Heating Help

sheathing

@ March 12, 2012 10:16 PM in Attaching Solar to 12" SIP Panels

I don't love to do it, but if you are installing on an existing SIP roof and there is no opportunity to get blocking inside the panels, it is possible to install a PV system into only sheathing.

Obviously it depends on the wind and snow load in your area as well as that particulars of the install, but in most cases you can achieve adequate fastening to sheathing alone. It isn't my favorite thing to do, but you can do it safely.  I can't remember the exact manufacturer, but in these cases we use a mounting foot which takes about a half dozen fasteners each, rather than a single lag, thus further spreading the load around to more fasteners.

A #12 wood screw with 1/2 inch engagement in C-D grade plywood has a 315 lb ultimate pullout strength. Do the math to figure out the maximum uplift generated by your array (paying particular attention to the array corners) and the specify at least 4-6x that much fastener (to account for the variation in plywood).

If you know the manufacturer of the SIPS, start with them as pullout strength varies for various types and thicknesses of plywood.

~Fortunat
www.revisionenergy.com

Radiator or Valve plugged?

@ March 2, 2012 12:49 PM in Waller House

What happens if you shut the valves to all the other radiators in the house while the circulator is running? Does the basement rad heat up? If so, then you have a balancing problem as others have pointed out.

If not, then you have a piping problem, major air problem, or the radiator or valve is plugged.

~Fortunat
www.revisionenergy.com

glycol choice

@ March 2, 2012 12:37 PM in Steve

Steve,

We've used Dowfrost HD, Tyfocor and others in systems with 'steamback' stagnation control and so far they've all held up well. Some have been in for years and the heat transfer fluid still looks as good as new.

One of the keys is in the near collector piping arrangement, which should be laid out so that it is forced easily back to the expansion tank when the system is in stagnation. If it does then only a very tiny percentage of the system's glycol actually ever sees the high temperature. When boiled at moderate pressure, about a teaspoon of water will make enough steam to completely fill a typical flat plate hot water collector so in a system that has 5 gallons of glycol in it maybe 1/3840th of the fluid is actually boiled or exposed to high collector temperature during a stagnation event.

Furthermore, in most PG/Water mixes you will find that it is the water that boils first, forcing the remaining fluid out of the collector before the glycol even reaches 300 degrees so I'm not sure that much if any of the PG ever actually changes phase.

hope that is helpful.

~Fortunat
www.revisionenergy.com

Bio Glycol ... any experience?

@ March 1, 2012 8:49 PM in Bio Glycol ... any experience?

Hey Solar Wallsters,

Have any of you ever used a 'bio' glycol in a solar system?

I've recently been reading about a product made by Interstate called Intercool Bio Green.

http://www.interstatechemical.com/images/ICBulletins/Intercool%20Bio-Green%20presentation.pdf

It seems to have some pretty attractive performance characteristics and the fact that it is made from plants instead of from petroleum products sure seems like a better fit for our values and mission to reduce fossil fuel consumption.

But glycol isn't someplace I want to take risks with an unproven product. Any experience? thoughts?

~Fortunat
www.revisionenergy.com

which degree days?

@ January 23, 2012 9:58 PM in Just Wonderin' About Propane Usage

Ah yes, but you also need to account for the fact that a building maintained at a lower temperature experiences fewer degree days (not just a lower load per degree day).

There are a number of degree day data bases which let you figure out degree days based on different indoor temperatures.

Adding that dynamic to the reduced heat load per degree day will increase the apparent effect of lowered setpoint.

~Fortunat

none of the above

@ January 16, 2012 1:30 PM in solar / radiant heat interface?

My suggestion would be to use the closely spaced T's, but to put the solar injection upstream of the boiler injection so that, as you note, the solar coil is always getting a crack at the lowest temperature heating.

In the case of your other drawing ( bottom drawing), you haven't achieved effective hydraulic separation between the loops so you'll be fighting ghost flow in the solar tank coil and uneven flow in distribution depending on which pumps are running.

good luck.


~Fortunat
www.revisionenergy.com

Lots of options

@ December 27, 2011 10:43 PM in solar / radiant heat interface?

I like both of the options that Rob (NRT) suggests, but I don't know that I agree that those are the ONLY choices which make sense. Generally I prefer simpler tie in where possible, and as rob says, the lower you can pull the tank temperature, the better.

Another design we've used in the situation you describe is to use a dual injection strategy from the tank and from the boiler (see attached sketch). If I remember right we controlled it with a Tekmar 363 which worked pretty nicely.

