Combi boiler water going hot cold hot cold and so on

[DavidEvans007]

hi there..

Ive just moved into a new house and we have a problem with the hot water supply upstairs...

I fitted a new set of taps in the bath to supply a shower head (temp measure till i get round to fitting an electric shower)... the problem is, the water goes hot, then gradually loses temperature till its stone cold.. then it gets warmer until its scalding hot.

I thought it might have had something to do with the boiler not coping with the demand for the hot and shutting down the feed to heat it up, so i turned the temperature on the combi right down... the water temp downstairs at the sink is cool to touch.. but upstairs its still scalding hot and doing its hot cold cycle again

does anyone have any clues as to whats going on?... ive been told by a mate that the combi might be too small, but i cant see this being the case as its doing this with just one tap on

I dont have the model number of the combi as the previous house owners went off with the instruction book and the name plate is missing... but if it helps, i can post a pic of the unit if required.

 

[Agile]

Because you have given so little information in technical terms I have to do a lot of guessing.

Although you did not say it, I will assume the hot water was fine until you disturbed the system with your DIY work.

My best guess so far is that you have somehow allowed cold water to mix with the hot.

You can check this by closing the cold water inlet valve under the boiler, it will be on the 15 mm pipe. Then see if you can get any cold water from any hot tap in the house.

Tony

 

[DavidEvans007]

Because you have given so little information in technical terms I have to do a lot of guessing.

Although you did not say it, I will assume the hot water was fine until you disturbed the system with your DIY work.

My best guess so far is that you have somehow allowed cold water to mix with the hot.

You can check this by closing the cold water inlet valve under the boiler, it will be on the 15 mm pipe. Then see if you can get any cold water from any hot tap in the house.

Tony

sorry... this being a DIY forum i didnt realise i had to have a degree in plumbing technology to post problems

also.... i didnt do anything to the pipes.. i fitted one of those over the taps mixer adaptors.. so the actual plumbing is the same as it was originally...

i did have one day where everything was ok when i turned the water temperature right down on the boiler and the temp remained constant, but it hasnt happened again

 

[Agile]

If you would like us to try to help you then you will have to answer our simple questions to enable us to better guess at what your problem is.

Can you tell me if the problem only started after you fitted this new thing?

If you take it off does it work properly?

Can you do the simple test in the last paragraph of my previous posting?

If you really dont want to do a DIY fix if it proves possible then you may be better off calling a professional to do it for you.

The best advice on DIY comes from professionals, NOT other DIYers!

Tony

 

[gazthepottertonengineer]

[
sorry... this being a DIY forum i didnt realise i had to have a degree in plumbing technology to post problems

Just the boiler make and model might have been helpful its normally written on the front to give you a clue

 

[DavidEvans007]

[
sorry... this being a DIY forum i didnt realise i had to have a degree in plumbing technology to post problems

Just the boiler make and model might have been helpful its normally written on the front to give you a clue

read the last paragraph in my first post

 

[DavidEvans007]

Can you tell me if the problem only started after you fitted this new thing? nope

If you take it off does it work properly? nope... still the same

Can you do the simple test in the last paragraph of my previous posting? done, all that did was cut the water off to the combi

 

[Bahco]

Obviously your boiler needs looking at by a heating engineer. Could be the DHW exchanger is scaled up.

Don't think you can diy it.

 

[Bahco]

sorry... this being a DIY forum i didnt realise i had to have a degree in plumbing technology to post problems

You are a smartarse by the way!

 

[kevplumb]

gentlemen please

 

[Agile]

Can you post a nice picture of the lower third with the control panel so that I can identify it please?

Can you also measure and set a flow rate of 9 litres per minute and then tell me what the temperature does when you run it for a few minutes?

Tony

 

[DavidEvans007]

Can you post a nice picture of the lower third with the control panel so that I can identify it please?

Can you also measure and set a flow rate of 9 litres per minute and then tell me what the temperature does when you run it for a few minutes?

Tony

I'll post a pic tomorrow... just as an add on for the second part...

ive set the hot tap at various positions, just on, just on and a bit right up to full on.... and the problem is still there.

tonight i switched the hot tap just on enough to get a flow through the shower head and it stayed at a constant temperature for about 3 minutes... then it started on its scalding, hot, warm, cold, warm, hot etc cycle again.
the cold water tap wasnt touched at all during that time

plus, the flow rate upstairs isnt exactly full on.... it takes me 10 minutes to run a bath to the level my 2yr old son baths in (just above this belly button when sitted)

 

[Agile]

Can you watch the flame when it is delivering the rated 9 litres per minute and describe EXACTLY what the flame does?

To help you it may get big or small or go on and off. I need to know just what it does!

 

[DavidEvans007]

right then...

this morning the missus got up at 5 to go to work... she had a shower....

no problems with the water temperature

then i went for a shower about 8.... no problems with the water temperature

the way i did it??

last night i turned the temperature control on the boiler right down to this position...

the water is hot enough for a shower, it doesnt need the cold on at all... i just turn the hot tap so that the pressure is enough to be able to throw the lever on this..

to allow it to stay in the shower head feed position

so is the problem like i originally said... that the boiler cant cope with the demand and shuts down till the water reaches a set temp then releases it again?

heres the control panel too

if anyone can identify the boiler then i'd be chuffed cos then i can go search out a user manual for it

 

[DavidEvans007]

also... are the black area's on the dials the optimum operating range of the rad and water temps?