MPO or mod con?

Patrick_North

A neighbor is facing imminent boiler replacement and is looking for guidance. While I have researched steam systems for our own home quite a bit, I know much less about hot water boilers.

One contractor has recommended a Burnham MPO. From the Wall I know this boiler is generally well regarded, but I wondered- why not a mod con?

In my limited understanding (or perhaps misunderstanding) a mod con can add efficiency but also adds complexity. There also seem to be some doubts as to the real savings associated with mod con technology. Any rules of thumb or words of wisom to impart? Should they look into a mod con? What mitigating factors would affect such a decision?

Related: they are currently using an electric water heater while their boiler is busted and are wondering about adding an indirect with the new boiler. It's been suggested that adding the indirect with the new boiler will be cheaper than adding it later, but they're reluctant to ditch a perfectly servicable electric heater that has more life to live. Thoughts?

Thanks,

Patrick

Paul Pollets

Mod Con Vs. CI

The mod con will outperform a cast iron boiler when the heat emitters are low temp (radiant) or the radiators are oversized and can operate at lower temps.  The mod cons work at highest efficiency when operatiing under 130 degrees, or the dewpoint of nat gas.  If copper baseboard is the heat emitter, savings or efficiencies depend on the amount of BB, or if they've been oversized.  Do a heat loss to be able to tell if the heat emitter can perform at design temps of 140, rather than 180.  Mod cons usually have a limit of 165.  They also ramp up to high temp when connected to an indirect tank. Electric HW heaters cost much more to operate than an indirect,have much longer recovery times and have higher standby losses. 

Jean-David Beyer

Modcon limits

My W-M modcon can run up to 190F on any of three output settings.



The manufacturer's defaults are:

190F for fan-coil, or indirect-fired domestic hot water.

180F for finned tube baseboard, cast iron baseboard, cast iron radiators.

160F for below floor staple up radiant

140F for radiant thin-slab, radiant above-floor (sleeper system)

120F for radiant slab at grade.



The boiler has three thermostat connections, and the parameters can be adjusted for each of them. Indirect is priority 1, Radiant slab is priority 2, and finned tube baseboard is priority 3. Any output can have its own outdoor reset curve except indirect.



Mine is set to supply the indirect with 165F water. I want 125F water at the heater and 120F at the taps, and my usage is low. For faster recovery, I would supply it hotter.

I set the radiant slab to run between 75F and 120F, but it never got up to 120F because it did not get cold enough around here for it.

I have excess finned tube emission upstairs on purpose, and it is set to run between 110F and 130F. It actually got that hot one day when it went down to 6.8F outdoors. Design day is 14F.



So I get condensing all the time with the slab, a lot of the time with

the baseboard, and a little of the time with the indirect.



I have not measured the temperature drop through my baseboard at 140F. Remember as the temperature is reduced, so is the drop. With 110 supply temperature, the return comes back at 109 to 110, so it supplies very little heat. I suppose I could replace the 007 circ. with an 005 to get more drop through that zone. I just assume the return and the supply are the same, and that is pretty much true on the warmer days.

Jean-David Beyer

Modcon limits

Sorry for double post.

Jean-David Beyer

Modcon limits

Wow. Three times. Ugh.



It seems as though it posts as soon as the Post button is pressed, but today it took a very long time to respond and take away that screen. Minutes. So I pressed the Stop button and tried again, with the same apparent result. Third time it seemed to work. I do not think it should take that long to work, but maybe the weather is too hot for the servers or the Internet backbone.

Robert O'Brien

MPO

MPO is oil,mod-con is gas. Will teh mod/con be NG or Propane?

CMadatMe

Depends

The MPO is a nice boiler. You could go with it, add some outdoor reset for additional system efficiency savings and be on your way.



Question is, what is the customers goal? Do they just want a better system then what they have now or would like the best system for their home? Would they like to invest in a long term energy plan or are they just looking for the quick fix?



I'm going to assume when you say mod/con you mean they may want to conver to gas.



A mod/con in my opinion is the best fuel/energy saving option but that is dependent on the installation. They also don't need to be complicated and there are many that are not. As for your doubts about savings. That goes back to the installation and paragraph 2.

I think the biggest mistake made is that most contractors only look at replacing the equipment and most homeowners only know the yellow lable on the side that tells them how efficienct a product is suppose to be. With mod/cons that little yellow label is only telling you what AFUE that boiler is capable of providing. It's not telling you about the installation and setup.



System efficiency in my book is the most over looked. It generally never gets even a look at by most contractors. Honestly, most don't know how to calculate flow rates, btu output of board at given temps etc. The guys you find on the Wall for the most part are the exception to that rule. The others, good mechanics. The job will look pretty and the installation from a piping standpoint will be outstanding and you will probably be happy with the service.

