Vaillant ectotec Cycling Problem

[Broards]

Hello, looking for some help.

I have a Vaillant ecotec 428 fitted in september with a honeywell programmer and honeywell wireless thermostat.

I have issues with the boiler cycling on and off all the time, it does it on the way upto reaching the wireless thermostat termperature and once at temperature it is on and off all the time to maintian its temperature. I'm used to having a traditonal boiler so i'm not familar as to if all the cycling is correct or not but its all the time. Does this sound normal ?

I've started reading about modulation to solve the problem and was considering if vaillants own controllers would solve the problem by allowing the boiler to run at a lower rate for longer periods of time. On looking at the issue i have found a variety of problem with 'over cycling' of this boiler on the web but they seem to relate mainly to a weather compensator which i dont have.

I've had the heating calculations redone and it suggests a requirement of about 20kw and is currently set a 24kw. Water flow time is set at 68.

My original installer tells me all is well but given the things he's got wrong so far i dont really trust what he says. I had my parents engineer out (the one who found a range of errors made by the installer which have mostly now been put right).

I now dont know if condensing boilers do cycle all the time and its correct or if its a boiler issue or a controller issue ? In addition I've had a suggestion of another possible cause of a problem of water flow 'pinching' ? due to a mix of microbore and 15mm pipes.

Anybody able to suggest as i'm now stuck and just dont know where to turn ?

Thanks in advance.

 

[b13kal]

Hi

Look on the manufactures instructions on how the room stat should be working . On a general basis when you set the room temp on the wireless it should reach to the temp and cut off the boiler. Then when it drops from that temp it will cut in again.

You can be abit cleaver and get a timer that when you go out it drops to 18 degrees and maintains that temp until you come back in and when you want the heat it bumps it up to 21 degrees saving to hear the house from 5 degrees on full rate. However it's a very tricky programmer . Does you head in when you get it wrong.

 

[sooey]

It's a well known problem with the 428, if you do a forum search there are many threads discussing it.

 

[petertheplumber12]

Hi

Look on the manufactures instructions on how the room stat should be working . On a general basis when you set the room temp on the wireless it should reach to the temp and cut off the boiler. Then when it drops from that temp it will cut in again.

You can be abit cleaver and get a timer that when you go out it drops to 18 degrees and maintains that temp until you come back in and when you want the heat it bumps it up to 21 degrees saving to hear the house from 5 degrees on full rate. However it's a very tricky programmer . Does you head in when you get it wrong.

Do you see any error codes displayed? have you got a manual? have you looked in the manual?

 

[Agile]

20 kW heat loss is a pretty large house! Can you describe the house and the wall and loft insulation?

Your boiler can only modulate down to about 8 kW and it seems the usual heat loss is less than that so it can only modulate lower by on/off switching.

Can you measure the boiler on and off time durations when the house is up to temperature?

Allso tell us what d40 and d41 show when its firing when up to temperature?

Tony

 

[Broards]

To Sooey -
many of the problems i've seen relate to also having a weather compensator (which i don't have). Not found anything about how to stop it.

Petertheplumber / bi3cal -
no error codes on the boiler or the programmer. I've not taken the thermostat of constant and just move it up and down manually as we go in and out, the thermostat appears to be working fine. I have manuals for all items and all are new.

Agile -
the house is 4 bedroom timber frame house following recent extention. From memory it's about 127msq. Built in 1986 original part has some insulation in the walls and the loft (loft insulation would not meet modern spec i'm sure). New part is full of kingspan insulation as per building regs. Also has a 3 pannel bifold door. Upstairs is warm and radiator thermostatic controls are on 3.

On heat up from cold the boiler runs constantly for a while and then once up to a certain point starts cycling. It goes off for about 2-3 minutes and then runs for about 30 seconds before going off. Looking at the temp on the display it goes off when it gets to 68 and on again when it drops to about 40. It can do this for several hours on its way up to temperature.

Once up to temperature its on for about 1 minute and off for 4-5 mins (cycles about 11-12 times an hour). Temp display does a similar thing as when getting upto temp ie 68 and then drops back down.

I can find the d40 and d41 mentioned in the mannual. Flow dial is set on 68. (Is that enough info with above on this or do i get the d40/41 info from the boiler, sorry not very technical with this stuff).

