Baxi 105E - CH only reaches 50 degrees - Genius required!

[Silvana]

Hi can anyone help as my heating engineer has come to a dead end. The heating on my boiler (Baxi combi 105E)only reaches 50 degrees which leaves the radiators warm but not working at full heat. The hot water is fine, it actually reaches the maximum temperature on the boiler of 70 degrees but the heating won’t go any higher than 50 degrees. I do not have radiator thermostats or a room thermostat and the pressure on the boiler is fine, as is the pump. The radiators have been bled and some of the radiators been taken off to check for sludge but they were clear so it doesn’t appear to need a powerflush, it’s just that the heating won’t go any higher on the boiler than 50 degrees (as per the display panel) when it should be able to reach 70 degrees. One of the radiators was also taken off to see if that improved the heating but it didn't. Has anyone got a suggestion as to what the problem can be as my heating engineer and I are at our wits end!


Thanks
Silvana
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[Hardy1]

have you had any new rads added on to the existing system?, has your engineer checked for trapped air? cause that is probably where the fault is, also has he checked for failty thermistors?, are the valves fully open?, would also recomend upgrading to trvs and adding a room thermostat.

 

[tipintim]

Thermister/potentiomitor ?

 

[Silvana]

Thanks just bought a thermistor so will get him to try that and also check for trapped air, thanks so much for the suggestions!

 

[Hardy1]

where did you buy the thermistor from?

 

[diamondgas]

The control knob spindle snapped is a possibility if the heating thermister is okay! The knob may be turning but it aint spinning the potentiometer on the pcb

Really need to be checking thermister resistances, bp's and modulation IMO

 

[arran197]

:iagree: I'd go with that. Or the knob hasn't been put on in the correct place on the potentiometer itself. Seen it quite a few times on Baxi products, Duo Tecs and other.

 

[Jonwells]

.Arran 197 may have hit the nail on the head, baxi control knobs can be fitted out of line, max on knob isn't max on circuit board potentiometer, I think the contol knods are fixed, so circuit board will need to be dropped out slightly, then turn with electrical screw driver to make sure when control knob is max then so is circuit board potentiometer. Jon

 

[moogwai]

Also check the filter inside the return valve....may stop water circulating.

Sent from my Desire HD using Tapatalk

 

[sparra1100]

have you had a new board fitted as the potentiometer nobs mite be in the wrong place then need to be back to zero when new board fitted or as above said broken spindles ave had that a couple of times

 

[Silvana]

Ebay £7.99

Baxi Potterton Thermister Thermistor 5108265 Was 247394
Item Id:	120520526162

 

[jncalderc]

This is a simple problem if you remove the PCB, the temperature control for the heating can be turned up with a normal screwdriver on the board where the dial on the casing goes through to connect to the board, max is turning anti clockwise and refit the board and dials accordingly obviously as you turn the control knob you have to make sure the dial is in line with the way it fits in. A two minute job! Good luck

 

[Silvana]

Thank you so much for yours and everyone’s advice on this forum, my heating engineer bypassed the thermistor to see if the boiler worked without it in place and it did, rads were boiling but when he put the new thermistor in again the heating wouldn’t go over 50 degrees, so he looked at the potentiometer. The knob on the outside casing of the boiler was turning the spindle on the pcb to the max possible, so he tried your recommendation of taking off the pcb and checking the potentiometer underneath was set at the maximum and BINGO it wasn’t, it was only half way!! He adjusted it to the max, put everything back together and for the first time in 4 years since I moved into my house I have proper heating. The rads are hot to the touch and the difference it makes is amazing.

Thanks to your advice I won’t freeze this winter, my engineer was really chuffed too as he didn’t know to look at the potentiometer setting under the pcb, just on top, so he was happy as he’d learnt something new too. Thanks so much again, you have saved me a fortune as without your advice we were going to change the pcb next and then if that didn’t work, which it wouldn’t have, I might have needed a new boiler. I know it’s only a token gesture but if you have a paypal account could you send me your email address and I’ll transfer £10 over so you can buy a bottle of wine or something. I really am so greatful, you are a genius!!!

Best wishes
Silvana

 

[jncalderc]

you are welcome, sometimes we all need a little help. Knowledge like that only comes after a lot of head scratching and flat refusal to be beaten.

 

[Billy Bob Bob]

you are welcome, sometimes we all need a little help. Knowledge like that only comes after a lot of head scratching and flat refusal to be beaten.

a good call,which worked,however they dont leave the factory like this,so that pcb has been out at some time just for your info and something worth checking if its a HE version the RH heat exchanger o ring can let go,water then runs down the wiring loom into the pcb we come along as engineers and the customer has this exact fault DHW fine ch wont go over 50 degrees,if a siemans pcb is fitted its scrap and you need a new one if a honeywells on there there is a slight chance it can be saved with a good drying from a hair dryer ,or preferably a dip in distilled water(stops corrosion of the connections) and a through hair drying