Oil / Heating Problems

prospect

Dear All,
I could really do with your help / advice on this.
I built a house last september, it is 2900sq feet, split 50:50 upstairs and downstairs.
Downstairs has concrete walls and underfloor heating, and upstairs is timberframed and radiators. There is a large outdoor oil burner.

When choosing underfloor our builder told us that the boiler is left on constant, and the stats control the amount of 'boiling' required.

Since we have moved in, we have used 1000 litres of oil per month! The builder says this is normal for a big house, and that the drying process also uses more oil. But 1000L p/m ???

My arguement with him is this:
1. My parents house is bigger, with all rads, and they get 8-9 weeks from a tank.
2. Underfloor heating is supposed to be more efficient.
3. We have no rads on upstairs, so effectivly we are only heating about 1500 sq feet.
4. I turned off all rads and stats one night. And when in bed, I could hear the boiler come on every 2 minutes, for 3 minutes (I timed it). So does this mean it takes the boiler 3 minutes to heat the water back up to temp after only 2 minutes of cooling time?

Any thoughts or advice? I would like some solid info for when I meet the builder next week.
Many Thanks

KoNiT

what temp are your room stats set at & what is the boiler cut out temp set at?

lomb

underfloor heating is a disaster. u are loosing all ur heat into the concrete.

Borzoi

prospect wrote:

When choosing underfloor our builder told us that the boiler is left on constant, and the stats control the amount of 'boiling' required.

I don't see why this would be the case. Most heating systems turn on for when the building is occupied and people awake, and are then thermostatically controlled.

As you know under floor heating is more efficient because it you can use a lower room temperature to feel as comfortable compared to a standard rad system

KoNiT

underfloor heating is a disaster. u are loosing all ur heat into the concrete

and the conc heats the room evenly at a lower temp, as opposed to a rad which relies on higher temp & convection create an air flow, etc....

Has the builder done UFH before?

I would be worried about "drying out" the house too quickly though

Macy

Borzoi wrote:

As you know under floor heating is more efficient because it you can use a lower room temperature to feel as comfortable compared to a standard rad system

However, takes longer to heat up a concrete slab, so it has to be on longer?

Off topic - The debate we had when we were building - ended up choosing conventional rads. (Whatever about with a heat pump, I remain to be convinced with oil fired boiler - people I know with underfloor heating seem to use more oil than the people with conventional rads).

Anyway, first tank will go quick, as you do have to dry out the house. However, should still cut out if the thermostates are down I would imagine....

lomb

Macy wrote:

people I know with underfloor heating seem to use more oil than the people with conventional rads).

..

makes sense if u think about it. would take an eternity to heat up as well. meaning its on 24/7 basically. i would switch to convectors unless u want to spend 500 euro a month on fuel.

BaZmO*

I work in the Buliding Services trade, i.e. the company I work for installs heating and ventilation into all manner of buildings so I kinda know what I'm talking about here.

It is a bit of a misnomer that underfloor heating costs less to run than a conventional heating system. While it's genereally a more effective way to heat a room compared to using the convection principle with rads it generally costs about the same as rads to run.

You can lower costs by having the boiler timed to go off at night but because you are just after installing the system it's probably just running constantly to dry out the concrete.

If you want to read up on Underfloor Heating you can go here and here. They're Irish companies too so if you want you can give the a bell if you have any questions.

B.

Macy

lomb wrote:

makes sense if u think about it. would take an eternity to heat up as well. meaning its on 24/7 basically. i would switch to convectors unless u want to spend 500 euro a month on fuel.

Exactly the conclusion we came to, and infact it was our engineer who told us it costs more to run than conventional (even though he was installing it himself!).

Like I said, with a heat pump it would probably work, but we just didn't have the money up front for that...

prospect

Thanks all for the replies.

The boiler is currently set to 45 degrees.
Most rooms are set to 18 degrees, except bathroom which is 22 degrees.

BTW, the heating works fine, all the rooms are lovely and warm.

A neighbour of my parents in a 3100 sq foot house, all concrete and precast floors upstairs, all underfloor heating. He uses 1000L over 8 weeks, during winter...

I wouldn't mind using a tank every 6 weeks, (which i would consider normal, in a 2900 sqft house), if i was using all the rads etc. But a tank every 4 weeks, with only half the house heating? But my main concern is why the boiler was consistently coming on (every 2 minutes) even though there was no hot water being used in the house, at all!