System efficiency is like having this beautiful car. It's suppose to provide 35 miles to the gallon but the owner never keeps the proper air pressure in the tires and lets the oil filter go a little longer than its suppose to. The car will get him from point a to b easily and comfortably but he always complains that he only gets 25 miles to the gallon. Is combustion efficiency the problem or system efficiency?

The anwser to your question relies on the proper heat loss, design and installation. It also can be somthing that is achieved over time. The mod/con today and some system updates phased in over a few years. In the long run you will probably end up with a much better system and you keep adding fuel/energy savings over years. If I could cut you fuel/energy bill down 20% in the first year and then another 10% each year over a 2 year period giving you a 40 percent savings would you take a hard look at the mod/con?

Patrick_North

Oil only...

I should have mentioned- this would be oil only. Anything's possible, but they'd be very reluctant to go to the expense of bringing gas to the house- at least without crunching some serious numbers. Even then, it sounds like it's not in the immediate budget- this is an unexpected boiler replacement.

Are there even any reasonable oil mod con options? They've got loads of (oversized) CI rads- sounds like a good match for a modulating boiler.

I will urge them to keep the indirect, and I'm loaning them my Slanfit heatloss software- I'm sure their oil company (who's given an initial estimate) didn't do a heatloss.

Thanks,

Patrick

CMadatMe

MPO

Properly sized MPO would be a nice replacement. There are truly only 2 90' plus oil boilers and Bob who posted above could give you some nice feedback on the Peerless Pinnacle oil as he has installed a few.

Jean-David Beyer

Depends on gas company...

I converted from oil to gas last year here in New Jersey. I had no gas in the house.

The gas company seems to have been looking for customers because they brought the gas from the street to the house and installed the meter for free. I did have to pay my town $150 for a permit to open the street for them to conenct to the main that runs down the street.

shoudabeenaplumba

Depends on where the gas line is

If gas is at the street then it should be reasonable or possibly free.  If they have to bring it down the street it will be expensive.  A friend of mine got a quote of 3k but it would have brought gas past 10 other homes before her's.   I told her to get together with the neighbors but she didn't have that kind of time.  She was already boiling water on the stove to wash!

I'm not a pro but I've obsessed over the same question when it comes to condensing oil boilers.  The thing that convinced me not to worry about it is the simple fact that there isn't that much more heat available when it comes to oil.  There's roughly 1/2 the condensate in oil exhaust compared to gas/propane so the return on the extra equipment is hard to justify.    I'd want at least a 3 pass boiler with primary secondary piping so I could take advantage of the large mass stored in the CI radiators without fear of condensing.    I'm guessing after the fuel becomes cleaner we're going to see add-on heat exchangers you can add to either heat your combustion air or preheat your DHW.

Sal Santamaura

Isn't the FCX oil condensing?

http://www.monitorproducts.com/pdf/brochures/fcx.pdf

bob eck

MPO VS MOD-CON

If staying with oil the Burnham MPO is a great oil fired three pass cast iron boiler. The MPO boiler now comes with controls to add outdoor reset. How old is the oil tank? does the oil tank need to be replaced? do you need to install a stainless steel chimney liner? if going to nat gas mod-con take a look at using triangle tube prestige solo with their smart ss indirect water heater for domestic hot water or triangle tube prestige excellence model PE110 110,000 btu input 95% AFUE boiler with 14 gallon built in stainless steel indirect water heater. The 14 gallon indirect water heater in the Pe110 boiler will deliver 180 GPH or 3 gpm flow. The triangle tube boilers are side wall vented with pvc pipe and fittings if you can not sidewall vent look at running the pvc vent pipe up the old chimney if it is strait and there are no other appliances run into the chimney. fresh air can come in from any side of the house. I have a PE110 boiler in my house and on the domestic hot water side I can run two showers at one time using 1.6 gpm alsons shower heads. Yes there is plenty of water that comes out of the alsons 1.6 gpm shower head no need to still use 2.5 gpm shower heads. I have cast iron radiators and took out a 33 year old three section cast iron oil fired weil mclain boiler with domestic coil and my heating and hot water cost went from $2100.00 to $980.00 for a year. Make sure there is a heat loss done on the house to size the boiler right.If you have copper baseboard. Add more copper baseboard so the boiler can run at lower water temps where the boiler is condensing most of the heating season. Also the mod-con if 95% AFUE qualifies for the federal tax credit of 30% up to $1500.00 and some states have rebates for upgrading to higher efficiency heating systems and some gas utilities also offer rebate money. find a good heating company and do it right the first time no matter if you are staying with oil or going to nat gas. A good system installer right will save you money year after year and energy costs are always going up. good luck