ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Alan's Underfloor Heating Installation

Just a little aside,
Did you know that Lead-based solder is about to be banned here.
Not sure what the alternative is, but I've got a mountain of 60/40 here.
That will increase the price of electronic repairs.
Repairs are cut-throat as it is.
Your thoughts Paul?.
{Sorry about the thread-jack Alan}

Mike, Interesting point. Plumbers and Electricians use solder with entirely different specifications. For electrical wiring work, it's the eutectic alloy of lead and tin, 60-40, which has the lowest melting point, c. 200C. This reduces heat damage to components, & it sets solid without a tertiary stage. For plumbing, the alloy chosen was 70-30 or even 50-50, which goes though a 'pasty stage' like soft putty, for wiping joints. I can see the point in replacing plumbers' solder because of the lead poisoning risk. This only occurs in soft water, hard water is not a problem, but with the growth in water-softeners....
Since joint-wiping is now mostly antiquated, using a cu-sn-al-? alloy is not really a problem. In fact, a lead-tin capilliary joint forms a copper/lead/tin alloy in the thin solder film, which is why they are strong but a bugger to take apart later! As to electrical work, I can't see how the eutectic can be displaced by a trick alloy without introducing other toxic metals, or frying components with higher temperatures. What really got up my hooter in the UK was some idiot deciding that 'boss white' was dangerous for potable water joints made with hemp/oakum. It's only ground chalk and linseed oil! The green muck that replaced it had all the attributes of boss white bar one-the bloody joints all leaked!

Alan

Oddly enough Alan,
You've caught me out here.
In all of the Refrigeration work I've done with installing and jointing copper Air Conditioning and Freezer Gas and Suction lines, I've only ever used Silphos rods.
We use graphite paste here with Brass Hot-Water Cylinder elements, in combination with the Hemp.
I've used it since the start of my Apprenticeship and I are'nt going back now!.
Oddly enough Alan, do you think that we should start a new topic?.
Different solders and other such engineering things never seem to get a mention here.

Next year it will be lead-free solder for electronics in Europe.

The choice is simple: Raise the temperature and use cheap solder or stay put and switch to some exotic expensive solder. It is no bold guess that most companies will go for the higher temperature: approx 220C. Components that withstand higher temperature gradually replace the old ones.

I remember reading about the proposed ban on lead in solder a few years ago.

I can't help wondering what real effect the ban is supposed to have. 90% of equipment is imported from the far east these days. Is there going to be a ban on the importation of equipment using lead-based solder too?

Is the relatively small amount of regular 60/40 solder used here going to make that much difference?

As for use of solder for equipment repairs, the effect would surely be tiny. Even if manufacturers switched to lead-free solder, I can't see that the tiny amount used in maintenance and repair work is going to be a problem.

Is anywhere going to have an exemption to allow leaded solder to be sold in small quantities after the deadline? (Like we had for leaded gasoline in the U.K.)

Either way, I guess it will come as no surprise that I'm planning on laying in big stocks of regular 60/40 solder.


[This message has been edited by pauluk (edited 08-25-2005).]

Yes. In fact, the Japanese (and through them the Chinese) took the early talk of a ban seriously and many have already gone lead-free.

This lead to a completely new situation: I was at a fair earlier this year where an European electronics manufacturer explains that they will be able to adjust to the new rules with the assistance of Chinese experts!

Neither can I. For repairs, yes.

RESULTS HEATING TRIALS
As I studied the first set of results, the numbers didn't make sense. I appeared to have 'lost' 15kw of heat into the floor! An investigation showed that the boiler, which I got 'nearly new', had had a smaller jet fitted, and has a far lower output than the maker's plate implies.

Makers data: Burner output, 0.5gph jet with preheater, 12 bar pump, diesel fuel,
18.4kw gross, 16.5kw net.
Estimated transmission losses allow 1.0 kw
Net output to floor(s)= 15.5kw = 53000btu/hr
Water/ethylene glycol, 33%, btu/lb/degF= 0.92
specific gravity = 1.04, taken as near enough 1.0
Ambient t during trials = 19C(66F), and to avoid math complications, all ambient temperature readings were adjusted to 19C as they varied during the trials.
All thermometers were calibrated with an electronic medical thermometer.
C= centigrade scale, K= degrees Centigrade, F = Fahrenheit scale, dF = degrees Fahrenheit.

Results
Second (first Europe) floor trial.
Foil/bubblewrap insulation layer over 7/8" t&g softwood ceiling, ( so we could walk on it laying pipes), under 15mm OD/11mm ID X-linked polythene pipes laid as 3 discrete loops of 100 metres (328ft.) at 200mm (8") centers, fed from 22mm OD copper pipe/ manifolds. Floor 1" t&g cedar of lebanon boards. There is a 1" airspace over the pipe, and the floor is sealed at edges to prevent convection currents. This is a low wattage emission design.

