Boilermate II.

Hello, i hope you can help me regarding my boilermate II. It does produce hot water on demand but only a small amount, and then starts to run at a lower temperature and then cold after not being able to fill enough for a bath. if i wait 10-15 mins it produces some more, then cold again. and so on. the mixer valve is very hot to touch,and the temp control is turned to winter setting. the gas boiler is turned high... there is quite a bit of sludge in the top tank, which i have tried to scoop out.... got quite a bit out, but not 100%.
the system is covered by a gas contract ( sort of ) and they have said they will fit another mixer valve, but im unsure if this is the problem?? they also said that the system needs a powerflush at a cost of £1000.00..... this is extorsion and wont use british gas for this if its needed.
In the meantime, any ideas??

thank you.

sounds like the oventrop mixer valve is in need of replacement.
1. have you noticed a reduction in actuall water pressure from the hot taps ?
if the answer is NO then DO NOT POWERFLUSH ive been to hundreds the BG have wrongly diagnosed and the highest price ive seen charged was £1,955.98 and still did not cure the problem !!!!!!!!
99.9% says mixer valve .
it has 3 connections
1. left hand side where it exits boiler is very hot.? correct
2 bottom connection cold . correct
3 outlet where hot/cold is mixed through the valve and then exits to your taps.
hope this helps.
mark.
www.gledhill-repair.co.uk

Thank you for your reply, British gas returned to replace the mixer valve which has increased the temperature of the hot water, but it still wont run enough for a bath.....the pressure from the hot taps is fine.... how do you suggest i move forward with this?

regards,
Mark.

they will need to confirm that the boilermate is reaching full temperature via the boiler thermostat and the green led which will confirm that the unit is reaching the temperature that you set the stat too.
hope this helps
mark.
www.gledhill-repair.co.uk

Thanks again for your reply. i have just realised that the valve they replaced is the top l.h valve, with the green cap. To recap then, the water is now very hot from the tap, the pressure is good...... the green light at the bottom is not lit at any time??...... there is hot water, but the quantity is not enough to run a bath... it runs cold.... but after 10/15 mins, runs really hot again.... but then runs cold. i can do this 3 or 4 times to have enough bath water..... i may have caused some confussion previously, sorry.... do you have any further thoughts please, as will then ask B.G. to return to the problem.?

regards,
Mark.

Hi Mark,

On a Boilermate II the hot water service is very simple. A long coil of pipe inside the store of hot water with a blender valve on the outlet to mix in some cold to limit the hot termp to a safe level. The fact that yours delivers very hot water initially tells us the store water is definitely hot. The tap water sitting inside the long coil of pipe when the taps are OFF rises to the same temp as the store water, and this is providing the initial run of hot water you get when you use a hot tap.

The problem you are describing is that as fresh cold mains water entering the coil is passing all the way through the coil and out the other end without picking up enough heat to give you truly hot water at the taps on a continuing basis. This suggests that something is preventing heat energy flowing through the wall of the copper tube coil quickly enough to fully heat the tap water in the short time it is in the coil. You can prove this is the effect limiting hot water performance by trying running a bath with the hot tap running verty slowly, just above a trickle. I predict the hot water will run continuously hot and the cooling effect you describe will disapear and your bath will fill up with hot water.

The reason will be that the (now slow running) water will now be spending more time inside the copper coil and picking up more heat. If I'm right and this happens, the most likely candidate causing the problem is water scale deposited on the inside of the tube. I'd suggest descaling is the next step, if only to rule it out, but I'm almost certain that adequate descaling will fix it.

The only thing that bothers me slightly is you say the green lght never comes ON. This light comes ON when heat is being is being called for from the boiler. If the boiler lights then the green light should be ON. If it isn't then I suspect broken green light bulb, but there is always the possibilty that a previous repair technician has done something stupid to the system and introduced a major fault that is resulting in this hot water problem, although I can't imagine what is might be! One of those things that can only be identified but coming and seeing the Boilermate for real.

Hope that helps.

Cheers, Mike

mike, thank you again for the reply. you are exactly right..... once the flow to the bath is slowed down, the water continues to be hot. i am now preparing to descale as you suggested at the weekend. Any tips i should know about?

thanks again for your help,

best regards,
Mark.