Hey all,

We're getting ever closer to this boiler replacement, and I come up with ever more questions . . . (funny how that works!)

In reading about primary-secondary piping, I've learned that one of its major benefits is in limiting the chance of thermally shocking the boiler with cold water from the system.  Most of the articles I've read also have to do with copper fin-tube exchanger boilers, which run at much higher temps & don't like exhaust condensation.

I'll be running water pretty cool (like 120 or less - no carpeting or wood on the floor, just the stained slab), no high-temp domestic hot water loop (yet), and the Munchkin contender has a stainless exchanger obviously DESIGNED to condense its exhaust gasses.  I'd guess the water in the slab right now is probably at around 40 or 50 degrees (soil temp), so is that 70-80 degree temperature difference enough to "shock" the exchanger and cause damage over time?

I now believe my system is zoned, but it has only manual balancing valves (I think - will post pics soon) and the only pipes I can get to are the two that stick out where the boiler goes!  The house is 1000 sq. ft. and the mod-con is a 50kbtu unit.  I'm getting a (or two) grundfos 3-speed pump(s).  Think that should cover the details . . .

Some earlier advice on this site led me away from primary-secondary design, but continued research always highlights new fears I feel the need to allay.

Thanks everyone!
charlie

you can't shock a mod/con boiler. you can run an excessive dt through the heat exchanger if you have insufficient flow.

primary/secondary is fine, if no one is running any numbers it's safer than trying to go primary only blind. but naturally a preferred way to go would be to drop a pump if your system allows it.

I am curious,
how many feet of pipe?
1/2 pex?
average loop length?
Fuel available?
Dan

What is the heat load for the house?

I wish I knew, fellas. This is a replacement. The house was purchased thru HUD and the infloor is original and cast-iron with a balancing valve (I think - again, pics soon) for each room. We obviously have NO diagrams for the system, as the three POs are long-gone. I'm skeptical that the last boiler replacement (2000) was done properly: It's pumped towards the boiler and expansion tank and was a Raypak copper exchanger unit (114kbtu output) which died of condensation. The freshwater makeup is piped directly into the floor from the crawlspace (nowhere near the expansion tank). The old pump was a single-speed taco 011 series, but it may have been a bit big.

I took a look at the neighbor's boiler (identical houses) and they've got theirs primary-only pumped, like ours was. In running a 3-speed Grundfos, won't I be covered against low-flow (and high delta-t conditions) by the boiler's control over the pump speed? If it's something I've gotta do, I'll find the space, and as a percentage, the cost of another pump is no biggie. The biggest issue is that the utility room is SMALL and I'd like to conserve as much room as possible! Could I alleviate the issue by choosing a higher volume multispeed pump?

The house is a mere 1000 sq. ft., and based on past gas usage and monthly temp data, we were using an average of just shy of 40,000 btus/hr for the coldest billing period in the last 5 years. I realize these are averages, don't take into account daytime/nighttime temperature swings, and are nothing to base one's boiler purchase upon. However, as soon as it gets warm enough to cure stucco, we will be installing 1 to 2 inches of Polystyrene on the outside of our home, at minimum upgrading the walls and slab-edges from R-1 to R-4. With a four-fold increase in insulation, I'm not worried about a 50kbtu boiler keeping up with our heat load. We made it through this winter quite comfortably with a woodstove for primary heat, and temps were well below average for a few stretches there . . .

thanks for the help folks,
charlie

40KBTU/hr isn't a useful number unless it's correlated against heating-degree-days for the identical period. Raypaks run ~80% combustion efficiency, so your output would be 32KBTU/hr. If you can correlate it to heating degree days for the precise days of the billing period, you can then work backwards to a fairly precise whole-house peak load at your outdoor design temp. But if you have solar/woodstove/other inputs all bets are off (unless you have hard data on how much you got from those sources too.)

