Jay's Kitchen Remodel

[Warmsmeallup]

Just curious, what type of cementous material are you putting over the element, under the ditra?

[JMingrone]

Russ-

I'm using the Warm Wire system where you roll wire out and hold it down with the strips they provide. I used mats before in my '06 bathroom remodel. They work great, but I had 2 issues with them:

1) The mats are a little difficult to use in small and/or "non-square" areas where you have to cut and flip them to fit.
2) The mats didn't lay flat enough to screed them down with thinset (ended up using SLC)


This project is much bigger and I'm not confident I can do the SLC with the size crew i have (1) and lack of specialized equipment.

So my plan now, based on a technique i saw on another tile site (http://floorelf.com/how-to-install-s...heating-part-2) is to screed over the wires with thinset, let dry, then cover with DITRA. No CBU (which I also hate!).

Have a look at that site.

[JMingrone]

Russ-

Visited your low-voltage site. Interesting. Never knew there was such a thing. Question: How many watts per square foot can you get with the mesh?

For my floor, at 15 watts/square, 240 volts, i'll draw ~6.25 amps.

To get the same power from low voltage (even 30 volts), we're talking 50 amps, no?

Sounds thin and robust, though.

[Warmsmeallup]

Unless I'm not understanding something, if you cover 250sf with 15 watts psf at 240v your amps will be 15.625, not 6.25.

250 x 15 = 3750 watts /240v=15.625

A watt is a watt from low or line voltage. We are not locked into 30 volts. The transformers we use come in 1 - 6 kVA with multiple taps for different length elements. The low voltage element is cut to length in the ield and spliced to the cold lead.

We recommend the element based on the design. If you're all hardwood, Zmesh all the way. Nail through it all you want, no problems. If you have tile everywhere, I recommend either line voltage mats or low voltage, again, depending on the application.

If you're just floor warming, Zmesh has two elements; 9 watts psf and 13 watts psf. You don't need more than that but most of the good cables in mat form are already at 15 watts. 7-8 watts will warm a floor. On the other hand, if you're looking for primary heat, then a heat loss calculation will tell you how much heat you need and I don't recommend line voltage for primary since, at some point, it will cease to function where the low voltage will not.

[JMingrone]

Russ-

I'm only heating a portion of the 250 sq ft, so 6.25 amps at 240 is what i'll end up with. I'm HOPING this will provide most of the heat i need. Haven't done a heat calculation, but 12.5 watts/ sq foot in my bath heats the room ok. But just in case....i'm putting a couple toekick heaters in.

The ZMESH is intriguing. But at 13 watts per square, that's 43 amps (for my coverage). I assume the thermostat switches high voltage to the transformer, and the transformer steps it down to drive the mats? Transformers aren't 100% efficient, so what do you quote for losses through it?

Your comment "....at some point, it will cease to function" (referring to line voltage heat wire) got me concerned. I went with electric heat for RELIABILITY reasons. After all, it's just wire, right? Connections can fail, and thermostats can fail, but once the wire's safely embedded in morter and working, what's the failure mechanism of the wire itself? (House wire doesn't degrade). More importantly, what makes low voltage wire immune to the same failure?

I'd like to consider this product further, so please help me out.

[Warmsmeallup]

Let's first approach the primary heat idea. I'm guessing that the bathroom you did previously didn't have more than one window and one exterior wall so minimal heat would be fine. Does the area you wish to heat now with the line v. have more windows, exterior wall or doors? Keep all that in mind later if it isn't sufficient. I would NEVER just supply a heating element that covers the area and then guaranty primary without the loads in-hand.

Like I said, a watt is a watt. If the mats you purchased produce 15 watts and draw 6.5 amps @ 240v (approx 100sf) than so will a low voltage covering the same area. Ohm's law. I'm not sure where you're getting your calculations from.

Also keep in mind that we supply both low and line voltage systems. I don't have a preference, it's strictly what fits the application/budget of the client. If there's an open budget, we always suggest low v for the longevity of the element first. The low voltage advantage is the element, not the efficiency (accept for snow melting applications where low v is superior over all for longevity and efficiency). Line voltage elements (like toasters/ovens/water heaters) are not housewiring, they are something akin to a filament and are designed to last 10 years + due to the nature of the 'beast'. Some line v mfrs are now giving 25 year warranty's to keep up but you'll have a heck of time prooving it's the embedded element in 15 years.

The low voltage element is a just a single copper stranded THHN wire where low volts/high amps are used to create resistance/heat. Keep that resistance well below the wire's max capacity and it will last as long as housewire.

The low v transformers we use are AC/AC so the loss is about .3%. Insignificant. And, since the transformers get warm themselves, they make up for more than the loss if installed in the heated area.

[JMingrone]

OK, so a lot of progress has been made on the kitchen reno. I ended up shoring up the floor with a 12 ft double 2x6 beam with 3 equi-spaced 4x4 posts afixed to the concrete floor with galvanized post bases. This divided up my 12 foot joist span, which didn't pass Deflecto, to an 7 ft and 5 ft span. This passes Deflecto and FEELS great. Couldn't put the beam at the 6/6 point because of a furnace, but the location actually puts it right under the main walkway thru the kitchen. Glad I did it. Next up is the layer of 3/4 ply, which will be run perpendicular to the joists, NOT glued, screwed only to the subfloor, not the joists.

One question on the Ply... i'll have a some smaller pieces as I work my way through a small hallway and into the tiny bathroom. Is it still recommended to NOT glue and NOT screw the small pieces to the joists?

Thanks

Jay

[JMingrone]

This question may have gotten lost at the bottom of my last post....

When putting down plywood over my subfloor, i'll have a some smaller pieces as I work my way through a small hallway and into the tiny bathroom. Is it still recommended to NOT glue and NOT screw the small pieces to the joists?

[Houston Remodeler]

Jay,

Optimally you'd like one huge piece of plywood but we are limited to 4x8 sheets. You can use smaller pieces if they are oriented with the face grain perpendicular to the joists AND you have T&G or use blocking at the seams. Glue and screw to the joists is ideal for the first layer.

[bbcamp]

You should try to keep the smaller bits to at least 2 feet wide and span 2 joist bays. That size will be easy to follow the general fastening instructions. Smaller than that will not provide the maximum stiffness for the subfloor assembly, so you should avoid that where possible. Some situations may occur where strips are necessary, and gluing would be OK if you use a waterproof carpenter's glue and make sure you spread it over the entire piece.

[cx]

Jay, I don't know what you're calling "small Pieces," but you'd want to avoid such if you can. If gluing is the only reasonable way to get them installed, glue them. I'm personally in favor of gluing all parts of a wood framed subfloor, but you must glue the second layer of subflooring to the first correctly with a full spread of wood glue.

Part of the prohibition against gluing that second layer is the fear that it will be done incorrectly and cause more problem that it solves. Don't let that happen to you.

My opinion; worth price charged.

[JMingrone]

Thanks guys, i'll keep the pieces as large as possible. The bathroom is the area i'm concerned about. Not sure if I can wedge a single piece in around the nooks and crannies and plumbing stubs. Was thinking it would be easier to split it in two.

IF i split it i'll put a full layer of glue.

[JMingrone]

So, if used, carpenter's glue, NOT the "subfloor glue" you get in the tube?

[bbcamp]

Right. Subfloor adhesive is for gluing the plywood to the joists.

[Houston Remodeler]

You'll be applying the glue with a roller so you can make the speed needed to prevent it from skinning over. Trace the outline of each piece to prevent making a mess.

Sent from my new crappy phone