Biasi HE hot water goes cold

[thegoose]

Tony

just checked the temp. about 74 flow and 60ish return checked a dozen time and then on the last check the return temp went down to 40 and repeated this about 5 more times and got 40ish everytime then bak to 60.
yes matrix i mean heat exchanger. iwas thinking heater matrix.

brother is still trying the temp check and cannot get the 40 temp to happen again.
the system still reaches 75 and burner goes out weather the return is at 40 or 60.
when the flow runs up to about 70 deg the return runs up to 40 or 60 very quickly then the last 5 degrees from 70 to 75 when it locks out takes about 1.5 mins the return seems to stay at the 40 mark or the 60 depending on which one its happens to have chosen if thats the right word.

cannot get the 40 to happen again tried lots of times now but it did do it like you said.
Taking the mickey out of my broth now for missing it.
He's not to chuffed. to be fair though he tried lots of time now and it still won't do the 40 again but he has seen it do it.
He cannot explain the intermittent blocking or flow reduction.

Have you ever seen this type of intermitent flow.
when it running 70 flow and 60 return why does the flow temp creep up and turn the flame
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[Agile]

The only cause of an intermittent temperature difference is an intermittent flow!

However the temperature should not go up to 75° anyway except as an overshoot.

Has your brother bothered to inspect the eye of the pump ???

Has he measured the cold resistance of the sensors?

Tony

 

[thetortoise]

Hi, I have the same problem.

Thought it was the HE so powerflushed...still not working.
Took it out and cleaned in Fernox System Cleaner and boiling water...still the same problem?

Could be related to the "DHW sensor probe NTC"? Because I've had intermittent hot water problems on a Vaillant before and that was because the sensor that sits on the plate HE had come off! I simply put it back on and everything was hundreds! Another reason is it doesnt seem to be "intermittent" really, it seems to just be getting too hot, too quickly and then shutting off, dropping back to 30 and then starting again, which makes me think that a sensor or something isnt doing its job?

Did you ever solve the problem there Goose?

Any help would be greatly appreciated!!!

Cheers

 

[Agile]

You have added to a two year old thread. Few posters bother to report back what has happened or to thank those who gave advice.

Your description seems typical of a blocked plate HE.

Just because you have done something does not mean that its been cured.

Tony

 

[thegoose]

Hi thetortoise.

If you've read this thread from the beginning you'll find that most of the replies to my post were to complain about me fitting the system myself. All in all i got very little help and i had to ask what i'd done to offend the members. so tread carefully if your not a fully certified gas expert with decades of experience. Agile seemed to be very upset and as usual he's still insisting its a blocked plate HE.

Agile you are wrong!!!. the problem was the pump. As you insisted it was the a blocked plate, i had the plate HE removed and performed a physical examination, then a flow check and like or lump it the plate is fine.

The pump on the other hand had an intermittent fault which deteriorated to a point were it ran so slow you could hear the strain. i replaced the pump and hey presto problem solved.

As for thanking those who gave advice. I had to beg for the advice, apologise for asking questions, suffer the ego's and lets face the YOU ARE WRONG and i fixed the fault myself so not a lot to thank you for, or perhaps i'm showing all the signs of a blocked plate HE.

 

[thegoose]

thetortoise,

if you find the fault and its not the HE please post your findings.
Perhaps Agile will thank you for your help.

Your observations are identical to my experience. i to thought a sensor fault because of the lack of modulation or modulating to late then lock out.
How much did the power flush cost?

 

[Agile]

I dont need any help repairing boilers and I am sorry that you dont seem to appreciate the help I tried to give you.

90% of problems with newish boilers is caused by dirt in the system.

I did ask for more technical details several times as the only way to diagnose a boiler fault is to be there in front and do tests. Asking a third party who is not a boiler engineer is nothing like as good.

You should have noticed that on the 3rd march 2008 I did ask if your brother had checked the pump impeller. Being CORGI registered I expected he would have checked the simple parts of the boiler first.

The symptoms of a blocked plate are similar to a blocked pump or one with limited torque. Those Wilo pumps virtually NEVER fail EXCEPT as a result of dirt which causes the impeller to get stiff. Rotating the pump shaft to feel if its free to turn would be in the first checks a CORGI would do first.

The FAQ includes the "finger test" which anyone trying to find a fault on a boiler would usually do.

You can rarely actually see anything wrong with a plate as the blockage is usuallly inside. Unless its virtually completely blocked then a simple visual flow test in not accurate enough to identify any fault.

Tony