P.S. We have checked for oil leaks and there are none. Also the pressure in the system is pretty constant (looses about 0.5 bar every 5 weeks), which means there is bugger all water leaking.

Once again, thank you kindly for your advice.

slayer92

What can of underfloor insulation did you use, ie thickness?. You should have 50mm min and at least 70min recommended. Do you put 25mm side insulation between the slab and walls. Was the insulation installed edge to edge and all edges sealed with the proper foil tape.
You may have lots of gaps in the insulation and the slab may have leaked through these gaps when poured to form thermal bridges with rest of the foundation. Bad news if this happen as some of the underfloor heating is wasted on these themal bridges.

What floor covering are you using on the underfloor?? Tiles good, carpet, wooden floors very bad.

Except to use that amount oil for the first year winter season as the slab dries out. If it continues, consider the heatpump option, oil is only going get more expensive

Regards

lomb

i dont understand the attraction of underfloor heating at all tbh. is it just a 'gadget' thing?

i know that 50 liters lasted us 27 hours of constant heating during a cold week a few months ago(long story) this equated to 4 days with it being turned off at night. (2000 sq foot house)

prospect

slayer92 wrote:

What can of underfloor insulation did you use, ie thickness?. You should have 50mm min and at least 70min recommended. Do you put 25mm side insulation between the slab and walls. Was the insulation installed edge to edge and all edges sealed with the proper foil tape.
You may have lots of gaps in the insulation and the slab may have leaked through these gaps when poured to form thermal bridges with rest of the foundation. Bad news if this happen as some of the underfloor heating is wasted on these themal bridges.

What floor covering are you using on the underfloor?? Tiles good, carpet, wooden floors very bad.

Except to use that amount oil for the first year winter season as the slab dries out. If it continues, consider the heatpump option, oil is only going get more expensive

Regards

Buddy, I have no idea what you are on about here, , thanks no i am more confused...

We have tiles, slate and laminate flooring. I did notice the bathroom always seemed to perfom the best. Although the laminate floor guy said it was suitable for underfloor?

We chose underfloor for 3 main reasons:
1. We were told by our builder it is cheaper to run
2. I don't like radiators taking up wall space
3. We were informed by a heating specialist that it is healthier, less dust, even heat, blah blah, etc, etc.

Still not happy though . I have convinced myself there is a problem with the boiler.
Does anyone know, regarding an outside boiler, if it is on constant, but there is no hot water being used, if it should burn evey 2 minutes for 3 minutes, i.e. 3 minutes on 2 minutes off.

gregos

Try posting a question here:-

http://www.plumbingpages.com/forums/

I've found them very helpful.

lomb

prospect wrote:

Buddy, I have no idea what you are on about here, , thanks no i am more confused...

We have tiles, slate and laminate flooring. I did notice the bathroom always seemed to perfom the best. Although the laminate floor guy said it was suitable for underfloor?

We chose underfloor for 3 main reasons:
1. We were told by our builder it is cheaper to run
2. I don't like radiators taking up wall space
3. We were informed by a heating specialist that it is healthier, less dust, even heat, blah blah, etc, etc.

Still not happy though . I have convinced myself there is a problem with the boiler.
Does anyone know, regarding an outside boiler, if it is on constant, but there is no hot water being used, if it should burn evey 2 minutes for 3 minutes, i.e. 3 minutes on 2 minutes off.

its burning like that because the water is loosing its heat quickly to the uninsulated concrete. if i was u id tear it all out and fit convectors.

Cushtie

so is the general consesus so that Undefloor heating is not worth the hassle / Cost?? I was thinking of installing it but reading the above makes me wonder?
I always thought that although it was more expensive to install it was cheaper to run and you got a much better distribution of heat.

sorry for dragging thread off topic*

Macy

Cushtie wrote:

so is the general consesus so that Undefloor heating is not worth the hassle / Cost?? I was thinking of installing it but reading the above makes me wonder?
I always thought that although it was more expensive to install it was cheaper to run and you got a much better distribution of heat.

sorry for dragging thread off topic*

With Geothermal/Heat Pump then it probably is the way to go. With an oil fired boiler I don't think so. Had to make the choice ourselves last year, couldn't afford the heat pump route, so went with conventional rads.

Everyone I know who has underfloor heating with an Oil Boiler uses more oil. Like I say, the engineer that got us through planning was building at the time - he told us it was more aesthetic than efficiency as to why he was fitting it (although he tried to talk us into geothermal to go with it).