~Fortunat
www.revisionenergy.com

not triple coil but the same idea

@ September 21, 2011 7:48 PM in solar tanks

There are a bunch of tanks now for sale in US that are designed for solar combi systems. I haven't seen any actual triple coil tanks here yet, but these multi tap tank in tank water heaters do essentially the same thing.

-Wagner CombiPro 450
-Buderus Logalux PL750/2S
-Triangle Tube Smart Multi Energy Tank

Any of these would probably be suitable for what you want to do. Because the outside tank is full of boiler water and has lots of different tappings it allows you to tap in for the boiler and even multiple different space heating temperatures at the same time.

~Fortunat
www.revisionenergy.com

I'm not a fan of drainback

@ September 15, 2011 8:50 PM in Drainback on flat roof

I'm not generally a fan of drainback systems cause I think they are a pain in the ass, ugly and failure prone.

But in this case we were unable to convince the specifying engineers to change their plans and so we did do drainback...on a flat roof no less. I think this sounds similar to what you are planning:

http://www.revisionenergy.com/solar-projects/schools-nonprofits/durham-elementary/

If you are interested, I can probably find some install detail photos or plans that I could send your way.

~Fortunat
www.revisionenergy.com

thermal storage

@ August 28, 2011 8:15 PM in Anyone have any Daikin Altherma experiences??

I'm too am somewhat interested in thermal storage with the Altherma but I wonder if you can actually justify it. It seems like the COP curve may work against you as you try to justify the cost of the storage.

The Altherma's performance is fairly sensitive to both ambient temperature and water temperature and using it with thermal storage might hurt you on both of these.

Off peak electricity tends to be available over night (among other times) when ambient temperature is low. If COP slips by a point at night, that eats significantly into any savings you might be seeing from a lower electric rate.

On the other end, if you are using thermal storage, you are necessarily heating the tank to some temperature higher than what you need for heating. For a 600 G storage tank, every 10 degree increase in tank temp stores about 50,000 BTU, so to get you through a day in a somewhat average house you might be talking about a 40 degree rise or so. Heating water to 40 degrees hotter than what you need for distribution also comes with a substantial COP penalty for the altherma and so again offsets some of the pricing advantage of off peak electricity.

I suppose that if you had details on the electric rates, a bunch of COP data for the altherma and a years worth of hourly temperature data you might be able to accurately model the whole thing and see if it is worth it.

My instinct is that in the kinds of homes that the Altherma is built for (reasonably well insulated buildings with modest heat loads and low temp distribution), you might find that it takes a very significant off peak electricity discount to overcome those other two factors...that's just my guess though...I haven't looked at it closely.

~Fortunat
www.revisionenergy.com

does it come in other colors

@ August 17, 2011 11:52 AM in Outdoor pipe wrap

Matt,

Does it come in other colors? I only see white and gray?

~Fortunat

really?

@ July 20, 2011 8:06 PM in Anyone Know Who the Lucky Guy

forgive me, but a 72,000 sf second home cannot credibly be described as 'sustainable' or 'energy efficient'. 

'Abomination' and environmental catastrophe seems more apt.

~Fortunat

roofer

@ July 20, 2011 7:59 PM in Outdoor pipe wrap

Thanks Rod,

That's interesting. Thanks.

Coincidentally in the couple days since I posted this question I've had two customers ask for a custom 'better looking' solution. In each case we're dealing with a standing seam metal roof so I think I'm going to ask the roofer if they want to try bending some roofing material for pipe wrap.

Not sure how we're going to deal with the elbows, but I'll snap some photos when they are done.

~Fortunat

www.revisionenergy.com

Outdoor pipe wrap

@ July 13, 2011 8:04 PM in Outdoor pipe wrap

Hey Wall,

I'm curious what other installers are using to protect outdoor insulation from UV. Though Armaflex and others claim to be UV rated, I think pretty much everyone agrees that they won't last uncovered on the roof and so something has to be done.

On commercial projects where we often sub the insulation, the piping is usually wrapped in a metal jacket. but we tend not to do that for residential as it looks a little industrial for most people's tastes.

For Residential we've always just covered all exposed insulation in PV wrap like this: http://store03.prostores.com/servlet/buyinsulationproducts/the-PVC-Fittings/Categories

And that works well when properly installed. The only complaint is that people want colors other than white, and as far as I can tell, only the White is actually UV rated. We used black for about a year (a couple years ago) and it does curl and fade and looks bad after a few years.

The tape wrap or the pre-covered line sets tend to look pretty crummy too.

