How often does your underfloor come on?

[Fly100]

Interested to know how often your heating come on for the underfloor. I have an odd problem that Im not sure is a problem. Mine only fires once a day, call it a Charge up if you will. Its set to bring the ground floor of the house to 20c by about 7:30am. While I understand its not that cold yet mine is only coming on once a every 24hrs. My issue is that each time it comes on its a 'fresh start' from cold. 

The house is a new self build and the floors are 150mm in Kingspan then pipes and a 70mm screed and pretty well insulated with a large amount of glass. Each fresh start results in a boiler run time of approx 90-120 min using apporox 6 litres of Oil.

 

How often does you boiler fire ?

 

Thanks,

FLY

[PeterW]

So it doesn’t matter how long it runs for, you will use the same amount of oil as it is purely balancing the heat lost with the heat required. 
 

As you’re on oil, when the slab heats is irrelevant as the cost is the same. If you were on E7 or something like that then time of heat and time to heat is key. 
 

I’ve got E7 set to run overnight and tbh the boost in the evening hasn’t kicked in yet but that’s with a set temp of 20.5c. 

[DOIGAN]

Hi,

 

I have a similar issue, although my system is air to water. I know that underfloor heating should be treated like a giant storage heater but mine never seems to be at the right temperature for when I need it. Won't come on during the day as the ambient temperature is higher than the floor heating, but when that temperature drops and I want heating it takes too long to raise the room temperature, finding it very frustrating and lie you feel that I am wasting energy heating the slab when I don't want to. Starting to feel that underfloor heating is not as great as some make out.

[PeterW]

A lot of the issues are down to usage and knowing when to programme. @DOIGAN if you set the programmer the second time in the day for a degree higher then using the thermostat it will trigger the heat pump to run but be adding heat as the stored heat in the slab tails off to ambient. 

[Declan52]

You need to think of it as a completely different method than using rads. You can't just click the heating on and bang 20 mins later you can feel warmth in the room. Depending on how thick your slab is and the amount of insulation under it you could easily be waiting 2 hrs for any heat to come through. But the slab will then stay warm for much longer after the heating is turned off compared to a rad. 

I basically have 2 set programmes in my boiler, an autumn spring setting and a winter one. The autumn spring one comes on about 6am and the boiler runs for 3 hrs. The first 2 hrs is to heat any zone of my ufh that is calling for heat. The next 30 mins the rads upstairs in the kids rooms get a 20 mins blast and then the last 30 mins is used to charge the tank back up for showers etc during the day.

The winter setting will do the same run in the morning but also come on around 7 for 90 mins. If it's really cold and any zone needs heat it gets it and the rads upstairs get a 20min blast as well. 

With the way our climate is there are days in autumn spring where it gets really cold in the evening and you have to manually start the boiler to get some heat and the same goes in winter where you get days where you don't need the extra boiler run. Any time the boiler fires up and there are no ufh zones calling for heat it will just run until the tank has reached its set temp, 63 degrees, and then it will power down. 

At the minute the boiler is still not set to come on as the house is still sitting at 20 degrees. Ufh does take a bit of getting used to but I much prefer it to a full rad system.

[Nickfromwales]

1 hour ago, Fly100 said:

Interested to know how often your heating come on for the underfloor. I have an odd problem that Im not sure is a problem. Mine only fires once a day, call it a Charge up if you will. Its set to bring the ground floor of the house to 20c by about 7:30am. While I understand its not that cold yet mine is only coming on once a every 24hrs. My issue is that each time it comes on its a 'fresh start' from cold. 

The house is a new self build and the floors are 150mm in Kingspan then pipes and a 70mm screed and pretty well insulated with a large amount of glass. Each fresh start results in a boiler run time of approx 90-120 min using apporox 6 litres of Oil.

 

How often does you boiler fire ?

 

Thanks,

FLY

Does the house stay at an acceptable temperature throughout?

[joe90]

Mines not come on yet this year even tho the other half thinks it should!!!!, House is a constant 20-21’. As said above it’s a different mindset. I keep temp monitors in most rooms to prove it is warm enough (and I only wear a t shirt). I do have a buffer tank which is constantly topped up through winter so I have 80ltr of hot water ready to heat the slab when it’s called for.

[Nickfromwales]

8 minutes ago, joe90 said:

I do have a buffer tank which is constantly topped up through winter so I have 80ltr of hot water ready to heat the slab when it’s called for.

That buffer only comes on when ‘heating on’ is selected and the heating is running, yes?

[joe90]

32 minutes ago, Nickfromwales said:

That buffer only comes on when ‘heating on’ is selected and the heating is running, yes?

no, during the heating season (when I decide) the ASHP heats the buffer (indirect)to 30’ and when the room stat in the hallway calls for heat the pump on the UFH  manifold starts up and blends down to 23’. Any heat lost from the buffer remains in the house just like the heat lost from the DHW tank (48’) but at these low temps the heat loss is minimal. As I have said elsewhere I would probably not have a buffer if I were to do it again, but it works just fine. So my Dads old motto springs to mind “ If it ain’t broke don’t mend it!”.?

[Nickfromwales]

I still prefer a buffer / hydraulic separator to allow the ASHP to ramp up to max without having to worry about what the final heat load is. My 2-cents is you have the right configuration ?