What`s the point?

[charliechaplinspants]

For a bog standard combi install, is my last post right, generally? So should I expect the installer before fitting bog standard combi to check mains flow rate?

 

[doitall]

There is no such thing.

The installer must :- check the flow rate and pressure.

If he doesn't/hasn't get another installer, You are spending a lot of of money, and you have a right to demand a reasonable system that meets most if not all your specification.

 

[doitall]

I should add to that and say he should check it at peak and off peak times.

A combination boiler may not be suitable, certainly in some parts of London that is the case.

 

[charliechaplinspants]

Ok, cold mains flow rate is approx 14 litres per min using a flowcup so I need a combi that at least delivers that then? How do I measure the pressure?

 

[doitall]

With a gauge usually.

Get yourself a 10Litre bucket and time how long it takes fill, at peak and off peak times, then deduct 10% for cold use.

 

[charliechaplinspants]

Right, brilliant, thanks probably do that tomorrow, thanks for advice, will be back, just a quick one before I go, why measure the pressure, sorry if I sound a bit thick.

 

[doitall]

The pressure is related to the volume.

For example you could have 3bar, and a small or damaged service pipe so the volume is only 10 L/min, or you could have a good service pipe and the pressure is very low, say 1 bar. and get 12L/min

 

[charliechaplinspants]

So if I had high pressure & low volume I would assume there may be a problem?

 

[doitall]

So if I had high pressure & low volume I would assume there may be a problem?

Yes, it could be an old lead pipe or even a squat pipe in the ground.

High pressure is good because you can always upsize the pipe to increase the volume.

 

[bengasman]

Bengasman, you get a call from a client who wants a CH system and a UV cylinder. How do you work out what to purchase for the job (size, quantity and output)

I never included the cylinder in the heat calculation, as I always use independent timing on heat only systems.
For rads: quick look, educated guess plus at least 20%; have never been wrong so far.
Very rare that I get asked to install entire systems anyway, and for existing rads you don't need a heatloss calculation.

 

[bengasman]

I should add to that and say he should check it at peak and off peak times.

Do you really make to visits, just to determine if you should quote for a combi or for heat only?

 

[doitall]

I've only fitted one combi in my life Bengasman, and supervised my apprentice on another.

On the type of installation we did, the quality of the supply was the be all and end all to the design.

So yes as many times as it took.

My last job in London wanted 67L/min. and we were getting 10L/min out of Thames water.

 

[bengasman]

67 litres per minute? Not much chance for a combi then I guess. They must have had a fair size watermains.

 

[doitall]

Needed a 1500Ltr sectional storage tank and a 6bar pump.

3 x Gemini 500Ltr unvented calorifiers at 5bar, and 54mm copper pipe, 28mm to each shower.

 

[bengasman]

All that for a 2 up, 2 down? Seems a bit over the top to me.