In a concrete floor, the pipes have to heat the slab, before they heat the room. So it's on longer, at a lower temperature, to heat up the room.

Also another complaint, albeit minor (except for the one's with two small twins, where it was a major issue) - no where to hang clothes to dry!

lomb

[QUOTE=Macy
In a concrete floor, the pipes have to heat the slab, before they heat the room. So it's on longer, at a lower temperature, to heat up the room.

Also another complaint, albeit minor (except for the one's with two small twins, where it was a major issue) - no where to hang clothes to dry![/QUOTE]

that really is all true, especially the last sentence

prospect

gregos wrote:

Try posting a question here:-

http://www.plumbingpages.com/forums/

I've found them very helpful.

Thanks for that gregos, I'll check that out.

prospect

We got the builder out on saturday, with a heating engineer (?)

Immediatly the engineer dude said the boiler is too small for the house.
It is a 90,000-120,000 BTU unit, and it should be a 150,000-180,000 BTU unit.

Does this make sense to anyone in the know?

BaZmO*

It makes perfect sense if the boiler was sized too low, therefore making it less efficient.

90,000-120,000 BTU (British Thermal Unit) is 26-35kW (Kilo Watts)

150,000-180,000 BTU is 44-53kW

so as you can see, there is quite a big difference.

B.

lomb

expect to spend the same or moe on fuel, just the boiler will be working less hard and not on all the time like a v12 6 liter vs a 1.3 4 cylinder.

prospect

Thanks BaZmO* and lomb,

lomb,
The plumber/engineer dude said the fuel costs would drop dramatically. Putting it simply for silly old me he said something along the lines that the current unit would burn 1 litre per minute for 20 minutes to heat the system. But the new unit would burn 2 litres per minute, but only take 5 minutes.
These are obviously just simplified made up figures, but the basic concept is there.
Do you mean the unit will cost as much to run, but will be on less of the time, or will I not see any difference in efficency?

Cheers

patrido

almost all UFH suppliers say that it is cheaper to run, not just more efficient.

- rehau say "As there are savings in running costs and low maintenance costs, there is a rapid payback on the extra investment. "

- atec say "It has been shown that underfloor heating can offer savings of 15 to 25% on the household heating bill."

etc etc.


i wonder has anyone who has had a bad experience, taken a legal route to redress. if you make a 5-10k investment based on a supplier/manufacturer's claim that it is cheaper to run, they should damn well deliver on that.

i have heard quite a few "tank of oil per month" stories, and I have never heard a definitive reason, or solution to them.

a few things seem clear though...
- insulation is crucial. not just underneath, but at the sides too. highest spec u can afford, no gaps, etc.
- u must have a good control system, especially with oil/gas.
- if using oil/gas u must use a good boiler, big enough for the task, and efficient. a condensing boiler seems to be particularly suited to ufh.

however, none of the suppliers seem to make these clear. none of them say that if you don't follow the instructions, it could end up costing a fortune. all of them claim to work fine with wood floors and carpet. if people keep having these bad experiences, then it's only a matter of time, before they get their asses hauled into court.

Macy

The evidence against is anecdotal. I have heard that a large factor is the relative extremes in temperature in Ireland in the same season. Underfloor heating more suited to countries where the temperature is fairly consistent rather than our's changing day to day/ hour to hour some days. (Obviously then so does our heating requirements).

Basically, UFH may be more cost/fuel efficient in theory, but in practice in Ireland where our needs change so much it isn't.

That's my take on it anyway.

flocker

Have to agree with Macy.

I have yet to be convinced about the economic benefits of UFH using oil or gas boilers. Our climate is not suited in my opinion, even with external stats, setback stats and the like.

rooferPete

Hi,

Sorry no advice or opinion, a question.

Was the density of the insulation discussed with anyone who installed UFH ?

Hi Prospect,

The size of the rooms or the ground floor and the ceiling heights are used to calculate the size of your boiler, I have a 150,000 btu output from my oil boiler and it is very efficient because if anything it is oversized for my house.

I don't have ufh but I have been watching the system with interest, so far I would still recommend radiators.

.

gregos

rooferPete wrote:

I have a 150,000 btu output from my oil boiler and it is very efficient because if anything it is oversized for my house..

That's right. A boiler needs to be working well within its limits to be most efficient: you don't want it to be slogging hard. The heating guy was probably right.