Baxi Duo Tec Combi 33 HE ( Issues and advice needed )

VUDuo2 · 25-04-2016 10:09AM #1

Baxi Duo Tec Combi 33 HE

Moved into a 4 bed semi-d with one of the above gas boilers installed.
The boiler is connected straight onto the incoming water mains, therefore there’s no tank in either the attic or airing press.

The previous owner of the house said:
"We removed both tanks when we installed the boiler.
A boiler like this needs more pressure than a water tank can provide, especially since it can consume more water than fits in the tank. So it uses water straight from the mains.
This was only possible because the water pressure in the estate is very good.

I have to say it’s amazing to have very fast hot water flow on demand, however we have a couple of issues while having showers or baths;

· En-suite shower;

While having a shower (pic of mixer attached ), sometimes the water completely turns off & after a few minutes it starts to flow again, also it can take a while to get the temperature right in that it’s either scalding hot or Arctic cold – very frustrating to say the least !!!

Went onto the Baxi website and this is what I found;

combination boilers can only supply one tap at a time. Turning on additional taps will reduce the flow of hot water. If the water is not hot enough you may have to reduce the flow (by turning the tap down) to increase the temperature. This may be necessary especially in winter when the water supply to the boiler is colder.

Before having a shower, I warn everyone not to use the taps, flush the toilet, or make sure that no appliance is turned on (washing machine or dishwasher).

We are thinking of fitting an electric shower / & or pump but is there a particular type that works directly connected to the water mains ??

Or, what would you do ??

The Bath issue (kids);

The mixer tap is very hot to touch and the immediate flow of scalding hot water is a huge concern when the kids are in the bath, we have to ensure the tap is closed tightly otherwise they could be par-boiled within in a few seconds!!!

Can we fit a thermostatically controlled bath mixer, would this the best way to go and which brand / model are best??

25-04-2016 03:16PM

When you test a combi for performance you do so at a kitchen tap or a tap without a mixer.

You do that to see what the boiler is really doing.

If you find the hot water is satisfactory at your kitchen tap then the issue(as I suspect) is with your mixer.

Have your boiler serviced and ask the RGi to check the operation of your hot water and to identify the reason for you hot water issues.

As for what to do regarding changing anything I would first establish the incoming water mains pressure before I did anything.

VUDuo2 · 25-04-2016 03:29PM

gary71:

Both flow of water and temperature (scorching) is perfect at the kitchen sink.

If the problem is with the mixer (bath, shower) - would you recommend any particular brand / model

Thanks a mil for your input.

K.Flyer · 25-04-2016 07:42PM

You say that the water temperature from the hot tap in the kitchen is scorching hot, have you not tried turning down the temperature of the hot water output at the boiler first.
It sounds like it is set way too high for the thermostatic cartridge on the shower mixing valve, which in turn is shutting down to prevent scalding.

Dtp1979 · 25-04-2016 08:08PM

K.Flyer wrote: »

You say that the water temperature from the hot tap in the kitchen is scorching hot, have you not tried turning down the temperature of the hot water output at the boiler first.
It sounds like it is set way too high for the thermostatic cartridge on the shower mixing valve, which in turn is shutting down to prevent scalding.

Sometimes the simplest answer is staring you in the face.

25-04-2016 08:21PM

Dtp1979 wrote: »

Sometimes the simplest answer is staring you in the face.

Its always simple when you know, very few installers check if they have gas before they call me out for a no ignition fault.

VUDuo2 · 26-04-2016 08:34AM

K.Flyer wrote: »

You say that the water temperature from the hot tap in the kitchen is scorching hot, have you not tried turning down the temperature of the hot water output at the boiler first.
It sounds like it is set way too high for the thermostatic cartridge on the shower mixing valve, which in turn is shutting down to prevent scalding.

Just seeing your reply there K.Flyer
I'm certain we varied the temperature before but I'll turn it down later on (when it's my turn for a shower !!)

However, while one of my kids was having a shower (in the en suite) last night another one washed her hands in the kitchen and bosh, shower water stopped??

I have a boiler service planned for tomorrow, so fingers crossed .

K.Flyer · 26-04-2016 09:06AM

VUDuo2 wrote: »

Just seeing your reply there K.Flyer
I'm certain we varied the temperature before but I'll turn it down later on (when it's my turn for a shower !!)

However, while one of my kids was having a shower (in the en suite) last night another one washed her hands in the kitchen and bosh, shower water stopped??

I have a boiler service planned for tomorrow, so fingers crossed .

When you say stopped, do you mean that the water stopped flowing or the water in the hot tap went cold, but kept flowing?

VUDuo2 · 26-04-2016 09:14AM

K.Flyer wrote: »

When you say stopped, do you mean that the water stopped flowing or the water in the hot tap went cold, but kept flowing?

The water stopped flowing.

I asked the other kids to turn off the taps if they were using them and within a minute the shower water started to flow.

Dtp1979 · 26-04-2016 09:37AM

Have you limescale in your kettle?

VUDuo2 · 26-04-2016 09:39AM

Dtp1979 wrote: »

Have you limescale in your kettle?

Probably - I'll check that later, and if there is ????

Dtp1979 · 26-04-2016 10:14AM

VUDuo2 wrote: »

Probably - I'll check that later, and if there is ????

Your secondary heat exchanger might be partially blocked

DGOBS · 26-04-2016 06:47PM

You mean the plate-to-plate heat exchanger.
These can be flushed, but usually the symptom is wildly fluctuating water temperature at the tap under constant flow as boiler keeps hitting stat limit on the dhow and knocking off.

VUDuo2 · 28-04-2016 11:06AM

K.Flyer;

- you were spot on -

I had a shower the night before last, (while there was no one else in the house & while no appliance was running ) and there was no water stoppage while showering.

After my shower, I left the water turned on, turned on the kitchen tap and the shower water stopped.

After reducing down the boiler temperature, in stages, the shower water continued to flow while the kitchen tap was turned on.

The boiler was serviced yesterday and is apparently in top condition.
He agreed that reducing down the temperature would resolve the issue while showering.

He suggested, to have an uninterrupted shower, to install an attic tank and connect an electric shower to it, only.

The kettle has some limescale but it's no different to what we are used to in the area.

Many many thanks to all for your help.

Dtp1979 · 28-04-2016 06:30PM

VUDuo2 wrote: »

Dtp1979 - you were spot on -

I had a shower the night before last, (while there was no one else in the house & while no appliance was running ) and there was no water stoppage while showering.

After my shower, I left the water turned on, turned on the kitchen tap and the shower water stopped.

After reducing down the boiler temperature, in stages, the shower water continued to flow while the kitchen tap was turned on.

The boiler was serviced yesterday and is apparently in top condition.
He agreed that reducing down the temperature would resolve the issue while showering.

He suggested, to have an uninterrupted shower, to install an attic tank and connect an electric shower to it, only.

The kettle has some limescale but it's no different to what we are used to in the area.

Many many thanks to all for your help.

It was k. Flyer who diagnosed it. Not me

VUDuo2 · 28-04-2016 06:36PM

Dtp1979 wrote: »

It was k. Flyer who diagnosed it. Not me

Quite right and amended

Baxi Duo Tec Combi 33 HE ( Issues and advice needed )

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