Ferroli DomiCompact F30B - DHW getting too hot

[xreyuk]

Hi guys,

I'll start by saying I'm not a plumber or anything, as the site is for, I'm a DIY'er.

I have a Ferroli DomiCompact F30B Combi boiler and have recently replaced the clip on DHW temperature sensor as the temperature was jumping all over the place. When I moved it around it would temporarily fix it and then go again.

Now I've changed the sensor, the water seems to be holding temperature correctly, and I've set it to 50c. However when running my bathroom sink tap, and downstairs sink tap, which are on single mixer taps with a single handle (left for hot, right of cold etc) the water temperature is heating up to around 70-75c, before slowly dropping down (the max I can set on the boiler is 55c)

When I run the bath taps, which is a mixer tap with two separate handles, the water temperature slowly rises to 55c with just the hot water on, but when I run the cold a little bit with it, it stays around 53c. I didn't try just leaving the hot water on alone to see what temperature it reached.

Any idea why my hot water is getting so hot despite being set to 50c on the boiler?

 

[Groovejet]

Was the stat a like for like new part?

Somethings not correct. First of all you said you changed the stat?

In the service manual it states that by going into test mode you can adjust the heat output from 99% - down??
Also the boiler has a comfort mode , which pre heats the boiler so that there is'nt a lag in hot water getting to the taps.
Turn this mode OFF, and turn to Eco mode. See if this helps with the temperature issue, then you'll know where to go from here.

 

[xreyuk]

Thanks.

Since I posted this, it's started behaving as expected for all taps. I had something similar happen for the heating last time the boiler was powered off, the heating was reaching 90c.

It wasn't an exact like for like part, but it was a genuine ferroli part for my boiler, it looks as though it's been improved since manufacture. It was a brand new part.

Since my temperatures have been as expect, should I still give your Eco mode a go?

 

[Groovejet]

Dont ruffle the feathers!!
If its doing ok , leave it. But your not going to break anything, so balls in your court

 

[xreyuk]

Well I thought this was getting better but I guess not.

It's still doing the same thing with two of the sink taps, the bath tap/shower and the downstairs kitchen sink tap are heating up normally to 50c. The other two taps immediately heat to 75c.

I turned off comfort mode and put Eco mode on but this made no difference.

The only thing I can think the temperature is similar to is that the heating usually heats to 75c before shutting off.

 

[Terry7556]

Not sure if this will help in this situation or not but I have been told by others on here and by a Ferroli agent that with this group of boilers if swopping one thermistor you must swop both
Don't know why, possibly something to do with the Pcb
They must be Ferroli parts as well, not oem ones

 

[xreyuk]

I'll have to have a look at the instructions for the other sensor.

It was a genuine part.

 

[Ahades]

Hello mate, I know it's an old thread but having the exact same problem, how did you manage to fix it if you can remember..