chris mason
|
| posted on 13/12/10 at 01:06 PM |
|
|
Underfloor heating
Seeing as this forum has more specific knowledge than google, thought i'd ask the question here 
We are currently looking at buying a bungalow on a reasonably large plot of land (considering the area)
If we can strike a sensible deal with the vendor then we will hopefully have access under contract (lease/buy) to the house while ours sells.
The house currently has warm air central heating, and i'd like to rip the entire system out and replace with water underfloor heating before we
move in, as the house is currently unoccupied this isn't a problem, so we intend to do as much work as we can.
At the minute i've yet too find out what the floor is (wood or concrete) but fingers crossed it's concrete.
So the point of the post is, has anyone had water underfloor heating fitted or is this your job?
Any information would be appreciated.
Thanks
Chris
|
|
|
|
|
loggyboy
|
| posted on 13/12/10 at 01:26 PM |
|
|
In my experience wet is more complicated but works better for 'heating' where as electric is simpler but tends to be more for floor
warming than heating.
However having good insutlation beneath the system is a must to reflect the heat in to the room, rather than towards the ground, so having timber
floors may acctually be a blessing.
[Edited on 13/12/10 by loggyboy]
|
|
|
jossey
|
| posted on 13/12/10 at 01:34 PM |
|
|
im looking at getting ground souce heating to run our under floor heating. but ive been advised that air source heating is better.
ground source into heat exchanger then out of blowers. 15-16 degrees all year round so warms the house ok.
anyway not sure how that helps i guess it dont but i hate paying gas bills.
dave
|
|
|
big-vee-twin
|
| posted on 13/12/10 at 02:40 PM |
|
|
Ground Source (GSHP) and Air source (ASHP) utilise the same technology which in effect it the same as your fridge but running in reverse.
The efficiency of a heat pump is expressed as a Coefficient of performance -COP.
A GSHP has a COP of around 7:1 which means if you put in a kilowatt of electricity you will get 7 kilowatts out- this has to be offest by the system
efficiency of pumping lots of water through a series of pipes underground and reduces the COP to around 5:1.
An ASHP has a COP of around 4 : 1 therefore compares well to GSHP when you consider the immense difference in cost between the two.
Both provide water at 45 degrees into the heating system and can be used with underfloor heating, or radiators. But with radiators these have to be
oversized as they are working at a reduced temperature.
The main issues with ASHP is that their rated output is at +7 degrees ambient, so when you have -4 ambient the heating capacity is greatly reduced to
around 60% i.e a 16kw unit at -4 will have an output of about 9KW and the colder it goes the situation gets worse, also the COP reduces to around 2.5
which when you consider that electricity is twice the price of gas roughly, when its cold they start to cost the same to operate.
In addition, you also need to take into account the defrost cycle as the box out side gets frozen when working hard this happens around every 90 mins
and takes 12-15 minutes, at this time the ASHP is putting cold water into the heating system, so you need to utilise a buffer vessel complete with
electric heater to take account of this. GSHP do not suffer from this issue.
So if your house needs lets say15KW to heat the house you will need to install at least a 28KW ASHP. I design these systems every day and would urge
you to be carefull when discussing the purchase of one of these systems as many retailers do not really know how they work.
In short a ASHP is good if sized correctly, because they are a heating product that looses capacity when it gets cold!
There is a bit more to it that the brief explaination above, but hopefully you get the idea.
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
|
|
|
rallyingden
|
| posted on 13/12/10 at 02:42 PM |
|
|
Did it myself in my new extension, quite easy. I clipped pipe to my insulation but these days you can get insulation complete with grooves to take the
pipe this will allow concrete or wood to be used as floor material.
See this LINK
RD
[Edited on 13/12/10 by rallyingden]
|
|
|
BenB
|
| posted on 13/12/10 at 02:44 PM |
|
|
I'm doing it as we speak for our kitchen. I was going to by a Danfoss consevatory system (just runs in parallel to any rads in the house) but
found I could buy the bits seperately from BES for about 50% of the price
Try looking at UFH1 on the web, they have nice PDF how-to tutorials on wet UFH.
|
|
|
nick205
|
| posted on 13/12/10 at 02:45 PM |
|
|
quote:
Originally posted by big-vee-twin
Ground Source (GSHP) and Air source (ASHP) utilise the same technology which in effect it the same as your fridge but running in reverse.
The efficiency of a heat pump is expressed as a Coefficient of performance -COP.
A GSHP has a COP of around 7:1 which means if you put in a kilowatt of electricity you will get 7 kilowatts out- this has to be offest by the system
efficiency of pumping lots of water through a series of pipes underground and reduces the COP to around 5:1.
An ASHP has a COP of around 4 : 1 therefore compares well to GSHP when you consider the immense difference in cost between the two.
Both provide water at 45 degrees into the heating system and can be used with underfloor heating, or radiators. But with radiators these have to be
oversized as they are working at a reduced temperature.
The main issues with ASHP is that their rated output is at +7 degrees ambient, so when you have -4 ambient the heating capacity is greatly reduced to
around 60% i.e a 16kw unit at -4 will have an output of about 9KW and the colder it goes the situation gets worse, also the COP reduces to around 2.5
which when you consider that electricity is twice the price of gas roughly, when its cold they start to cost the same to operate.
In addition, you also need to take into account the defrost cycle as the box out side gets frozen when working hard this happens around every 90 mins
and takes 12-15 minutes, at this time the ASHP is putting cold water into the heating system, so you need to utilise a buffer vessel complete with
electric heater to take account of this. GSHP do not suffer from this issue.
