Vokera 20-80 R.S. Flowmatic merely warming the water

[Martin Bonner]

I have just moved (so expect lots more posts with idiot questions).

The current problem is that the boiler is only producing warm water (not hot). As specified on the subject line, it is a Vokera 20-80 R.S. Flowmatic produced by Beretta. It has a maximum power input of 28.6kW, and an output of 23.3kW.

The hot water can be made reasonably hot if I switch on the central heating as well.

There is a knob running from 1 to 9 for central heating (currently set at about 3), and another for hot water (I've tried 1, 5, and 9 without much difference - I did once get hot water from 5, but it wasn't repeatable.)

There is a temperature dial which seems to relate to the output hot water temperature and it won't go above 40 C (I'd prefer 60).

There is a pressure dial which is currently reading 0.5 bar. It is above a note which says that I need to maintain the pressure between 1 and 1.5 bar.

Underneath the work surface there is a mess (I'm not impressed by the plumbing) of hot and cold pipes. There is one flexible connector with an inline-valve on both ends. One valve is clearly shut. The other valve doesn't have a knob on it it; instead it appears to have an Allen key fitting.

If I open both of these valves carefully, will this repressurise the system? (Or am I likely to just flood somewhere?) Is the low pressure what is causing the lack of heat? (If so, why does switching on the central heating make a difference). Do I need a new thermostat somewhere?

[Ed Sirett]

Have a read of the SealedCH FAQ you may need to top the system up a little. However that's not going to fix the problem with the hot water.

When you draw water at a reasonable flow rate the boiler should be flat out whilst the tap is running. I was doing a Landlords last week on one of these units but I did not take note whether it had seperate sensors for CH and HW. I suspect it doesn't and that together with the other info you gave suggests the temp knob, pot, wiring or just maybe the PCB are suspect.

But there are many other tests I would want to do before narrowing down what to replace.

[Martin Bonner]

Yes. I should have done that BEFORE posting. Sorry for the noise.

I actually tried refilling before waiting for your reply (I don't have the net at home yet). I now have an overpressured system. I switched off the filling tap when the dial read 1.5 bar, but it kept on rising until it reached 2.5 bar (and reaches 3 bar when hot). Having read the FAQ, I now need to release a little from the drain valve.

It didn't :-(

Don't know whether it is or not :-(

Given that you haven't suggested which other tests *I* should do, can I assume that it has reached the point where I need to pay somebody who knows what they are doing? (I'm perfectly happy to do that; I just want to have some idea what is going on first.)

[Ed Sirett]

There is a little window on the combustion chamber for observing the pilot light and flames. However you really need to check the gas pressure to the burner to be sure. You are now looking in the realms of professional help, 9.5mb IIRC is full tilt.

There are many reasons why the HW performance may be poor. Given that it suddenly happened it is less likely that the problem is something progressive like limescale (you may even live in a soft water area for all I know).

[Martin Bonner]

Right. That's what I thought.

Can't say that it started suddenly - it wasn't working properly when we moved in on Saturday is all I know.

Hardly! Cambridge (but I *like* hard water - both for drinking, and for washing).

Thanks for all your help. It really is appreciated.

Martin Bonner