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NRT_Rob

NRT_Rob

Joined on August 20, 2009

Last Post on February 28, 2014

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I'd question primary/secondary

@ October 16, 2009 2:40 PM in Radiant install questions

on systems this small.

the first and most important question is what boiler is best serviced locally?

no boiler is worth much if you can't get parts or anyone to work on it. all else being equal I agree the solo 60 is a great boiler.

with a 32kBTU load, it should be possible to run this system without secondary piping at all, and either of those boilers should be fine as long as no zone runs with less than 1 GPM.

I think this arguement is old

@ October 16, 2009 2:37 PM in high efficient or not

mod/cons have been around long enough now that it should be clear that they typically last long enough to make them worthwhile. the efficiency difference is quite significant compared to a non-modulating boiler in most cases.

that doesn't make any sense to me

@ October 15, 2009 1:33 PM in Controling Grundfos Alpha on boiler with DHW coil

If you're going to spend the money on a low energy pump, I don't see the wisdom of powering it up 24/7 if you aren't running it.

I'd run it like a regular system pump, and if nothing is calling, it turns off.

where did you get that?

@ October 15, 2009 9:02 AM in Pump SIze

18 feet of head? that's huge.

you need to know your flow rate requirements to know what size pump you want. that requires a heat loss. or you can ballpark it. If you're zoning by pump though 4 loops is nothing. I would not normally recommend zoning by pump though unless you only have a couple of zones.

in a basement

@ October 13, 2009 11:37 AM in 6" centers

your heat load will almost never break 10 BTUs/sq ft.

at that load, going tighter than 12" o.c. is a waste of money. If you do *anything else* in the system, on the upper floors, they will already require hotter water than this so you are saving exactly nothing dropping your water temperature another, at most, 5 degrees here.

and in basements you can routinely run very long loops without problems too. we do 12" o.c. 400 to 500 foot loops regularly in insulated, buried basements, and we do NOT upsize system pumps NOR do we raise water temperatures in our systems to make it happen. without design, 300 is safe in a basement.

Exception: walkout areas, which aren't really "basement", and perhaps greatly exposed areas with carpet flooring. In those areas you might tighten up the on center.

or do 6" o.c., it's only money.

man, that's an interesting question

@ October 13, 2009 9:35 AM in Increase in system run time question to ponder

if you assume a min mod of 25kBTUs and a boiler non-mod output of 75kBTUs, you'll get 3x the runtime for all loads that result in the mod/con cycling. for all loads above the min mod on the modulating boiler, you improve the non-mod 1/3rd run time to 100% run time (assuming perfectly sized boiler, from 25kBTU load to max load) all the way to 100% the whole time.

without bin data it might be hard to calculate that, but it stands to reason it's a huge increase in run time.

the *real* question is what does that mean? for instance, if you had enough thermal mass to just run all of your hours continuously, and then pull heat off of the mass for the rest of the winter, run time wouldn't help you in any case... you would get a single steady demand in both cases, it would just last a different length of time. So run time would not be a helpful metric for that hypothetical system... I think.

what you're really interested in, I think, is cycle count, given that each cycle is much less efficient for the first few minutes? and that gets the system mass into the equation, with standing CI radiators especially.... and I have no idea where to go from there right now.

hm

@ October 12, 2009 3:31 PM in Can I create a cost-effective system to do this?

adding heat exchange to the tank water heater would be better than trying to do small heating with an on demand.

what "cost effective" means depends on your actual heat loads though, not just square footage.

that's a gross overstatement

@ October 8, 2009 11:06 AM in Radiant vs Efficient Furnace

a well designed air system with a 95% eff. furnace will NOT require 35% more energy than a radiant system in most cases. no way.

that may be true for some systems, but there is nothing inherent in the use of radiant heat that makes that extreme statement true.

i'm not sure your observation is correct

@ October 8, 2009 11:01 AM in Recommended Temperature

I can only think of a single mechanism that would allow a hotter water heater to run less often unless you are also changing your differential. your air handler would run less frequently, because it would satisfy the thermostat faster. however when it does fire you are likely to be using "more energy" per unit time because it's dumping faster into the air stream.

you don't get to cheat physics this way, and you'd be best off turning down your water temperature, UNLESS you are short cycling, which might happen if you are spoofing a sensor in the tank with your return water temp.

If you're doing domestic, the tank should be 140 with a tempering valve out to prevent scalding.

heh

@ October 6, 2009 11:22 AM in NRT Rob in the news!

Thanks Dan, are you a regular reader of the KJ?? ;)

we do plan to document the construction fully. I'm really looking forward to having our very own mad scientist laboratory to work from!! the base system will include slab, warmboard, and radiant ceiling elements and the plan at this time is to go for a cold climate air to water heat pump, radiant heating/cooling, with solar thermal and subslab air handler preheat. we still have some budget shifts occurring though so the final design is in limbo still, and the fact is whatever we do on year one will probably be completely revamped by year 3, and again by year 5, etc...

but the real beauty will be the flexible design. we'll be setting it up to be able to meter all energy inputs and outputs, and also to be able to reconfigure our loop lengths, at least, and in some cases on center as well.

Also we're designing the second floor so we can lay down any panel product we like right on top of the floor and do output testing for overfloor panel products... any suggestions for particularly good BTU meters will be heard with interest!!

The first thing we have to figure out is how much we really want to play... I can sink $1500 in pipe in the ground under the slab pretty easy if we want to be able to really experiment with on centers and such down there....

that's what we use

@ September 21, 2009 10:34 AM in Hydro Seperators

I'm asking if any resorbers are built into hydro separators, or whether the air removal devices in hydro separators are simply air vents.

