Hot Water Radiator- Efficient??


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Old 11-23-07, 07:30 PM
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Question Hot Water Radiator- Efficient??

Hi All:

I have a 93 yr old home in New England and I've gutted the entire house. Only thing I haven't touched is the HVAC. I have a 30-40 yr old Weil boiler that was originally a steam system but now runs hot water. I've put $1,000 into it for Honeywell ignition problems and now the circulator has seized and I'm ready to get a new system. I had about 14 radiators on 3 floors running in one zone. I am planning to have 6 radiators on one zone, 6 on a second and baseboard/toe kicks on a third. The gas company will give me $500 for an 85% efficient boiler and $1000 for a 90%. My HVAC contractor says that because my radiators are made for steam that any efficiency will go out the window.

We do not want to convert to 100% baseboard so what are my options? I've read online that because steam radiators are not linked at the top water has a hard time flowing through the unit. Is this true and should I be concerned? I'm ready to spend a lot of money and want to do it wisely. Any help is appreciated!!
 
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Old 11-23-07, 07:36 PM
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Get the boiler maintained properly and any faulty crap replaced, but I'd leave it is as and focus on the rest of the house. Think about your heating while you are renovating... maybe match the heatloss of your cast iron rads by heating your floor and keep it all simple.

Better boilers are coming but your big savings will come from really tightening up your house/envelope. Then you'll be able to get even better savings from rightsizing a system. You may need to drop coin however on an A/C system if that is best done with a gut.

I'd get the old Weil running its best and hang on... the envelope is where you should focus.
 
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Old 11-23-07, 08:30 PM
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I can't speak to the "aren't linked at the top" bit about the rads (I couldn't say definitively), but in general large cast iron radiators are about the next thing to radiant floor heating in terms of comfort and efficiency. Pair those rads with a modulating/condensing boiler with outdoor reset, and you will have a very, very efficient and comfortable system.

I do know that steam to water conversions are not uncommon, and use the same rads.

If you have good flow through the radiators (when the circ isn't seized), and you are prepared to drop some bucks on a good boiler, here are some suggestions.

Look into a 93+ efficient mod/con boiler. Personally, I am leery of the aluminum heat exchanger models. They appear to be very sensitive to water chemistry, among other things. The stainless steel heat exchangers seem to be much less affected.

At the inexpensive end, there is the Munchkin. In the mid-range, there is the Triangle Tube Prestige, the Lochinvar Knight (my pref, based on an acquaintance who installs a lot of them and is very impressed), and the NTI Trinity. At the high end is the Viessmann Vitodens.

The outdoor reset function monitors the outdoor temperature and raises/lowers the supply water temperature as the outdoor temp gets colder/warmer. The modulating burner increases/reduces the energy spent firing the burner to maximize efficiency. The condensing part extracts heat from condensation in the heat exchanger when you are running low return temps (
 
 

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