Boiler frequent cycling with underfloor heating - Common problem??

[Onoff]

On 05/01/2020 at 18:50, Temp said:

Short cycling reduces efficiency, a bit like stop start driving a car. Its worse for an oil boiler than a gas boiler.

 

My oil boiler short cycles like a mad thing.  Really noticeable now it's gotten super cold weather wise. Presumably this is due to all the rapid heat loss points through the fabric. 

[Gus Potter]

Hi Onoff.

 

Don't knock the oil boiler too much, had one of those when living in country. It did the UF heating over two storeys each with timber suspended floors. For all, is your boiler is going Off for a little bit then coming back On for a while, or is it really short cycling.. Onoff...Onoff..and again Onoff? If off for a little bit and on for a long time then as Onoff says this may be because the house is a bit drafty.

 

The great thing about an old oil burner is that it's (reputably) quite easy to get a handle on how it works. For me I thought I did but maybe I was just living in ignorant bliss. From memory it has a thermostat that detects when the water in the box surrounding the burner cools below a certain point. It struck me when I first open it up that it was basically the same as a wood burning stove that also heats the water but instead of putting wood in it you just shoved a blow lamp into the front where the door should normally go on a stove.

 

 

That stat triggers the burner to come on.

 

Once the water gets to a certain temperature the stat turns the burner off. Maybe you can add a pipe stat in series so that you can allow the temperature of the return water to drop more before the burner triggers ( thus over riding the internal boiler stat range), but not too much as often they are linked to the hot water cylinder. It occured to me that if  you set the return temperature to the boiler too low then you could start sucking the heat out the hot water tank, in other words the coil in the tank might start to work in reverse? I'm not sure if this concept works yet.

 

Also, another past reason (it's hearsay) for not knocking the oil boiler is that in the bad snow and when the garages are shut you could top up a Bedford van with a bit of kerosene in an emergency. I think that those days are in the past... but it can make for a good story?

 

 

[Temp]

On 05/11/2020 at 20:13, Onoff said:

 

My oil boiler short cycles like a mad thing.  Really noticeable now it's gotten super cold weather wise. Presumably this is due to all the rapid heat loss points through the fabric. 

 

Problem is boilers can cycle for different reasons. Its unlikely to be due to the weather. Its usually because the boiler is too powerful for the load. For example when just one (or two) UFH loop is calling for heat. That can happen when the house is upto temperature. 

 

[Onoff]

2 minutes ago, Temp said:

That can happen when the house is upto temperature.

 

Should that ever happen I'll let you know!

[Fly100]

On 05/11/2020 at 21:04, Gus Potter said:

Hi Onoff.

 

Don't knock the oil boiler too much, had one of those when living in country. It did the UF heating over two storeys each with timber suspended floors. For all, is your boiler is going Off for a little bit then coming back On for a while, or is it really short cycling.. Onoff...Onoff..and again Onoff? If off for a little bit and on for a long time then as Onoff says this may be because the house is a bit drafty.

 

The great thing about an old oil burner is that it's (reputably) quite easy to get a handle on how it works. For me I thought I did but maybe I was just living in ignorant bliss. From memory it has a thermostat that detects when the water in the box surrounding the burner cools below a certain point. It struck me when I first open it up that it was basically the same as a wood burning stove that also heats the water but instead of putting wood in it you just shoved a blow lamp into the front where the door should normally go on a stove.

 

 

That stat triggers the burner to come on.

 

Once the water gets to a certain temperature the stat turns the burner off. Maybe you can add a pipe stat in series so that you can allow the temperature of the return water to drop more before the burner triggers ( thus over riding the internal boiler stat range), but not too much as often they are linked to the hot water cylinder. It occured to me that if  you set the return temperature to the boiler too low then you could start sucking the heat out the hot water tank, in other words the coil in the tank might start to work in reverse? I'm not sure if this concept works yet.

 

Also, another past reason (it's hearsay) for not knocking the oil boiler is that in the bad snow and when the garages are shut you could top up a Bedford van with a bit of kerosene in an emergency. I think that those days are in the past... but it can make for a good story?

 

 

 

 

if you look back to page 1 that's what my box does. Basically it has a Temp sensor on the flow pipe 150mm from the boiler. Its currently set as a thermostat. The boiler runs and at 60C it stops running. Latent heat takes it upto to 63C, the pump continues to run. When the flow drops to 47C the boiler fires back up to 60C. Its reduced my boiler cycles to about 4 or 5 an hour.  

 

FLY