Vaillant ecoTEC plus 428 operation block function

[jjasper]

Hi! My ecoTEC plus 428 boiler fires up and runs for a short period but the radiators don't get very hot. Pressing the "i" key displays diagnostic code S.53 - Appliance is within the waiting period of the operation block due to water shortage (VL-RL spread is too big). I have checked the header tank is working properly and the radiators are not full of air.
What causes the VL-RL spread to be too big and how can it be rectified?

 

[gas4you]

Lack of flow is the main cause. This an all too common problem with these boilers

Your pump should always be set on max speed, usually 3, for this range of boilers.

Also the 428 is a rather large boiler. What size house, no of rads do you have?

Could be it needs range rating down to suit your system.

 

[Biggles..]

Calculate your heating need, 6btu/cubic foot is a rough calc and then range rate your boiler down in D0(D0 gives KW so you'll have to convert btu to KW).

Like dave has said pump should be on 3 but would recommend for an average sized house upgrading pump to a 15-60 minimum.If you need all 28KW then you could be looking at an even bigger pump.

S53 is caused by the massive restrictive load of the heat exchanger on these boilers and the boiler/pump not being able to shift the heat build up quick enough causing a deltat of greater than 20deg to occur between flow and return.

Sealed system and pump on return is normally a good cure.

 

[jjasper]

Thank for the replies! There are 13 radiators in the house but only 8 are used. The pump is a 15-50. As I wasn't using all the radiators I had switched from setting 3 on the pump to setting 2. I hadn't realised that this has probably caused the problem.
I thought these boilers modulated their output to suit the heat requirement. Will reducing the maximum radiator temperature on the boiler reduce the chances of this happening again?

 

[kevindgas]

i would check the setting D.0
press i & + together to get D.0 adjust to 21 using +/- then press i and hold until it for 10 secs
this will set the output to 21 Kw which sound be about right for the 13 rads and a cylinder.

 

[Agile]

Yes but he only has 8 turned on for reasons he does not sharge with us.

I would suggest you turn the heat output down to anout 10 kW that is d0=10.

That should greatly improve the situation and assuming you have already put your pump on "3" then it will probably be cured for good.

Tony

 

[jjasper]

Thanks! At the moment D0 is set to 30. I'll try it at 21 and work down to 10 and see what works best. The reason I only use 8 radiators is that we prefer the bedrooms to be on the cool side. The upstairs landing radiator and heat from downstairs keeps the upstairs at a comfortable temperature. When the kids are back from University they switch theirs' back on.

 

[Agile]

I wonder why you ask for our advice and then dont take it?

 

[jjasper]

I wonder why you ask for our advice and then dont take it?

I don't follow. Kevindgas advised me to set D0 to 21 and you advised 10. I said I would try it at 21 and then work down to your figure of 10 and see what worked best. I don't see how this is not following your advice. When I started D0 was set at 30. It therefore seemed sensible to change to 21 in the first instance and then drop to your figure of 10.
Despite your rebuke, I appreciate you taking the time to assist me.

 

[gas4you]

Tony has a special way of making friends

 

[Biggles..]

Tony uses we and our to generally mean him,like talking about yourself but using the third person.

Because he's always right, he gets offended easily when you dont quite follow his advice.But he's harmless.

Starting at 21 and working down is a long winded way,waiting for the boiler to cool,house to warm etc to ensure boiler modulates and cycles as it should.

Quick guide that'll tak you no more than 5 mins is:

Length of house X width of house X height in ft (bungalow 8ft,2 story 16 etc)

Take this and multiply by 6 (6btu/cubicft)

That is btu for house.

Divde by 3.412 to give KW for house

Ad 3Kw for standard cylinder.

Set DO to this figure for a standard room temp of 20degc.

Oviously if you have glass,walls,no windows etc it wont work out but itll give you a starting point to work up from o achieve the required internal temp.

 

[jjasper]

Thanks Icgs. Using your formula D0 should be set at 22, so at the risk of upsetting Tony, I'll leave it at 21. I prefer to keep the house cool and wear a wooly. I'd have thought that setting it at 10 would have me wearing thermals as well.

 

[Agile]

Kevin suggested 21 kW based on your 13 rads but you had already said you only had 8 turned on.

Recalculating for just 8 rads gives 12.9 which I increased to 14 kW.

When saying "we" I meant Kevin and I !

So my expectation was that you would set it to somewhere between 10 kW and 14 kW for your 8 rads.

But instead you said you had set it to 21 which still seems way over what is required.

I appreciate that many people in this world dont understand the need to size boiler output power to give the most economical operation but 21 kW is about TWICE what is likely to be required.

To assess what power is required you can start your heating and when it has warmed up, time how long the burner is on for and then how long its off for. To increase the accuracy time a few cycles and take the average.

Tony

 

[Biggles..]

Kevin suggested 21 kW based on your 13 rads but you had already said you only had 8 turned on.

Recalculating for just 8 rads gives 12.9 which I increased to 14 kW.

When saying "we" I meant Kevin and I !

So my expectation was that you would set it to somewhere between 10 kW and 14 kW for your 8 rads.

But instead you said you had set it to 21 which still seems way over what is required.

I appreciate that many people in this world dont understand the need to size boiler output power to give the most economical operation but 21 kW is about TWICE what is likely to be required.

To assess what power is required you can start your heating and when it has warmed up, time how long the burner is on for and then how long its off for. To increase the accuracy time a few cycles and take the average.

Tony

What dont you get Tony, the op has carried out a heating engineers rule of thumb calculation and its come back at 22KW to warm his house to an average of 20degC.

Turn it down to what tony wants but you'll find your boiler wont satisfy your demand by constantly firing.

You didnt increase it to 14KW at all,you told him to set D0 to 10Kw.Make up your mind.

 

[Biggles..]

So with your new and improved radiator calculation at 14KW, and seeing as the 400 series are heat only boilers you'd add 3KW for a cylinder making 17KW.

A 7KW increase from your original postings of 10KW being all an average house requires.


Lee