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Joined on November 26, 2011

Last Post on April 19, 2014

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Internet hydronic parts sellers

@ March 18, 2014 12:37 AM in Scott's radiant heating project

are fine for pipe and fittings and hydronic accessories.  Boilers are a different matter -- you have to carefully read the fine print from the manufacturers.  Many of them will not warranty (or not warranty fully) if mail-ordered.  Find a factory-trained installer for whatever brand you select and see if they're willing to work with you.  Be sure to mention that you're planning to sell the house soon and see if you can transfer the warranty.  Sometimes the factory trained installer can negotiate things that you as a homeowner can not.  If you can get yourself classified as a 'builder,' your buyer becomes the 'homeowner' for warranty purposes.  If you're lucky.

Solar PV

@ March 18, 2014 12:29 AM in Any solar pros here?

Panels, mounts, (possibly) trackers, DC GFI's, DC disconnects, possibly MPPT optimizers, inverters, AC coupling gear, controls, monitoring, and more.

A big topic with a lot of evolving technology. has some basic background info.  Spend a few weeks of evenings reading and you should be "buzzword compliant."

Yes, they work

@ March 18, 2014 12:16 AM in main line water filter

They also cause problems.  I would recommend various types (or not) depending on the particular water conditions and use.

The short version is in the post above.

Thats $0.048

@ March 17, 2014 12:03 PM in Heat pump only, or combo?

not $0.48

Rhinoflex inner pipe is PEX

@ March 17, 2014 11:39 AM in In ground condensate line replacement

and that 204ºF limit is probably ~30ºF lower than that of the PP-R which Aquatherm is made from.

mod/con cost

@ March 17, 2014 11:31 AM in Scott's radiant heating project

Assuming it is properly installed will be lower than anything else burning NG.  With some history, you could derive a BTUs per square foot per degree-day number and estimate from that.  I think you'll be just fine with the Cadet.

You sound like a good candidate for PV.

PEX-A for sure

@ March 17, 2014 11:26 AM in Pex

Uponor AquaPEX for plumbing -- like the availability of colors (including purple.)  F1960 fittings mostly from Uponor (the EP fittings are immune to our hard water and have essentially zero theft potential) plus a few from Sioux Chief and Dahl Brothers.

Nobody in the entire southern half of our state stocks barrier PEX.  Given that we have to ship it in, we recently started buying Mr. PEX, (nicer pricing than hePEX.)

Electric resistance boilers

@ March 16, 2014 10:52 PM in Scott's radiant heating project

Can PWM themselves down to nearly zero output.

How do you manage to hit the third tier with only 1550 square feet?  Time to step back and look at the big picture.  Lighting and appliance upgrades could be a smart move.  Are you heating your DHW with an electric tank?  High flow shower heads or a huge soaker tub?

20 cents per kWH

@ March 16, 2014 12:55 AM in Scott's radiant heating project

is definitely on the high side, but total annual use must be taken into account when making decisions like this.  If your boiler only runs a few hundred hours per year, the math is entirely different than it is for someone living in the northeast (especially this winter!)

My current rule of thumb is that the minimum firing rate of a boiler should be no higher than 1/3rd of the design day heat loss.  I might be wrong, but I doubt it will be by a whole lot.

∆T control

@ March 16, 2014 12:41 AM in Delta p vs delta t

of larger zones generally means installing supply and return thermistors and adding a 0-10V module to the pump.  Simpler and less expensive to have a pump with built-in controls, but not so many options there.  For larger commercial projects the added costs (two thermowells, two sensors, two control inputs, installation and programming) generally pan out.

On the return

@ March 15, 2014 11:39 PM in Why would i want a mixing valve for my indirect hwh?

Membrane expansion tanks and circulators both live longer when their lives are spent exposed to lower temperature water.  Fire-tube heat exchangers have allowed us to return to this "old" way of doing things.

DDC = Direct Digital Control

@ March 15, 2014 4:27 PM in Delta p vs delta t

In our case, programmable BACnet devices from

The Honeywell TB7980 outputs 0-10V or 2-10V, but has fixed PI parameters optimized for coils.  Viconics has a few stats with a bit more programmability.  Noting in the "small zoning box" category of which I am currently aware.

Characterized Control Valves

@ March 15, 2014 2:22 PM in Delta p vs delta t

From Belimo  We pair them with DDC using 2-10V outputs.


@ March 15, 2014 1:06 PM in Propane and condensate

mine didn't balance.

Third time's the charm

@ March 15, 2014 12:27 PM in Scott's radiant heating project

Aggggggravating!  Turns out using a less than symbol will truncate everything you write afterwards.  Starting over -- again.

Fire-tube HXes

@ March 15, 2014 12:16 PM in Confused about "pumping away" and Knight WH installation

In primary/secondary arrangements work quite well with multi-function hydro separators. 

Be sure to size the primary pump carefully (it will end up one or more sizes smaller than anything listed in the manual.)  Look at the curves on p.36 of the IOM.  For a 35ºF ∆T (maximum efficiency) the 055 needs only 3 GPM.  Given that the HX presents 0.1 feet of head at this flow, even a 003 is oversized for most installations.  Take a look at the B&G ecocirc e3 auto.

Slab Jacking

@ March 15, 2014 12:05 PM in Has a sink hole ever tried to swallow up a boiler you service?

Might be able to save this one, assuming you can fix the leaks of course.


@ March 15, 2014 11:59 AM in Propane and condensate

CH4 + O2 --> CO2 + H2O

Two pumps

@ March 15, 2014 11:55 AM in boiler bypass

are required with a 3-way valve, whether thermic or motorized.  A 4-way motorized valve can often work with a single pump, as long as the boiler HX presents sufficiently low restriction.

Ramping up

@ March 15, 2014 11:51 AM in boiler

sounds a lot like the "boost" feature found in many mod/con controls.  If heat call is not satisfied after X mniutes, raise supply temp by Y degrees.  Repeat until call is met or high limit is reached.

Well said

@ March 15, 2014 11:43 AM in Delta p vs delta t

∆P pumps work like a charm with the proportional zone valves we use (think electric TRV.)  I save the ∆T pumps for zones large enough to actually need their own pump.  Given that the smallest smart circs currently available have curves roughly equivalent to a 008, the overwhelming majority get CCVs.

Dealing with the facts

@ March 14, 2014 10:23 PM in Scott's radiant heating project

We encounter design day heat losses under 20k on a regular basis here.

The smallest gas-fired boilers currently available in North America have output ratings ranging from around 32k to 50k.  This means you'll be short-cycling on a design day and have a truly unhappy boiler the other 95% of the heating season.  A mod/con with a sufficiently low minimum firing rate will fare far better here (see Cadet suggestion above.)

If you have sufficient solar gain and a well-insulated house, an electric resistance boiler can actually make sense.  They're compact, inexpensive, and don't need any venting. has the smallest models I have found with onboard ODR.
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