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Joined on November 26, 2011

Last Post on August 19, 2014

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System washing machine?

@ May 4, 2012 10:03 AM in PRV blues.....

I'm intrigued...

appropriate use

@ May 3, 2012 10:07 PM in Critical article on Tankless water heaters

Tankless water heaters make a lot of sense for some very specific applications.  Selling them as the be-all and end-all of efficiency is just garden variety greenwashing IMO.

it's really about the storage

@ May 3, 2012 3:56 PM in Buffer or Indirect Tank 4 DHW

If you store at 180F and your system design temp is 120F (just guessing here) your 2,500 gallon tank will hold about 7.5 million BTUs.  AHS can help you figure out the BTU value of a load for each of their boilers based on species, dryness, and size.  Then you decide how often you want to load the boiler and how much you want to spend...

wood-fired heat sources

@ May 3, 2012 3:39 PM in Buffer or Indirect Tank 4 DHW is an excellent resource.

wood gasification

@ May 3, 2012 3:22 PM in Buffer or Indirect Tank 4 DHW

Will hit 80-85% efficiency - that's the point.  If you already have storage, check out the AHS (a domestic gasifier with a long track record)  There are quite a few European manufacturers of similar designs, though neither shipping costs nor exchange rates are favorable at the moment.

The idea is to load the boiler once per day (usually less) and consume the entire fuel load, storing all of the BTUs.  I'd store at 180F, then mix down with a motorized mixing valve and ORC.  You can pipe the mixed output in series with your GSHP if you coordinate the setpoints, and the GSHP will not kick in until the tank runs out of BTUs.

heat loss calc

@ May 3, 2012 1:24 PM in Buffer or Indirect Tank 4 DHW

Do you have a heat loss calc at design temp?

It's starting to sound like you could use a bulk heat source during the colder months, then let the GSHP handle the shoulder seasons.  I'll ask again about wood, because if you have that on site, a gasifying cordwood boiler plus storage (or something like a Garn) would be a great fit.


@ May 3, 2012 11:41 AM in Buffer or Indirect Tank 4 DHW

How much of the time does the GSHP have to run 24x7 to satisfy the heating load?  The remaining portion of that time (if there is any) represents headroom which can be used for DHW heating.

If you have a reliable supply of wood on site, biomass gasification could save you a pile of money and give you some security against fuel price uncertainty.


@ May 3, 2012 12:54 AM in Treasurer-Condo Assoc

Can't take you up on the bet, but I do have a few fantastic 1990's left that I'd be happy to share with the right 'company' if you know what I mean.

I think a lot of the efficiency numbers are related to radiation differences.  Convectors versus radiators y'know...

how much headroom

@ May 3, 2012 12:41 AM in Buffer or Indirect Tank 4 DHW

From the space heating loads?  A big tank might just do the trick, and keep the delta-T down to where the heat pump can work well.

Any other fuel sources?  How much sunshine there?


@ May 3, 2012 12:30 AM in What is this?

Great story.  Ring voltage is a 20 Hz AC signal that starts out (at the central office) at 90V.  Pretty annoying even though the current is quite low...

One more time

@ May 1, 2012 10:45 AM in Navien Combi opinions wanted

1. Use a DHW heater with a heat exchanger to separate potable water.
Assuming you need both DHW and space heat, this will require two pumps, a heat exchanger, a motorized mixing valve, and an outdoor reset controller.  And the DHW heater will almost certainly die an early death.

2. Use a boiler in a closed loop system.
Whatever you use, the heating should be in a closed loop system.  Assuming the boiler modulates, has built-in ORC, and can be directly pumped (has a low head loss across its HX)  this is by far the simplest way to get the job done.  If you're only heating 500 sq ft of radiant floor, your pump can probably run on 10 Watts (really - check out the little ecocirc e3 and compare power use with a Taco 003.)  The big one here is to make sure the boiler is not oversized.  From my perspective, that means a small electric boiler is your only real option.  It also happens to be the cheapest option here by quite a bit.

3. Use a boiler with an integrated DHW tank (like the Triangle Tube Challenger)
Assuming this would replace your existing DHW heater?  The Challenger is tankless.  You're still going to be short-cycling if it only heats this little space.  The Prestige Excellence (which has an integrated DHW tank) is even more oversized for this application.

4. Use a boiler with an indirect hot water tank.
Could work if you get an indirect that's big enough to buffer the boiler, preventing it from short cycling on your miniscule heating load.  It's going to cost at least 6x what the little electric wall mount boiler I suggested will, and it's going to need about 25x the space.

Good luck with the addition.


@ May 1, 2012 1:15 AM in Can we split tankless on-demand hot water unit for hydro air & domestic hot water?

you don't, if you value your liability insurance and your ability to sleep well at night.

There are ways to make things like this work and still meet code, but economic viability can suffer.

dump loads

@ April 30, 2012 10:24 AM in Solar Thermal is Dead

Can make sense in some situations.  If the PV output goes up 20% (they claim as much as 30%) in the hot months, the effect on net metering or REC revenue could be quite significant, especially with TOU metering.

thread drift

@ April 30, 2012 10:17 AM in Navien Combi opinions wanted

I fear we may have overwhelmed poor SaraJ on this one.

(mostly) agreed

@ April 30, 2012 10:07 AM in Solar Thermal is Dead

With PV module prices where they currently are, PVT really is a tough sell.  There are a few cases with limited collector space where it can make sense, especially if night sky cooling is involved.


@ April 29, 2012 8:47 PM in Solar Thermal is Dead

Is available in the US - click on the 'Contact' link -- and give Reinhard my regards.

Remember that from a thermal perspective, this is basically an unglazed flat plate collector.  Still plenty of uses, but not much good for space heat other than in a few very mild climates.  If you have a use (or a dump load) for low temperature heat in the summer, the PV output can significantly exceed that of a standard system.

not a prepackaged product

@ April 29, 2012 8:31 PM in Trapping a mixing valve?

Just a temp sensor hooked to the DDC system and alarmed at setpoints.

Dwyer and ACI and many others offer prepackaged solutions.

financial "modernization"

@ April 28, 2012 2:09 PM in The Propane industry

Frontline (one of the last bastions of hardcore investigative journalism in the MSM) just dug into this deeply


@ April 28, 2012 12:06 PM in Broken evac tube.

Try an high-solids dry silicone spray.  There is no oil in these, just a bit of high volatility carrier which evaporates in seconds.  I get mine from an industrial hose supplier - not expensive, but simply not available at the auto parts store or a big box retailer.

Combo PV-Termal panels

@ April 28, 2012 11:27 AM in Solar Thermal is Dead

Many of us have been waiting decades for these.  The Germans are close

the Internet

@ April 27, 2012 8:04 PM in The Propane industry

Was a product of DARPA and the National Science Foundation.  Ma Bell sold point to point lines and collected the rent from those agencies. 1995 began a relentless privatization of what was once a public commons - frequently by converting taxpayer-funded infrastructure to private property - without bothering to reimburse the taxpayers.

All well and good, but

@ April 27, 2012 7:58 PM in The Propane industry

Domestic natural gas supplies are off the charts right now and prices are at historic lows, especially when you look at the cost per therm compared with oil.  As I understand it, so much profit is being made off the condensate and the liquids that they don't actually care much about the price of the NG.  How would more drilling help this situation?