The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Correct rotation, wrong sequence
by Potseal
Today at 03:14 PM
Industrail Control Panel bonding per 409.108
by sparkyinak
Yesterday at 06:29 PM
Calling all Non-US members!! (Non-US only)
by aussie240
12/07/16 02:39 AM
Photo Upload Tutorial
by DanK
12/06/16 11:35 PM
Sprinklered equipment 26-008
by bigpapa
12/02/16 04:24 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 11
HotLine1 10
Potseal 9
sparkyinak 8
Texas_Ranger 7
Who's Online
0 registered (), 215 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Page 1 of 3 1 2 3 >
Topic Options
Rate This Topic
#143582 - 08/05/05 10:10 PM Power Boost to Floor Heating
Jamesnz Offline
Junior Member

Registered: 08/05/05
Posts: 7
Loc: New Zeland
I have a project in hand which involves a 500W 230V. ac heater coil bathroom floor installation that does not do the job it was intended. ie It barely reaches 21C. Apart from lifting the tiled floor and starting again I am going to use a "Buck - Boost" transformer setup to increase the heating output by using a 285V ac input to the circuit instead of the normal 230V. mains. From my calculations ( with the heater coil at approximately 105 Ohm)this should up the present current reading from 2.1A to around 2.75A giving a wattage of roughly 770W.I would be interested if anyone else has done this and how far can one go ? The transformer I am going to use , when it arrives, is a 230V ac to 55V. ac.
Kiwi2
_________________________
Kiwi2

Top
Test Equipment:

Large Selection of Test Equipment For Electrical, HVAC, Test & Measurement
Large Selection of Test Equipment For Electrical, HVAC, Test & Measurement

#143583 - 08/06/05 12:01 AM Re: Power Boost to Floor Heating
Alan Belson Offline
Member

Registered: 03/23/05
Posts: 1801
Loc: Mayenne N. France
Before you do anything, run the system up and measure the actual floor surface temperature. Once it's stabilised, if it's around 35 degrees C (95F), you are already at or near the limit. A higher floor temperature, created in an attempt to boost performance, might make walking on the floor in bare feet a distinctly unpleasant experience, if not dangerous to babies and pets. Depending on the cover material over the heater element, its temperature may already be close to the limit too, and it may even have a thermostat buried with it, which will negate all your plans. I'll let my betters here comment on the electrical implications, but my gut feeling is that this is a bad idea.

Alan
PS. Noticed you stated a 'tiled floor'. You can expect a maximum performance of around 10W per sq foot, (100W/M2) on ceramic/cement flooring, less on wood/plastic.

[This message has been edited by Alan Belson (edited 08-06-2005).]
_________________________
Wood work but can't!

Top
#143584 - 08/06/05 12:12 AM Re: Power Boost to Floor Heating
mxslick Offline
Member

Registered: 10/24/04
Posts: 785
Loc: Atomic City, ID USA
I see a fire or injury in your future....your best bet is to consult the manufacturer of the heater coil. As Mr. Belson has suggested, the heater most likely has an imbedded thermostat which will simply cut power to the heater faster if you try to boost the voltage. That assumes of course that the heater doesn't instantly burn out from the excess voltage.

I would think that since it's tile above, the type of tile cement is crucial for proper heat transfer. You may end up having to lift the tile anyway.

What about the floor itself? Is it open on the underside? (like a second floor or built over a basement/crawlspace?) Could you insulate the bottom side to help avoid heat loss?

Please, consult the manufacturer, there are too many risks associated with your idea, and it would be unfortunate if someone got hurt!

Can you post the name of the manufacturer here as well?
_________________________
Stupid should be painful.

Top
#143585 - 08/06/05 12:35 AM Re: Power Boost to Floor Heating
Jamesnz Offline
Junior Member

Registered: 08/05/05
Posts: 7
Loc: New Zeland
Thanks for the replies. To answer, the installation is on a cement floor and the best it can do re the surface temperature is, as mentioned, only 21C.
Kiwi2
_________________________
Kiwi2

Top
#143586 - 08/06/05 01:05 AM Re: Power Boost to Floor Heating
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
James,
Welcome.
What I'd be interested to know is how you're going to interface a 55V transformer in with the 230V mains?, to derive 285V.
What sort of a thermostat and controller are you using on this system?.
Besides, a 500W element is just that, it won't dissipate any more energy than what it is designed for.
This set-up sounds like it could easily end in tears to be honest.
I'm not aware of any underfloor heating elements that would enjoy being subjected to that sort of over-voltage and I'm pretty certain that that would instantly void any warranty in place.
Additionally, this type of heating system is required to have RCD protection.
I could be wrong, but 500W should be more than enough to heat the largest of Bathrooms.

