A REALLY basic hydronic question

Scott_Mountain_View_CA

Did a quick cost comparison between copper and the ProPEX expander method including the M-12 and it was close enough to warrant going ProPEX. And the upside is a faster install.

The website I viewed carries both Uponor and Mr.PEX tubing. Uponor is a bit more $ but is only in white, while Mr.PEX is red. To avoid confusing supply & return as I make my emitter connections, it seemed to make sense to buy some of both e.g. red supply white return. The EP fittings are a nice price point.

Rich_49

uponor and Mr pex are very similar . Mr Pex tubing is a bit less rigid than Uponor and is a PexA product . In either case you'd be golden . The Axial press fitting system that Mr pex uses is really nice also . You'd be surprised how closely connected these companies are .

Scott_Mountain_View_CA

I'm not sure I have a correct understanding of the Cadet CDN040 with regard to EWT water temp. Is there a control on the unit that can be set to a specific design EWT? If not, then how would I determine the EWT of that particular unit? Probably a stupid question, but......?

Zman

All right, you drive a tough bargain, I will mail the hand expander tool and give you $20 to get it out of my garage.
After buying the M-12 it has just sat their. It still very shiny...

Scott_Mountain_View_CA

Sorry for not getting back to you Carl. Some of the manual tool reviews mention things like "my arm almost fell off" and "you need to be the Incredible Hulk to use this thing". I'm leaning toward the M12, but if you can ship a Franklin with the manual tool I might reconsider

Scott_Mountain_View_CA

I think I may have answered my own question re: EWT control on the CDN040. Looks like I'd need to install an optional System Temperature Sensor (KIT3078) into the heating loop downstream from the boiler hot water piping. This would seem like an indispensable item and I don't know why anyone would not install it. Without the sensor to control EWT how would one size their rads?

Zman

The boiler has internal supply and return sensors that are all you need for a simple setup like yours.
I'll get the biceps master in the mail!
Think of the money you will save at the gym..

Scott_Mountain_View_CA

If you sized your rads to 155 SWT but didn't have temp sensor controls on the boiler, if the boiler output 180 degree SWT wouldn't it be constantly short cycling? I'm missing something here.

SWEI

The boiler has its own temp sensors. If you sized the radiators for a 155°F SWT at design conditions, the boiler will look at the OAT, determine the appropriate SWT, and then modulate as needed to keep the SWT there --until the TT terminals open.

Scott_Mountain_View_CA

"The boiler has its own temp sensors. If you sized the radiators for a 155°F SWT at design conditions, the boiler will look at the OAT, determine the appropriate SWT, and then modulate as needed to keep the SWT there --until the TT terminals open."

But isn't the trick setting the radiator size to a level that, at design conditions, the water temp will be lower in order to attain max efficiency? For example, if I size the rads for 180 degrees I'll save $ on rads but lose efficiency which will increase operating cost over time, correct?

I talked to Lochinvar tech support today...they told me that the CDN040 does not come with a SWT temp sensor....it's an option that has to be ordered. It does come with an outdoor air temp sensor. Do I understand you correctly that both sensors are needed for a mod con to operate efficiently? That would make sense....which tells me I'm probably wrong again.

I've got to sit down tomorrow and do a refresh of mod con operational technology in the Stiegenthaller book.

Bottom line in my situation is I'm willing to sacrifice a few % points of efficiency if it saves me significant $ on radiator (size).

Scott_Mountain_View_CA

Are you going to install this boiler yourself?

I had considered it, although I've been in contact with a hydronic heat contractor that could do it. Do you recommend against my doing it, just using the manual and diagram? I do have some plumbing experience.

Scott_Mountain_View_CA

I agree on the RTFM comment, although I wasn't calling the factory for installation advice per se. I was trying to find out how the SWT temp was controlled as part of my thinking through the radiator sizing question I raised above.

