Vaillant EcoTec Exclusive 838 13 rads

[mickyg]

This boiler should work absolutely fine at factory settings. It doesn't need any adjustment. If it doesn't work properly call your installer to investigate, as either the boiler is faulty or there's a problem with the system. I would strongly suggest resetting to factory settings.

 

[spudkey]

What type of controls are you using if you have a vrc 430 or 400 maybe the compensation slope is not set correctly

 

[D_Hailsham]

after a quick tally up, make that appox 30 kw +/- a Kw

You have forgotten that they are only 52cm high rads.

From the Myson catalogue, if the doubles are type 21 (one set of fins) then it adds up to 19.2kW and if the doubles are type 22 (two sets of fins) it adds up to 24.2kW

Incidentally, a 1000mm long, 600mm high Myson rads single (type 11) only produces 894 watts. The type 21 produces 1286 watts and the type 22 produces 1634 watts, so assuming a double rad produces twice the output of a single will produce wildly exaggerated figures. The same is true for Stelrad radiators.

 

[D_Hailsham]

In an earlier topic the OP said that he was aiming for a flow temp of 70°C. If that is the case and the return temp is 50°C, then the rads will only be producing about 73% of their nominal output.

 

[Agile]

In an earlier topic the OP said that he was aiming for a flow temp of 70°C. If that is the case and the return temp is 50°C, then the rads will only be producing about 73% of their nominal output.

Are current rad outputs not usually quoted for that flow temperature?

Tony

 

[gas4you]

I would say set the over run ( d1 ) to three minutes as that will reduce the problem which you currently have although correcting the bypass should solve that

The worst advice you could give a Vaillant owner

You obviously don't know Vaillants Tony

 

[Agile]

I seem to go to repair quite a few!

One today and one yesterday for example.

Tony

 

[D_Hailsham]

In an earlier topic the OP said that he was aiming for a flow temp of 70°C. If that is the case and the return temp is 50°C, then the rads will only be producing about 73% of their nominal output.

Are current rad outputs not usually quoted for that flow temperature?

No. They are quoted for a flow temp of 75°C, return temp of 65°C and room temp of 20°C. The mean radiator temp is be 70°C.

If the rad is run with a 20°C differential then the output will reduce to 85% of nominal output for 75°C/55°C and to 73% of nominal output if 70°C/50°C.

 

[mickyg]

all this argument is completely off topic and unhelpful to the OP.

 

[D_Hailsham]

all this argument is completely off topic and unhelpful to the OP.

However even on the default of 27KW when I have the pump on auto and bypass at default of 250mb it takes ages to get the rads hot and the system struggles to get the house to 21 degrees even after being on for 5 hours. Even with the bypass at 350mb it does not make much difference. If I put the pump at 100% it can heat the house to 21 degrees just. However, on auto the heating seems to keep cutting off to over run so never seems to be on long enough to get to the target 21 degree room temperature.

The OP's problem is nothing to do with the setting of the various parameters; his problem is that the house is not heating up properly. This can be due to two main factors: too small a boiler; insufficient radiator capacity.
It's unlikely that the boiler is too small as it produces 27kW. The rads are a nominal 19-24kW of rads, which may be producing only 13-18kW of heat. We don't know how big the OP's house is so we can only speculate whether that is sufficient.

The OP needs to use an on-line calculator, such as the Boiler Sizing Wizard to get a better estimate of his heating requirement. (I know the wizard assumes a HW cylinder, but an extra 2kW of heating is not too important).

 

[kevplumb]

you on commision for quoting that poxy program

 

[Agile]

The OP's problem is nothing to do with the setting of the various parameters; his problem is that the house is not heating up properly. This can be due to two main factors: too small a boiler; insufficient radiator capacity.

I agree that his problem is insufficient heat.

The rads might be undersized.

However, he has already stated the boiler cuts off and stays on a 5 min over run.

I suggested setting the over run back to three min but Dave disagreed. I still take the view it would help as in my view would setting the heat to about 20 kW.

Of course there is a combination of factors and without considerable further investigation which is most relevant is not known yet.

Dave's disagreement was, I suspect, specificically in relation to over run at end of heating cycle and not actually in relation to anti cycle delay which the boiler calculates differently.

So we dont know but I think those two changes would assist but there does sound like a problem with rad output.

I have seen customers who complain about too little heat but have placed thick curtains in front of their rads!

Tony

 

[D_Hailsham]

you on commission for quoting that poxy program

No, but I wish I was

I have compared the results from all the detailed heat loss programs, including the SAP ones and compared them to the result given by the Boiler Wizard and they all agree within a few percentage points. As the Boiler Wizard is now the recommended method for sizing a boiler and is easy for most people to use, I recommend it where necessary.

I know there are some "old school" die-hards who size a boiler based on "experience" or the total length of radiators in the house or some other arcane method they learnt 40 or more years ago, but the evidence shows that these methods will tend to oversize the boiler, which is not acceptable with the reduction of global warming a priority.

 

[mickyg]

doctorflip. are the rads new or old? did you have this problem with the old boiler?

 

[Agile]

I was in the local merchants with Dan Robinson and this fellow came in asked for a radiator to heat a room 5m x 4m or whatever.

Surprisingly that did not phase Ian the counter hand who wipped out a Mears calculator and started to enter some figures.

Dan wipped out his pocket computer and started entering some figures in his sizing program.

I wipped out a fag packet and started to think about it and then wrote down my figure. Dan produced his and Ian gave his.

If we say Dan's was right, mine was about 10% higher and the Mears about 14% higher.

What did surprise me was just how close the three methods ended up being!

Tony