Boilermate 2000 only heating to 70 degrees C.

Hi, I'm wondering if anyone can offer me any advice. I moved into a house a year ago (house built in 2004) and I have a Boilermate 2000 working with a Potterton Suprima 40L boiler. Ever since I've moved in I've had a minor but rather annoying problem. The Boilermate 2000 only charges up to 70 degrees C. The store reaches 70 degrees C without any problem but then the boiler re-lights about four times during the next 20 minutes before the Boilermate eventually switches the boiler into standby. Its quite annoying that the boiler keeps re-lighting every five minutes but no further increase in temperature is acheived in the Boilermate.

My boiler is set to maximum temperature on the control dial and I've measured the flow pipe just above the boiler with a calibrated temperature probe. The flow is 83 degrees C just seconds before the boiler switches off. At the same time the return pipe into the boiler is 64 degrees C. All three pumps in the boilermate are set to III (full speed) and all sound like they are working fine. Also I have what I think is a manual vent upstairs in my airing cupboard on a loop of pipe which gets hot whenever the boiler is running (even if the heating is off). I've unscrewed the vent and I just get hot clean water coming out.

I have no problems at all with my hot water supply and I have two showers running off the system. They never seem to run out of hot water. Also in the winter the central heating works fine too.

I've just drained a downstairs radiator since I'm decorating and the water was crystal clear with no sludge so I'm not suspecting corrosion or sludge. Any ideas please.......could it even be a problem with the way the system was installed ?

Hi mattalsop,

More questions than answers I'm afraid!

1) How do you know the store temp is at 70 degrees C?

2) Is the boiler still being asked for heat by the Boilermate after it shuts down at 83 degrees C?

3) Which version control board do you have in the boiler? The new(ish) Siemens or one of the multiple previous Potterton boards?

This sounds to me more like a boiler problem than a Boilermate fault. The Seimens Suprima board often develops a subtle fault that the Boielrmate can show up in sharp relief but this set of symptoms actually sounds more like thermistor failure in the boiler to me.

Cheers, Mike

Hi Mike, thanks for your reply. I have measured the thermal store temperature using the same calibrated probe I used to measure the boiler flow and return temperatures. I switched off the Boilermate then carefully removed the store temperature probe from its tube on the Boilermate and measured inside there. I got 69 degrees C using my calibrated probe. That agrees within 1 degree C with the red LED display on the Boilermate 2000 circuit board.

The Potterton Suprima 40L Boiler still has the original Potterton circuit board from 2004. When I moved into the house last summer I had the “lockout” problem where the red light would flash every few days and I would have to press the reset button. I removed the boiler circuit board and re-soldered some diodes (I’m an electronics / electrical engineer) where the solder joints had become hot and cracked. I’ve had no problems since with the boiler. I’ll just describe what the boiler does when heating the store. The boiler lights when the Boilermate store temperature goes down to between about 63C and 67C depending on how much hot water I’m using in the house. The boiler runs for about 10 to 15 minutes and then I can hear what I think is called a “kettle” noise from the boiler. About 2 minutes after that the boiler shuts down and the red light comes on for about 4 seconds with the green light flashing at the same time. I think that means the boiler has reached the temperature set on the dial. My dial is set to maximum and I’ve measured my flow temperature and its 83C. The red light then goes out but the green light continues to flash for a few minutes. The green light then changes from flashing to permanently on and the boiler lights again. This goes on for about 20 minutes with the boiler lighting a few times during that time. The Boilermate then switches off the boiler by cutting the power from the SL wire and the boiler goes into standby. About 3 minutes after that the boiler pump inside the Boilermate 2000 stops.

With a BM2000 the water in the boiler should be very close in temp to the store water. The big difference you are seeing (70 deg/83 deg) suggests poor circulation through the boiler. This is reinforced by the boiler cycling on and off.

I suggest identifying the pump that circulates store water to and from the boiler (left hand one of the three, from memory) and checking it is spinning during demand on the boiler. (Do this by removing the big chrome screw in the centre to expose the motor shaft - catch the slight water dribble in a cloth.) If it is not spinning it may be seized (often can be freed using a screwdriver in the slot in the end of the motor shaft), or it may have not have 240v across its terminals. (Control board failure.) If it IS spinning, make sure the speed it set to III and if temp diff persists I'd be inspecting the pipework for pysical damge or blockage.

Cheers, Mike

Hi Mike,

Thanks for the advice. I have now just measured the supply to the boiler circulation pump and it does measure the full 240v. The pump also sounds like its running fast at a constant speed. I'm pleased you asked me to check the voltage on the pump since I forgot that completely.

I've reached the conclusion that you have suggested that there is poor circulation for reasons unknown. I've inspected as much of the pipework as I can find which isn't much of it. One interesting observation is that I can find no sign of the auto air vents that the BM2000 manual shows should be fitted on both the flow and return lines above the boiler. My installation is with the boiler above the BM2000 but with dipped pipes since the pipes enter the BM2000 from below .(The BM2000 is raised about 6 inches off the concrete floor to allow the pipes to enter from below). I can't see too much of the pipework above the boiler but the pipes have 90 degree elbows about 12 inches above the boiler where they go into the space between the ceiling downstairs and the floor of upstairs. I expected to see the auto air vents but I don't think any are fitted. I have one manual air vent in a cupboard upstairs and its free from air and the water is crystal clear. I'm wondering whether the system has been like this since 2004 when the house was built and that I have a poor installation design. I can't check all of the pipe sizes since most is not accessable. The pipes on the boiler and BM2000 are 22mm but the manual vent upstairs which gets hot when the BM2000 is heating (even with central heating off) is only 15mm pipe. Maybe the pipe on the cicruit is reduced to 15mm somewhere then goes back up to 22mm again further along.

When I moved in I also found my garden tap was plumbed into the BM2000 15mm fill pipe so I'm using water from the small loft header tank when watering the garden !!! Needless the say the flow rate is very slow indeed.

Hi Mike, I just thought I'd report that I've now fixed the problem. The BM2000 was incorrectly installed. There was a 15mm loop of pipe in the airing cupboard and it was connected directly across the boiler flow and return pipes. I've fitted a ball valve and limited to flow to force the water to go through the boiler now instead. The store is now heating to 78C and its happy...........and so am I. Shame I don't know the "professional" who installed the system since they need to be taught to read the instructions !!!!