I tend to agree with your suggestion on letting a contractor install the boiler around my specs. I've got my hands full with the system design and rad install, and there are a few other major projects I've got to complete prior to selling the home.

I appreciate all the advice I'm getting here. I've done a fair amount of homework/reading but still have some obvious knowledge gaps.

I'm self taught in the trades and I couldn't do it if I didn't love it.

Paul48

I am self-taught myself Scott. Over the years, I have found that sometimes I have to read technical manuals many times, before it finally "clicks". But I find that that is the most important part of the learning. You're very thorough, and should not have any problems, but keep in mind, you're doing something that is done by trained, skilled, craftsman. Do your homework. Read and (most importantly), understand, every aspect of the boiler manual. Sign up for Taco's FloPro University. It's free, and you'll enjoy the tutorials.

Scott_Mountain_View_CA

Hatterasguy said:

Scott_Mountain_View_CA said:

I agree on the RTFM comment, although I wasn't calling the factory for installation advice per se. I was trying to find out how the SWT temp was controlled as part of my thinking through the radiator sizing question I raised above.

Page 4.

Item #7.

Page 35, item 12.

I wonder how these 2 sensors differ? Sounds like the pg 7 sensor is built into the unit, while the pg 35 sensor is placed in the supply pipe just beyond the boiler. Sounds like they're both measuring supply temp.

Scott_Mountain_View_CA

Do you understand when we refer to p/s piping?

The primary loop (for the boiler) will be at a different temperature than the secondary loop (for the building).



I think I understand the general concept. Secondary piping off the primary piping allows the use of circulators in individual zones, maybe operating at different flow rates and temps depending on how they're sequenced. So I'm guessing that the optional system sensors mentioned on pg 12 are intended to monitor temps in the individual secondary piping zones? This scheme doesn't apply to my situation since I will have a single zone, and the OWT for that zone will be monitored by the temp sensor built into the boiler output.

How'd I do?

Scott_Mountain_View_CA

Thanks for explaining.

RobG

This is the longest "Really basic hydronic question" thread I have ever seen. I don't even remember what it started out as.

SWEI

Hey - at least it managed not to degenerate into a food fight.

4Johnpipe

FOOD FIGHT!!!

Scott_Mountain_View_CA

What are the forum rules regarding posting copyrighted material? In this case I've scanned a graph from the Siegenthaller book....I'm trying to understand some of the terminology he uses. Is this allowed if I give proper author attribution?

RobG

Scott_Mountain_View_CA said:

What are the forum rules regarding posting copyrighted material? In this case I've scanned a graph from the Siegenthaller book....I'm trying to understand some of the terminology he uses. Is this allowed if I give proper author attribution?

No problem,

Scott_Mountain_View_CA

I'm trying to understand the dynamic between water temperature and mod/con boiler efficiency. The attached graph is from Stiegenthaller's book Modern Hydronic Heating, page 76. It shows a relationship between boiler input temperature and boiler efficiency %. What I don't fully understand are the high and low parameters that bracket the "Performance Envelope", i.e. "Efficiency at 25% output" and "Efficiency at 100% output". What is the literal definition of these terms, including the percentages? I searched and couldn't find a clear explanation/definition.

Looking at the graph, it appears that at boiler input temps above ~130 degrees, the efficiency gap narrows considerably across the higher temp range. I see relatively little efficiency loss between ~130 degrees and ~160 degrees boiler input temp compared to the loss between ~100 degrees and ~130.

Am I interpreting the data correctly?

How does "boiler input temperature" relate to LWT?

Thanks

Scott_Mountain_View_CA

Thanks for the explanation.

Check my thinking on this: If there is relatively little incremental efficiency loss between 130 degree and 160 degree LWT, then in my situation it would make sense to size my rads for the higher temp, which would lower rad cost by 25-30%, a fair amount on Runtals. I'm in the SF Bay area where the heater fires up rarely from April to October.