It seems on the high side for a 1000' house though, even in a record cold month, but since you've identified a bunch of heat leaks and are addressing them with EPS the thermal performance of the envelope will improve by quite a bit. You'll likely still need to supplement the Munchkin with the wood stove for peak load periods. (Even small wood stoves put out a LOT of heat for a 1000' house.)

Posted By Dana1 on 05 Mar 2010 11:13 AM
40KBTU/hr isn't a useful number unless it's correlated against heating-degree-days for the identical period.

I'd think that this correlation would be rather esay to do.  For example, I might find out that the average temperature here in Monterey for all of last month was, to make use of this example, 47 degrees.  That's 21 heating degrees (assuming that the outdoor temperature was never over the indoor 68 degree indoor temperature, which is probably a very-close-to-accurate assumption) times 28 days x 24 hours = 14,112 degree hours. 

If I really knew that my heating energy consumption was 40,000 BTU/hour, that'd make my monthly total consumption 40K x 28 days x 24 hours = 26,880,000 BTU.

Divide 26,880,000 by 14,112 and you get 1,905 BTU / degree / hour.

It's not perfect, and you have to make assumptions about hot water use and gas for cooking and other things, but I bet that you could get to a pretty close swag.  The hardest part would be to get the number of degree hours, but as I say above, I don't think that that's a far stretch if one has access to daily weather or temperature data.

Jeff

Posted By jbaron on 05 Mar 2010 03:03 PM

Posted By Dana1 on 05 Mar 2010 11:13 AM
40KBTU/hr isn't a useful number unless it's correlated against heating-degree-days for the identical period.

I'd think that this correlation would be rather esay to do.  For example, I might find out that the average temperature here in Monterey for all of last month was, to make use of this example, 47 degrees.  That's 21 heating degrees (assuming that the outdoor temperature was never over the indoor 68 degree indoor temperature, which is probably a very-close-to-accurate assumption) times 28 days x 24 hours = 14,112 degree hours. 

If I really knew that my heating energy consumption was 40,000 BTU/hour, that'd make my monthly total consumption 40K x 28 days x 24 hours = 26,880,000 BTU.

Divide 26,880,000 by 14,112 and you get 1,905 BTU / degree / hour.

It's not perfect, and you have to make assumptions about hot water use and gas for cooking and other things, but I bet that you could get to a pretty close swag.  The hardest part would be to get the number of degree hours, but as I say above, I don't think that that's a far stretch if one has access to daily weather or temperature data.

Jeff

But on this very forum when trying to explain this methodology people have mis-correlated monthly data with billing-period data  and ended up with WILD variations on heat load estimates.  It's an easy method to use, but slipping even 1-2 days on either end of the sample period can easily run well into double-digit errors- it has to be correlated perfectly to the meter reading/tank filling days.

You also have to use the DOE ratings of the heating appliance to calculate the actual heat load, not the input-fuel rate,  which will vary with the efficiency of the burner.  (A tired 50 year old cast iron pig of a boiler will use considerably more fuel than a mod-con to achieve the same output.)

In the middle of the heating season other uses can be ignored.  Most of the cooking fuel ends up as heat inside of conditioned space, as does about 10-25% of the hot water heating fuel, but both are typically a small fraction of the total fuel use when there's a real heating load.  They might add up to as much as 1/4 of the total annual fuel use in some places, but it'll be well under 10% of the fuel use during a 800HDD+ month for most homes.

Dana,

Thanks for the replies. We got the data from the gas company - details in another thread, not sure you'll remember - so the temp data comes from the wellhead and I'd assume it is drawn at the same time they input the volume data for the gas. It's an average for the billing period, not the month. As I said, we've covered this in another thread. My current questions deal with near-boiler piping and whether or not a multi-speed pump controlled by the boiler's "brain" will alleviate the risk of a high Delta-T across the boiler, allowing me to forego primary-secondary pumping.

Should I assume the Taco 011 was properly sized and try to match its performance curve with one of the "options" in a 3-speed pump?

