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Joined on November 26, 2011

Last Post on August 31, 2014

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and the good news is...

@ May 17, 2012 8:26 PM in Need help converting from oversized CI Rad to CI baseboards

That those oversized CI radiators will work like a charm with ODR and lower water temps - which merely exacerbates the consequences of mixing undersized baseboard into the equation.  Your best bet is to run the numbers for the existing radiation in each room, taking into consideration any insulation upgrades and derive a supply temp for design conditions based those numbers.  After that, you will know how much radiation you want for the room in question (at the new supply temp).

Have you considered panel radiators instead of baseboard?


@ May 17, 2012 11:28 AM in Is this why we make fun of engineers

Are given a solid grounding in the basics during their first two years of college.  Unfortunately, they're rarely educated about the realworld solutions which preceded their time.

TRVs, anyone?

nothing can approach

@ May 17, 2012 11:22 AM in How to calculate COP on air source heat pump.

100% conversion efficiency from fossil fuel.  But almost any well-designed cogen (or trigen) setups will do 75-80% overall (thermal plus electrical output.)  The electrical efficiency of a good fuel cell is typically about 40-44% - a marked improvement over the 32-34% from a non-recuperated turbine or a recip engine.  Lifecycle costs on fuel cells so far have not panned out, and Bloom remains a big question mark.  They're holding their data very close to the vest and their customers are under NDAs, which I do understand.

The bottom line is that cogen/trigen (by whatever means) is still our most efficient way to utilize NG.

outdoor reset

@ May 16, 2012 9:36 AM in replacing heating distribution pipes with pex

Is so important to both comfort and savings that I'd probably implement it first - even if I had to defer putting TRVs on the radiators.  With a properly tuned reset curve, the system circulator will run nearly 24x7 and the boiler (even a conventional one) will run more efficiently.  The required near-boiler piping changes are much easier to make now than later.  You can install TRVs and even change out a conventional circ for a smart circ with minimal labor later - perhaps even DIY if you're capable.  Depending on the actual heat loss and the boiler sizing, a buffer tank might be in order.  They also make excellent hydraulic separators.

have you considered

@ May 14, 2012 7:25 PM in Using an indirect HW with smaller boiler

A heat pump water heater?  Assuming you're using electricity as your energy source and that you're running it mostly in the warmer months, the math could be rather favorable, plus you'll get some free cooling of the space where the HPWH lives (might even be worth moving it to the laundry room or other semi-occupied space.

yes, but

@ May 13, 2012 10:25 AM in A Venting Issue

on a draft hood?  Yikes.

is that

@ May 12, 2012 6:53 PM in A Venting Issue

4" ABS DWV pipe?

a picture would definitely help

@ May 11, 2012 6:39 PM in OWNER

I think I'm almost there, but it's not quite clear.

I'm a huge fan of reverse return piping for hydronic distribution and am somewhat shocked it's not more widely used (or understood, for that matter.)  I've had to explain it multiple times - to the same plumbers - on the same job.

Double counter flow?

@ May 11, 2012 10:08 AM in OWNER

You got my attention - what is it?


pellet boilers

@ May 6, 2012 8:35 PM in Why Is the US Always Last

KWB makes truly impressive condensing pellet/chip boilers, but has no interest in importing them here.  They won't even consider licensing (I tried) to a domestic manufacturer.

a small buffer tank

@ May 6, 2012 4:00 PM in Primary/Secondary piping

Makes a fantastic hydraulic separator, and would reduce your cost (both CapEx and OpEx) by eliminating a pump.  If you have zone valves or TRV's, then a smart pump on the secondary will be perfect.

I'm not really a fan of auto-fill valves on closed loop hydronic systems.

just curious

@ May 6, 2012 3:54 PM in Best non-codensing modulating residential boilers

Why non-condensing?  Is it a venting issue? 

(non) autofill

@ May 6, 2012 2:05 PM in PRV blues.....

On a commercial system, the cost of the autofill plus a reduced-pressure zone backflow preventer is more than that of a pressure transducer with alarming.

yes, asking you

@ May 6, 2012 1:16 PM in PRV blues.....

because I have not read the book and wanted to know where to start.  I understand the physics but am always looking for writers who do a great job of explaining it (like Dan!)


We work mostly on small-to-medium-sized commercial projects and do not use auto-fill valves - in fact I remove them from existing systems once the problems are remediated.  I wire a pressure sensor to the BAC system and alarm on low pressure, forcing a human to examine (or at least acknowledge) the problem before adding make-up water.  Caleffi ships air vents with their hydro separators, but we close off the valve once the system has de-aired itself and proven tight (and chemistry is checked.)

positive displacement pumps

@ May 6, 2012 12:46 PM in PRV blues.....

are still the most efficient way to move water.  Believe it or not, we still have pumps in the tradition of the Myers being made today.  I know several of these on remote PV systems that are still running after 15-20 years of continuous use (with maintenance, of course.)

Water and Pipes

@ May 6, 2012 12:32 PM in PRV blues.....
Would you be so kind as to point us at the chapter with the O2 info?


TRV alternatives

@ May 5, 2012 4:51 PM in Why Is the US Always Last

do exist, but are hardly common here.  I can buy a Belimo CCV with a modulating actuator and 2-10V input for about what a Honeywell zone valve costs.  I control them using distributed DDC via software which can look at setpoints all over a building, read multiple outdoor sensors, wind speed, and factor in historical trends to decide where the reset curve should be.  There may be a packaged residential system which can do this, but even a stat with a proportional output would be a good start.  Keeping the control valve separate from the stat allows the temp sensor to be placed optimally (away from the heat source and out of the sun, etc.), looks more familiar to a US customer, and allows system logic to handle setback, home/away, etc.

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.