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Andrew Smith
Andrew Smith, Plumber
Category: Plumbing
Satisfied Customers: 3586
Experience:  City and Guilds qualified plumber
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Hello, Ive got a 2005 Keston Celsius 25 with a problem.After

Customer Question

Hello, I’ve got a 2005 Keston Celsius 25 with a problem.
After approximately two minutes with only the central heating switched on and the boiler modulated to full power, a ‘water flow’ led flashes about once/twice a second. After a period of time with the boiler still modulated to max sometimes, but not always, the flow light extinguishes. No flow LED is ever shown with hot water only, or when both HW and CW are running together.
The system is sealed with a Flexcon expansion tank. The resting pressure at the boiler is 1Bar and with everything going full belt never gets above 1.8 Bar. The boiler modulates through its range without any problems and the ‘water flow’ never displays below level four.
I have also replaced a faulty auto air vent on the boiler heat exchanger manifold; there is also an auto bypass. The return thermistor reads 7.8 k ohms and the flow 6.4 k ohms. Other than that it seems to be running as sweet as a nut, no kettling – nothing.
Assuming there was some kind of partial blockage I cleansed the system with a de-sludger, flushed it through, emptied and cleaned the Magnaclean and very little of anything came out. After refilling the system with Fernox and venting the system I still get the same water flow problem!
Where can I go from here?

Thanks
Submitted: 3 years ago.
Category: Plumbing
Expert:  Andrew Smith replied 3 years ago.
Your flow overheat thermostat and flue protection thermostat run a heat protection loop, I am wondering if a faulty component in the loop would give you an overheat or poor circulation light?
Customer: replied 3 years ago.
Hello, I do have a spare flow thermostat that I will change in the morning. If not, do you think it's worth ordering a flue overheat thermostat?






Expert:  Andrew Smith replied 3 years ago.
I would, but with it being in a circuit also, I would strip and clean all the connections too.
Customer: replied 3 years ago.
I've been very rash and ordered one any way, should be here by the end of the week. I'll change the both out and clean the connectors and I will be back in touch later.
Do you know if there is much circuitry involved with this within the PCB, or is it pretty straight forward?
Expert:  Andrew Smith replied 3 years ago.
The ignition side is quite complex, but you should still be able to follow it.
Customer: replied 3 years ago.
The bits won't arrive for a while yet, if they work - great, I can't make any assumptions. many decades of faulting telephone exchanges has taught me that one.
Expert:  Andrew Smith replied 3 years ago.
No problem, just let me know
Customer: replied 3 years ago.
Hello, my flue overheat thermostat arrived this morning. I had previously cleaned all contacts on the PCB and replaced the flow overheat thermostat.
Unfortunately, the same problem exists. The water flow still LED flashes at, what I assume to be, 1Hz.
I've been round an vented everything in sight, including the pump, just to make sure it's not an air lock.
Any documentation I've got doesn't seem to mention much about this. As there is no lockout alarm or diagnostic LED to point the way I feel a little lost.
Thanks
Expert:  Andrew Smith replied 3 years ago.
Ok, I will have a dig through the manual although it sounds a strange fault
Customer: replied 3 years ago.
Thanks
Expert:  Andrew Smith replied 3 years ago.
I may be stuck with this one.
The boiler thinks you have poor circulation or an overheat problem.
We have confirmed the overheat stat and flue stat are not a problem, we have confirmed the pump is ok and that the heat circulates around the system.
I will open up the question and see if someone else can help?
Customer: replied 3 years ago.
Thanks, XXXXX XXXXX looking at the web and the consensus is that keston's can be a bit of a problem to fault, any extra advice is always good.
Expert:  adamd-mod replied 3 years ago.

Hello,

It seems the professional has left this conversation. This happens occasionally, and it's usually because the professional thinks that someone else might be a better match for your question. I've been working hard to find a new professional to assist you with your question, but sometimes finding the right professional can take a little longer than expected.

I wonder whether you're OK with continuing to wait for an answer. If you are, please let me know and I will continue my search. If not, feel free to let me know and I will cancel this question for you.

Thanks for your patience,

Adam

Thank you!

Customer: replied 3 years ago.
Thanks, XXXXX XXXXX to wait.
Getting the right outcome is important to me.
Expert:  adamd-mod replied 3 years ago.

