Newly installed boiler is boiling my pi#%

[Beretta687]

Might be a bit early to share this saga but I've had sleepless nights and vaguely warm showers because of it Long story but bear with me!
A week ago I had a brand new boiler fitted as my old one was 15 years old and although gave me very hot water and radiators in double quick time with brilliant water flow and pressure, the new one simply does not.
The new one doesn't provide anything like warm water even after minutes of running, so washing up and hand washing is usually done in cold water unless running the water for 5 minutes or more. My thermostatic shower is useless as it requires a supply temperature of 55-65°C which looking at the boiler output temperature display never even comes close to that.
The boiler controls for hot water and radiator temperatures are on 65 and 70°C respectively. Vaguely warm water for handwashing will happen after wasting unacceptable amounts of water first and radiadiators will eventually, very slowly, get hot. If I restrict the tap flow to virtually nothing, water temp seems to go up and get warmer quicker. Preheat function does not seem to make any noticeable difference.
So why am I extremely fed up? Well the authorised installer says its fine and all the settings are correct but what he's left me with is taps that waste water trying to get warm water and a thermostatic shower which doesn't function properly I wish I kept the old one!!

The hot water setting of 65 degrees is a maximum,not what the boiler will produce especially when the mains water is about 7 degrees. My boiler won’t heat water above 58 degrees at the tap even in summer,it’s a safety limit. You should be able to get hot water at about 48 degrees now,at 8.3 litres a minute with a 24kw combi.

 

[Beretta687]

How many radiators have you got? If its 10 or more you'll need a boiler with an output of 28kw or higher. However, even if it's under powered, it should give preference to domestic hot water (taps) and they should heat up fully. 60°C is actually a regulation on minimum output temperature to prevent Legionnaires disease.

A combi gas boiler will not heat the water so high in winter because the cold mains is maybe only 7 degrees,therefore 47-50 degrees would be the maximum. In summer when the mains is about 18 degrees you may get 58-60 degrees. Many boilers cut out at almost 60 degrees to prevent scolding. The only way to get hotter water in winter is to reduce the flow going through.

 

[Tillygti6]

A combi gas boiler will not heat the water so high in winter because the cold mains is maybe only 7 degrees,therefore 47-50 degrees would be the maximum. In summer when the mains is about 18 degrees you may get 58-60 degrees. Many boilers cut out at almost 60 degrees to prevent scolding. The only way to get hotter water in winter is to reduce the flow going through.

I've got the ideal logic+ 24kw myself. It really struggles as the incoming water temps drop.
The shower is fine as the shower head restricts the flow . Run a bath and have to have the taps at around 1/2 open to slow it enough to transfer the heating/energy to the water flying through it at a rate of knots.

 

[Radlad]

The installer should also be registered with Gas safe or whatever the latest iteration of Corgi is and he will probably take a threat to talk to them seriously as will they if you do talk to them and it is an unsatisfactory installation.

Gas Safe is only bothered about the safety and legalities of and installation , not it's performance. If it's been installed to manufacturers spec, the appliance should be doing the job it is designed to do

 

[Beretta687]

Something not right have you looked at the switches under the flap on the front the end one usually has water only-or water and heating this usually has a rest also what temp is the read out showing? ours sits at 76 it was very low when fitted fitted i turned the switch up teh gas fitter said it was law to be set at 58 i new he was talking out of his ---le --if its under warranty you need to complain

Approximately 58 degrees is the maximum for a gas combi on safety grounds,they should cut out when reaching that temperature,in winter about 48 is the limit for a small 24-28kw combi unless the flow is reduced. My 28kw Baxi is flat out at 9.5 litres a minute given 41 degrees above the mains temperature,with 58 degrees the maximum in summer.Heating flow temperature will go higher of course to about 75 degrees.

 

[confidis]

That really does sound rubbish.
A good bit of learning regarding new boilers.
Go big. Next size up as it were.
Very very annoying .
I despise new rubbish like this . I work with pellet boilers, they are made of cheesium and melt .

