Topic: Underfloor heating. Concrete slab - Which options??

Re: Underfloor heating. Concrete slab - Which options?? 

TC, Im beginning to understand the technology now.
So effectively I need a different beast for 60C than the one for 30C. I didn't realise the technology was more primative than I had thought :)
To use your car analogy, I had assumed that the 'range rover' would be running smoothly for 60C and would just be idling/ticking over when producing 30C.
It does seem a little crazy, bit like a one speed car eh. eg I need car A when I go shopping or drive at 50K, but I have to have car B when travelling on a state highway at 100K. Or to use another analogy. I need oven A to cook a roast, but oven B to cook a meringue. No one would put up with such nonsense. May be I should do as Russel says and just install the UFH pipes and hope that HP technology improves over the next few years. Sounds similar to cast iron back boilers moving to modulating condensing boilers back in Europe as the technology improved.

Pete

Re: Underfloor heating. Concrete slab - Which options?? 

Re EEV

there is a whole discussion on these at
http://www.refrigeration-engineer.com/forums/showthread.php?t=3114

Pete

Re: Underfloor heating. Concrete slab - Which options?? 

Hi Pete,
Good point about the oven, but the oven does have many elements, (fans) and controls to cook your different product, so for the 2 in 1 heat pump it is basically a similar product (where certain parts are common, but seperate parts, where required to achieve best results.)
The technology is not primative, you just cannot change fundemental rules of physics!
Remember that a heat pump is a device to convert low grade energy into a higher grade of energy. The bigger the difference the more external energy has to be introduced.
Refrigeration (Hest pump) is all about managing changes within the system, being a loop any change effects the rest of the loop. And whilst all this can be done technically, the cost would be prohibative. A fine balancing act?

Re: Underfloor heating. Concrete slab - Which options?? 

TC

Re: Underfloor heating. Concrete slab - Which options?? 

Was thinking of gas ovens, forgot these are as rare as rocking horse droppings in NZ :)

Thanks TC, your input has been invaluable. Trouble is now I have a better handle on how HPs work I'm back to where I was a few months ago and need a rethink on heating :(

Hamish, hope you found some of the above useful, sorry I hijacked your thread somewhat but I think its all relevant stuff

Pete

Re: Underfloor heating. Concrete slab - Which options?? 

Pete,
Comfort first!
Purchase a dual heat pump, twin heat exchanger (HWHP Auckland "I drink VODKA" hint) or 2 singles, one for under floor one for DHW
TC

Re: Underfloor heating. Concrete slab - Which options?? 

TC you make me laugh.

I've no bl**dy idea what your hints are on about

LOL

Pete (thick POM)

Re: Underfloor heating. Concrete slab - Which options?? 

Hi, Thanks VB for your very long, and enthusiastic message on my phone this morning. I didnt know my phone could store messages that long =)

Hot Water Heat Pumps Ltd web site is still having product uploaded to it - it takes a long time when you have over 100 products and a lack of man power. Dual Purpose heat pumps are all custom built so there is not a lot of information, but it is coming. We make a couple of hundred of these per year.

A dual purpose heat pump will mean that you will not have one unit redundant for 6 months as would be the case having 2 units and it is lower capital cost to having two units. It is likely it will be a little oversized for the DHW as it will be sized for the slab heating but it also meant your recovery will be quicker.

TC, I get the hint =P As TC says, we are competition but not opposition. A good way to put it. We are both in the NZHWA. www.nzhwa.org.nz

I had a good conversation with TC several weeks back about EEV's. There some some supply problems of good valves for R410A early in the piece but that has since been resolved. We currently use a mechanical expansion valve from Japan. Very reliable, very acurate. But without some of the interesting features of the electronically controled valves (usually from China) "dig dig"

Pete, your welcome to give us a call to ask any questions.

Kevin

Re: Underfloor heating. Concrete slab - Which options?? 

Hi Pete, for those in the know, it is a small industry.
Kev, I will take the dig dig, as long as you take the hints (make sure its a big one!!) LOL
Well I hope you 2 hook up, and sort a solution.
Remember for heat pumps and under floor
FLOW FLOW and FLOW
TC

Re: Underfloor heating. Concrete slab - Which options?? 

gee, I had no idea you guys all knew eachother.
So where is my bottle of vodka?