I'm assuming Delta T = 20, based on a comment in a prior post made in light of my single zone design.

Scott_Mountain_View_CA

Hatterasguy said:

You keep referring to "LWT" which I believe is the supply water temperature (SWT)?

If so, it's not directly relevant to efficiency. It's the return water temperature (RWT) that matters.

From the Runtal technical note on Flow Rate Calculation:

"The flow rate through a Runtal radiator (or series of radiators) is dependent on the length of the radiator (or combined length of the radiator series), and the design Entering Water Temperature (EWT) and the design Leaving Water Temperature (LWT).

The designer picks the design EWT and LWT. For example, he might pick 170°F as the EWT and 150°F as the LWT. The median point between these two temperatures is called the Average Water Temperature (AWT), and in this example the AWT is 160°F."

I believe in this context LWT=RWT. If not, then please provide another education suppository

Scott_Mountain_View_CA

I believe you're correct...I found few references to LWT on a Google search. Maybe it's a European term?

I'm gonna sacrifice those last few points and keep the coin in my pocket, with apologies to Al Gore.

Scott_Mountain_View_CA

Yeah, that guy.

Rich_49

An Inconvenient Truth for Al

SWEI

If you design for an AWT of 140°F using panel radiators, you will be condensing all of the time. Even if your ΔT ended up at 10°F due to overpumping, you would still be condensing over 90% of the heating season.

http://www.fcxalaska.com/PDFs/AshraeCondensingTechnology.pdf has more of the story if you are interested.

Scott_Mountain_View_CA

I just glanced at the presentation, looks interesting, I'll have time to go through it later today or this evening. Thanks.

It looks like the release of the latent heat of condensation increases as both the return water temperature and firing rate decrease, and because the dew point of natural gas is fixed at 130 degrees the efficiency gain from condensation would kick in at 140 degrees AWT and lower assuming ∆T=20? Is this the general concept?

SWEI

It's a continuum. The lower the return temp, the higher the combustion efficiency. The slope of the curve increases as you cross the dewpoint (which itself actually depends on multiple factors.) 130°F is close enough, so yes -- at a 20°F ΔT a SWT of 140°F will ensure condensing even at design conditions. Remember that 'design conditions' by definition means either 2.5% or 1% of the heating season hours (depending on which ASHRAE chart you choose.) Being even ten degrees above that (RWT of 140°F) at design conditions, you will still condense well over 90% of the time, and again, we are talking about a difference between perhaps 89% efficiency and 92% efficiency here. If you were on LPG, this would be a far bigger deal economically.

Scott_Mountain_View_CA

I looked at Buderas, Myson, Veha, and Hydronic Alternatives to compare with Runtal. Runtal has all of them beat by a wide margin on panel dimensional size options (width and length combinations), and none of them offer tall and narrow vertical panels. I didn't really see anyone out there competing with Runtal on breadth of product offering and options. No wonder they cost more...they own their market.

SWEI

Runtal and Myson actually make radiators. Both have quite an array of different designs. Some are true bargains, some are spendy. The others I'm not so sure...

hot_rod

If you want nice, or unique, look at the Zendher or Jaga offering. I think some of the Zehnder are built in WNY.

Jaga is a fun company with an interesting story to tell.

Many of the brands are owned by the same company now..

http://www.international.zehnder-systems.com/products-and-systems/decorative-radiators

http://www.jaga-usa.com

Scott_Mountain_View_CA

The Zehnders are spectacular, both in appearance and price. If I were going to stay in my home for years I'd consider them, but my situation calls for a more economical solution.

I'm selling my home in <1 year. I'm upgrading from crappy rusted 40 year old fin tube baseboards. I could install Slant Fin rads or similar, but I thought I'd invest in a more contemporary design that would increase sales appeal without breaking the bank. Runtal seemed to be a reasonable compromise.

