Hi,

I’m hoping you can offer some assistance with a 5 years old (Approx) Eurocal Oil-fired combi boiler

Problem

Hot water comes out hot to start with and then cools down until its just luke warm this takes only a couple of mins tops (No other water is being used at the time of the test)

Background

Boiler has been regularly serviced

Boiler is set to 80oC

My girlfriend has had this problem with her boiler for a couple of years and has at considerable expense replaced a number of parts none of which has made any significant improvement, the heat exchanger being the last part replaced earlier this year. Since then she has just lived with the problem as she ran out of money to carry on trying to solve the problem. She has spent in excess of £600 replacing parts and having the boiler serviced

Parts replaced in the past year or so in order

Expansion Vessel
Thermostatic mixing valve
Plate Heat exchanger



Some trouble shooting I’ve done

There are 3 pipes that go into the thermostatic mixing valve

They start

Top - Warm
Back - Warm
bottom – Warm

When Tap is turned on

Top - Changes from hot to ice cold
Back – Stays Warm
bottom – Boiling Hot

Not sure if this helps or wher to go from here

any trounleshooting advice would be appreciated

Simon

Simon, October 2009

New divertor valve diaphragm needed (Gionnani)

billy, August 2011

Have had this trouble , cured by flushing the heat exchanger with DS 3 solution. DS 3 can be purchased at any plumbing shop. The heat exchanger isn't too difficult to get out, pays to use new fibre washers. Make sure the mixer valve is adjusted properly.....Min to 5...5 is hottest. Hope this is of some help.

Pat Quin, August 2011

I had the same problem for ages - found a very subltle wiring difference between what is termed "high flow" and "Low flow" model on these boilers - basically, with the low flow, which was my model i found out - you only really get the 30-40l of hot water that is stored in the boiler. when you run any more, the boiler cannot keep up.

On the high flow model (or after i modified the wiring, as i'm an electical engineer, on mine) the burner comes on the moment the diverter valve operates to provide hot water - this means the boiler is up and running, before the thermal store is depleted and the boiler temperature has fallen enough to bring in the burner on the normal control stat.

however, i do still have to switch the heating off if i want a really good shower or bath with piping hot water - it builds up the thermal store to 85 deg before hot water draw off. hope this helps.

Mike S, February 2010

Hi Simon
Did you ever get any joy sorting this problem out, I have the exact same problem and have done a lot of work on the boiler.
Jonathan

Jonathan, January 2010

Hi

Thanks for the reply not sure if this is going to help

I ran the tap for 5 mins , none of the radiator felt hot


Looking at the heat exchanger with taps running from top down the pipes are as follows:

|O ...| Hot
| .. O| Hot
|O O | Hot Cold
Front

The diverter valve is as follows with tap running looking from the Side

.......................| .. |............|C |......._
.......................| H|............| O |......| |
.......................| O |............| L |......| |
_______ ____| T |______| D |___| |
HOT.....................................................| Front
________________| H |----| C |--| |
................................| O |......| O |...| |
................................| T |......| L |....|_|
................................| .. |......| D |

sorry about all the dots, the formatter seems to delet blank spaces :-( hope the diagrams make sense
Simon

Simon, October 2009

I wonder if the radiators come on when you are demanding hot water...if so, and the burner should light up and stay lit, it would indicate a diverter valve problem but without testing the system its difficult to be more specific.

John, October 2009