New Vaillany 428 switched on/off all the time, is it normal

[BingoBongo]

The boiler is 28 kW whereas your bungalow probably needs about 11-13 kW.

The cylinder probably only adsorbs about 5-6 kW.

The boiler power output setting needs to be reduced to about 10 kW. Look in the book to see how to do that.

So many in this business dont know what they are doing and put in seriously oversized boilers and in your nupty's case dont even know how to range rate them!

Tony

the op has 15 rads

the boiler modulates itself

 

[Deleted member 105431]

the 400 needs to be range rated!

press "i" and "+" simultaneously. "d.0" will be displayed, press "i" and a figure will be displayed probabley 28, repeatedly press the "-" until this figure is down to 16 (it will be flashing) then press and hold "i" for 5 seconds until the display stops flashing.

***pump should be on max too***

this will down rate it to 16kw, see how this runs then, in coldest winter this may need increasing again, it would be worth doing a heat loss calc for your house to find the true system requirement.

 

[Deleted member 105431]

...

 

[mickyg]

a figure will be displayed probabley 28

probably 30. Don't know why that is on the 428 but found every one to read 30kw

Anyway, as has been mentioned, 15 rads and a 28kw boiler sounds like overkill to me. High recovery cylinder as has been mentioned will do the trick, just backing up what others have said really. I'm not surprised 4 engineers have specified an oversize boiler without questioning the issue with a low rated cylinder coil, industry is full of idiots.

 

[rickp]

Thanks for all the replies guys, its been a real eye opener.

Rick

 

[Agile]

Rick, I think Tony is missing a bit of essential information when he says the boiler be 'adjusted'. Boiler is, as it stands able to do this down to 5.3kwatts. You need do nothing.

Unusually, I have to disagree with Danny on this occasion. Its true that a new cylinder will improve matters but you can make it far better without any expenditure at all.

I will try to explain but please read slowly and try to understand.

You have several problems:-

Your boiler bangs out 28 kW and within a minute the return pipe is up to temp and turns the boiler OFF.

It stays OFF for the set anticycle time of perhaps 3-4 minutes. It only actually runs to heat the cylinder for just 1 min in 4-5 min! 20% of time?

The flow rate through the heating coil, a 28 mm pipe designed for gravity, is very high and your nupty installer did not add a lockshield valve to set the flow rate and temperature differential to give the most efficient boiler operation.

The situation will be improved if you set the heat output to about 10 kW as the boiler will stay on LONGER thus providing heating for perhaps 3 min in six minutes. 50% of time

To improve matters you need to set the heat output ( d0 ) to 10 kW and perhaps reduce the anticycle time to 1 min although that would not benefit heating operation and defficiency.

YOU can do the settings if you take the time to study the book at NO further cost.

Dont just read all this ( conflicting ) information, start changing the settings and then see what effect that has! You have nothin g to lose and I think you will significantle improve the situation.

There was a recent posting where we showed this lady teacher how to do it and virtually solved the problem with fine tuned settings! Search for that and you may find it interesting reading.

Tony

 

[DP]

Tony, at 10kw heat output, what happens when heating (15 rads) switches on and water is to be heated as well?

You earlier post suggested cylinder coil rated at 6kwatts. That leaves 4kwatts to heat the rads.

I would be pushing for a new cylinder to comply with regs and acceptable boiler operation

 

[rickp]

Thank you to Dangermouse,
I followed instructions and have reset the boiler down to 16kw. Fired it up and I can report not much success, boiler shut off at around 40 seconds. I will try it lowerat around 10k tomorrow morning.

Regarding the lockshield advice from Tony, there is a valve on the system as far as I know that the Heating Eng, turned down at the advice of the Vaillant helpdesk. He said it would slow the flow rate down, this made an immediate effect, but the wrong way, the boiler was shutting off after 5-6 seconds, we tried it several times to make sure it wasn't a fluke.
When we opened up the valve again it was back to its normal cycle 30-60 seconds.

Tony, after the burn it anti-cycles for about 2 minutes.

