Megaflow cylinder temperature and legionella

[fezster]

Looking at the megaflow manual, it shows approximately 7pm on the dial being 60 degrees. I've recently increased the stat a little to make sure this is the case (previously was about 6pm). This has led to two problems:

1) Had to increase the boiler flow temp to 75 or 80 to stop it short cycling when the cylinder is almost up to temp.

2) The water coming out of the taps is VERY hot.

I'd like to have the temperature lower. I can then run my CH temp lower, and get more efficiency, and the water coming out of the taps wont be so dangerous. Do I need to be worried about legionella ? How do most people run their systems ? Having the water so hot seems inappropriate. I wonder, given the megaflow instructions say 7pm is approximate, whether my stat at 7pm represents a temperature higher than 60 degrees.

Ideally, Id be able to control the HW temp separately and use the anti-legionella programme on the vaillant controls (currently using honeywell controls on a standard s-plan), but Im inclined to just lower the stat and get sufficiently hot water without it being scalding. I'd like to hear others opinions on this though.

Thanks.

 

[Agile]

Only a qualified person should work on any unvented cylinder.

An Engineer will measure the temperature!

It should be set to 60 C and the boiler to 10 C higher!

You have increased the temperate and now complain its too hot! Amazing!

Tony

 

[fezster]

Agile, I do appreciate your advice, but sometimes I think you live in a deluded ideal world !

Unless I've been very, VERY unlucky, I've had nothing but incompetency from almost every "heating engineer" that has come out. I've been sensible and always checked they have their G3 ticket. But unless a vaillant / megaflow combination is extremely rare, very few understand what is going on. My installer was good in many ways, but in setting the megflow stat, there was no measurement of temperature. He simply adjusted the dial to about 5pm, and left it. It was only when I told him the water wasnt hot enough, that he increased it to 6pm. And then much later I read the megaflow instruction manual and saw that 60 degrees is roughly 7pm.

Besides, I dont think I need to be "qualified" to adjust my hot water temp. Correct me if Im wrong.

 

[mfarrow]

If you can't read the thermostat, then you need a new thermostat!

The temperature control system by vaillant will use their own temperature sensor; it'll be a lot of expense for not much gain. Have you got a pocket for the sensor?

 

[fezster]

If you can't read the thermostat, then you need a new thermostat!

The temperature control system by vaillant will use their own temperature sensor; it'll be a lot of expense for not much gain. Have you got a pocket for the sensor?

When you say can't read the thermostat, what do you mean ? The Megaflo stat does not have any markings. The manual shows 7pm as being, and i quote, 'approx 60 degrees'.

 

[Agile]

My installer was good in many ways, but in setting the megflow stat, there was no measurement of temperature. He simply adjusted the dial to about 5pm, and left it. It was only when I told him the water wasnt hot enough, that he increased it to 6pm.


Besides, I dont think I need to be "qualified" to adjust my hot water temp. Correct me if Im wrong.

The thermostats in those cylinders are not calibrated precision device. Consequently any complaints of incorrect temperature should include a measure of the actual temperature by a conscientious engineer.

Perhaps you think that engineers should only need to be conscientious in an ideal world. My view is that all engineers should be conscientious and make the required measurements when dealing with cylinder faults and adjustments.

I would interpret the requirements of the legislation to be that only a qualified engineer should be adjusting the preset temperature on the cylinder.

Tony

 

[fezster]

Perhaps you think that engineers should only need to be conscientious in an ideal world. My view is that all engineers should be conscientious and make the required measurements when dealing with cylinder faults and adjustments.

This we can agree on. If only all engineers were as conscientious as you. Or at least some!

 

[gigz]

Have you got a blender valve fitted on the megaflo ?

 

[Steelmasons]

Did the engineer not turn up fezster? , the engineer you were referring to in your other thread , I thought you said he was visiting you today or was it yesterday?

I have a sneaky suspicion that it is you that installed your heating system and boiler. any talk of previous engineers is just a fallacy IMO.

 

[fezster]

Have you got a blender valve fitted on the megaflo ?

I havent. Is it normal to have one fitted ? I was reading about this earlier. Effectively, you'll end up with more hot water by mixing cold with it to get the temperature down.

 

[fezster]

Did the engineer not turn up fezster? , the engineer you were referring to in your other thread , I thought you said he was visiting you today or was it yesterday?

I have a sneaky suspicion that it is you that installed your heating system and boiler. any talk of previous engineers is just a fallacy IMO.

Haha. I've got a day job thanks, but I must admit, I have found learning about heating systems interesting, and if nothing else, I've learned a lot more about how this all works.

Tony had it spot on above:

It should be set to 60 C and the boiler to 10 C higher!

It seems obvious now, but the boiler short cycling as the cylinder reached it's temp was because the boiler stat wasn't set high enough. I've found 75 degrees to be a good compromise. The return temp with just the HW zone open and the cylinder stat turning off is 68 degrees on the boiler. I'm not sure if there's a way of calculating what this means the boiler stat is set to, but I'm guessing it's probably just over 60 degrees.

I'll post an update on the other thread regarding the engineer visit. I'd still like to keep this thread open for other megaflow owners to comment on how they run their boiler and / or if they have their hot water piping hot or not.

 

[Steelmasons]

Once set the megaflo thermostat should not be adjusted as it is not a user friendly device , the stat control is numbered from 1 to 5 which is hidden under a screwed cover , end users "meddling" with temp control stat will in some cases cause "air bubble" to deplete at a rapid rate not forgetting nuisance tripping/TPRV discharge , if you have any questions regarding my comments then obviously a sure sign you should not be "meddling" with something you are not familiar with.

 

[fezster]

Once set the megaflo thermostat should not be adjusted as it is not a user friendly device , the stat control is numbered from 1 to 5 which is hidden under a screwed cover , end users "meddling" with temp control stat will in some cases cause "air bubble" to deplete at a rapid rate not forgetting nuisance tripping/TPRV discharge , if you have any questions regarding my comments then obviously a sure sign you should not be "meddling" with something you are not sure familiar with.

Absolutely. I can at least say I know each of the things you have mentioned above, but even then I'm not inclined to mess about with it. My adjustment consisted of increasing the temp stat from a 6pm position to a 7pm position, as shown in the manual. This was only to ensure the water is heated to the recommended 60 degrees, something I think my installer should have done in the first place. A point of note though - the megaflow I have does not even have a numbered dial. There's literally no markings to indicate what it is set at, except to describe it as a clock position.

 

[Agile]

That's why the qualified heating engineer will be measuring the hot water temperature.

Although you should not be adjusting the setting because you are not qualified, you could measure the HW temp with a thermocouple sensor and meter.

Tony