Keston C36 Jet Engine!

[diy_disasterman]

I had a Keston C36 fairly hefty combi boiler installed last November.

The central heating part is still nice and quiet, but Direct Hot Water has got progresively noisier over the last month or so and has now got to the stage where it sounds like concorde taking off.

Also, once I've turned the tap off, the temperature display on the front of the boiler often seems well over the DHW temp setting, like 71 degrees.

It then takes up to 4-5 minutes for the boiler to "wind down" and turn off.

It's got to the stage where I'm scared to turn a hot tap on, except for something major like a shower or a bath!

Any clues as to what the problem could be?

 

[werewolf]

first call your installer to check boiler is installed and set up correctly( not saying he hasn`t).After that contact Keston as it`s u/g

 

[ollski]

Usually because the condensate pipe is blocked in the boiler.

 

[diy_disasterman]

Thanks for the responses guys.

I spoke to my installer who told me how to check the pressure in the system. It had dropped to 0.9 bar.

Topping it up to 1.7 bar has sorted it out nicely.

Always the simple things with me!

 

[Agile]

I am surprised it made that amount of difference! Most boilers are quite happy at 0.9 bar.

The installer should have taught you when and how to top up the pressure.

Tony

 

[croydoncorgi]

The whole situation sounds very suss to me!
If the 'cause' was actually low pressure, the actual noise was presumably some form of extreme 'kettling' in the main heat exchanger. But Keston C36 is not usually prone to that.
But if there was another source for the noise, why did changing the pressure make any difference?

After a hot water run, the boiler will continue to make a noise for a while, due to the pump over-running as it cools down - it's supposed to do that. The burner is NOT running at this point (or shouldn't be). But does it still do Concorde impressions during this period?

 

[diy_disasterman]

Yes, it was still making a horrendous racket after the DHW was turned off, until the pump stopped.

It can't have been sleight of hand or the guy telling porkies, surely, as I topped the water up myself so I know for sure that nothing else was changed while I wasn't looking.

The installer I think did mention the pressure but it had slipped out of my mind.

My old boiler had a physical gauge on the front, so I couldn't miss it when it needed the occasional top up. The Keston has it hidden away on a menu type system, so it's just down to me forgetting really.

I don't really know what "kettling" means I'm afraid to say.
If it happens again I'll make a little movie and stick it on the web!

 

[ChrisR]

I suppose it's possible that there is air in the boiler and the auto air vent is shut instead of open. Doubling the pressure would reduce the volume of any air. The aav is inside, and the case seals are rubbish, so it mght be best to call the installer back.

 

[uncleted]

Had the same problem with this type of boiler the pressure kept dropping but there was no leak but mine sounded like the local RAF station were trying to land in the house. Keston played dumb about it at first but after a few irate phone calls from my plumber they did turn round and say there was a problem with the instalation that was not covered in the manual. I didnt see what was done but it looked like the boiler needed some extra bleeding done which only took 30 seconds to do and it has been fine ever since

 

[merlinj]

Your problem is simular to mine scaled and clogged DHW heat exchanger

 

[humbleton]

I have a similar problem to this, although my jet engine takes off mainly when CH switches on first thing in the morning. It's just out of guarantee, so I'm loath to call someone out if it's a simple fix. I had someone called out a while back when it was making a noise and he said pressure was too low and lo and behold it got rid of noise. He also said there was some kind of bug in the chip and pressure reading could be 0.5 bar out! Since then I've always kept it up to about 1.7 bar, but I do have to frequently top it up. The other thing it does, which is pretty scary, is 'explode' sometimes when switching on for CH or water. Enough to make you stand back when you know it's coming on! This seems to happen when boiler temperature is low.

I'd be grateful if anyone can enlighten me on what's going on, via these questions:

1. If pressure is ok, what else could be causing the noise? I live in an area of quite high limescale, if this is the problem, what's the best way of cleaning it out?
2. Should I be concerned about regular topping up. On average about every couple of months.
3. What's causing those explosions?

Thanks in advance, Rob