Sabre HE 25 Hot then Cold

[EllieMae10]

Hiya,

I've signed up to ask a question about the boiler in my house.

Recently the hot water is hot then cold frequently, but only when the hot water is started while the central heating is on.

If the boiler is left off over night then the hot water is started from cold the water most times stays hot. Even though on rare occasions it does it but its guaranteed if you switch to hot water while the heating is on.

From what I've heard the venturies have been cleaned, a small screw in part on the tonight hand side of the chamber has been changed (NTC or something like that) and the ignition board?

The central heating is working fine (used to goto to red but since the above has been done its been fine). What shall I ask to be replaced next?

Thanks everyone for trying to understand this.

 

[petertheplumber12]

I was going to say it.s secondary heat exchanger but it looks as if it is something to do with the divertor valve or the signal to the divertor valve being faulty

 

[bucksplumber]

Yeah sounds like the diverter valve. Hot water should take priority so if the central heatings on and you open a hot tap you should get hot water but no heating. Sounds like its getting stuck, maybe consider replacing the diverter?

 

[joe-90]

This is a problem I've just got a bit of but not bad enough to sort yet. What I don't understand is what is happening in the secondary heat exchanger to make the water temperature fluctuate? The flow rate doesn't change. Same question re diverter valve - how does it make the temperature fluctuate? Just curious.

 

[EllieMae10]

I think that it isn't cofuddled, it does switch over too the hot water, it just starts running hot and cold. If I was to turn the heating off at the switch and leave it off overnight not any timers e.t.c then switch the shower on in the morning 9 times out of ten its fine. The heating is in now fine if I goto washup now the heating flicks off and the green light starts flashing then lights permenant. I get some hot water then the lights starts flashing again and the water goes cold. The green light indicating its all burning just starts flashing again.

 

[petertheplumber12]

It is possible the secondary heat exchanger is partially block with sludge, on that side of the sec heat exchanger the hot water would keep switching on and off, but that would happen regardless of whether the heating was on or not, so I think it may be something like the flow switch that tells the divertor what to do. but a couple of electrical checks while boiler is operating would isolate the problem.

 

[EllieMae10]

I'll get them back out to look at that and I'll post what they do. Gonna end up an expert on boilers the way it's going on.... Maybe not. Just want everything to work.

 

[mikefsway]

I just wanted to leave a quick note in case anyone is googling for this same problem. I also have a sabre he25 which packed up recently. Engineer suspected the problem might be a blocked secondary (or dhw) heat exchanger. BE WARNED. The dhw heat exchanger on this boiler is difficult to access, requiring removal of many other parts before it can be reached. I'm no expert, but the engineer said that it was one of the most time-consuming dhw heat exchangers to reach of any boiler he had worked on (in 20 odd years). The instructions in the installers manual are also misleading -- following them it seemed like it would be impossible to remover the heat exchanger as access was blocked by the expansion vessel. We called up support and they said to remove the gas valve, which isn't mentioned in the manual but does allow access to the dhw heat exchanger.

I guess the message is just to be pretty sure you have ruled out other possible problems before trying this option, otherwise you are in for a time consuming job just to see if it might be an issue...

 

[EllieMae10]

Starting to feel sorry for the lad that keeps having to come round. He told me as its being done on insurance they only get a certain amount of time on the job. Hopefully it's an easy one this time. At least it's not intermittent like the last one. He had to hang around everytime to see if it had worked or not :0/

 

[mikefsway]

Likewise, this heat exchanger thing took hours to remove, clean and replace and it wasn't even the problem so the engineer didn't charge for the time, which I really appreciated.