New boiler + old radiators, pitfalls?

Mike T., Swampeast MO

If yours is a hot water system, you have MUCH to benefit by using a condensing/modulating boiler.

If steam, boiler efficiency hasn't changed much in decades. The key to a good steam system is making certain that everything is in proper working order and works together as a system.

Stuart Oglesby_2

I'm a homeowner in the midst of looking into a new boiler, and am getting a ton of good info here. Except the one thing I haven't been able to find yet is if there is anything in particular we should look out for with getting a new, more efficient boiler while keeping the old cast iron radiators. Though a recurring theme in many post seems to be probable oversizing, and finding a contractor that will do a proper estimate to eliminate that problem. Anything else we should be looking out for?

Any help or input is greatly appreciated.

Thanks!

thfurnitureguy_4

Leaks in your system. Bad valves, small or missing main vents, stuck or inop radiator vents. What killed your old boiler? why are you installing new? ( what killed your old one will mess up your new one if it is not repaired.)

If steam make sure that your water leavel is the same on your new boiler as it was on your old system to keep your wet returns wet. IE, you want to have the boiler's water line at the same height as the old one. Better yet you want to make sure all your radiators and returns drip to a wet return (1pipe system) Missing pipe insulation. Broken pipe hangers and sagging pipes.

Advice from someone who was there last year. Pay to have some one from this site come look at and design your new system. It will save you a ton of money, time and disapointment.

Rich Lowenstein

New condensing boilers are an excellent match for old radiators in a hot water system.

swanmech

Spiral trap

> New condensing boilers are an excellent match for

> old radiators in a hot water system.





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swanmech

Spiral trap

If installing hot water condensing boiler (any brand) with old radiator system, install a spiral trap on return. Very small investment on protection of $$ boiler.

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Stuart Oglesby_2

Forgot to put in there it's a water system. It's not dead yet, just a 28 yr old Weil-McLain. By chance IF it does go out I don't want to simply replace with the first thing I can get in here to replace it, I want something efficient and done correctly. Plus with the price of oil now I figure it could well be worth our while to replace it with something better anyway.
No leaks at the moment, and everything looks solid. Had one guy look at it and another coming Wednesday for an estimate.
I'd love to have someone here check it out, but there's no one close(Western suburbs of Phila).

Stuart Oglesby_2

OK, that's 3 recommendations for condensing boilers. I have to admit that this part is confusing me no end. We have a
1700 sq/ft single home (2 floors) built in 1928 with an oil-fired boiler and cast iron radiators. Nothing fancy, no spa or hot tub, no dishwasher(yet), 1 bath(eventually to be
1.5 or2), and our hot water is from a summer/winter setup(tankless coil?).
I'm waitng to see what the estimates recommend, but I'm completely lost on whether to stick with a "classic" cast-iron
replacment or the condensing boilers, and I'm not even sure yet what to lok for in a condensing boiler.
On a related note, would something with outdoor reset be overkill for a home this size?

Thanks!

Jim Cheung_2

Outdoor reset has nothing to do with home size. If you do a search you will find thousands of threads about it here.

Outdoor reset varies the water temperature so that it is only as hot as is needed, avoiding that intermittent searing-blast-of-heat-from-radiator feeling. It's absolutely wonderful even in a one-room shack.

Mike T., Swampeast MO

True condensing oil-fired boilers seem rare in the US. Something about high-sulfur fuel oil. Fairly common in Europe where fuel oil has different standards.

You might want to check out the new Weil-McLain Ultra Oil boiler. From the little I read, it seems quite intriguing. Am fairly certain that it's using an aluminum heat exchanger, so water quality, treatment and monitoring are especially important to ensure the longest service life.

wilbot_7

type of boiler

do you have gas or oil? If you have gas then a condensing boiler is the way to go if you can.If you have oil then you are limited as far as combustion technology.
Cast iron radiators are a great source of heat. I would design the system to have constant circulation with trv valves that will allow you to adjust the temp in every room. Also put an indirect in with the new boiler,tankless heaters are inefficient and can cause problems down the line.
As far as what boiler to install we all have our favorites. Oil i like the viesman or buderus and when it comes to gas munchkin is my first choice it has all the bells and whistles as all the other boilers do, but the price is also lower so more people can afford it.
These are just my personal opinions and i hope i helped.

