not resolve the water flow with an accumulator alone.

You will need a pumpset on the front end.
 
If you have a static pressure of about 1 bar you will not resolve the water flow with an accumulator alone.

You will need a pumpset on the front end.

I see why not with 1 bar. Just set the pressure in the accumulator correctly and size up the accumulator right. I have never come across one that low (1bar) though.

I searched and you say you have done it with 1 bar. Did you have problems? How did you hitch up the pump?
 

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