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hot rod

Joined on August 27, 2007

Last Post on September 1, 2014

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not easy to model

@ August 15, 2014 11:07 PM in System's Architect

I asked Siggy once about modeling tank loss, on an inside storage tank for my wood boiler, with his FEA program. The tricky part is the stratification, which could have a different heat loss every inch or so of the tank height.

A tall tank could be 140F at the bottom, 180F at the top so that loss number gets fairly complicated to nail down. And that would have been in a fairly consistent ambient air temperature space.

Obviously if the tank were in service that water temperature gradient would be ever changing.

In ground brings a lot more variables. The ground temperature changes across a time period. In the fall the ground may be 55F at a 6' foot depth.

I have thawed water mains that were 6 feet deep in Utah during low snow, cold winters. So you could potentially have a 100°∆T or more, fluid to ground temperature, in portions of that tank in winter.

I suppose a data logger with sensors ever so many inches could help pin down a number.

But would the heat loss of a tank of still water be that useful, knowing that an active system would never produce those conditions? has an interesting article on underground insulated piping on a job in Finland, MN McKinstry Mechanical did some heat loss calcs on the old fiberglass pipe compared to a new Ecoflex system. You might contact Bernie to see how he ran the calcs.

As you eluded to, any water around that insulation would make those numbers, if you did crunch them, all but useless.

I have seen some outdoor wood furnaces lose 60 degrees from the heat source to the building when ground water surrounded the insulated pex. Waterproofing and drainage, possible a sump pump might be wise.

Keeping a jug of water hot in the ground may not be as easy as it sounds.

Thermal storage is the holy grail of solar energy, all sorts of methods have been tried. One of the more interesting thermal storages was Nevada 2 solar farm where they could store a days worth of thermal at super-heated temperatures, in molten salt.

Plenty of salt across a State border, not far from your project :)


@ August 15, 2014 2:16 PM in System's Architect

I have done a number of jobs with various brands. I have several projects at my own place here in SW Missouri. I'm having problems with the in-ground ICF being eaten away by bugs? I am not sure if the warm temperature from the radiant slab contact, moisture, noise, ?? Something attracts some burrowing insects to ICF as well as the blue or pink boards.

I spoke with one local ICF supplier that had lived in Australlia. He indictate they wrap all the in-ground ICS jobs with a stainless screen type of material, down under. Some versions have waterproof membrane included.

Wonder if you have any experience in the dry western areas with this? The builders I worked with in Utah tried ICFs 20 years ago and have all moved away from them.

I did a small in-ground pool with ICFs and it is heated with a radiant floor. I should check on that job someday :), it's been in service about 9 years now. I threw in some aluminum transfer plates also.

I've heard a Borate treatment helps, but needs to be retreated from time to time.

got it

@ August 15, 2014 9:52 AM in System's Architect

I was involved with some radiant cooling slabs in Utah back in the 1990. Granted they were in a mountain climate with low cooling loads, but they were installed with the early rubber tube RadiantRoll product, about 1/4" ID!

The main complaint, as they were both commercial buildings with office personal , was the cold feet issue. Folks sitting at desks ended up with rubber mats under them for some insulation away from the chilled slab.

Ceiling radiant or emitters like the Zehnder products would be sweet, if the budget could allow.

My last word of caution would be to not install products that are not listed and approved for solar. Many of the system failures in the 70s, 90s and even 2008 era were caused by product failure. Plumbing and hydronic products are not up to the task for solar.

I've been installing and servicing solar since the 1970's and I am in contact with a lot of designers and installers in my current position as a trainer, too many horror stories out there, still.

We lose a lot of customer confidence when systems fail or are obsolete several years after they are installed. Both product failure and poor installation workmanship, continue to haunt us, it's worth doing right.

There are plenty of domestic solar products and components available with 30 plus year track record, just a thought.

There are a number of engineers i work with that could do some modeling for you. Or maybe NREL would take it on as a research project, they have the knowledge and staff to do that model.

Have you considered PV to thermal with resistance elements?

volume vs flow and temperature

@ August 14, 2014 10:54 PM in System's Architect

true you can store more energy in more volume.

Heat transfer is accomplished by flow rate and temperature difference ∆T.

It you are talking stored energy, volume buys more stored energy.

Transfering energy, flow and temperature change are the main drivers.

Rate of Heat Transfer= 500X flow rate (∆T)

assume a 300 foot circuit of 1/2 pex about 3 gallons of fluid
1.5 gpm flow rate, 120F supply 100F return

500 x 1.5 X 20= 15,000BTU/hr.

Changing nothing but the tube size, and the volume of fluid, will not change the heat transfer rate that much, perhaps a small amount due to increased surface area.

Pump a loop so the flow rate is between 2-4 fps is a common industry standard. Larger tubes can move more energy because they allow higher flow rates.

It will have more energy available to transfer in the additional volume.

Of course with 3/4 tube you could at least double the flow rate and transfer more energy.