 

[colinb]

I was told a few years ago that if I replaced my 24 year old 26kW boiler I would save £550/year in gas bills. Strange. At the time, including standard charges, my fuel bill direct debit was £50/month and I was in credit by at least £100 a year. Even today my direct debit is £70/month, even after huge increases. The moral of the story is "keep it until it can't be mended"

 

[confidis]

If mine can't be fixed it's this a system flush and a new tank . Diy

.https://www.plumbnation.co.uk/ideal-mexico-he24-regular-floor-standing-boiler-natural-gas-250-13561

 

[Widow]

I gather it’s a 24kw combi boiler? With it being winter the cold mains will be about 7 degrees centigrade,and a 24kw boiler should heat the water by 40 degrees at 8.5 litres a minute when fully warmed up,If it’s getting a higher flow rate of say 10 litres a minute the water will only reach 41degrees(34 rise+7) this isn't hot enough even for a bath. It could be the gas valve needs tweaking to produce the correct co2 in the flue on high and low settings.
I had a Baxi combi fitted 7 years ago,not getting hot enough at the taps,when a different engineer did the first service he discovered the settings were way out,made adjustments at the gas valve and the water got 3 degrees warmer.My Baxi has a 7 second delay before it ignites which wastes water but it’s the way they are,my old boiler from 1988 ignited immediately the tap was turned on.
As a temporary solution to get hotter water you could turn down the stopcock to give you a lower flow rate which will help.
You should have a 22mm gas supply pipe of course and probably have,but a 15mm pipe won’t supply enough gas to a modern combi boiler.
Another thing that causes low tap temperature is a faulty diverter valve which sends hot water to the radiators and tap at the same time,again this shouldn’t be the case with a new installation.

The gas pipe does not necessarily need to be 22mm, some boiler manufactures will work down as little as 14mb...
Although pipe sizing according to the regs say <1mb dro from meter to appliance. But as manufactures instructions overrule gas regs it can be done. Obviously if the the appliance is operating satisfactory.believe it or not some vaillants used to work down as low as 13mb, although the new normal seems to be 17mb.

 

[Hanibal]

Hi all. I'm sorry that I haven't responded to your threads today and thank you all for your concern. I have no idea what my water pressure is. I have calculated the flow from the cold to the hotside. 13 and 10 L/min respectively. Yes the installer flushed the radiator system thoroughly. There was a tiny amount of crap produced. I do have a Magna clean Professional fitted. He showed me the filter and it was very clean. Engineers coming out on Friday so fingers crossed something will be found.
Worst thing is not being able to have a decent shower anymore. Apparently the Mira Minilite needs an input of 55°C to allow the thermostatic operation to function. Currently showering isn't a good experience!
Someone said I should have had the old one fixed until it couldn't be fixed anymore. In hindsight that is something I should have done. But all will be revealed on Friday
One last thing, I wish some of you could take a look at it as you really know your stuff. Hopefully I will be sent someone as knowledgeable as you who can address the issues.

 

[pjgtech]

The gas pipe does not necessarily need to be 22mm, some boiler manufactures will work down as little as 14mb...
Although pipe sizing according to the regs say <1mb dro from meter to appliance. But as manufactures instructions overrule gas regs it can be done. Obviously if the the appliance is operating satisfactory.believe it or not some vaillants used to work down as low as 13mb, although the new normal seems to be 17mb.

Hmmm, not sure that boiler manufacturers instructions do overrule current Building Regs/Gas Safety Regs? Where do you get that info from?
Building / gas safety Regs are the rules people have to comply with legally, boiler manufacturers instructions are not, so.....
And I'm also pretty sure that building / gas safety regs require 22mm gas supply up to 1.5m from the boiler, its not optional!

 

[Widow]

Hmmm, not sure that boiler manufacturers instructions do overrule current Building Regs/Gas Safety Regs? Where do you get that info from?
Building / gas safety Regs are the rules people have to comply with legally, boiler manufacturers instructions are not, so.....
And I'm also pretty sure that building / gas safety regs require 22mm gas supply up to 1.5m from the boiler, its not optional!

Pipe sizing and pressure loss is one thing,
What I said was you don't necessarily require a 22 mm gas pipe to boiler.
We all know about working out correct pipe sizing and getting enough gas to supply all appliances before any branch etc... but if a manufactures say it can run as low at 14mb it can run at 14mb.

