Valliant ecoTEC Plus 428 - Anti Cycling

[heating12numpty12]

This thread sort of follows on from a previous of last week regarding boiler locks on the domestic hot water (which I have now resolved by heating water in the morning for 30mins and again in the afternoon). This time I have established that boiler anti-cycling are occurring on the central heating as well.

The chart attached shows exactly what is happening.

So I have a 1 year old Valliant ecoTEC Plus 428 which once the system has completed a heating burn of say 1 hours duration, the room thermostat then shut off for say 15 minutes, then calls again for heat again, the boiler ignites and completes its purge checks and during this process shuts down due to the boiler temperature being very close to the set Flow Temperature.

These are the system characteristics that I know:
D0 set to 20KW
Pump over run set to 5 minutes
Anti-cycling set to 20 minutes
Flow temp set to 45 C
18 radiators on the system equivalent to 24KW
Yonos Pico 25/1-8 pump running at 40 Watts equivalent to 4.5 m head
House is 15 years old
Floor area 300sqm
Heating bill per year 24000KW
Don’t know the heating loss of the building.
There is a bypass valve that is fitted and is set to 0.3
All other boiler settings as factory set.

I have learnt from the thread of last week that reducing d0 is not going to help, as the boiler completes its purge checks on high power, and d0 does not adjust the power during the purge checking phase.

My limited assessment is that the boiler fires up and gets up to temperature, shuts down and flows the water around the bypass circuit and if this time is only 15 minutes the water is still quite hot, boiler fires up again and the water very quickly gets close to the set flow temperature and then shuts down. You can see from the second burn cycle that once some cooler water from the central heating system has flowed through the boiler it’s a lot cooler and will start up normally.

I have tried to provide all of the information that I can. Any recommendations as to what I should try?

 

[ScottishGasMan]

Either leave it as is. Or you could phone vaillant out to change the PCB, (new PCB has different software to "Reduce" these instances) although Im not sure when that came into effect so you may already actually be running the new software. (might be worth a call to vaillant)

How is your cylinder heating efficiently if your running a flow temp of 45*c?

Also what are you using to take these readings and make charts?

 

[Agile]

In spite of asking three times we still don't know your house heating load.

You seem to have good technical skills so calculating that should be well within your capabilities.

Or you could assess the radiator output from the number and sizes.

Tell us the general style of your house and we can guess the heat loss.

You assume its 20 kW which implies a six bedroom detached with poor insulation!

Why not set "d0" to 12 kW which is typical of a three bed semi over 30 years old?

I would also say reduce the anti cycling to the minimum.

Tony

 

[heating12numpty12]

Either leave it as is. Or you could phone vaillant out to change the PCB, (new PCB has different software to "Reduce" these instances) although Im not sure when that came into effect so you may already actually be running the new software. (might be worth a call to vaillant)

How is your cylinder heating efficiently if your running a flow temp of 45*c?

Also what are you using to take these readings and make charts?

I have to manually increase the flow temperature for the hot water to 60C.

It's a temperature data logger, cheap and very effective:
http://www.ebay.co.uk/itm/RC-4-USB-...16000-Point-/221295330667?hash=item33863ac56b

 

[heating12numpty12]

In spite of asking three times we still don't know your house heating load.

You seem to have good technical skills so calculating that should be well within your capabilities.

Or you could assess the radiator output from the number and sizes.

Tony

Could you let me know a good resource on the internet for the house heating load and I will complete the calculation.

As above 18 radiators giving 24KW.

The house is 15 years old, 5 bedrooms, 300m2, 24000KW pa to heat, at home all day, brick built, concrete floors, 300mm loft insulation, cavity wall insulated.

 

[mogget]

Stelrad STARS is comprehensive but not terribly user friendly.

Otherwise http://www.idhee.org.uk/calculator.html

 

[heating12numpty12]

I completed the simple heat loss calculator and it came out at 20KW.

 

[Dan Robinson]

Any is the heating 45 degrees?

 

[heating12numpty12]

yes heating on the boiler is set to 45C

 

[Dan Robinson]

Why?

 

[heating12numpty12]

I understand that for maximum efficiency I should keep the flow temperature as low as practically possible. 45C gives me a warm up time of 90 mins which is fine.

 

[Agile]

As above 18 radiators giving 24KW.

The house is 15 years old, 5 bedrooms, 300m2, 24000KW pa to heat, at home all day, brick built, concrete floors, 300mm loft insulation, cavity wall insulated.

Well I would expect the heat loss of a modern well insulated house like that to be much lower than 24 kW.

However, you have already demonstrated this with your info.

You say rads rated at 24 kW. But this is with a flow temperature of 70 C however you say you get adequate heating with a flow of 45 C.

That's indicates to me that the actual heat loss is really about 12 kW which is in line with what I expect!

I suggest you reduce the d0 setting to 14 kW ( to allow 2 kW for water heating ).

The heat loss may well increase during periods of significantly lower outside temperatures than the 7 C we probably have at the moment. Then you might need to increase the flow temperature although probably not the d) setting of 14 kW.

Tony

 

[heating12numpty12]

I just wanted to check my understanding of these modern condensing boilers. You run the flow as low as you can such that you condense as much as possible, that way you achieve a better efficiency.

An analogy would be taking a journey in a car, (i) at 80 mph and the other at (ii) at 65 mph, both will get you to the same destination, one slightly longer than the other, but the slower speed would be more fuel efficient. Do I have this right.

 

[Dan Robinson]

that chart is up there which a chocolate kettle....


What's the story between the right side of the pump overrun comment and the left side of the 2nd burn comment?

What is the S code of the boiler.

Have you even tried to change the D.0 to 14 like suggested?

 

[DP]

I suggest you reduce the d0 setting to 14 kW ( to allow 2 kW for water heating ).

Can see 14kw struggling a bit to heat 18 radiators and high recovery cylinder