Anti-cycle software & Greenstar 24-28 i Junior Combi

[ericmark]

Simple question does the Greenstar 24-28 i Junior Combi have anti-cycle software, if answer is simply no, and it just retries after a fixed time then there is nothing I need to do.

However if it does have anti-cycle software then I am worried that the way it has been installed may defeat the software.

My engineering back ground tells me there are two ways to detect if all TRV's are closed so the boiler is no longer required to run.
1) Return water temperature.
2) Differential water pressure.

Once all TRV's are satisfied with an all TRV system the return water will be forced through the by-pass valve and will return hot. Either monitoring the lifting of by-pass valve or water temperature can tell boiler to turn off. With anti-cycle software that off time should vary, if on restart the boiler turns off again within a set delay time then the off time is increased, and if not it is decreased, so as summer arrives the boiler has longer and longer between re-tries. That is what I consider as anti-cycle software.

However on my mothers system we had two things which may defeat this from working, one is three towel rails without TRV's the other is there is an external by-pass valve as well as the one built into the boiler.

The boiler in Autumn and Spring does not seem to alter as far as off time goes, so if there is anti-cycle software it would seem it's not working. However until I know how the software works, trying to get it working is rather hit and miss.

So can anyone either tell me there is no anti-cycle software, or if there is, what does it monitor?

 

[DP]

Regardless of anticycle or bypass bring fitted or not, there should be a room thermostat that switches the boiler off when room at desired temperature.

Modern boilers have modulating burners that adjust to maintain set boiler temperature. Overshoot results in burner going out but pump keeps running (hence need to have circuit available to allow pumped water to circulate). Predetermined time later burner fires.

If there is no room thermostat, boiler does this for duration the timer is on. If thermostat fitted, boiler goes out when room reaches thermostat setting.

 

[Hot&Cold]

Ask the experts at https://www.worcester-bosch.co.uk/support/send-enquiry

 

[bernardgreen]

What is anti-cycling software going to acheive ?

If the heating load is less than the minimum output from the boiler then there is no option but to turn the boiler on and off in a ratio that provides the required heating load as an average output over time. Many short periods of burn starts will provide less fluctuating temperatures in the home but will increase the wear and tear on the boiler due to the number of time the boiler has to purge and then a few minutes later re-start. A few prolonged burns will give less wear and tear on the boiler but temperatures in the home may be more variable.

But what the heck, a 48Kw combi sized for the hot water supply to small well insulated home is the best option for the installer who will not be living in the house [/sarcasm]

 

[ericmark]

Regardless of anticycle or bypass bring fitted or not, there should be a room thermostat that switches the boiler off when room at desired temperature.

Modern boilers have modulating burners that adjust to maintain set boiler temperature. Overshoot results in burner going out but pump keeps running (hence need to have circuit available to allow pumped water to circulate). Predetermined time later burner fires.

If there is no room thermostat, boiler does this for duration the timer is on. If thermostat fitted, boiler goes out when room reaches thermostat setting.

Thank you, I in fact do have a thermostat in the hall, however I was lead to understand that is no longer required or a good idea, I thought with a modern system the eTRV talks to a hub and if any eTRV calls for heat boiler is powered and if not then boiler is switched off by the hub rather than thermostat on the wall.

The whole idea is the wall thermostat is last resort, it switches off boiler in summer, but in the winter it should never operate, the TRV controls the room temperature by gradually opening and closing so there is very little hysteresis, and the boiler adjusts flame height to match return water temperature so giving a seamless control. As the weather improves it will reach a point where the thermostat finally gets warm enough, this point depends on both setting on thermostat and lock-shield valves, the latter should be set to only allow the thermostat room to get warm enough after all other rooms are satisfied. As to which happens first, the boiler starting to cycle or the thermostat turn off is a little hit and miss.

 

[ericmark]

What is anti-cycling software going to acheive ?

If the heating load is less than the minimum output from the boiler then there is no option but to turn the boiler on and off in a ratio that provides the required heating load as an average output over time. Many short periods of burn starts will provide less fluctuating temperatures in the home but will increase the wear and tear on the boiler due to the number of time the boiler has to purge and then a few minutes later re-start. A few prolonged burns will give less wear and tear on the boiler but temperatures in the home may be more variable.

But what the heck, a 48Kw combi sized for the hot water supply to small well insulated home is the best option for the installer who will not be living in the house [/sarcasm]

Yes anti-cycle software reduces wear and tear on the boiler, that's what it is there for. My son says mothers boiler is too small, however it has never failed to keep the house to temperature set, so to my mine it has proved to be big enough. It would be nice to see a output, to know if flat out, or running with loads of spare capacity, when we get a smart meter then we will I assume know, but as it stands I don't, putting a clamp on ammeter over gas pipe simply does not work.