3/4 pex for example needs a flow rate of 2.3 gpm to provide 2 fps velocity
At 4.6 gpm you will be moving 4 fps.

Flow a 500 foot loop of 3/4 pex at 2 gpm and at 9" on center you could expect a floor output over 50 btu/sq. ft./ hr. I can't imagine any residential loads even close to that?

Spread to 15" on center and expect 30 btu/sq. ft./hr. But wide spacing allows for uncomfortable striping. RadPad calculations.

That is why the 3/8 or 1/2 diameters 6- 9" on center are adequate and much easier to install.

If you go with 3/4 pex, install it on a warm sunny day. It's a gnarly tube to uncoil and install when it is cold.

I wonder

@ August 14, 2014 4:49 PM in System's Architect

what the over-heat protect mechanism is for that direct solar?

If you size the array large enough to cover some of the heating load, beyond the DHW load, what happens in the summer months and during low DHW loads?

Most flat plat collectors stagnate well above 300°F.

Certainly you would not want pex anywhere near those temperatures.

I see that he offers glycol and drainback methods. You may be better served with DB if you have lopsided loads as mentioned?

I applaude you concept and project, but no need to re-learn some of the solar "lessons learned"

In fact grab Tom Lanes book "Lessons Learned" to help avoid some costly mistakes with the solar design.

Here is my experience with pex and solar. It sounded like a gun shot when it let go.

be careful

@ August 14, 2014 4:33 PM in System's Architect

with large diameter tube, especially on small, bedroom zones. With short loop lengths your flowrate may drop below 2fps. This makes air elimination tough, and heat transfer can be a problem if the flow rate drops too much.

The RPA suggests 500 foot loops for 3/4 and 1.2 gpm flow rate.

Also 3/4 is tough to make tight loops.

If you are going to zone bedrooms and small micro zones, 3/4 may not be a good choice.

Tighter tube spacing allows lower fluid temperatures which is huge with solar or heat pumps. Here is a graph to show that relationship. My next radiant slab would be all 6" OC!

The volume of fluid in the tube has little to do with the heat transfered.

either or

@ August 14, 2014 3:01 PM in Boiler Room Layout Mock-up – reasonable, flawed or both?

will work just fine, the LLH or hydroseparator chamber allows the entire device to see, or become the PONPC.

If Viessmann prefers boiler side, go with that.

The separator you show, and shown a few posts up, if it is a Sep4 has a built in microbubble air removal , much more than a LLH and it commonly gets installed with Viessmann equipment.

good catch on performance

@ August 14, 2014 11:16 AM in System's Architect

of that collector, it does drop quickly at category "D".

You can plot the performance of the collector across all operating conditions using that SRCC data, the method is explained in this idronics


That collector design looks a lot like the old Olin RollBond built in the 1970's. An Italian company produces a similar design.

I like the machines he has designed to fab them, odd dimension 21 square feet? 7X3 perhaps?

lake loops

@ August 13, 2014 11:02 PM in Geothermal vertical loops

would be my first choice if that can be salvaged. Could be the piping to and from is undersized even if you could increase the lake HX. You really need a qualified designer to start with a load calc, and system design. Most of the GEO manufacturers have fairly simple programs to do calcs for you.

Perhaps start with a search for GEO associations to get a lead on a nearby designer. It's helpful to find someone that knows the "lay of the land"

In my area the DNR limits GEO wells to 200', you might check to see what is allowed in your area.

I'm surprised that allow lake loops in the bay?

Read all the specs

@ August 11, 2014 9:46 PM in In series Heat pump WH 50g and two electic 80 gallons

On the hpwh mainly recovery rate and room size where it will be located

If you have access to off peak electricity possibly a large insulated tank to store the daytime dump load would have the lowest operating cost.

As Carl mentioned, you need to nail down the actual consumption number

I consider it a consumable

@ August 11, 2014 7:19 PM in Please Help - Leaking Hy Vent

part, those small air vents., it will need service or replacement, just like a thermostatic valve or any other tight tolerance valve.

I'd call that white crud dirt, or minerals, I suppose. The only way to avoid it is fill the system with de-mineralized water.

And some contractors do fill with DM water that they filter at the job site.

That small Sorbox recently shown here demineralizes fill water for small systems. Several other manufacturers are bringing out small DM systems that connect by the fill valve.

It is wise to use DM water for blending glycols on the job site, Dow requires it.

lot of work putting that together

@ August 11, 2014 10:41 AM in System's Architect

nice work.

A few comments, I wonder about the 85% savings with ECM circs, seems a bit high?

Check on your description of braze plate HX, sounds like you are describing a tube and shell?

I question the actual performance of the hybrid collectors. Unless you have a large demand for that thermal energy, or a huge storage that can keep the fluid temperature to those PV modules, I wonder how much that adds? Along the lines of co-gen units. Unless the thermal load is high not sure the $$ payback is there?