Boiler trial #1
t'stat set 57C-65C. Mean= 61C; range 8K, (14.4dF)
time burning= 1645 sec. (about 2mins 30sec per burn).
time off= 5960 sec
total time= 7605 seconds
Burn time= 22%
THEORY
22% burn, 15.5kw net= 3.41kw to floor, but allowing 400W loss to the room below;
To floor = 3.0kw on 72 m2 = 41.7W/m2
Using the well known emission coefficient of 11W/m2K (3.5btu/hr/sq ft./dF) -
Floor temperature should be 3.8K ( 6.8dF) over ambient.

PRACTICAL RESULTS
Flow into 2nd floor @ 40C (104F). Return from floor 35C (95F) Range 5K (9dF)

Find the exact flow rate through the floor, without instruments!!
Boiler shell holds 14 litres (30lb) and cycles approx. 9 minutes off, 2.5 minutes firing. 30lb falls 14.4dF = 30x14.4x0.92= 394btu drop between firings. Water returning to boiler drops 9dF losing 9x0.92= 8.28 btu/lb of flow.
In 9 minutes, return water cools boiler at 397/9 = 44btu/min..
So flow must be 44/8.28 = 5.3 lb/minute or 0.04 litres / second.
Now the mix valve takes in water, (from thermometer reading) at 55C (131F), so 1lb at 55C + 3lb at 35C = 4lb at 40C. Flow through the floor = 4 x 0.04
Flow = 0.16 litres/second, 3.52 lb/second

0.16 litres/sec = 1267lb/hr x9dFx 0.92= 10491 btu/hr= 3.06kw, and in a 72m2 floor output is 42.6W/m2 ( 13.3btu/hr/sq ft)
Using 11W/m2K, floor temperature should be 3.87K, 7dF above ambient.
Floor temperature measured at 22.5C @19C = 3.5k ( 6.3dF)

Estimated actual power = 42.6W/m2= 3kw, ( 10,489btu/hr) at the second floor.

First (ground) floor trial.
Base layers plus 50mm extruded PS foam under 75mm dense concrete floating floor slab. Pipe layour as per second floor, except there are 4 x 100 metre loops. Cover over pipes 50mm. Weight 12.4 imp. tons, floor will have a ceramic tile finish.
Edges of floor have a thermal break.
Area heated, 84m2 (904 sq ft).
At 28C mean slab temp., from a 20C start, slab requires 14.4x0.2x12.4x2240= 80,000 btu or 23.5kwh to raise to working temperature.
Boiler trial.
The required power of this floor is only 50W/m2, bearing in mind the insulation and venting design. Circulators can only deliver a fixed quantity of heat, and this is less than the boiler output. A stable condition was never reached, I still have no room stats (French supplier!), so trial was terminated once 50W/m2 was achieved. A boiler trial is thus pointless. This meant a flow rate could not be calculated, so I will assume it is about 0.16 litres per second.
Floor cover of 50mm concrete will drop temperature from the water by;-
R=p/y; y=1.1W/mK, p=0.05m, so R=0.45W/m2K
t drop thro' concrete, y/R = 2.4K, so mean water temperature required is 28C, 82F
From this figure, floor requires 3.8kw plus an allowance for losses into the earth.
Downward heat loss to earth is not math for the faint hearted! So I used tables!
50mm of EPS in a concrete floor of this size, 1/R= 0.5W/m2K , at 28C loss = 1175W
So total power required = 5kw, 17000btu/hr.
If flow is 0.16 litres/second, similar to upper floor, = 1267lb/hr at 1165btu/dF, the temperature drop should be 14.4dF at 17000btu/hour, and exit water should be 35C or above.

TRIAL DATA
Time to reach approx. 50W/m2 from 19C start, = 5 hours 11 minutes
Floor temperature was 24C(75F) = 5K (9dF) rise, at trial end.
Input water 43C (109F)
Return water 35C (95F) at trial end.
8K achieved = 50W/m2 approx.
TRIAL STOPPED.

Phew!

Alan

ps. I reasoned that at an ambient temperature of around 19C, the emissions from the floors would be roughly the same as if all the insulation had been installed. A lucky break in the weather.

Edits for spelling and typos.
Edit, decimal place error.

{Message edited to remove edit notices}

[This message has been edited by Trumpy (edited 03-24-2006).]

Alan,
You've obviously put a LOT of thought and calculation into this installation.
I hope it serves you well, mate!.
Mind you, not the sort of thing that you want to screw up.
Do it once, do it well. (the way I was bought up)