Besides the sleek design, Runtal also offers vertical panels in a wide range of sizes. This gives me the opportunity in three of my (small) rooms to place the rads off the floor and in tall narrow locations that would not otherwise be blocked by furniture, shelving etc. None of the other brands I've looked at offer the same sizing flexibility.

In other rooms I'm placing horizontal wall panels beneath windows, and in one location will install a baseboard.

I'm submitting an RFQ to the Runtal sales rep this afternoon and will then decide whether the ROI justifies the cost. If not then plan B would be the Runtal lower cost, in-stock wall and baseboard units....less design flexibility but workable. Plan C is Slant Fin Fine / Line 30 or similar.

hot_rod

I see SlantFin now offers 9 colors of the #30 BB. Maybe just some new fin tube is the best and least $$ way to go.
There will be a bit of work involved when you remove old BB and replace with panel rads, beyond them mechanical side.

https://www.slantfin.com/images/stories/Product-Literature/decorator_series_trifold_215.pdf

Scott_Mountain_View_CA

Actually, the old fin tube bb was ripped out prior to a major remodel I completed. Long story short it would actually be a lot more work to run tubing for baseboard vs wall panels. But point well taken....under ordinary circumstances I'd agree with you.

I received a quote back from Runtal...the pricing is compelling. The exception is the price of their TRV sets, both chrome and, to a lesser degree, their nickel plated versions are crazy expensive. Is there any reason I can't use an after market 1/2" NPT angle TRV? I found this Danfoss TRV but couldn't find a Danfoss shutoff in the same style.

Scott_Mountain_View_CA

13KB picture wouldn't upload so here's the link to the Danfoss TRV. http://www.supplyhouse.com/Danfoss-013G8014-1-2-Angle-Thermostatic-Radiator-Valve-5553000-p

Mark Eatherton

Pay particular attention to the flow patterns and recommended TRV sensor location. Installing it backwards will result in a continuous thumping sound when the needle approaches the seat (thump, thump thump, thump) and having the sensor too close to (right next to) will result in the radiator being shut down most of the time and associated discomfort. Danfoss is not the only manufacturer of TRV's.

I have Oventrop remotes in my mountain home. They come with a 33' (max length) capillary tube that will allow you to connect numerous radiators to one distribution manifold and allow you to control a bunch of radiators with one TRV.

http://www.oventrop.de/ArticleInfo.aspx?art=1012296&CountrySelect=en-GB&AspxAutoDetectCookieSupport=1

The use of TRV's is a guaranteed way to provide excellent comfort. They track demand with supply to within 1/2 degree F. At my mountain home, I have an internet based PC powered home/energy management system. There is no hard wired "interface". It's what I refer to as a soft interface. The TRV's are set for 68 degrees F., and the electronics are set to 70 degrees F. I have seen some programmable set back thermostat TRV's that are battery powered, but I am not a big fan of deep set back for radiant emitters. Too slow of a cool down, and too slow of a recovery. Set it and forget it. Keep sleeping areas turned down if that's your preference, and turned up in common living areas.

At my mountain home, when I leave, the "system" resets the space temperature to an unoccupied condition of 40 degrees F.

2 days before I go back (which is 2 weeks in some cases during the Winter) and the home is perfectly warm upon our arrival. And there is not ONE panel radiator in the home. It is radiant ceilings, radiant walls, one small radiant floor area and electric radiant windows.

ME

Scott_Mountain_View_CA

Actually I'm not interested in controlling a bunch of radiators with one TRV. I'm planning to install a TRV on most or all radiators so that I can control individual room temperature.

I realize that Danfoss isn't the only manufacturer of TRV's but they're one that meets my price point, and have a decent cosmetic appearance.

Scott_Mountain_View_CA

Yeah, I wasn't sure Mark understood what my objective was....sounds like he's doing something entirely different.

For a single zone residential design, I can't think of a good reason NOT to install TRV's on most or all rads (other than cost?).