I don't know all the physics behind their usage though, so basically I'm just asking if any of the hydo-separators out there have air removal devices that are as good as spirovents. It may be that with simpler construction they are just as effective due to the velocity/pressure situation in the hydroseparator.. I don't know.

But If not, the vent on on the hydro sep is not serving the same function as a spirovent, and I couldn't offset the cost of the sep by dropping the spirovent.

air sep plus vent?

@ September 21, 2009 8:06 AM in Hydro Seperators

when we use a microbubble air separator in a system, we almost never use additional air removal vents. It shouldn't be necessary.

Can any current hydro separators reduce the oxygen saturation level of the water to the point where it absorbs air from other parts of the system? or are they just good vents?

pumping

@ September 20, 2009 6:05 AM in Variable speed compressors for GSHP systems.

then all we need to do is show them that pumps come in fractional horsepower and they are quite adequate on the load side of most units, if they would lower the pressure drop and flow requirements a little bit...

nothing like pairing up an alpha with whatever monstrosity they require on the geo load side circuit.

closed side non-ferrous?

@ September 18, 2009 9:24 AM in convert open system to closed system

I think the X-block has a cast iron pump on the system side? I might be wrong, but I think it's only non ferrous on the expected open side.

If I am right though, you can do what the xblock does with heat exchange, and non ferrous pumps on both sides.

depends on what U-type you mean

@ September 13, 2009 8:31 AM in budget quick trac

Thermofin "U" is 1/20th of an inch thick and 4" wide. it's extruded, solid aluminum, good stuff, slightly thinner than thermofin "C". we use it in sandwiches all the time, but you can also use "C".

Lightweight omega "U" plates are a different breed. they work fine in sandwiches, especially if you get the aluminum on the right side of the plywood (unlike quik trak). however, with light plates I always recommend PEX-AL-PEX to help make sure you don't get expansion noises. you lose some output too, but you'll still beat subray, thermalboard, quik trak, and the other "weak panels" out there. however, it's more labor to cut your own infill and such, of course.

use P/S when needed

@ September 13, 2009 8:19 AM in TT-110 to p/s or not

and "when needed" means when your GPM/head requirements are too high for system with the boiler heat exchanger pressure drop and the pump you are using (internal, for that boiler).

otherwise, install a pressure bypass for your minimal flow requirements (assuming radiators are TRVed or that there is any other possible way you could have total system flow below the min flow of the boiler).. which you'd need for the secondary circuit in any case... and go primary. saving a pump is great if you can do it.

and big pipes are known as "long, skinny buffer tanks". they are awesome. be glad they are there. but insulate them in cold space.

yes

@ September 8, 2009 3:23 PM in budget quick trac

rabbit the sleepers so the thermofin plates can sit flush (1/20th inch) and put the aluminum on top of the sleepers.

Thermofin will rock the output a lot more than quik trak would as well. or you can use lightweights on top of the subfloor with no rabbiting, which is also cheaper, but you'll lose some output.

my personal favorite

@ September 6, 2009 12:37 PM in moving heat between tanks in two-tank solar hot water

is cold solar tank. perhaps with a top coil for heating system extraction, perhaps not. solar coil in bottom.

electric on demand, or gas on demand rated for "boost" applications (I've seen an "eternal" hybrid heater that fits the bill nicely) for DHW. Even if electricity is expensive, it's reduced usage in the first place, so no problem.

then you never heat the tank, you maximize your storage, and every BTU you get offsets a BTU used (minus tank loss), whether it's "hot enough" or not.

Logs

@ September 6, 2009 8:21 AM in A friend has radiant heat with outdoor reset.

Logs do cost a lot. they aren't very good insulation and the mass effect isn't very helpful in new england.

that said, we use indoor feedback teknet 4 systems on probably 3/4 of our projects. it is a totally sweet system and in many cases it more than justifies its cost, but indoor feedback (and this is true indoor feedback) will not save 10 to 20 per cent over outdoor reset. it's about fast response, precision, and some efficiency gain, but not that much.

it has other features that do help though, like zone synchronization to manage multiple zone firings to minimize short cycling, boiler firing controls, etc.. Depending on the system, THOSE features might save 10 to 20 per cent.

if he's got multiple low mass zones, he could probably save some bucks adding a buffer tank too.

how did his blower door go? logs are tough to seal but some outfits seem to be better at it than i used to be able to count on.

but

@ September 2, 2009 9:46 AM in moving heat between tanks in two-tank solar hot water

if you do not transfer heat from hot tank to cold tank, you will always have the "gas tank is firing even though the solar is hot" aggravation from the client. People hate that.

I would stick with a basic differential control and recric. If solar is hotter than water heater storage tank, transfer occurs. cools down the solar tank (more solar transfer, you've effectively increased your available storage volume), provides de facto heating integration if the solar is hot enough to do so, and solves the psychological teeth gnashing of hearing the combicor fire when the solar is hot.

This is why I don't really like two tank designs, typically, but in a retrofit you get what you get for sure.

no offense taken

@ September 1, 2009 8:13 AM in Tankless for Radiant Layout

though remote design is definitely possible, all things equal I can't beat a competant designer on the ground. I also can't design a system in a forum post.

That said, with a 17kBTU load, unless the original poster is in a very, very cold climate, he's probably best off with a tank heater, and his k3 was just unnecessarily expensive for the relatively non-existent benefit he's going to get from the tankless. so rather than laying out the components he's got, he should send some back and get something more appropriate to his system.

still depends

@ August 31, 2009 1:22 PM in Tankless for Radiant Layout

on your heat load, but you're probably closer to a tank heater than a mod/con boiler.
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