boiler vs. Hot water heater

Constantin

Another fellow homeowner here.

I would be highly surprised if your heat loss could approach 50kBTU/hr if your home is "insulated" on two of the major surfaces. I suggest using the slant fin program (it's free) to calculate the heat loss for each room and subsequently for the house. There are two main benefits:

1) You now have a better idea what the heat loss actually is (my bet is in 20kBTU/hr or less range) and

2) You'll now have a better idea what upgrades you could contemplate for the house and what the benefits would be. For example, you could perhaps blow cellulose insulation into a properly-prepared attic space, upgrade windows or doors.

Indeed, your load may end up being so small that a traditional heater will be overkill, even on a design-day. Yet, I would still consider either a modulating condensing boiler (if in budget) as the benefits of very high effciency while running, low mass, and rapid recovery of indirect-fired water heaters is a really nice combination.

One of the benefits of all the panel radiators you have is that they do not have to run hot all the time to keep you home comfortable. In fact, you'd probably love the benefit of a outdoor reset controller that modulates the temperatures of the radiators down during warmer weather, which makes your home a pretty ideal candidate for a condensing boiler.

For instance, the T50 from HTP is fairly inexpensive and for the fastest hot water recovery possible, could be coupled with a Smart III water heater from Triangle Tube or the same thing from Weil McLain (private label). It is true that all mod-con boilers available in the USA right now would be oversized though some like the T50 can modulate down to 10kBTU/hr, IIRC.

Even less expensive are stainless water heaters like the polaris that are also meant to heat homes. However, I have read reports that the polaris does not handle very low internal tank temperatures well in the long run (due to condensate dripping on the ignitor). The voyager series from HTP may be interesting as well.

I'm not a great fan of instantaneous water heaters in home heating applications because most of them weren't built for the purpose (though some are). I prefer devices that were built for a specific purpose and the cost of gas in NYC is so high that it probably makes more sense to buy a mod-con boiler than a instant water heater to keep the place warm. Savings from an energy-efficient home are not taxed, after all.

Whatever solution you are proposed, I would run it by the BI office to be sure that it meets local codes. Municipalities are funny that way and you wouldn't want to jeopardize the sale of your home at some point in the future because the inspector doesn't like what was installed, or how. Most importantly, stay away from open-system solutions and anyone that promotes them. That's legionella waiting to happen.

Hopefully, you're within striking distance of one of the regular contributors here, have you tried the "Find a Pro" feature?

M. Ostrowski

Boliers vs. hot water heaters

I'm renovating a row house in New York City, with an estimated heat loss of about 50,000 BTU/H (the house is just under 1000 square feet). I'm planning on putting in a hydronic system with flat-panel radiators. My plumber, who is kind of old-school but does beautiful work, is pushing for a 140K BTU boiler, which is obviously oversized. Hours of research online & talking to various hydronic companies (who are all pushing their choice products) hasn't helped me too much, and I'm looking to be as energy-efficient as possible. What's the best option: a full-on boiler, or a water heater? if the latter, tank or instantaneous? Can anyone tell me objectively the virtues and drawbacks of each?

thanks,

M.

Todd_15

NYC

I don't think that you can use a water heater for space heating in NYC. I believe you would need a unit with an "H" stamp and an MEA number, probably not a good application for a water heater.

Uni R_2

50K for 1000 sq ft?

Fellow homeowner here...

If your renovations include proper insulation, I can't see how you'd have a heatloss of 50K with that square footage. You should calculate that properly first.

I would also recommend that you pipe to the panels from a central manifold, and install TRVs on most of panels.

If your heatloss were low enough, I'd actually opt for an electric boiler with outdoor reset, but you need to first determine that. Click the heat loss calcs button at the top to start with. Water heaters aren't for heating homes.

M. Ostrowski

Thanks for your responses. (I was indeed planning on installing TRVs on the panels). I had the heat loss calculated by a hydronics company, did it myself online 2 or 3 different ways, & picked the biggest number. in which direction does it seem unrealistic? (it is a row house, with the longest walls adjoining other buildings).

Does anyone out there with row house experience have bright ideas about dealing with newfangled venting systems for condenser boilers? I gather i can't use my perfectly functional masonry-lined chimney, and don't have a lot of other access points to the outside world from my basement.

i'm so happpy i found this list....

M

David_41

Electric Water Heater

Hello M... I read your post with interest. I have an 800 square foot house which had a fuel oil boiler that was installed in 1947. It was extremely inefficient. I looked at a lot of options and every one was out of my budget. I decided to 'cook' by own and purchased a water heater, pex piping & more. I had every hydronics guy in the world tell me it would not work and would cost a fortune to use a water heater. I proceeded nonetheless and, as expected, my heating costs were cut by two-thirds. Please be warned! This IS NOT as easy as simply buying a hot water heater. You will need a lot of electricty and a heater with dual, simultaneous heating elements. You also need all of the safety items required! It is very easy to create a hydronic bomb!

