Boiler Hot Water Output

[pototea]

Hi,

I had my new boiler installed which was completed on Tuesday. It is a Worcester 440Cdi (combi) and installed in the loft.

There is bathroom adjacent to the boiler (same level). There is another bathroom directly below. The kitchen is directly below the bathroom. So they are all in the same part of the house but on different floors.

In the kitchen, I only get hot water out of the tap if I turn the tap all the way on. When I had the boiler in the kitchen, I could turn the tap just a little bit and I got hot water. The bathroom is fine, I get hot water if I turn the tap half way.

Is this a pressure adjustment which can be fixed for the kitchen or is it because the boiler is now further away?

Yesterday I also tested out two showers at once. I turned both showers with the hot tap on full and did not use the cold. The pressure was fine. The water was luke warm. Is this because the boiler cannot cope with the hot water demand? I would have thought that the pressure would drop when both are on, not the water temperature?

Before I call the plumber back, can anyone help with the two issues if they are "faults" or "working as designed"?

 

[Agile]

Without technical details I cannot guess.

Its possible the gas supply is undersized and reducing the power output or as you suggest it may be more than the boiler can handle.

Can you measure the combined flow rate in litres per minute?

It sounds as if your installer has not discussed the performanance to be expected with you properly.

I hope that he is at least CORGI registered.

Tony

 

[gas4you]

Jesus, how the hell did they get that lump up into the loft

If nothing else, being the size of a washing machine, how did it fit through the loft hatch

I hope they strengthened the roof trusses with all that weight

 

[swbjackson]

The 440 is capable of delivering 20l/min at a 35C temperature rise so it sounds like something is wrong.

Part of the commissioning procedure is to check hot water delivery rates and temperatures. Check what has been written in the log book.

 

[pototea]

What temperature (relatively) should I expect if I have two showers running at once?

Less temperature, less pressure or both?

 

[Agile]

There is no answer to that as it depends on the FLOW rate hence my request that you measure that!

Can you find the Benchmark document with the boiler papers and check that the installer filled that in with his cORGI number etc.

Tony

 

[bengasman]

quite simple; if the system is not performing to spec, call the installer back

 

[ctp]

did they test the incoming mains water pressure ?i would also test the inlet gas pressure, this unit requires 3.1m3h so if it is in the loft i might exspect to see 28mm gas pipe at the meter ,also check the operation of the govenor.

 

[pototea]

The cold flow rate was 12 litres/min, pressure 4 bar. That was with the old lead piping. Now that has been upgraded, I don't know what it is but it is definitely better. I also had the gas regulator changed to increase the pressure. I will see if I can measure it today. My installer is coming round this morning with all the documentation so I will ask him to look into it.

 

[David937]

My Vaillant ecoTEC+ 937 which is set up correctly with an incoming mains of 24lpm and a gas supply of 28mm supplies two outlets at the same temperature but at a slightly reduced flow.

 

[pototea]

My Vaillant ecoTEC+ 937 which is set up correctly with an incoming mains of 24lpm and a gas supply of 28mm supplies two outlets at the same temperature but at a slightly reduced flow.

Thanks for all your help. The the output you are getting from your Vaillant is what I was expecting from my Worcester. My plumber came round this morning, measured the gas output at the meter with all the taps on and said it was measuring 15 when it should be measuring 22.

So he asked me to get the gas regulator looked at again. The gas man came round one hour later and said the regulator was fine. Incoming gas pressure is 28. He measured at the point after the regulator with the taps off and it was 21, which is what he said it should be. With the cooker and taps on, it drops to 15. He made a few phone calls and said it is my gas piping which is undersized (it is 28mm).

So I called my plumber up and he said he is sure it's the gas regulator. So he will come round later again. This time I will ask him to arrange to meet himself with the gas company to avoid going round in circles.

 

[David937]

Good luck with sorting it out

 

[gas4you]

What regulator is on the gas meter?

Just because your gas pipe run is 28mm does not automatically make it ok. Things are not this simple.

It depends on distance from the meter, number of bends and how many appliances are on this gas pipe run.

 

[Agile]

]

My plumber came round this morning, measured the gas output at the meter with all the taps on and said it was measuring 15 when it should be measuring 22.

So he asked me to get the gas regulator looked at again. The gas man came round one hour later and said the regulator was fine. Incoming gas pressure is 28. He measured at the point after the regulator with the taps off and it was 21, which is what he said it should be. With the cooker and taps on, it drops to 15. He made a few phone calls and said it is my gas piping which is undersized (it is 28mm).

So I called my plumber up and he said he is sure it's the gas regulator. So he will come round later again. This time I will ask him to arrange to meet himself with the gas company to avoid going round in circles.

I think that you are being confused!

If the pressure on full load at the meter is only 15 mB then either the regulator is faulty OR the pipe from the street ( or the street ) is low or undersized.

I had a case a few weeks ago where the regulator was replaced but the output was not measured on load by the meter nupty.

The pressure on load at the meter output should be 20-21 mB.

Its important to fully understand the relevance of these measurements and where the problem is.

In very cold weather its quite common to find that the street pressure is low at the times when everyone has their heating on.

Tony

 

[pototea]

My plumber came back this morning and said the gas pressure is now working fine. But there is still the problem that I only get hot water when I turn the kitchen sink on full (hot water is fine when I turn the tap half way when the heating is on) and I get luke warm water when both showers are on simultaneously. He assures me that these are faults and the boiler should produce hot water when I turn the tap on half way and there should be no drop in temperature or pressure when I use two showers at once. So he has called Worcester and they believe that there may be a problem with the diverter valve or heat exchanger and they are coming on Thursday.

He did point point out that at the boiler, the incoming mains is 15'C cooler than what Worcester recommend but he said this should not cause the issue of me having to turn the sink tap on fully to get hot water (it's freezing cold unless I turn the tap all the way).