Anyone have a better product or solution they use?

thanks

~Fortunat
www.revisionenergy.com

Sucking air

@ June 7, 2011 10:28 AM in Solar Drainback

Your engineer friend's descriptions sounds plausible.

What's the water level in the drainback tank when the system is operating and how is the water returned to that tank. If the water level is low or the return water is entraining air in the tank I could see how it could make its way around to the pump.

~Fortunat

spirovent

@ June 2, 2011 9:15 AM in potable water air elimination

Mark,

when you say Microbubble resorber, you mean something like a spirovent, right?

Do they tend to be rated for potable water pressure? I noticed that the Taco 400 series Hyvent says 150 psi on it.

~Fortunat

potable water air elimination

@ June 2, 2011 8:02 AM in potable water air elimination

I know this is a heating forum, not a plumbing one, but I'm hoping someone here can help answer this question anyway:

We have a customer who has some sort of water cleanup system that involves basically aerating the well water on the way into the tank. The water then flows through a 'burp' tank which removes the air and then on to our water heater.

What we're finding is that (unsurprisingly) additional air is coming out of solution in the water heater and ending up in the hot water line where it sputters and pops when the tap is opened after a period of non use.

So, my question is, is there any acceptable means of air separation on a potable water line (ideally the potable hot water line). I presume that high vents and spirovents are generally not rated for potable pressure, right? any other options?

Thanks for the help.

~Fortunat

bump

@ May 19, 2011 8:55 PM in triangle tube challenger

Now that its been a couple months, I wonder if anyone has opinions about the Challenger boiler yet?

We've been fans of the Prestige Solo and Excellence and I haven't actually seen the Challenger yet, but I'm curious what others are finding?

~Fortunat
www.revisionenergy.com

facts have no place in marketing...

@ May 19, 2011 8:29 PM in In the Morning News.... 1st Solar Car Wash!!

It is pretty surprising that they'd make a claim like 'first solar car wash' when a google search for that phrase brings up about 4 Million pages.

here is our recent solar car wash:

http://www.revisionenergy.com/blog/black-dog-car-washs-new-dover-location-shines/

but it isn't thermal, it's PV. Because apparently around here, most of the car washes use cold water in the summer, which makes solar thermal a bum deal.

~Fortunat
www.revisionenergy.com

copper powder

@ May 6, 2011 7:29 AM in Broken evac tube.

I think Kevin is basically right. I believe the 'antifreeze' in these heat pipes is often just some fine copper powder or something similar. I don't know exactly how it works, but I don't think it actually prevents freezing, it just (in theory) prevents damage from freezing.

It sounds like Sunrain (and other chinese manufacturers) have been doing some tinkering to get the formula just right for the US's northern climates. Actually I think a lot of the Chinese tube manufacturers buy both the tubes and heat pipes from others and just build manifolds and frames so many different brands of collector could be using heat pipes coming from the same factory.

Hope the new heat pipes solve the problem.

~fortunat

seems unlikely

@ April 26, 2011 7:50 PM in heat transfer between storage tanks

unless there is a difference in elevation, it seems unlikely that heat would move back to the solar tank in this configuration, but I suppose it is possible. What diameter is the water piping? I don't know if it is true, but I've read that single pipe thermal siphoning really only happens in larger diameter pipe.

You could test it by running all the hot water out of the solar tank some day and the checking to see if that line heats back up.

I'd also have a careful look at the mixing valve plumbing as without check valves, they can sometimes allow hot water to siphon back into the cold line.

We have lots of systems set up in the way you describe and I've never witnessed any of them bleeding heat into the solar tank (though as you note, unless I happen to visit after a series of crummy days, I'm not sure I'd notice).

Just another reason to prefer dual coil tanks systems.

~Fortunat
www.revisionenergy.com

What IS a short cycle

@ April 21, 2011 9:29 PM in short cycling in shoulder season, fact/fiction/improper design ?

A related basic question:

What constitutes a 'short cycle' in various boilers? High mass, low mass, mod con?

I've seen some data on cast iron oil boilers and how long they take to come up to steady state efficiency? what about mod cons?

If my boiler is firing at minimum input in the shoulder season and shuts off after 90 seconds and then starts again 60 seconds later and repeat on an off for 30 minute heat call, is that actually bad?

It's not like the boiler is starting from cold? other than a bit of extra heat loss during the pre and post purge cycles, what's the harm in the cycling?

If it is bad, what is the limit? 2 minutes? 5 minutes? 10 minutes?

If we had that number we could design around it....but I've not seen a credible number anywhere.

anyone ?

~Fortunat