I realize I was urged to have a pro design the system & do an analysis, but the companies I've researched in this area are all "plumbing and heating" outfits and don't exhibit evidence of even knowing what primary-secondary pumping IS, let alone being knowledgeable enough that I'd feel comfortable allowing them to put the boiler in my home. I feel much better, with what is obviously a SIMPLE system, doing the learning (yes, I've read Dan's book), and installing the boiler myself. Believe me, as an arborist, I'm the FIRST to advocate hiring a professional to do one's pruning. However, if one lives in a place where the "professionals" are hacks, I believe the homeowner is better off doing some reading, buying a saddle and doing it themSELVES! Out East, you seem to have plenty of options for hydronic contractors. Here in the Wild West, hydronic is limited to apartments (to my knowledge) and super high-end residential buildings. The most "pro" company I could find had pics on their website showing complex, high-dollar installs pumped "backwards" with fresh water lines in the wrong places. I'm sorry, but if they can't get John Elway's house right, I'm not real confident they'll get my little 1000 ft. job designed properly.

Sorry for getting on my soapbox. I'm tired of being told I need a professional's help when the professionals I've already hired have screwed up more things than they've fixed! 75* pvc slip-joint fitting on a POTABLE hot water line, anyone? Yeah, we had one of those. I now know better.

Thanks for your time,
charlie

If all it took was a book...on hydronics i.e. heat load analysis, controls, combustion analysis, boiler chemistry, pumps sizing, delta P, delta T, design water temperature. Oh, then some trade skills; plumbing, heating, ventilation, gas fitting, electrical and low voltage control work.

Funny you should mention pruning, as I just pulled away from my own boiler job yesterday to talk to a tree man. I installed my first condensing boiler in 1987 after nearly 10 years in the plumbing and heating trade and had been cutting on trees before that.

I own two chain saws, but it doesn't make me an arborist. I am hiring the guy who does it for a living. I am going to pay him with the money I make designing and installing ModCon driven hydronic heating systems.

Prudent DIY boiler aficionados will check the manufacturer's warranty before starting their boiler careers on a ModCon.

Don't get me wrong, I work with DIY boiler clients every day, fixing mistakes and guiding them through the "re-does" that might have been avoided. Fortunately most call me before they start. I should say, nearly all the "problem job" clients started out with condescending remarks about the local trades (usually including the outrageous prices) and a heavy dose of false confidence. Then the boiler is junk and the factory won't back me up!

Good luck!

DIY design; always the first mistake.

@BB: No, two chainsaws doesn't make you an arborist, but if you lived in anysmalltown, CO, you'd be doing WORSE to hire an "arborist" who would come out to top your trees, strip the insides and set them up to fall on your house 30 years before they have to begin declining. I would hope a homeowner was smart enough to do some homework before hiring a tree guy. That way they can pick out the hacks from 100 yards, avoiding the lowest bid-highest cost mistake. Trust me, I DO understand.

Also, I would LOVE to hire someone who installs ModCons for a living and pay them with the money I earn 50 feet off the ground, but there is a bit of a disconnect: I earn a whopping $15/hr before taxes, while I'm sure, as a hydronics professional, one pulls down substantially more. In your field, you're regarded as a professional. In my field, I still work with lots of clients who view me as "the help." Explain this: If you do your job wrong, someone ends up with CO in their house, gas leaks, discomfort, what have ya (all very bad/deadly things to be sure). If I screw up, someone ends up with a cottonwood through their livingroom. Why is it that I'm seen as a glorified landscaper while you're a Pro?

There's a reason we bought a HUD home. It's not an easy thing to maintain solvency through a slow winter with a wife in school. Don't get me wrong, I feel blessed to have been able to purchase a home, especially one where our mortgage is $150 below what we were paying for rent! Furthermore, $10,000 seems a bit steep to install an oversized aluminum Buderus, we don't have that cash available, and I'm not confident that the company that delivered the quote is capable of doing any kind of quality design themSELVES!

If you've got a suggestion on a QUALITY hydronics specialist in the Front Range who's willing to WORK with a DIYer and not scoff at the house, the price point, or the "waste of time," PLEASE speak up!