Hello,

Thanks for replying.

We will continue to look for a Professional to assist you.

If you decide on a refund, or wish to keep the credit for a future question, then of course we'd honour it.

Thank you for your patience,

Adam

Customer: replied 2 years ago.
Hello, I have just been asked to leave feedback on your service, which I won't until the problem is solved - it wouldn't be fair. However, I have not heard from you for two days and my boiler problem is still the same.
I would be grateful to be put in touch with one of your Keston technicians; as promised on your opening web page.
Expert:  adamd-mod replied 2 years ago.

Hello,

Please understand it is rare for us not to be able to find the right Professional to assist our customers. We can close this question and return your good faith deposit to the original funding source on request.

Please let me know how you wish to proceed and again I apologize for any inconvenience this may have caused.

I hope you will give JustAnswer a try again in the future,

Adam

Customer: replied 2 years ago.
Thanks, all I want is the correct analysis from an expert.
It's the wrong time of year to have a dysfunctional boiler.
Hope to hear soon.
Expert:  adamd-mod replied 2 years ago.

Hello,

Thanks for replying.

We will continue to look for a Professional to assist you.

If you decide on a refund, or wish to keep the credit for a future question, then of course we'd honour it.

Thank you for your patience,

Adam

Expert:  adamd-mod replied 2 years ago.

Hello,

Please understand it is rare for us not to be able to find the right Professional to assist our customers. We can close this question and return your good faith deposit to the original funding source on request.

Please let me know how you wish to proceed and again I apologize for any inconvenience this may have caused.

I hope you will give JustAnswer a try again in the future,

Adam

Customer: replied 2 years ago.
what are the chances of an expert being available to answer my question in detail (the option I paid for), within the next week?
A realistic answer would be appreciated.
Thanks.
Expert:  adamd-mod replied 2 years ago.
Hello

I honestly don't know
The only thing I can do is reopen it and ask experts to see if they can help, which I've already done twice.
I can continue to leave the question open for you, or refund you and close it

Let me know!

Adam
Customer: replied 2 years ago.
If it's OK leave it until Monday, if there's no reply by then I'll have a refund.
Expert:  adamd-mod replied 2 years ago.

Hello,

Thanks for replying.

We will continue to look for a Professional to assist you.

If you decide on a refund, or wish to keep the credit for a future question, then of course we'd honour it.

Thank you for your patience,

I'll keep this open till monday for you and then if no reply, I'll refund you asap.

Adam

Expert:  Andrew Smith replied 2 years ago.
It look there is no-one else to help?
I have been doing some digging but have got no further. Are you able to disconnect the overheat circuit and drop a link between the two connectors - this will rule out a faulty wiring loop.
If it still fails with the same fault, the only other possibility is the PCB?
Customer: replied 2 years ago.



Sorry I won’t be around for a couple of days, thanks for the advice.


I see what you mean the CN9 connector houses the flue stat, cab stat, flow stat, water pressure stat plus a thermal fuse. I can make a link from sleeving and wire to join terminals together, but which ones to join, I’ve only got a schematic diagram.


Two questions: how do I know that the pump is running at full speed apart from the visual representation telling me the boiler is at max?


Why is there no alarm present when both CH and HW are running together or when the modulation drops from maximum?



Thanks

Expert:  Andrew Smith replied 2 years ago.
The pump may have a speed adjustment on the top where the power lead goes in. If not then there is only one speed and you need to take the centre screw out and make sure it is spinning freely.
You could take the centre screw out and put a small screwdriver bit in a battery drill and see if you can get it to run faster?
With reference to which ones to link out perhaps you may have to use a couple of short links to link them all out at once.
Customer: replied 2 years ago.
The pump speed is automatically controlled and there is no manual adjustment. I've already checked the pump runs smoothly, I just don't know if the speed is high enough.
Expert:  Andrew Smith replied 2 years ago.
Ok, from here I can only suggest you change it or at least check the flow and return connections on the boiler in case there is a filter that may be partially blocked.
Also if you are going to drain the system then check the state of the water and the connections to the heat exchanger.

Water flow rates can be affected by a partial blockage, the pump or a boiler or system restriction somewhere.

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