He did say he could reduce this, I know it would give me a longer period of heat but what is the detrimental effect on economy etc.

Thanks

 

[rickp]

Wife just had a bath and daughter a shower, so no more hot water, thought I would give it a quick try tonight down at 10kw.

Yippee
Worked like a dream, boiler been on now for 10 mins without stopping, is that good.

Water temp on front dial set to 72c

cyclinder stat to 55c

excellent work lads.

Rick

 

[Deleted member 105431]

set "d.1" to 8 using the same procedure as before and this will help reduce the boiler cycling. 10kw won't be enough when you put the heating on in winter. I'd seriously question the "engineer" who chose this vastly oversized boiler and doesn't even understand how it works. . . . .

 

[rickp]

thanks again,

I am going to change the cylinder in the next few weeks for a faster heat up model as this old one is obviously got limitations and I am not going to get the best out of my new boiler but thanks to you blokes I am getting the best out of my current setup.

At least I get a tank full of hot water now in about 45mins than the 3 hours I was experiencing before due to all the shutting down.

4 engineers recommended this boiler model and size, in the end as a "no nothing much householder" you take there advice. And when 4 people in the trade give you the same advice you tend to think its good advice. These guys are all very busy in my area and well known. I had to pester 2 of them for the estimate once they had been to look and they gave me dates to fit well into the future.

Maybe they are all too busy to do the calcs, I just dont know.

Thanks again to all.

Rick

 

[rickp]

Dangermouse, the current D1 setting on boiler is 5, I have looked in the book and that is minutes, setting to 8 means its on for longer. Is that good.


I have just reset the D0 to 11 and it seems fine with that, the tank just about keeps up.

Rick

 

[Agile]

Wife just had a bath and daughter a shower, so no more hot water, thought I would give it a quick try tonight down at 10kw.

Yippee

Worked like a dream, boiler been on now for 10 mins without stopping, is that good.

Rick

Wow...

That took me a lot of continued persuasion to get you to do that!

Unusually, with some opposition from some of the regulars on here!

Now that you have proved my point you can play with the settings and see what works best.

Leave the anticycle at 2 min. Even if the boiler goes off after 10-15 minutes thats quite normal and you have still got it providing heat for most of the time.

I am glad I have got it right for you!

Now you can check the reheat performance and see if about £400 for a new cylinder is justified. It would certainly reduce the reheat time but may not really be necessary. Thats your choice.

Tony

 

[rickp]

Tony, Thanks for the encouragement. I feel as though I know a lot more about the boiler and its capabilities. I will monitor how things go over the next few weeks and see if the new cylinder is required.

It is staying on now for about 15 mins before doing its first recycle which is getting the water to a good initial temp.

It was a total nightmare before.

I have tried to discribe the procedure to the missus. As I was getting plenty of grief, not sure why as it wasn't me who installed the bloody thing!

I put it in these terms and she is up to speed. When you are boiling spuds, after a few mins on maximum heat, the spuds start to boil over, so you turn it down to simmer and they cook through nicely. Imagine not being able to turn them down, just off.
Then when they go off the boil, you wait for 2 mins to cool before wacking it back on full again. Repeat this over and over and over again until they cook. Result = ages. That was what was happening to the old setup. Full power, then off, full power then off.

Now thanks to you guys the boiler is matching the cylinder much like the simmering spuds, enough heat to cook quickly without going over the top,

Brilliant and thanks again.

All heating engineers SHOULD know this sort of stuff.
Rick

 

[Agile]

Tony, Thanks for the encouragement.

Now thanks to you guys the boiler is matching the cylinder much like the simmering spuds, enough heat to cook quickly without going over the top,

Brilliant and thanks again.

All heating engineers SHOULD know this sort of stuff.

Rick

Actually its only the Mouse and I to be thanked !

The others all wanted you to replace the cylinder.

You may decide to replace it anyway some time but as you have realised its not at all bad when the system is adjusted properly.

Next tip:

When you start using the heating, set the hot water in the mornings to come on 30 minutes BEFORE the heating so the boiler can ensure the cylinder is hot.

Tony