VB

Re: Underfloor heating. Concrete slab - Which options?? 

Geeze - this is my thread you buggers have hijacked - surely I deserve a vodka too!

Re: Underfloor heating. Concrete slab - Which options?? 

Well I've just spoken with Kevin. So if we're having a party then line a Vodka up for me too

Pete

Re: Underfloor heating. Concrete slab - Which options?? 

If we all drink the vodka, we get that warm fuzzy feeling, do not need the heating. Solution Maybe??

TC

Re: Underfloor heating. Concrete slab - Which options?? 

Hi VB, and Hamish, with or with out the Vodka,
(mine's a Drambuie actually, much more warming, even if it is imported)

The space heating for the (proposed) house is at least 90% direct solar gain and internal occupants and appliances - fridges, cookers, computers, et al.
This is where your proper heat recovery ventilation system will be excellent value. We've just installed the Lossnay into the 1928 bungalow that we are temporarily residing in (cheap specials recently advertised even if it isn't the most efficient) and high efficiency heat recovery ventilation systems are one of the core items to get the German 'Passivehaus' spec'd houses to be so liveable with no introduced heating.
On the very few days that a properly designed Auckland house might need heating, you can throw a log in the fire - preferably a 'chippy' that puts more heat into a water jacket or wet backs than into the room - which heats up the thermal storage unit from which heat is supplied to various uses.
I haven't run ALF3 or Accurate (is it possible for one to get free downloads of this?) yet as the house isn't sufficiently designed yet.
However the basic principle that I described in the earlier post is common in Europe where they have thermal storage units that can be up to 5,000 litres, but normally using gas boiler, pellet boiler, or similar.
But in Auckland, if you can be bothered to chop a relatively small amount of wood, then you can get by with just renewables (solar) and biomass (wood).
The other benefit of the hydronic slab heating is to protect resale value. If Hamish, or we, sell in 5 or 10 years, what are going to be the motivators for the potential purchasers? Too many soft or rich Aucklander's don't seem to understand that they can get by without extensive underfloor or other grand heating systems.

regards
Russell
(NZCE - HVAC, and lots of junior engineering time spent doing proper heat flow calculations through different construction types)
:)

Re: Underfloor heating. Concrete slab - Which options?? 

Hi Russell, Auckland is a mild climate and is more suitable for your type of system, but all the theroy in the world needs to be tempered by a large dose of reality.
For example I have been asked to look at newly built house (money no object, many experts involved).
A design similar to what you are proposing. The therory was correct all being equal, "But" all the engineers, architeicts did not allow for the interior designer.
The floor is polished white marble. (looks great)
Only problem is the 100M2 of glass north facing allows all the energy in, the floor reflects back into the room, so during the day the room is unbearably hot, floor is cold, the sun goes down, temp drops very quickly, no thermal store in floor, house is cold.
But they have 1000L storage as you propose (solar heated 48m2 panels) This is absorbed very quickly into the concrete, not much use. 5000L would be much better.
TC

Re: Underfloor heating. Concrete slab - Which options?? 

Hello TC and Russell,

A design that solved this problem, is laying dark slate in the area adjacent to the glass for a distance back from the glass of 2500mm which is close to the winter angle of 38 degrees that sunlight through a 2000mm high window hits the floor.
This angle and therefore distance, varies depending of latitude but a generalization for Auckland is 38 degrees in winter and 83 degrees in summer.

Rex

Re: Underfloor heating. Concrete slab - Which options?? 

Hi Rex,
I also like to lay piping in this area and leave the water pumping running, transfer the energy to cooler parts, aslo gives added benifit of energy absorbed, and reduces peak temps. (keeps the darker area cooler) Often people misunderatand the difference between energy and temperature
Controlling can be a little more difficult. I often "thought" about using LUX (light) as a control mechinism in conjuction (more than just temp for solar home heating)
It could be deemed ar predictive, not reactive.
TC

Re: Underfloor heating. Concrete slab - Which options?? 