So if your house needs lets say15KW to heat the house you will need to install at least a 28KW ASHP. I design these systems every day and would urge
you to be carefull when discussing the purchase of one of these systems as many retailers do not really know how they work.
In short a ASHP is good if sized correctly, because they are a heating product that looses capacity when it gets cold!
There is a bit more to it that the brief explaination above, but hopefully you get the idea.
That's very interesting reading indeed.
Not wanting to hijack the thread, but can you give an idea of the land area required for the GSHP approach to work?
|
|
|
big-vee-twin
|
| posted on 13/12/10 at 03:18 PM |
|
|
Depends on the size of heating system and also which type of Ground source design slinky, straight pipes or plates.
However I designed a 60KW Straight pipe system a few months ago and I think there was just over 3km of pipe in the ground.
Another system I did was 120KW and consisted of 23No, 100 metre deep bores
Duratec Engine is fitted, MS2 Extra V3 is assembled and tested, engine running, car now built. IVA passed 26/02/2016
http://www.triangleltd.com
|
|
|
Canada EH!
|
| posted on 13/12/10 at 04:39 PM |
|
|
I have both a ground source heat pump in the house and in floor heated concrete in my 600 sq ft garage.
The house system converts the heat from the pipes in the ground to warm air through a heat exchanger (large radiator), it is not as efficent at
heating as fosil fuel sourced heat, large amounts of air are circulated to provide heat.
As an air conditioner it is superb. The present outside temp is -13C and the house is at 20C, when it gets to -25C outside the backup electric heater
comes on (very expensive).
When thinking of this type of heat very good insulation is required in the building, The house walls have 7" of insulation and the ceilings
have 15". The garage has 6" wall insulation and the ceiling 8".
The in floor heating in the garage is 1/2" pipes imbedded in the concrete with a small circulation pump circulating water heated by a 40 gallon
electric water heater, there is 7 gallons of water in the floor.
The system is good as the floor is warm when working on the car, however it takes a a day to raise form 3C to 10C , so it is left at 10C all through
the winter.
Again because electricity is used as a heat source it is expensive $100.00 CDN a month in winter. The temperatures are much more severe here as the
daily high is -5C, lows -15C this time of year, gets colder in January and February.
|
|
|
dhutch
|
| posted on 13/12/10 at 05:53 PM |
|
|
Ive not looked into it any details, but i would look seriously at installing a ground source and wet underfloor system if building a house.
My parents house has night storage underfloor electric (15kw worth) installed 20 years ago when the house was built and it works really well
In term of retro fitting it a wet system wouldnt be night storage so you wont need the massively thick floors, but i would assume that it would make
sense to add additional floor insulation below the system. So i guess you would be looking at maybe 1-2inchs of polyurethane, then an inch for the
system, and prehaps an inch on top of that?
Daniel
|
|
|
goaty
|
| posted on 13/12/10 at 06:35 PM |
|
|
Ground source has a massive installation cost and wil take a while to make it back, plus space to install it etc. Snow def wont be helping either but
it must be installed either on a decent size plot or very deep pile. both cost a hell of alot.
Air source is the cheaper option but believe me, unless you have somewhere to put the units, tey wil annoy you, they make more noise than you think
they will and do take up some space, unless you are fortunate enough to have a nice bit of land.
Wet underfloor systems are very good, very very easy to install but can be used with any heat source you desire.
As above though on a ground floor insulation is must or just dont bother installing it.
Wouldn't consider electric as running costs to produce heat to match a wet system will be silly.
rads would be cheapest and produce heat quicker but not to everyones tastes now days.
Dont bother with these designer ones, alot of them are terrible at producing decent heat.
|
|
|
Xtreme Kermit
|
| posted on 13/12/10 at 07:37 PM |
|
|
We put a gas to water underfloor system in an extension we did in a previous house and loved it.
The extension was about 4m x 8m and had a twin loop system run from a valiant boiler. Although the boiler ran the rads as well, each circuit was
controlled separately because the rads get a room up to temp in 30 mins to an hour where as the floor was gigantic block of concrete that took two
hours to heat up.
Underfloor heating is great in my opinion and give a great spread of gentle heat. The house with extension and new boiler cost no more to run than the
old system with it's boiler that Noah used previously in his ark
Good insulation under the floor is essential as is a good control system. The plumber I used was not experienced enough, and I had to point him in the
right direction a few times (I am no plumber but have a background in control systems).
Floors suit ground and air source heating because they generally run at temperatures in the mid 20's as apposed to rads which run at 50 to 60 (I
think).
|
|
|
scootz
|
| posted on 13/12/10 at 07:48 PM |
|
|
Maybe I've read it wrong, but is Chris not just asking about installing underfloor heating (not ground source)?
In any case, we explored the whole ground-source and solar-panel 'stuff' and having discussed it with the experts, we came away with the
impression that it's good for environmental reasons, but isn't going to save you a great deal of cash (if any).
As for underfloor heating, well having lived with it now for a year I can say with some certainty that our system is terrible! Takes too long
to heat up and too long to cool down!
It's Evolution Baby!
|
|
|
chris mason
|
| posted on 17/12/10 at 01:22 PM |
|
|
Thanks for all the replies
Yet again LocostBuilders Font of Knowledge has the answers.
The house is no longer on the cards, we feel the work required to bring it up to a liveable standard and the vendors being unflexible in his requests,
we have decided to leave it to someone else.
|
|
|