 

[pjgtech]

Sorry you are wrong.
UK Building regs state the min pipe size for gas supply pipe is 22mm, regardless of what any manufacturers says.
A manufacturer stating what min pressure a gas boiler is capable of running at, is not the same as complying with building regs.
Its also stated by Gas Safe.

 

[CJD]

Sorry you are wrong.
UK Building regs state the min pipe size for gas supply pipe is 22mm, regardless of what any manufacturers says.
A manufacturer stating what min pressure a gas boiler is capable of running at, is not the same as complying with building regs.
Its also stated by Gas Safe.

I’m afraid that is simply wrong.
So you are saying a gas hob or a gas fire would need to have a minimum 22mm gas supply ?
A Worcester 12kw boiling will happily run from a 15mm supply - obvious depending on it’s position to the gas meter, and other appliances installed.
As long as you do your due diligence and calculate your pressure drops correctly you are ok.

 

[Widow]

Sorry you are wrong.
UK Building regs state the min pipe size for gas supply pipe is 22mm, regardless of what any manufacturers says.
A manufacturer stating what min pressure a gas boiler is capable of running at, is not the same as complying with building regs.
Its

 

[Widow]

 

[pjgtech]

I’m afraid that is simply wrong.
So you are saying a gas hob or a gas fire would need to have a minimum 22mm gas supply ?
A Worcester 12kw boiling will happily run from a 15mm supply - obvious depending on it’s position to the gas meter, and other appliances installed.
As long as you do your due diligence and calculate your pressure drops correctly you are ok.

No i did not say that at all.
Only the last 1.5m run of gas pipework to the boiler can be 15mm, the rest must be 22mm, and no I'm not talking about a hob, I'm talking about a boiler.
EDIT: The (small) boiler you mention above is not a combi, the above only applies to a combi boiler.
EDIT 2, and on this thread, we are talking about a combi boiler [sigh]

 

[shergar]

Those of us living in a house with DHW cylinder are familiar with waiting for hot water to reach tap, pushing out colder water sitting in the pipes. The logic being faster the flow the quicker hot water will arrive.
This is not applicable to Combi.
With a Combi when hot water tap is opened movement of water is picked up by hall sensor which sends signal via pcb to activate fan.
The fan purges combustion chamber to reduce risk of a critical gas/air explosive mix.
Pressure switch confirms fan is doing its job and feeds back through pcb which then starts the ignition process, boiler fires up, heating the primary flow, which diverted through secondary heat X, heats the incoming cold water, sending it hot to the taps.
High flow at tap does not bring hot water quicker, rather the opposite. Better, once fan has kicked in, reduce flow to minimum necessary for the hall sensor to detect flow and keep boiler firing.

 

[CJD]

No i did not say that at all.
Only the last 1.5m run of gas pipework to the boiler can be 15mm, the rest must be 22mm, and no I'm not talking about a hob, I'm talking about a boiler.
EDIT: The (small) boiler you mention above is not a combi, the above only applies to a combi boiler.
EDIT 2, and on this thread, we are talking about a combi boiler [sigh]

You’ve already stated that you have never been a gas engineer.
Although you have been a plumber 30 years ago, so admittedly you will have some idea about pipe sizing etc.
How do you know without actually looking at the installation that the gas pipe to this boiler must be 22mm ?
For all you know it might need to be 28mm or bigger all depending on the distance from the gas meter and other appliances involved.
I realise that you are only trying to help here, but there has been a lot of misinformation on this thread (not necessarily given by you)
Sigh.

 

[zakdingel]

You’ve already stated that you have never been a gas engineer.
Although you have been a plumber 30 years ago, so admittedly you will have some idea about pipe sizing etc.
How do you know without actually looking at the installation that the gas pipe to this boiler must be 22mm ?
For all you know it might need to be 28mm or bigger all depending on the distance from the gas meter and other appliances involved.
I realise that you are only trying to help here, but there has been a lot of misinformation on this thread (not necessarily given by you)
Sigh.

It.s usually a standard size of 22mm gas pipe that feeds a combi boiler from the meter sometimes they are upgraded into 28mm and even 35mm but that all depends on how far away from the meter and how many bends etc is needed google is your friend