Hot water only warm when on "timed"

[jonathan451]

Hi to all and thank you for reading!

We are renting a 40 year old country cottage and approximately 2 months ago we noticed the hot water only seemed "warm" when we set the boiler to work on "auto" ie "timed". When on constant the water seems properly hot.
We have an oil-fired Danesmoor 15/19 boiler, it seems to be heating the radiators just as well as ever. The radiators are the same temp on "timed" and on constant. We have a tank in the airing cupboard which also has an immersion system - this seems to work ok although if left on the water seems to get hotter and hotter until it is almost scalding. I would love a little advice as our landlord is quite elderly and relies on me to organise any work done on the house so I like to understand the problem before asking him to sign a cheque for any work done. I may not have given enough information about the system but if more is needed I will try and get it. I wondered if there is any simple adjustment I could try before calling for help. Prior to 2 months ago - the hot water was beautifully hot when on timed - summer and winter (we have been in the house about 18 months).
Any ideas gratefully received - thanks
Jonathan

 

[GreenArmy]

What times do you set the timer at? i.e what time does it come on in the morning and then go off. what time does it come on in the evening and go off? Has your cylinder got a jacket on? Is hot water needed during the day? i.e your at work and the missis is at home?
If as you say, when you use the immersion heater, the water gets hotter and hotter until its scalding then that is a serious problem and you need to get the immersion stat replaced, preferably with a cut off device.
Also, do you have a cylinder stat that may have accidentally been turned down?

 

[jonathan451]

Okay - thanks for responding Mark
Timer set to come on at 05.30 until 07.30 and then 17.00 until 19.00.
In the past with this setting, there was plenty of hot water for a shower first thing and then washing-up, etc through the day. On a day of heavy usage we might notice it running out at 2-3pm and then we knew we simply had to wait until 5.30pm for more.
The cylinder does have a jacket on. Hot water is required during the day but minimal. We have a young baby! Not sure about a cylinder stat - have had a look at the cylinder and can't see anything obvious - any tips on where it may be or what it looks like. I will get someone in to check the immersion stat and test/replace it. Thanks

 

[GreenArmy]

A cylinder stat will be strapped directly to the cylinder by way of a net curtain type cable or similar. Have a look under the jacket (unless of course the cylinder has the spray on lagging type in which case some will be cut away for the stat to make contact with the copper).
Have you tested the hot water by having it on constant? If so and there is no problem, then why not leave on constant, it can be more economical as your boiler will only cut in now and again to boost up the hot water, rather than heating up a cylinder full of cold water.
Let us know how you get on.

If once you've tested the cylinder stat. I would suggest you get up at 5.30am (yawn) and feel the flow and return pipes where they enter the cylinder and check they are getting very hot. If not there could be a problem with the three way valve not opening correctly.
Im sure other members may make a suggestion on your problem.