Re heat loss, i'd be interested in what the correct type of heat loss calculations should be (ie is what the installer's done correct ? / does everybody do the same calc's or are there better / more accurate ones), i've made the installer redo me what he says are the calculation which seem to be based around measuring the room and using some 'wheel calculator' to come up with BTU's. He says total is 46,350 Btu's for the rad's plus a guess of 9000 for the three towel rails (seems a lot to me) and 10,000 for the cylinder. Total 65,350 or 19.14 Kw. I've been assured by him / the builder that all rad's are over what is required but based on the figures he's given me that's incorrect. What concerns me also is the assurance that the boiler is fine as it is 'oversized' the more i read the more i get the impression that this is not a good thing at all. I mentioned about cycling and the boiler and the ability to modulate down and i got a blank luck (this also concerns me).

Thanks for your help so far

 

[petertheplumber12]

d40 & d41 are the flow and return temps, 68deg flow is about right, and looking at heat loss figures they appear to be about right, so there doesn't seem to be anything wrong with the figures, the cycling is often due to the boiler producing more heat than is needed, it is possible to adjust the heat output with the digital control but you would need to get the installer to do that. Any faults are shown as an F0-F78 boiler functions can be observed by pressing the I for information knob. As long as the boiler is producing heat when it should then you can try to ignore the cycling as it is a common occurrence with these boilers and is not a fault in itself.
Also did the installer fill in the bench mark log book? And did he notify the council so that a few weeks later you got a certificate from the council?

 

[sooey]

It's usually S53 that comes up, which means the difference between the flow and return temperatures is too great. Range rating helps but these need a big pump and correct size pipework to get the heat round the system.
One work around if the pipe work is too small is to install a manual bypass between the flow and return cracked open very slightly to allow some flow to trickle through and raise the return temperature a bit.
I'll get shouted at for saying that because it's a bit of a bodge, but there you go.

 

[Agile]

If the boiler can provide adequate heating with only running at 8 kW for one minute in 5-6 minutes then its seriously oversized and thats why its cycling!

For fun turn the d0 down to 10 kW and see what difference that makes once its warmed up.

Tony

 

[Broards]

Thanks all,

Benchmark had to be re done due to errors and I do have the certificate.

when I press 'I' it says 5.30 although I've just re done it and it said 5.7 ?

Do the heat calc's seem right ? I did an Internet search last night and some of the methods I found look more complicated than a simple room measurement ?

The pipes are a mix of either 15mm or 22mm with a big cluster of pipes down the middle of the house then they go off to microbore, I don't know what size that is but it looks small. All the new rads look to have 15mm attached.

Would I be correct in saying then that the boiler is oversized for the requirements ? And the mix of pipes is not helping. What I don't get is if the calcs are right then the boiler should be about the right size.

I don't know which way to turn I've yet to pay the builder the final bill so if things are wrong I have a chance to sort things out. Where is a consumer advised to turn in these situations ? I just want to pay competent trades people a fair days pay for a correct job. I'm now left disappointed and confused as to which way to turn.

All help appreciated.

 

[Agile]

The calculation for your less common construction is quite complicated as there are different heat losses involved.

If I was involved then I would actually measure the heat loss using electric heaters as I would not trust any calcs.

The microbore may be irrelevant if all the rads heat up. You should be measuring the flow and return temps on each rad. Should be about 75/60 in this weather.

Its obvious that it does not need to run at 8 kW constantly even though the weather is cold. So a 28 kW is oversized.

But set d0 to 10 kW as I suggested and see how much time that stays on/off once its up to temperature. That will simulate a 10 kW boiler.

Tony

 

[b13kal]

Isn't this just a case of balancing the rads so that the area where the room stat is gets the heat to control the boiler? These boilers have bypass built in? Try adjusting that too?

 

[Agile]

No, as far as I can understand the house is reaching the temperature and cycling the boiler for just one minute in 5-6 minutes!

 

[b13kal]

And it's not domestic hot water dropping tap or leaks ? (Simple things sometime)

 

[Broards]

From cold the house gets upto 18/19 in about an hour and then starts cycling. I set it to 25 c the other night as a test and from about 20 c it just takes ages to heat up from there, thermostat is asking for heat but the boiler is off for 5 minutes out of 6 so I see why it would take ages. By the end of the evening 5/6 hours later it made it up to 23.5. Which to me seems too long. My retired parents like it warm and they have it at 23 all day in there house and the boiler keeps running until it gets to temp (also a condensing boiler)

Two of the new rads take longer to heat than the others as they are the last on the run and I believe are sharing a feed (not my idea and I didn't find out till later). But once things get going they are all hot (particularly as upstairs heats up very quickly and the thermo rads shut off which I believe then sends all the heat downstairs).

Agile - from your comments I assume am right then that calc's can be done in different ways.

I'll look in the manual tonight and turn the boiler down to see what effect it has.

Thanks all