I'm FED UP with "professionals" who offer crap/dangerous work at a reasonable price, or who turn their noses up at any job not located in a high six-figure income bracket. Just because my house and income are modest doesn't mean I'm okay with sub-par work!

I can tell this subject touches a nerve for you. I hope it's evident that the feeling is mutual. I have nothing but respect for the people who take the time to get training and hone their trade (people like you, it would seem). I understand the business climate that leads these people to ignore the small jobs. It bugs the hell out of me that those of us trying to be smart about our decisions with a limited budget get hung out to dry.

you can be fed up all you like and I understand that. I'm also not a fan of BB's tone. That said, I too have seen many DIY boiler installers in my time. and for the record I do not sell or install boilers myself.

Sometimes it works out. Sometimes you can find a local pro who is willing to do the hookup and combustion analysis for a cheap price. Sometimes you get lucky.

I can tell you though when it does not work out, which is not entirely within your control, it sucks. excess fuel costs and year-long warranty nightmares are not so rare as to discount. it is not hard at all to spend more on rectification and/or fuel than you save for the install. and that ignores any safety issues.

I have several clients who regarding disregarding my advice to have a boiler professionally installed as one of the worst decisions they have ever made.

You can choose to roll the dice. You might get lucky. I would advise against it as strongly as I possibly can. I know you're in a tough market. so maybe a mod/con is not the best choice for you then. a conventional boiler, properly installed, may serve you better than a DIY'ed mod/con.

OK,
you have a 1,000 square foot house heated in slab.
Still not clear on pex pipe runs, circuits. I would assume 1 zone for the whole house, simpler and sub zoning 1,000 sq ft when you have a tight budget only adds expense.
You are natural gas, there are gas technicians as you need looking for a daily job in these times, they can do combustion analsis as needed.
As to DYI we design and support DYI and professionals daily.
The direction I would take on this project is a LAARS Mascot 1.33, It is same boiler core as munchkin, same ignition, fan, flame rectifier.
What is different is it has a primary pump built in (3 speed Grundfos), expansion tank, bypass loop, and a digital diagnostics on the front, built in combustion controls. There pretty complete.
With a 1,000 square foot home there is enough pump to connect directly to the manifold supply return. 4 connections
supply, return, boiler water make up, natural gas (125,000 BTU) remember it turns down to 25,000 BTU.
We can ship pre adjusted for your altitude.
My point the world is made of people clever enough to do there own work, as a kid we tore in to cars with no regard and fixed them. They ran, we learned. My guess is that 8 out of 10 on this site did the same.
If you get beyond yourself there are professionals willing to come out hourly and assist.
You might have to listen to there grumbeling, but some times we can only afford so much.
The alternate system for your home may be a simple NG dedicated water heater.
My thoughts on a 1,000 sq ft DYI.
Dan

Yes, you should hire someone desperate and out of work to calibrate your combustion gas appliance for maximum efficiency and safety. Ignore warranty issues, because nothing ever goes wrong with boilers. Especially not with boilers loaded up with electronics and extra components.

All 3 of us "pros" in this thread work with DIY'ers Dan. Two of us simply disagree that it's good practice to include boiler installation in the scope of that work. Oddly enough, it's the one who installs boilers, and the one who doesn't sell or install boilers. the one who sells boilers to DIY'ers, of course, supports the practice.

To be blunt, I think it's incredibly irresponsible of you and your company and others like you to do that. You might get lucky 9 times out of 10 or maybe the owner can get a local pro to do the hookup, great. but they better have that ironed out BEFORE buying a boiler. I don't see that in your professional recommendations there. Perhaps it should be.

DIY boiler installs are expressly illegal in MA, and doing so would void more than the manufacturer's warranty when things go disasterously south (try home owners insurance!)

I've had mixed experiences with the local pros (nothing dangerous, but wildly oversized & inefficient), but still wouldn't install a system without a reasonable vetting of the design by a local pro- somebody who was at least partially on the hook for making it work, and firmly on the hook for it meeting code.