[This message has been edited by Trumpy (edited 08-06-2005).]
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

Top
#143587 - 08/06/05 02:15 AM Re: Power Boost to Floor Heating
Alan Belson Offline
Member

Registered: 03/23/05
Posts: 1801
Loc: Mayenne N. France
Just looked up some data from my underfloor heating manual. For 100W/m2 emission, from a cement based floor, with ceramic tile over, the surface temperature should be around 28C, so you are low. The type of tile cement is critical for performance, as mxslick says, there are latex-rubber based flexible versions which will give poor heat transfer- a cement based product is best. An under-element insulation layer is vital, ( I bet this is your problem), or you will be warming the worms, [a few inches down, the earth's temperature will be 10C (50F), a massive heat sink].
My set up is hot water-pipe based, with a design heating of only 50W/m2, (wood floor, cork tiles over). The design floor temperature is only 23C so we are fitting supplimentary electric towel-rail heaters in each bathroom, using the floor as background only. If you want keep the aesthetics of a room uncluttered by radiators, rails or radiants, I'm afraid lifting the floor tiles may be the only option, since it seems you may need to put in a better insulation layer under. Also, for any underfloor heating to work properly, due to low emmission power per sq foot, the wall/ceiling insulation has to be really good too, R = 2.5 (metric) minimum = 100mm (4") of glass-wool minimum. Better is the new reflective foil multi-layer stuff, 7mm (0.28") thick is supposed to = 6" of rockwool but it's expensive. One thing all underfloor systems have in common is they don't work well in excessive drafts, ie. a ventilation fan tends to spoil the effect by dragging what little power you have outside to heat the sparrows! Since my guess is youre DIYing this project, get the floor tiles up, or improve the insulation and/or fit a heated towel rail and put this down to a learning experience, but leave the electrical stuff strictly conventional.
Stay safe,
Alan
_________________________
Wood work but can't!

Top
#143588 - 08/06/05 06:37 AM Re: Power Boost to Floor Heating
Tiger Offline
Member

Registered: 05/04/05
Posts: 714
Loc: Crystal Lake, IL USA
Check the manufacturers specs. and stay within the voltage range given. If you go to the top of that range you may boost the output.

I suspect that the concrete floor is sucking all the heat away from the system. I'd consider adding electric baseboard heat before tearing out a tile floor.

Dave

Top
#143589 - 08/06/05 07:12 AM Re: Power Boost to Floor Heating
winnie Offline
Member

Registered: 09/15/03
Posts: 652
Loc: boston, ma
Quoth Trumpy:
 Quote:

Besides, a 500W element is just that, it won't dissipate any more energy than what it is designed for.


Most of the heating elements that I've come across are simple resistors, dissipating power at E^2/R; bump the input voltage up 10%, and the power dissipated goes up by 21%.

A 500W element is _designed_ to dissipate 500W. Increase the input voltage, and the power dissipated will increase, but the element may not be able to _safely_ deal with the increased power dissipation. Increased power dissipation generally means increased temperature, which means reduced component or insulation life.

-Jon

Top
#143590 - 08/06/05 11:53 AM Re: Power Boost to Floor Heating
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
DO NOT DO WHAT YOU PROPOSE!!

I caution you for two reasons.

First, most products are intended to be used with a supply voltage no more than 10% over the nameplate voltage. You propose to exceed this.

Secondly, such systems are to be GFCI protected. Your GFCI would be the breaker supplying the tramsformer- and I fear the transformer will prevent it from protecting the circuit. Should you place it after the transformer, you will be exceeding the voltage it is designed for as well.

You'ld be better served by installing a recessed light in the ceiling, with a heat lamp bulb shining on the floor- assuming, of course, that this is outside the shower area!

Top
#143591 - 08/06/05 02:22 PM Re: Power Boost to Floor Heating
Jamesnz Offline
Junior Member

Registered: 08/05/05
Posts: 7
Loc: New Zeland
Thanks for the all the responses so far. To explain to you all further ...The original installation was made during an extension to an existing house. The area in question is roughly 5M sq. or 57ft. sq so a time clock operated 500 W underfloor heating element should have been ample. The bathroom is properly insulated and there are no drafts or such. I personally watched the installation which was carried out according to the manufacturers specifications. Laid on a floor base of concrete and encased with the appropriate insulator/grout/sealer, then over laid with ordinary thickness ceramic tiles. This contractor has never had a failure like this before. I and my Electrician colleagues cannot understand why it will not heat up as compared to other identical installations which reach a nice 27C.+ within the hour and operate on a time clock. The current draw is 2.1A at 230V. ac. I have tried out a 30V. 'Boost' giving a 2.6A draw. Which resulted in only a 1C. rise over an hour, so as most of you have suggested, I think it looks like a base board heater to supplement unless anyone else can see a way around this I certainly do not want to tear it all up and replace, all though the contractor has agreed to do so. For the sake of a trial I am borrowing a 55V. transformer just to see what will happen although as several of you have said 500W = 500 W !
Trumpy , you can see how I do the voltage boost, see "Buck/Boost/choke test drawings" by 'Scott35' in the technical area.
_________________________
Kiwi2

Top
Page 1 of 3 1 2 3 >



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals