Heating Help

floating neutral

@ May 24, 2012 9:58 AM in Electrical question

Remember that a neutral is the midpoint between two or more hots (ungrounded current-carrying conductors in NEC-speak.)  On a single-phase service, it is connected to the center tap of the secondary of the transformer supplying the service.  This means that if the voltage on one of leg goes down then the voltage on the other leg goes up, and by the same amount (since the sum of the two must be 240V.)  When the neutral is lifted (or has resistance between it and the center tap of the supplying transformer) the midpoint between those legs "moves around" or floats based on the balance of loads between the phases.  The net effect is that a 120V circuit anywhere on that service downstream of the problem can see wildly varying voltages as other loads turn on and off.  It's not uncommon to read 170V in situations like this -- and the results are usually bad.

sizing rules

@ May 24, 2012 12:49 AM in Gas Pipe Sizing

Are different for the utility, so what really matters is the CFH capacity of the meter.  It's quite common for a meter to have an exit pipe which is significantly smaller than the building main (mostly because they're so short, especially in comparison with the distribution system length.)

Another licensed sparkie says

@ May 24, 2012 12:44 AM in Electrical question

If I'm reading this correctly, you have a 120V air conditioner already powered through the 12/3 cable.  If so, then yes, you can power the other hot from the opposite phase and create a multiwire branch circuit.  You can use a two-pole breaker, though a handle tie on two single poles or a two pole non-common-trip breaker would be best.  These prevent a short on one circuit from taking both down, but comply with the NEC requirements for a single handle that disconnects both circuits.  There are a number of recent additions to MWBC requirements in both the 2008 and 2011 editions of the NEC.

See http://ecmweb.com/nec/code-basics/branch-circuit-requirements-20110101/ for an overview.

embodied energy

@ May 22, 2012 11:09 AM in US to add large tariff to Chinese solar panels

Actually works out pretty well for PV http://www.energybulletin.net/node/17219

To the issue at hand,

@ May 22, 2012 1:12 AM in US to add large tariff to Chinese solar panels

yes, but the Chinese also manufacture a high percentage of evacuated tube thermal collectors sold here.

A corollary

@ May 20, 2012 6:30 PM in help with load calculation results

Sizing a hot water boiler by measuring radiators alone is WRONG.

and don't forget

@ May 20, 2012 6:28 PM in US to add large tariff to Chinese solar panels

huge subsidies to solar manufacturers by the Chinese government in the form of low interest loans and free (or nearly so) land for factories.

Economics

@ May 20, 2012 4:32 PM in Oil to gas conversion burners

of gas conversions are hard to argue with at the moment thanks to what can only be described as a bizarre historical disparity of cost per unit of energy between oil and NG - especially here in North America.
http://seekingalpha.com/article/492991-oil-and-natural-gas-ratio-explodes-to-52-1
Note that the chart above is not corrected for cost per BTU - this http://www.eia.gov/todayinenergy/detail.cfm?id=5830 has both price and BTU ratios.  Looking for something which compares retail NG with heating oil.

engineers

@ May 20, 2012 4:18 PM in Is this why we make fun of engineers

My schooling as an electrical engineer was followed by a 2+ decades in broadcast and telecommunications, where having PE stamp is a rare requirement.  I've managed to acquire sufficient knowledge of building mechanical systems that I now find myself in the position of fixing work performed by licensed engineers - yet because I never bothered to take the EIT test or apprentice at a PE firm, I am not actually eligible to take the PE exam.  I'm contemplating hiring a recent grad just so we can stamp our own work.

mixing it up

@ May 18, 2012 2:44 PM in Need help converting from oversized CI Rad to CI baseboards

There are several factors at work.  Mass of the radiator, volume of water in the radiator, and radiation area all come into play.  The caution with regard to finned baseboard is due to the fact that it operates principally by convection (rather than by radiation.)  This causes a sharp drop-off in capacity as water temperature decreases.  There are two consequences of this - first, you need a lot more of it (linear feet) with lower water temps and second, the reset curve will not match that of other radiators.  You might consider something like Baseray, which is a true radiator and performs well with lower water temps.

mixing radiation

@ May 18, 2012 10:41 AM in Need help converting from oversized CI Rad to CI baseboards

How may recommendations do you need?  Stick around for awhile, they'll show up.

I don't know who told you that mixing cast iron and panel radiators was not OK, but I'd be interested in hearing their justification.

As to which is better, the answer is neither.  You need to run the numbers and decide how much radiation is needed taking into account the newly-calculated room-by-room capacity of the existing CI.  With that, you will pick a system temp and use the heat loss of the room in question to determine how much baseboard or what size panel radiator(s) will do the job.  Then you make a less technical decision: which will look better, cost less, pipe more easily, or fit the proposed furniture arrangement.

panel rads

@ May 18, 2012 12:43 AM in Need help converting from oversized CI Rad to CI baseboards

Runtal, Myson, and a few others.  Jaga if you want high design (and can afford it.)  This is what the rest of the civilized world uses by default when they need to heat a space.

No reason not to mix them with CI - in a properly designed system.  They do have less thermal mass, but with a proper sizing calc and system design, the two can happily coexist.  Mixing baseboard convectors with high mass radiators is harder.

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?

engineers

@ 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?

--thanks

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.