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Old 01-05-2013, 09:01 AM   #1
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in floor heat

Hey guys, ive talked to a few people i work with who have infloor water heating systems, some very complicated with boilers and lots of electronics and some with basically a pump heater and tubes...the first question i have is that for all the basic systems, they all seem to have a tank water heater for the heat source, is there any reason you cant use a tankless heater?

the only thing i wonder about is that once the tanked heater is up to temp, the tank turns its burner off, but my on demand water heater turns the burner on when a flow goes thru it, so if you had a closed circulated system, would the temperature of the water get too high?

since your heating hot water (well hotter than usual)
also, since the system would be in a basement, would it maybe just be way easier since you dont need quite the elaborate stainless venting like the on demand type? mine has a 10" diameter collar that goes thru the wall, so not sure how that works in a basement...
thanks for any info guys


Last edited by oh'mike; 01-06-2013 at 07:25 AM. Reason: added spaces
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Old 01-06-2013, 07:14 AM   #2
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You can use a tankless heating unit for the forced hot water provided that the heater has a high temperature cutoff.

There is still the disadvantage that a tankless heater, by definition without a reservoir of water (the tank), will have its burner start and stop a lot (using the high temperature cutoff), which puts more wear and tear on it.

Modern FHW furnaces have the burner operating independently of the circulator pump, using low and high temperature switches to turn the burner on and off while the wall thermostat controls the circulator. There is usually a second high temperature cutoff for redundancy safety.


The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.

Last edited by AllanJ; 01-06-2013 at 07:23 AM.
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Old 01-06-2013, 09:27 AM   #3
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thanks allen, and from other threads ive looked thru, basically the consensus is that the tanked heater is the way to go, and really since this is my diy project during construction, it will be much easier since the venting isn't as large as the direct vent from the tankless...not to mention a third of the price.
i was also talked out of using the roll out polystyrene insulation for under the floor, and just stick with the old school 2" blue dow insulation. just wondering what kind of tape is used to tape the seams, as well as, does the vapour barrior go under the insulation on the ground, or on top of it?
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