Has anyone had any success in preventing their boiler from short cycling?

dirtychinchilla

dirtychinchilla

dirtychinchilla

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Woking
I'm trying to get the temperature up in our house. It's only 2.5 years old, so well-insulated and a modern boiler (Vaillant EcoFit Sustain).

It doesn't seem to be able to actually get the house to temperature, and it's quite annoying. We're preparing for our first child's arrival in the next week or so, so I need it to be warm.

I think what's happening is that the output of the boiler is too high, so it sends heat out, the radiators can't give it off in time, and it somehow ends with the boiler short cycling.

I have adjusted the settings to set the output to "Auto" which apparently matches output to system demand, but the temperature in the house has only very slowly been creeping up.

Any ideas?!
 
dirtychinchilla said:
What would you do with it. 2.5 years old
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Ah thought you meant just the boiler not the whole lot. A new build should hold heat really well?

Is it a combi or system boiler/with tank?

I have mine set to a 50 degree flow rate. The rads don't get anywhere near as warm and it takes longer to heat up, but it is basically sipping gas rather than pounding it and cycling.

@danlightbulb is the smartest boiler guy though IIRC.
 
dlockers said:
Ah thought you meant just the boiler not the whole lot. A new build should hold heat really well?

Is it a combi or system boiler/with tank?

I have mine set to a 50 degree flow rate. The rads don't get anywhere near as warm and it takes longer to heat up, but it is basically sipping gas rather than pounding it and cycling.

@danlightbulb is the smartest boiler guy though IIRC.
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Hmm so I have upped it as the house is heating slowly, trying to do manual weather comp.

It’s a combi.
 
dirtychinchilla said:
They're the size that came with the house. It's 2.5 years old so you'd hope they'd be the right size.

TRVs are ****, though.
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That's the reason I ask, my mums got rooms with absolutely tiny single panel radiators, and the rooms just don't get warm.

I put new rads in our home and I overspecc'd to a degree so that the rooms get up to temp with a lower flow temp.
 
Hyburnate said:
That's the reason I ask, my mums got rooms with absolutely tiny single panel radiators, and the rooms just don't get warm.

I put new rads in our home and I overspecc'd to a degree so that the rooms get up to temp with a lower flow temp.
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Ah well I think the TRV's lack of control is more of an issue. I do think the radiator in our living room probably should have been two, and a lot of heat ends up going up the stairs. But the boiler stops pumping heat, so I'm putting it down to how the boiler is working being the issue...
 
dirtychinchilla said:
Hmm so I have upped it as the house is heating slowly, trying to do manual weather comp.

It’s a combi.
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The problem with combis is they can often be massively over specced to cope with hot water demand/showers and can't modulate themselves too well.

Your house shouldn't be cold though?

Edit: I said reduce flow temp FYI - not up it.

dirtychinchilla said:
Ah well I think the TRV's lack of control is more of an issue. I do think the radiator in our living room probably should have been two, and a lot of heat ends up going up the stairs. But the boiler stops pumping heat, so I'm putting it down to how the boiler is working being the issue...
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Your system may be imbalanced then --- try locking off upstairs a touch.

danlightbulb said:
Eh?

If your radiators aren't getting hot you might want to check the trvs and lock valves are open enough?
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I thought you were a heating engineer for some reason.
 
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Boilers turn off if the return temp is too close to flow temp or if the stat tells it to.

If the rads are actually hot (are they very hot or just warm?) then they still should be dissipating heat into the room.

You say you upped the flow temp setting, has this helped or not?
 
Unless I'm completely missing something you have ambient temp and target temp.

Ignoring opentherm etc etc

If it's 16 and you want it to be 21, your boiler is sending heat out at the flow temp until the thermostat hits 21 and then it stops sending heat.

Where is your thermostat? Is it in the coldest room?
 
So according to Google there's lots of reasons a boiler could short cycle.

It might be worth getting someone in to service the system OP.

Thermostat: A malfunctioning or poorly placed thermostat can cause the boiler to react inappropriately.
Pressure: If the boiler's pressure is too high, it can cause short cycling.
Air vents: Poorly functioning air vents can obstruct the release of air.
Steam traps: Malfunctioning steam traps can prevent efficient steam circulation or cause the boiler to overheat or lose its firing rate.
Oversized boiler: If the boiler is too large, it can cause short cycling.
Poor system design: A poor system design can cause short cycling.
Restricted pipe work: Restricted pipe work can cause short cycling.
Pump issues: A malfunctioning pump may not circulate hot water properly, causing the boiler to short cycle.
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Has this only just started to happen, or you've never been able to warm you house?

Is every single radiator piping hot, if you set 65c flow temp form instance?
 
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