Joe Brix

Electric rates in NYC

probably don't warrant it. What are you doing for DHW? The 50K BTU heat loss does seem high? Maybe 1K sq ft per floor?
You do have nat draft boilers under 50K.

hr

50 btu/ square foot

seems awful high with you longest walls being heated on the other side?

If you do go with a mod con boiler I have not found any under 50K input, so that handles that question

There must be contractors in your area that have done this type of retrofit. They would know the best methods for venting and locating the equipment. They would also be good at heat load calcs for that specfic application.

Bradford White has upgraded the old CombiCor, now available in gas, lp or oil fired.

It is a 50 or 75 gallon water heater with a large steel coil inside for the heating load.

I'm not sure if they are acceptable in your area, code-wise,but it would solve DHW and heating needs from a single appliance.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Dave Yates (GrandPAH)_3

more on the subject thanks to Robert Bean

From healthyheating.com's web site:

http://www.healthyheating.com/tools/Dave Yates H20 vs Boiler.pdf

EJ hoffman

Combicor

Last Combicor I installed I Piped it up like a voyager Put an 006 in constant circ on the tank and got a better output

Perry_2

A couple of things to consider...

I am a homeowner - but been around the block as well and recently replaced my boiler in a 1954 built 1700 sq ft home in Wisconsin. My calculated heat loss was about 57,000 Btu/Hr with the Slant Fin heat loss calculator for upstairs, main floor, and basement. I am now convinced that this was high based on the fact that at 10 F outside weather my mod/con boiler still cycles on and off because its minimum firing rate is still more than the heat load. 40,000 Btu/Hr seems a more realistic estimate now (and matches an estimate one of the pro's here on the site gave me for the size of my installed radiators).

So, yes - your estimated heat loss of 50,000 Btu/Hr for a 1000 sq ft house seems high. However, I admit it could be right if your house has no insulation at all - and extreemly drafty windows and doors. In which case I would recommend that you insulate the house and replace the windows as part of the project. I know that is not cheap - but long term that is the most cost effective solution.

I also note that if the house is wired with knob and spool wiring (individual bare wires supported on porcelin insulators in the walls) that you cannot just blow insulation into the walls. Replacing knob and spool wiring would cost more money - but I highly recommend it for other reasons as most of the electrical caused house fires are from knob and spool wiring (and it usually has fairly limited circuit capacity as well).

All that being said: If you have even a reasonably insulated house, reasonable windows, weather-stripped doors - your concept of an electric boiler may have merit. My guess that your real heat loss in such a house might be on the order of 20,000 Btu/Hr which is much smaller than any available mod/con boiler in the US - or even most non-condensing boilers. And that is for only a few days of the coldest weather of the year - most of the times it could be half of that. It will cost extra money to put in an oversized boiler - and you would never realize much of what can be achieved for efficiency in much larger buildings with the modern mod/con boilers. You would also most likely have to recondition or line your existing chimney - another expense.

If you go the electrical route - I would recommend to also install electric water and stove so that you are not paying up to several hundred dollars a year in "meter" charges for less than a hundred dollars in gas use (around here I am paying over $12 per month in meter charges and averaged less than $5 per month in hot water gas use). Of course, you will need robust electrical system to handle this - and don't forget to look at that cost as well (which would be fairly modest if you were already rewiring the house).

Perry

Steve Garson_2

Combicor

I heat the radiant in my home with a Combicore, which also provides the potable Hot Water. Works fine. My house is mostly steam heat but the additions are radiant.

Uni R_2

Subject to...


If that masonary chimney has nothing else venting into it then it can be used to vent a condensing boiler. Some conditions apply...

What size is the inside of the chimney?

D107

Go to the find-a-pro section on this site

HO here. I've heard good things about Gateway Plumbing and Heating (John Cataneo) in NYC who are listed in Find a Professional. Probably worth your while to get a pro down there at least for a paid consult and a proper heat loss. Was a blower test done? Like the posts have said it is possible you have 50kbtu loss but not likely. There may be alot of wall, basement (band joist) and attic insulation you can do that will achieve great savings before you put a boiler in.

You probably can use your chimney for the plastic exhaust vent and intake conduits. NYC MAY require roof venting for mod cons or mandate vent being a certain distance from any window. I know when I lived in the city our coop had a laundry put in and we were not allowed to vent even dryer exhaust from a side window. Ended up putting in a stainless steel liner up through the abandoned incinerator shaft.

David

Dan K.

Water heater or boiler

Another thing to consider is the water temp that you need to supply the panels with. If you use the water heater, you'll need larger (much more expensive) radiation panels due to the reduced water temp available to supply them with. Also, the life expectancy of a water heater is about 7 years, while a propoerly sized and installed cast iron boiler is at least 20 years. It's entirely your call, but I'd definitely go with the boiler!

And yes, 50k loss on 1,000 sf seems excessive to me as well.