Gentlemen,
I was confident before I wrote that the response would be a resounding WTF, but so it goes.
I suppose I am not a pro.....
30+ years in the trades, college degree, Licensed GC in Washington ( GC license in WA, mechanical contractor,Timber frame home builder from 85 -95 (French scribe tradition) 10 years as installer, now manufacture and distributor, and oh yes,,, still install the occasional job to stay familiar with products we sell.

"Yes, you should hire someone desperate and out of work to calibrate your combustion gas appliance for maximum efficiency and safety. Ignore warranty issues, because nothing ever goes wrong with boilers. Especially not with boilers loaded up with electronics and extra components."
Rob, did you notice that there is about 10.5% documented unemployed right now, are you referring to these fellows as well? That is a broad slice you took there.

DYI is an alternative to a lot of things a man can do with his time, a brain and limited funds. This society of specialist is a little trying.
You may live in a state where DYI is not an option (apparently Main boarding New Hampshire does not share that Live Free Or Die thing), done deal there. You may have specific codes, check up on what you as the DYI can do, will need to prove, what professionals may be required to provide. Sure there is a lot of details to any project. But this is America last time I checked and we still have options.

Bolting a boiler up to a wall, punching a exhaust/combustion air vent out, bringing in H20, Gas, hooking a supply return is not a big deal. For the most part these units fire and about calibrate using there built in logic. If not, yes why not bring in a gas tech at $150 an hr to calibrate, Is that hourly rate chump change not deserving of the regularly employed?

I see the fact that money is tight out there right now, Folks that can do for them selves can and will. DYI

Dan

not everyone who is unemployed is a hack, definitely. but you can be pretty sure the ones still in business are probably better than those who aren't. Those who are desperate are probably not investing in training, certifications, or equipment to do their jobs optimally either. but again... IF you can find someone equipped who is willing to test and bless a DIY gas installation, great. do that BEFORE you buy a boiler. and figure out BEFORE you buy the boiler, what you're going to do about warranty service, and whether or not you even have one if you do the install.

I have never said anything bad about DIY. I just put a boundary on what is safe and sane to do DIY. it stops at modern combustion appliances. In spite of your assertions, no DIY'er is equipped to do gas work safely, including the combustion analysis NECESSARY to determine if the unit is actually calibrated properly. without that step, short service life, inefficiency and even health problems can occur. it cannot be skipped. You can save a ton of money DIY'ing the rest of the system, but this is not an area to cut a corner on.

This is america and we do have options. We can choose to hawk dangerous equipment to people who are not educated in their use and handling, and hope that the worst that happens is that it fails to run efficiently instead of, say, killing or sickening someone. Or we can choose not to.

I choose not to. Just like we choose not to pretend that it's an ok choice. Someday the onboard diagnostics on boilers may be so advanced and bulletproof you can put them in and the boiler will simply refuse to run if anything is wrong or won't have any items outside the box it depends on to function properly. Until that day comes though, and that day is not today or even tomorrow, I am quite comfortable considering anyone who engages in that kind of salesmanship predatory in nature, who cares for nothing but money. Because if you cared about the efficiency of the systems, or the well being of your customers, you simply wouldn't do it.

At the *very* least you wouldn't do it without making sure they understand the need for proper testing and inspection by a trained and equipped professional. anything you do to minimize that requirement is, at best, wildly irresponsible, in my oh so very humble opinion.

But it's america, huh? Caveat Emptor? that's it? nice.