 

[DP]

How can 24kw boiler be too small for a house, unless it is a BIG house
ETRVs is a recent thing
It is the flow sensor that controls the flame size
Lockshields are there for balance, nothing else
Thermostat on the wall is there for switching the system depending on ambient temperatures, winter or summer. There are days in winter, could be negative figure temperature outside, inside due to good sunlight temperature could easily be higher than thermostat set point
A boiler can only modulate to minimum boiler power which could well be just below double figures. At this point if a rad or two were still calling for heat, boiler will cycle
A south facing room will heat up quicker, so a TRV will be beneficial; a north facing room will tend to be colder- TRV there may or may not be effective as it may well be set at max to get that room to good temperature

 

[DP]

putting a clamp on ammeter over gas pipe simply does not work.

Can you explain how that works?

 

[bernardgreen]

putting a clamp on ammeter over gas pipe simply does not work.

Can you explain how that works?

It does not work as a means to measure how much gas is being used by the boiler.

so a TRV outdoor be beneficial;

beneficial for what ?

 

[AGAS]

ffs

 

[DP]

Bernard, error corrected now. I would have thought you being a problem solver, you would have deduced what I was getting at

 

[ericmark]

I am reading the post by DP a few times, the flow sensor controlling flame size is a surprise, I thought the idea was to keep return water cool enough to condense any moisture in the flue gases, monitoring flow would not ensure return water is cool enough, could you explain?

Lock shield being there for balance, makes some sense, what words you would use to scribe it not sure, I considered it was so before any rooms get to temperature every room has a share of the heat, once rooms reach temperature the TRV takes over control, if the lock shield is left wide open rooms will heat in order of how easy it is for the fluid to flow, so near boiler heats first, however once house is warm it actually works better when they are wide open, it is only during warm up when it matters. This I found with my sons first house, with all TRV's wide open hot water was returned to boiler while it waited for first room to heat up and so the TRV would take over, and it was found the flame height went down and so took ages to heat from cold, however once warm it worked A1.

I would agree the thermostat on the wall needs to switch when the ambient temperature hits the temperature where you don't want the central heating this means it needs to be in a room which is normally not kept too hot, this has been a problem, should not be installed up-stairs and so we look at rooms down-stairs, now kitchen, living room, wet room, and front room all have alternative heating, so there is really only the hall left, however the hall has a door to outside, so it has a large radiator to re-heat the room after door has been opened and to dry coats, which is left with the lock shield valve more then just cracked will turn off boiler before other rooms are warm.

I also see point about sun, I find living room gets it in morning and front room in evening which was why I first started to look at the how to control rooms independently.

TRV outdoors that does not make sense to me, could understand a thermostat outside but not a TRV.

 

[bernardgreen]

I would have thought you being a problem solver, you would have deduced what I was getting at

It is the weak end. ( or week end ) hence the brain is on turn down, no cycling allowed.

 

[DP]

Lock shield being there for balance, makes some sense, what words you would use to scribe it not sure, I considered it was so before any rooms get to temperature every room has a share of the heat, once rooms reach temperature the TRV takes over control, if the lock shield is left wide open rooms will heat in order of how easy it is for the fluid to flow, so near boiler heats first, however once house is warm it actually works better when they are wide open, it is only during warm up when it matters. This I found with my sons first house, with all TRV's wide open hot water was returned to boiler while it waited for first room to heat up and so the TRV would take over, and it was found the flame height went down and so took ages to heat from cold, however once warm it worked A1.

A system set up properly will allow ALL rads to heat up evenly..TRVs shut the rads down as room reaches temperature. Sun belting in through the windows will provide additional heat so TRV shuts down earlier room having attained desired room temperature
If the nearest rad takes bulk of the water as you suggested (it will unless excessive flow through it is limited), far more than what it needs to take, no need to fit lockshield valve, let the rads heat up sequentially. Function of the lockshield valve is to set temerature drop across the rad and TRV to stop circulation through it when set temerature reached
A radiator requires a quantity of water per hour dependent on the the radiator size. Give it more water, it could to detriment of further away rads. This is the case for towel rails which often show little temperature difference between flow and return. It is not uncommon to crack the lockshield open by about quarter to a third turn, perhaps half at a push

Outdoor TRV. Read post again, now corrected, not autocorrected

 

[DP]

While I cannot categorically say every boiler works this way, at least one boiler ( I recall) looks at the temperature differential between the inlet and the outlet of the heat exchanger. Too great a temperature differential, boiler will shut down indicating lack of flow. Almost every boiler I have worked on (again cannot vouch for all boilers), the heated water out of heat exchanger is what controls the burner. I am sure I will be corrected if I am wrong
If as you suspected, return sensor were to modulate burner, setting boiler thermostat to maximum and say rads were at 20 degree temperature drop, you could have plus 100 degree of primary flow.
Return water, cooler it is the better the heat gain through condensing technology