TC,
yes, having what is effectively a 'run around coil' is a great way of catching and delivering that solar gain more evenly around a house. An in-slab temp sensor in the 'hot' zone and another in a permanently shaded area, potentially with a third space temperature sensor (black bulb sensor or similar that measures combined radiant and air temps), all wired up to a simple PLC could be used to help control (i) pump on/off and then (ii) floor circulation only or open valves to introduce external heat source.
Our budget won't include nice floor tiles. Just concrete, hopefully with a touch of dark colour added (Peter Fell's additives), and then 'cut' and grouted to look like large tiles (say 1m x 1m). And scatter rugs that can be used to both make feet 'feel' warmer (reduce conduction) or moved to slow the rate of sun's energy into the concrete if we are getting too hot in the summer. More focus though is looking at how we can get appropriate cross-flow ventilation passively through the house in the summer in a security minded manner for when we're all at work/school during the day. Not to mention optimised shading.

Hamish,
the main take out for you is you need 'joined up' or integrated thinking. Do not put decisions into silos of floor / insulation / water heating / space heating / glazing / etc. They all impact on and relate to each other. If they can build houses in Germany that don't need any heating, then why can't we, particularly in our mild Auckland. Look really hard at this first and then see if or how little heating you need after that. Eg your 'pipes in the floor' may be able to be much further spaced out. Although people may sense 'strips' warmer than others, which could be compensated for by having the pipes deeper down, which then leads to much slower response times.
EVERY decision is a trade off. Start with a list of your personal/emotional desires or needs for the finished house and prioritise your lists around alignment with those.
After all, the finished house is for the comfort (and ego) of the owners.
regards
Russell

PS what is the 'pay back' on a marble kitchen bench compared to formica? or a car with leather seats to one with cloth?

Re: Underfloor heating. Concrete slab - Which options?? 

Russell, excellent advice at the end for Hamish.
With a PLC, control becomes somewhat easier.
I know what I want out of PLCs, I let someone else program, everybody to their own.
TC

Re: Underfloor heating. Concrete slab - Which options?? 

I agree with Russell. The consideration of all aspects makes it possible in Germany to build for little or no extra heating.

There are many obstacles in NZ for this:

Builders
Architects
Short term economics
Poorly perfporming building components such as windows and glazing
Island mentality
Quantity goes over quality as houses are generally too big with too many expensive gimmicks to allow for quality in the construction and materials.

It is just a matter of time.....

Re: Underfloor heating. Concrete slab - Which options?? 

Rex, you ever walked bear foot on a black sand beach in summer? Like Tc says, if you had underfloor heating, (heat source switched off) you might be able to transfer some of that heat around the house. But otherwise, I dont think you will be walking the sunny areas of a house with black slate. more like hopping from couch to couch.

Someone needs to invent a stone thats black when its cold and turn white when it warms up.

VB

Re: Underfloor heating. Concrete slab - Which options?? 

Hello VB,

Your comment is very relevant if the floor is subject to hot summer sun. The Howick house I am referring to, has a heat transfer system in the floor as TC recommends, and large soffits facing north that cut out all summer sun, and the owner assures me that he can walk barefoot at all times (although him walking on slate barefooted is not normally his style).

Just goes to show that all elements in design must be interlinked and balanced for the whole to work in sympathy.

Thanks - Rex

Re: Underfloor heating. Concrete slab - Which options?? 

Hi All, should we do an energy mass balance on Pete house? (Pete willing of course), and lets see what results may turn up
TC

Re: Underfloor heating. Concrete slab - Which options?? 

Sound intriguing?

What do you need to know?

I'm a tiny bit cautious 'cos every time I post questions, you guys get me to change my mind on something :) My missus would have a fit if I did some major rethink (again!)
Joking apart, free advice from your combined fountains of wisdom is always welcome, may also assist other posters with their own design decisions

Pete

Re: Underfloor heating. Concrete slab - Which options?? 

Hi Pete, from previous post you have indicated what you think your heat load may be. (Starting pont)
When you did your calcs what was your inside temp and what was your out side temp?
Going to be a slow process!
TC