Heated flooring

[morgandc]

Any recommendations on ways to heat water for heated flooring while reducing KWH? I am looking for a very efficient LPG hot water heater or "boiler" that runs off DC and uses very little power. I can get a DC circ pump, but haven't found a DC compatible heat system that allows me to avoid an inverter.

• http://www.commercialwaterheatersale...s-100-000-btu/
• http://www.laars.com/neothermlanding_opa.aspx
• ???

Thanks,
-Dwight

[LucMan]

Standard LP water heaters require no power, and the the latest Energy codes have raised their efficiency. Still nothing in the 90% range as with the ac power such as the Bosch and others.
The latest water heaters should start to be available as soon as the existing supplies run out. Or you can contact your local supply house to see if they have any available yet.
I don't know of any high efficiency DC powered boilers, really not much of a market for them. If you you want to to go 95%+ you will need to use an inverter for the controls and the primary pumps, for the secondary you will be able to use DC pumps.

Bosch used to make a power less instantaneous water heater that was good for a delta T of 60 degrees at 1.5 gpm, but I haven't seen one of those in 30 years.

[inetdog]

Standard LP water heaters require no power, and the the latest Energy codes have raised their efficiency. Still nothing in the 90% range as with the ac power such as the Bosch and others.
The latest water heaters should start to be available as soon as the existing supplies run out. Or you can contact your local supply house to see if they have any available yet.
I don't know of any high efficiency DC powered boilers, really not much of a market for them. If you you want to to go 95%+ you will need to use an inverter for the controls and the primary pumps, for the secondary you will be able to use DC pumps.

Bosch used to make a power less instantaneous water heater that was good for a delta T of 60 degrees at 1.5 gpm, but I haven't seen one of those in 30 years.

The ones that I see require line power for the spark igniter, since current energy codes discourage standing pilot flames. And you are not likely to find any that run off DC except for units designed for RV use.
And a very small inverter with a low tare would not be that bad, especially if heater controls are such that you can use the "idle" mode on an inverter.
Finally, why not use an inverter with an on/off switch that you run off a timer or manually.
Other than that, what LucMan said.

[LucMan]

A Burnham Alpine 080 draws <2 amps x120 VAC for the controls, and 1.2 Amps for the 0010 Taco primary pump. So you could get away with a quality 400 watt full sine wave inverter.

[peakbagger]

I would tend to sticking with standard AC equipment as the modern generally European condensing units are about as efficient as possible. I would suggest looking at ECM type pumps for circulation. Pumps like the old familiar Taco's are effectively banned in new installations in Europe as being too inefficient. Yes you need to run an inverter, but you can get away with a small one as there is no starting surge to speak of with ECM pump and the heating unit.

[LucMan]

ECM pumps are not suitable for to primary pumps on 90+ boilers. The small heat exchangers reguire a preset minimum flow rate through the heat exchanger.
Some manufacturers now ship with either the Grunfoss or Taco specified pump along with a low loss header, both highly efficient pumps that are designed for use with the boilers. .
Nonuse of the specified pump will surely create operating problems & voids the warranty.
The energy saving are achieved by the variable gas input, as the boiler control software tries to maintain the minimum water temp to satisfy the load
Read about primary/ secondary pumping on high efficiency boilers.
On the secondary side you can use any pump you want.

[peakbagger]

Interesting, I am in the process of finishing a John Siegenthaler heating design course (heavy on radiant and condensing gas boilers) and ECM pumps were represented as the current standard. One of the operating modes available on at least brand pump was a minimum differential pressure mode that would effectively maintain a minimum flow. Of course you may be John under a pseudonym given your location so I guess I want to check his textbook ; )

[LucMan]

Interesting, I am in the process of finishing a John Siegenthaler heating design course (heavy on radiant and condensing gas boilers) and ECM pumps were represented as the current standard. One of the operating modes available on at least brand pump was a minimum differential pressure mode that would effectively maintain a minimum flow. Of course you may be John under a pseudonym given your location so I guess I want to check his textbook ; )

Get back to me once you have actually designed & installed several working systems and let me know how you made out.