Potterton Performa 24 (without central heating) has problems heating water?

Question

This is in a first floor flat (i.e. water has to travel up one story from mains). When turning on the hot tap, the burner light clicks on and the boiler 'sounds' as though it is working. It will stay on for up to about 10 seconds and then click off - as though a pre-requisite for heating water has not been satisfied. This may happen many times until eventually the boiler stays on and heats the water correctly. In some cases, it has continually clicked on/off for about 20 minutes (wasting water...) before I've given up.

An engineer has visited before and mentioned that it was due to water pressure coming up from the mains. Water company checked and said that wasn't the case.

The pressure on the boiler (I believe, not next to the unit right now) is normally around 1.5 / 2 bar.

With experience, it seems the lower the flow rate out of the hot tap, the more likely I am to get hot water.

I wonder if anyone has any advice before we have to call an engineer out again.

Cheers,

Chris

Thanks for all the responses so far, they are much appreciated.

I haven't been at the flat all weekend and therefore haven't had chance to look into some of the suggestions made. I'm back there this evening and will look into it then.

Thanks again,

Chris

I have some more details, having just looked at the steps the boiler goes through when trying to heat water.

1. When no hot water is running, the 'Power On' LED is constantly lit green. The pressure guage shows about 1 bar.
2. When a hot tap is turned on, the boiler 'activates'. Not sure exactly what it's doing, but it makes a noise and the pressure guage increases to around 1.5 bar.
3. After a couple of seconds, the burner light comes on and you can hear the burner light up.
4. The burner (and burner light) will then go out, before coming back on a short while later. The time that the burner is on or off seems completely variable.
5. Eventually, the burner will stay on and continue to heat up the water. The time to this point seems completely random (taking 10 mins or more).

Once we have had some hot water (i.e. the burner stayed on for a length of time), subsequent uses results in immediate hot water. Unfortunately, after an unknown period of time the process restarts.

Chris

Answer 1

On the front panel of your boiler there are a number of LED's, when the tap is run the LED above the tap symbol on the boiler should light. This proves the water flow switch is ok. If the boiler cuts off when this LED is lit the problem is not with your mains water pressure. On the other hand if this LED drops in and out the flow switch ( or flow switch diaphragm ) may be faulty.

The other possible problem is with the diverter valve, check the temperature LED's on the boiler control panel when you run a hot tap, if they go up toward 80oC and the water is cold the diverter could be faulty, the fault is usually with the diverter valve actuator. This is very easily replaced, about 10 minutes should do it.

And for my last effort, there could also be a problem with the fan venturi, not much you can do to check it but it can cause the same problem.

Hope that helps but without seeing it it's very difficult to diagnose.

P.S

Your boiler only needs 2.5 l/min from the mains to work so I'd shoot the last gasman that visited.

Answer 2

Potterton Performa 24

Answer 3

Hi Chris,
Most Boilers of this type work at approx 1.0 - 1.5 bar. and the problems may be with your Thermostat, the small rod that the pilot light heats up which in turn keeps the gas flowing?This also turns off the gas if not working correctly by conducting heat to keep the gas valve open.
Water companies (ie Thames Water) will only Guarentee 1 Bar at OSV or stop valve, and they refer to "flow" not pressure. this is sometimes resolved (if it the the flow) by reducing the diameter of the cold water supply near the boiler (from the standard 25 mm Mdpe if its a fairly new property to 15mm (the last 12 ")
If your propertie is older, and has Lead or Iron pipes it may be that they have the internal bores reduced by deposits???
It is something for a heating Engineer to solve really, get a Corgi approved guy in.
Good luck
Paul

Answer 4

Hi Chris, you dont say if you have a manual or not, may be first place to start as the led indicator lights can give you some indication. The ignition is going through its sequence but some thing is holding it off, maybe a flow switch (water or air). Download the manual and post some more info. I think the pressure you refer to is the CH pressure as this is a combi boiler and may be artificially induced to allow water heater to work. The water heater relies on flow not pressure and cutting back the flow will increase the temperature as the water is in the heat exchanger longer
http://www.potterton.co.uk/index2.php
then consumer>literature>performa 24

Answer 5

If you have no CH what about the CH circuit pipework? is there water in there. Maybe the divertor valve or pressure switch is worn out. I dont understand why you have a combi boiler with no CH! Have you tried the reset switch. Is the flue fan running. Does the orange burner light light up?

Answer 6

When you say "burner light clicks on" are you referring to an electronic ignition? if so, it may need cleaning.
There is a probe that periodically needs to be "steel wooled" or sanded with fine sand paper.
If you don't have electronic ignition, disregard.

Answer 7

Have you checked to make sure the circulating pump is working? Does it have one?