Combi Boiler Problem

Millerblade270608

Hi.

New house and never had a combi boiler before. When I run a bath it comes out hot but not hot enough that I need to add cold water to it and water in bath goes cold very quick.

What settings do I need to change on combi boiler. It's a betacom 2.

Thanks

jk0

I don't have that make, but the water temperature on my boiler cannot be adjusted. It is set at 52 degrees. However, the instructions say that in winter it might not even be able to manage that when the mains water is very cold. They suggest that I reduce the flow of hot water slightly, so that it gets heated more.

matelodave

Combi boilers heat the water as it flows through a heat exchanger so you need to slow the water flow down to increase the temperature.

Most combis have two temperature setting dials, one for the heating and one for the hot water.

The hot water one should be set fairly close to max at this time of year because the incoming water is much colder than it is in the summer and the boiler has to work a lot harder to raise it's tempertaure..

It also depends on the heating capacity of the boiler - some are quite undersized so try turning the tap down a bit and waiting a bit longer for the bath to fill.

There are two Betacom 2 models a 24 rated at about 10 litres per minute and a 28 rated at around 12 lpm. I reckon you need to reduce the flow to around 6-8 lpm

Millerblade270608

Hi. Any slower and I would never get a half sized bath! All the taps in the house come out realllyyyy slowly, especially the bath!!!:/

Millerblade270608

It is a 28

ChaunceyGardiner

The manual is freely available online. You press the mode button until the tap symbol is displayed, the adjust with the +/- buttons. If you have intelligent controls fitted, or an external sensor, the boiler adjusts it automatically and it cannot be changed. My combi takes at least 15 minutes to run a bath, yet it short-cycles like crazy when the heating is on (studio flat). That’s just the nature of the beast, unfortunately.

daveyjp

The Boiler may be too underpowered for the water pressure. It is important with combis they are matched, otherwise the water flows so quickly it can’t be heated up.

As others have said reduce the flow to match the heating rate which will be in the manual.

You can test your flow rate by timing how long it takes for a litre to be drawn.

matelodave

The flow rating is 11.5litres a minute assuming that the water temp is 25 degrees going in and 60 coming out ie a increasing the temp by 35 degrees.

If the incoming water temp is less (which it will be at this time of the year) then the output temperature will be less unless you reduce the flow rate. As suggested above you can check the flow rate by timing how long it takes to fill a 10 litre bucket - you really need to draw a bit more off than just filling a jug or kettle.

If it takes much more than a minute then it might be worth checking if theres are any restrictions in the pipework (eg half closed isolating valves) because someone previously may have reduced the flow to try and increase the flow temperature.

I've had a combi and both my daughters have them and none of us have had a problem with water temperature although filling baths does take a bit longer but you never run out of hot water like you can with a tank

Cardew

Cold weather and combi boilers, mean slow slow bath filling!

As said above most of the flow rates for hot water to taps are given for a increase of 35C from the mains input temperature. At this time of the year the mains input can be around 5C, so water leaving the boiler will be around 40C and a degree or two lower at the bath.

The guidelines for a hot bath vary but this is reasonable:

The NHS Estates Health Guidance Note, refers to maximum hot water and surface temperatures for safe use. These are recommended for all healthcare premises and those premises registered under the Registered Homes Act 1984 (Ref 3) but are applicable for other types of occupied building.
A 44ºC For an unassisted bath fill
B 46ºC For an assisted bath fill (**)
C 41ºC For shower applications
D 41ºC For washbasin applications
E 38ºC For bidet applications
** This high fill temperature should only be considered in exceptional circumstances where there are difficulties in achieving an adequate bathing temperature. The building manager should also have in place specific policies that prevent the possibility of persons judged to be at risk gaining access to the bath unaccompanied.

The average person in UK uses between 100litres and 200litres So even a 100 litre shallow bath would take nearly 9 minutes at your flow rate of 11.5 litres/min; and the water would not really be hot enough. So you would need to turn down the flow quite a bit to get acceptably hot water, and a 15 to 20 minute filling time would be normal.