Materials based on/containing Portland Cement cure to rated strength in about 28 days in the presence of sufficient moisture. If the materials dry out, curing stops and NEVER restarts. The fact that you question the manual and apparently consider the absence of posts on the subject to be the superior source of information really concerns me. And my post probably will be wasted effort. I waited two months to use mine- did my own installation. "Act in haste, repent at leisure".

I have been known to consider information gleaned here to be a superior source, so I really appreciate your concern and your taking time to post. My installation is not complete, I haven't used mine yet, and thanks to you, believe me, I won't.

I called and spoke to Suntouch. I didn't want to wait and see if it worked 30 days later. The guy told me that after 14 days, I could try it out but turn it off after I knew it was heating up. It was cold here and it took at least 45 min to heat up and then we turned it off. The guy never said anything about waiting 28 days. Since I am still waiting for the rest of the bathroom to get finished, I will wait the 28 days probably about the time Texas starts to heat up for the summer :).

Quite honestly, this is the first time it's even come up in here (that I can remember), and it's been a while since the last system I installed, and couldn't remember whether it was 7 or 28 days (initial set or full cure), which is why I abstained from answering.

Thank you everyone. I now feel a little less blonde than I did a while ago.

at the rate my remodel is going, 28 days won't be long to wait at all. :/

For me personally, the advice from the individual at Suntouch was not good. I am, among other things, an electrician. Using some of my test equipment, it is entirely possible to know within 5 seconds if the floor mats/pads/wires are heating properly. I cured the basement and garage floor slabs at my house 4 years ago to suit myself. Even my concrete contractor thought I went overboard, said a week was OK. I have no cracks at all at either place. Compacted before the slab with both power tamper and plate compactors. Take a few days/weeks to do it right and enjoy it for years.

What about radiant hydronic floors-- porcelain tile on kerdi? Is the modest temp of the water pipes going to be an issue?

Oh shoot, I had no idea we were supposed to wait 28 days!! Installer didn't say a word. B/c the rest of the bath wasn't done, it may have been, at the most, 2 weeks before we turned the heat on. And we've now had the system on 24/7 for 10 days. So I have 2 questions - would it do any good at all if I turn the Suntouch off now, or is it too late? Also, what problems could occur if not cured properly?
Thanks so much for your help.

Uh oh, we too had ours turned on within a week. In fact, our contractor (who read nary an instruction manual) turned it on. We had no idea. Well, I'll let you know if/when it all crumbles. And if it does, just as well, he failed to place any heat where my toes land under the vanity. brrrrrrrr.

What about radiant hydronic floors-- porcelain tile on kerdi? Is the modest temp of the water pipes going to be an issue?

Keep the temp down to50- 60 during installation, and then 65-70 for the first month, and you'll be fine.

would it do any good at all if I turn the Suntouch off now, or is it too late?

If it's going to do any damage, it's most likely been done already. If damage HAS been done, and the thinset and grout's been "cooked", you may see the grout begin to powder in spots within the next month, as well as tiles starting to loosen up due to loss of bond. If it's any consolation, it would happen WELL within your warranty period.

"Hey, what do you mean you feel a little less blonde?? ;-)"

I am a remodel virgin, I always search before posting, and I try not to ask "obvious" questions. Most of the people who post here do so kindly and patiently, and I am very grateful for them. Then, there are the occasional tools who want you to feel stupid for asking. Thankfully, the rest of you make up for that. No offense intended. Signed, the Blonde (aka ladycfp)