Stuart Oglesby

A new can of worms

It's an oil-fired boiler. Just looking around and only having one quote so far, I've sort of narrowed it down to Burnham MPO, WM Ultra Oil, and Buderus. A friend in the neighborhood looked into the Viesmann, very nice and _very_ steep prices, probably out of our reach unfortunately.
Only in the last few days have I started looking into TRV valves. Can they just be installed on the existing old system, or are they something that needs to be considered from the start if we replace the old boiler?
Thanks so much for the suggestions.

Uni R

Oil Ultra

That slim little oil-fired Ultra is a third of a ton of cast iron.

Constantin

Condensing Oil Boilers...

... AFAIK, the only true condensing boiler sold in the US at the moment is the Monitor FCX. A great little boiler with an DoE output rating of 76kBTU/hr. Allegedly safe with US fuel oil, which has a allowable contamination limit of 1,700PPM sulfur.

Regular EU Fuel oil isn't less contaminated, AFAIK, but it is more common to offer multiple "cleanliness" standards. The much larger hydronic market (99% market share there, 9% here), fiercer competition, wide-spread availability of clean oil, and the different liability laws over there probably account for the reason that we don't see more condensing oil-fired boilers on the US market.

Constantin

Solid choices...

... I went for a Vitola but the Burnham MPO and the Buderus G115 also have a good track record. Be sure to have them installed correctly, and you'll enjoy years of energy-efficient operation.

As far as the TRV placement goes, that depends a bit on how your radiators are piped. If they're on a mono-flo or similar system where each radiator has it's own quasi-independent hot water supply, TRV retrofits shouldn't be a problem.

However, if you have multiple radiators in series on a circuit that have been split across several rooms, a TRV won't help you balance that out because one TRV will affect the whole string of radiators. You can retrofit bypasses and the like to address this issue.

Rich_23

>Only in the last few days have I started looking into

>TRV valves. Can they just be installed on the existing

>old system, or are they something that needs to be

>considered from the start if we replace the old boiler?


???
A TRV has nothing to do with what boiler you have. A TRV is a replacement for your radiator's valve, it replaces a manual valve with automatic operation.

Dan_15

I dont know nearly as much as the pros who have posted above on this subject, but I can give you the benefit of my similar experience going through this same thing. I have 1800sf no wall insulation, high-mass converted gravity system. Last year I replaced the old pot-belly boiler with Buderus G215 w/Riello, indirect DHW tank, outdoor reset, indoor reset, constant circulation. So far I am on track to burn 800 gallons annually which is down from 1350 last year (which is down from 1760 the year before), representing about 45.5% fuel savings. I think you will find a huge benefit to outdoor reset and constant circ environment, particularly with your cast iron rads. Add TRVs and you will be happy in every room. I happen to love the Buderus because the controller's internal logic coupled with indoor reset room sensor seems to be particularly adept at sensing and anticipating the precise heat load needed to keep up with the heat loss. My experience so far is that this translates into incredible comfort and about as good efficiency as you can get with non-condensing cast iron.

Constantin

A G215 in a 1,800 sq ft home?

Wow, that's a huge boiler for such a small space...

Dan_15

Indeed, but I have a maze of 2-1/4" mains in the basement and 1-1/4" runs as holdovers from the original gravity system, which as you can imagine holds a lot of water mass to heat up. Coupled with zero insulation in the walls, its like a 2700 sf home in the body of 1700 sf. However, its really the perfect environment for outdoor reset and constant circ.

Stuart Oglesby

Right, that much I understood. I didn't know if, as Constantin pointed out about pipng arrangements, there would be other considerations in the system as a whole if TRVs were added that could be taken care of while we had someone in for the boiler install.

Someday I'll learn to write what I think ;-)

Stuart Oglesby

Thanks to everyone for the advice

...and I'll be printing this out to show the wife. The usual tug-of-war because the boiler isn't a "visible" improvement. On the other hand, she HATES being cold ;-)