ecoTEC Plus 428 - anti-cycling blips

[heating12numpty12]

I would appreciate some feedback on my boiler performance (ecoTEC Plus 428). I have noticed that during the hot water heating cycle the boiler goes into anti-cycling mode and then about 15 minutes later fires up for about a minute and then shuts down. Now I believe this to be as a result of the differential between the Flow and Return being too small when the boiler fires-up (approx full power). Please see the boiler Flow Temperature chart below.

From my reading I understand that the boiler cycles should be kept as low as possible to prolong the life of the boiler and this Blip is unnecessary.

In case this helps the d1 setting has been reduced to 20kw and the pump is a new Yonos Pico 25/1-8 running at around 40 watts.

I would appreciate any thoughts as to whether this is normal, and if not, what my course of action should be.

Thank you for your help

 

[ScottishGasMan]

What's the coil rating of your cylinder?

 

[ScottishGasMan]

Also what's the pump set at? Think they ones come factory set at 2 or 3m heads

 

[heating12numpty12]

How do I find the coil rating of the cylinder?

The pumps at 40 watts which I believe is around a 3.5 m head.

 

[ScottishGasMan]

The pump might be enough at that, the 428 requires about 2.5m just to push the water round it's own heat exchanger, so as a test I would consider trying the pump at say 5meters head to see the difference.

Cylinder normally has label on it with the coil rating, if not post up a clear pic of the cylinder till we get an idea what type it might be

 

[fezster]

One thing I learned is to make sure your boiler temperature is set higher than your cylinder stat, else the stat will never be satisfied and hence the boiler will continually cycle, unable to reach the final required temperature the cylinder requires.

 

[Agile]

As often happens we have a situation described with absolutely no information on the cylinder or much on the boiler output setting.

What is the heat loss calculated on the house?

What is the maximum absorption of the cylinder coil?

What flow temperature is the boiler set to?

What is the anticycle delay set to?

Tony

 

[heating12numpty12]

What's the coil rating of your cylinder?

I just checked the cylinder, and there is a dark patch where the label use to be, but it's not there any more.

So the best I can do is provide the physical size of the cylinder which is 1.5 m high and 0.5 m in diameter, these dimension include the insulation and the cylinder is some 15 years old.

Does this help.

 

[heating12numpty12]

As often happens we have a situation described with absolutely no information on the cylinder or much on the boiler output setting.

What is the heat loss calculated on the house?

What is the maximum absorption of the cylinder coil?

What flow temperature is the boiler set to?

What is the anticycle delay set to?

Tony

So I do not have all the answers to your questions, but this is what I do have.

The flow temperature for the hot water is typically around 55c, but the graph provided shows I tested at 2 different temperatures 55 and 60c.

The anticycle delay, is as factory set for the boiler, and as I understands varies with the temperature that the flow is set to.

The absorption of the cylinder coil I was unable to find the manufacturers label, but have quoted above the physical size.

 

[ScottishGasMan]

Is it the green insulation?

The chances are at that age its not a high recovery cylinder. which means the coil in it will probably have a maximum heat transfer rate about 3 or 4kw. your boiler ignites around 19kw, and its minimum power output around the 6KW mark. Which means it can not modulate as low as that cylinder thus there is nothing you can do to stop cycling.

I run a 24kw boiler on a cylinder with a 22kw coil rating. from cold it will burn constant for about 15minutes before modulating down, then it will run another 5 min or so on low before cyling maybe atwice before the cylinder is reheated.

To put it in perspective. Your using a boiler approx 116% the power of mine on a cylinder that can handle 16% of what my one can.

Cycling is inevitable on a perfect system, so on your it will happen a lot on the hot water (if that is a standard cylinder which it is likley to be)

 

[heating12numpty12]

Is it the green insulation?

Yes its a light green foam covering.

 

[heating12numpty12]

Cycling is inevitable on a perfect system, so on your it will happen a lot on the hot water (if that is a standard cylinder which it is likley to be)

So on the basis that the boiler produces 6Kw minimum and the cylinder is 4Kw (I did some research on my cylinder and yes its likely to by about 4Kw). Once the system get close to its final temperature anti-cycling will be inevitable.

Thank you all for helping my understanding.

 

[ScottishGasMan]

No problem at all, glad it makes sence. One other thing touched on earlyer in the post was about the temperature you run the boiler at.

4kw will be the rating of the cylinder coil when the cylinder is full of cold water and the flow temp to the cylinder is set at 80*c, which is when maximum heat transfer can happen, the closer the cylinder temperature gets to the temp of the coil the slower it will exchange the heat (again more cycling)

If it does takes ages then turn up the flow temperature of the boiler, but be aware this will also increase the flow temp to the radiators which you may not want.

Cycling is a small part of a big picture, its better to cycle less, but realistically any boiler is sized to max load, so for the likes of your heating, it should be sized with the radiators to heat your house with an outside temperature of -1*c or -3*c typically, most of the heating season in this country the outside temp will be somewhere between 5 and 10 degrees, so in a house specd for 20kw heat loss, a 20kw boiler could be fitted, but most of the time far less than that will be required to heat the house, add in to this thermostatic radiator valves and at different times of the day only one or even no radiators could be letting flow through.

When specing a boiler and system it is good to size things to reduce cycling where possible, but realistically it can not be stopped all together and much less likley when a boiler has been retrofitted to an existing system.

 

[heating12numpty12]

so in a house specd for 20kw heat loss, a 20kw boiler could be fitted, but most of the time far less than that will be required to heat the house, add in to this thermostatic radiator valves and at different times of the day only one or even no radiators could be letting flow through.
.

So running the heating system on thermostatic radiator valves, once the house is to temperature, is going to cause even more anti-cycling sessions. That's interesting, so I should now check what happens to the heating system in terms of anti-cycling.

 

[vulcancontinental]

But SGM now houses are being built with a heat loss less than 8KW and you have a cylinder rated at 22KW. Do you size for the cylinder? Not really. Even older 30's houses are becoming better insulated now to less than 10KW max heat requirement.

Better controls, or should I say more controls, mean greater range of heat load. What will become important, if not already, is the range of modulation. It's not the laughable 'save 40% with X y or Z improvement', it's as you say a package but all improvements are relatively small and the sum total not huge from a decent system to a 'cutting edge' system.