The control-ability of those high mass storage is the trick. That one looks like they insulate the mass from the slab? The slab right on top of the sand can be a little too much during cooling seasons.

Keeping the heat in the concrete tank will also be a challange, seems 8-10" of insulation is required?

a very simple device

@ August 11, 2014 10:08 AM in Please Help - Leaking Hy Vent

A stem, and an o-ring seal, are the shutoff mechanism.

It doesn't take much to cause them to seep, a grain of sand in that seal an do it. Dirty fluid is a main cause of leakers.

You could add a hygroscopic cap for a second level of shut off protection.

This Caleffi cap is ordered on many vents, it should fit other brands.

maybe try this

@ August 10, 2014 2:16 PM in Need to kno everything about Twintube...

Goo. I have used it on all types of rubber and plastics. Looks and smells like rubber cement, but thicker viscosity. I think you want something that "sets", not a pipe dope or gasket sealer.

How bad (black) is the fluid in the system? if all the zones flow, I'm not sure I would flush the fluid and replace it.

If it flushes out like old motor oil, or a thick heavy sludge, it will probably not exchange heat as designed, and it may plug the HX.

If the tube is getting hard or brittle in places, not much you can do to bring it back.

I remember Heatway trying various chemicals and additives to try and keep the tube from going south. I doubt anything really worked.

The lowest possible operating pressure, of course.

get some constant tension hose clamps

@ August 9, 2014 6:57 PM in Need to kno everything about Twintube...

they look like this. most auto suppliers have them, O-Reilly Auto in my area does.

They tighten and hold a constant tension better than spring clamps.

If the tube is hard and brittle be very careful, maybe dry everything and use some adhesive as mentioned.

You really should flush it, I know some guys are using this Fernox pump to clean out old non-barrier tube.

Really any pressure type pump, maybe a small 1/2hp fill pump or shallow well type pump. it may need to circulate for a few days.

how much $$

@ August 8, 2014 10:14 AM in Smart solution of outdoor shower

it could be as simple as one of those black bag solar camping showers.. Or a small collector on the roof with a 30 gallon solar tank, with electric back up.

There are a number of these free standing solar showers. I suppose a piece of 4" ABS pipe with a faucet attached.

i have seen really engineered ones with a couple evac tubes connected to a pedastal, just connect a hose.

Plenty of You Tube videos on clever solar shower DIYers

thanks gentlemen

@ August 7, 2014 4:18 PM in An interesting discussion.

for the support.

I like that idea of adding conditioner into the cap. Easy access on that fine thread, o-ring seal. i'll credit you with the idea, Harvey, in my training slides :)

You can

@ August 7, 2014 8:06 AM in How would you....? (daycare mixing)

Feed more than one fixture from the point of use valve. If you have multiple sinks in a restroom for example. You really do need to use that point of use valve. It is built to be tamper proof and is limited to 120 max. Output temperature

Your State should have a plumbing code they adopted, refer to that. Or hire an engineer to spec all the Appropiate valves if you are insure or concerned about liability

one method

@ August 4, 2014 10:39 AM in Pressure testing cast iron radiators

Start with a good flush, you may find mice of mud wasps have taken up residence inside. A garden hose from the bottom, then top to get all the crud out.

I use a Webstone valve with a 15 psi gauge, and a washer hose to connect to the hose bib.

Connect on the bottom connection, fill, cap off the top and take to 15 psi. You need to watch the pressure carefully, you can also add a Autofill set at 15 psi so you don't over-pressurize.

Once up to pressure, shut off the hose connection and watch the gauge for an hour.

This happens to be a 1" Webstone, 1/2" is fine.

older style

@ August 3, 2014 9:44 PM in Electric Boiler and short cycling

electric boilers had magnetic contactors, frequent, short cycling wasn't kind to those contactors. Plus the noise and lights dimming :)

Most of the current electric boilers have triacs controlling them, for variable outputs and soft starts. Triacs, electronic relays, are very rugged devices.

Doesn't AO Smith

@ August 3, 2014 9:39 PM in Emerson swan

own Lochinvar? I suspect you will see some really cutting edge tanks and boilers from them also. You already do, actually.

good reading here

@ August 3, 2014 3:56 PM in How would you....? (daycare mixing)

Any idea what the max GPM that will be required? On large flow buildings it may be best to use a Hi-Low mixer. It's hard to find a hi flow, large Cv valve that will regulate down to .5 gpm.

Your building official should be able to point you to the code they use. Day care centers sometimes limit to 100F for hand sinks, so a point of use 1070 valves may be needed at fixtures, with a point of distribution 1017 back at the water heater.

ASSE is a fairly complicated standard, and it changes every few years. Get the requirement from the AHJ. Manufacturers may not spec the valve as code requirements vary depending on codes used and AHJ moods :)

Typically a mix of ASSE 1070 and 1017 valves will work.

If there is a recirc loop in the building you need to be sure it is piped correctly with thermostatic mix valves.

Idronics 11 has some good info and piping schematics.
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