So,
The Mascot will not run if;
No flow through appliance
Gas pressure is not right.
Ignition is not confirmed (flame rectifier)
Water pressure is low
Electrical is not proper (reverse polarity)
Boiler becomes overheated
Combustion air does not flow properly
carbon monoxide is present in combustion air make up.
These are just some of the built in functions in this appliance.
Modern world stuff
Some jurisdictions require additional external (redundant) systems, Seattle forinstance will like to see a secondary High tempature and Low water cut off.
Now add the fact that the boiler core is the same as a Munchkin and several other mod-con boilers so any field tech that is familiar with the boiler core will recognize it and may have some basic service parts in there truck.
I do agree do your due diligence before buying anything, but in this world the times are that these products are available.
A DYI person should know there capabilities and there support system.
Dan

Really. so no mascot out there has any poor operation due to gas pressures or venting issues? as soon as it's out of spec, it just stops running and demands to be fixed? No rumblings, grumblings, corroded swirlplates, premature exchanger failures, fan problems or anything??

that's amazing. it's a wonder that the dozens of other modcons out there are not so advanced. this miracle machine must be ready to take over the entire boiler world since it requires nothing to install it! Did I miss the press conference on that?

I note that your last line, "A DYI person should know there capabilities and there support system", is just "Caveat Emptor" re-worded. good stuff Dan. Funny thing though is that if there are local techs who are familiar with munchkins or other such exchangers, who are stocking up to service these units, then the need to DIY does not exist. And if you want those techs to stay around, stocked up to service units such as yours, you better use them or they won't be... they are unemployed, remember, desperately looking for hookup work! Finally, you should be damn sure they are stocked up for the boiler you are buying. The FUNNIEST thing though is that this type of "boiler core" has caused one of my clients the biggest DIY mod/con nightmare anyone can imagine. because there ARE NO techs willing to touch the unit. because he did it himself. Of course his problems have nothing to do with the heat exchanger, just like very rarely is the problem the "core", and only a tech tooled up for THAT BOILER, not any boiler with this core, would be able to service it appropriately. and none of them will. Even the regional rep won't look at it. Guess why?

I can make up stuff that makes this ok all day too. Magic Pink Unicorns can stand guard over it at night, breath in CO and magically unicorn fart out pure oxygen and rose-scented oils. but sadly, saying so does not make it so. The boiler is not magic, you are not guaranteed a safe and efficient install or easy service if anything goes wrong, and you guys are preying on the ignorance and foolhardiness of people. I think it's wrong. The fact that it is done does not make it right.

Rob,
You need to step back.
Your pink unicorn horn seem to be stuck.
All appliances fail over time. So here is a question for you. If a General contractor builds a house using his subs, and sell it through third party, and 6 years later the boiler (any boiler) craps is it likely the home owner will open the yellow pages or search on his computer for a local service tech? This occurs with all appliances, the service industry is a part of our system.
Laars has a support net work of service techs available across the country. If they do not know the appliance they have the resource of Larrs corporation to assist them with diagnostics.
You have a thing about assuming the normal person can't read a tech manual and get an idea of what the problem is based on fault code read outs. He needs a technician to come out and read the manual and bill as needed.
Regarding fault issues,yes if the unit does not fall with in design spec on the control on multiple functions it will not run and will show on the face a numerical code for fault identification. Does that mean it is optimized out of the box for the absolute best performance, no. Does that mean that out of the box in 99% of the build outs we provide they will run efficiently with little adjustment yes. The on board siemens has a Fuzzy logic ability to correct its self. This has no relation to your Pink Unicorn Puffs. It is an actual application from the Siemens control on board that will optimize the unit over time adjusting flame and gas values. This is a real function of the boiler. Other boilers I assume also share this type of function.
The magic of hydronic heat currently is limited to about 5% of all heating work in america.
Perhaps if there was more installed systems there would be more work for our service technicians to work on, more visibility of in floor heating, more new installs for our service techs and home owners.
Right now the client we see for the most part does not want to pay the 10,20 or more thousand dollar premium for in floor heat.
Is that because the fear of god that there can only be special people involved in the work?
My company supplies a lot of product at affordable prices to a multitude of both professionals and home owners. When our clients run in to a wall we assist as we can or work with there field technicians as needed.
Yes, let the buyer be ware. use your brain at all times even when walking,
Where did you come up with rose scented pink unicorn gas? Will it increase the efficiency of my mod -con?
Dan