Radiant Floor with Oil Furnace?
Our home was built in '58 and has baseboard on both the first and second floors. Roughly 3000sqft it has an Oil Furnace (relatively new...2009) that also happens to have one of the very inefficient coil on demand water heaters inside. The furnace supplies a 4 port manifold for 4 zones/loops (2 first floor, 2 2nd floor)
In principle I want to remove the baseboard on the first floor, installing radiant floor between the joists of the crawl space and replace baseboard on 2nd floor with wall mounted Hydronic radiators (we had these in Europe with great success). Hot water temp in the shower has the classic too hot then too cold issue due to the coil so would like to fix that.
My primary question is should I use the oil furnace for the radiant heat (assume a mixing valve required due to temp) or should we look to install a electric water heater to handle heating of domestic and radiant water? Or retain the oil furnace and use a heatpump electric heater?
Second question is if we retain the furnace can I use the existing 2 zones for the first floor to feed a separate radiant floor manifold with approx 7 or 8 loops assuming I use a mixer to reduce the water temp entering the radiant floor manifold?
Looking for suggestions. I'll install heat transfer plates, PEX and insulation myself but likely need some assistance on the furnace/heater side of things.
Thanks in advance
Re: Radiant Floor with Oil Furnace?
Thank you for the photos of your system it looks like good workmanship was done during the installation (you have a BOILER there, not a furnace).
Strongly suggest you leave things the way they are until you can get several hydronic (hot water heating) contractors into the house (consult the Yellow Pages under "Heating") to look things over & make their recommendations (you can always opt to do the work yourself if you so decide, but strongly suggest you get the insight of several contractors first); unless you are having major problems getting the house adequately warm during the winter heating season, I simply can't see the benefit of the high expense of adding radiant, when the baseboard should be doing the job of heating the house; or for that matter adding a heat pump; perhaps there are other issues existing with the tightness of the windows/amount of insulation inside exterior walls (R19 required) or the attic (R40 required) that might be making the house feel cold during the winter months???
Some specific changes I would recommend (which should have been when the system was installed) is to have an indirect hot water heater installed, in place of the tankless coil you have now; a tankless coil is totally inadequate (even for a family of 1, since it produces little more than a gallon of hw before it runs out & the tiny hw coil inside the boiler has to be reheated several times to get more hot water--these tankless coils simply don't do the job) to produce the family needs for domestic hot water (dhw: that hw that is used for showers, dishwasher, clothes washer, etc.) an IHWH is typically a 40 gallon (use a 30 gal for a family of 1) stand-alone heat exchanger tank that stands beside the boiler & is connected to it by a continuous loop & is treated like another added ZONE; a t-stat inside the IHWH is set to approx 130 degrees & makes a "call for heat" to the boiler whenever the dhw temp falls below that value; the IHWH is heavily insulated so there is little heat loss; they last for years because there are no moving parts; 40 gal. indirects are made by Triangle Tube, HTP Superstor, Weil-McLain G0LD PLUS, Crown Megastor, Lochinvar Squire, TFI Everhot, Amtrol Boilermate & others----if you have "hard" water in your area a stainless steel (or stone-lined) IHWH is recommended; if you have soft water, the Amtrol & Crown Megastor (both non-stainless steel) are less expensive & will do the job.
Another important change, if feasible is to convert from oil to gas & have a natural gas line installed, if NG is available on your street; #2 fuel oil is OK for the time being, but it is much more expensive than NG & continues to go up in price because of a troubled Middle East.
I therefore think you should concentrate spending your money on an IHWH and a conversion to gas in place of oil; and perhaps on some exterior wall/attic insulation, if needed, & double-pane storms on all windows if you don't have them already.
There's a 500 page text by hydronic (hot water systems) engineer John Siegenthaler called "Modern Hydronic Heating" (below) that is a must read for everyone that has a hot water heating system---do not BUY this book---it is widely available at most local public libraries to read free of charge; if not, consult the library of your local trade school that offers courses in HVAC/heating---they almost always allow public access to their library.
Last edited by Pelton; 08-05-2014 at 12:30 AM.
Re: Radiant Floor with Oil Furnace?
Good to hear your views on the prior work. I have to say, I've always thought it did look tidy.
I totally understand the point re keeping existing system however its more a cosmetic thing. The entire first floor is having new floors installed and my wife wants the baseboard gone (hey, she's the boss!). That being said, any thoughts on whether the 2 zones feeding the existing baseboard could be used to feed Radiant floor manifold & mixer?
I'll take a look at the Indirects you suggested.
I got in touch with the local contractor who installed the boiler in 2009 so will have their recommendation but appreciate the education folks like yourself offer on here.
Originally Posted by Pelton
Re: Radiant Floor with Oil Furnace?
Yes, the 2 zones you now have for the floor can be used to feed the new PEX flooring with a mixing valve for the new radiant floor heat---but you must hire someone EXPERIENCED in installing PEX radiant heating---there are CALCULATIONS that have to be done by the heating contractor as to how many feet of PEX tubing is snaked back & forth in an adequate number of loops (according to accurate heat loss calculations) so that each room will be warm during the coldest winter days---each foot of the PEX emits a certain amount of heat & there are formulas that the installer must use to make sure that each room is adequately covered.
There is a question as to whether the existing zone circulating pumps now at the boiler can pump the correct amount of hot water (in gallons per minute-gpm) thru the PEX tubing, or whether they will have to be replaced with different pumps that have a higher or lower gpm output; quite a number of pumps (circulators) are used in radiant applications (as noted in the site below), as a way of feeding hw to all the loops in the system.
All of these calculations & PEX floor layouts are covered by numerous diagrams in the Siegenthaler book, as well as the various PEX PIPING DIAGRAMS & layouts, & I'm sure you can also find many examples on the internet via a Google search of "residential radiant heat installations" (one example below).
Note that there are many different ways to install in-house radiant heat; some systems place the PEX tubing directly under the sub-floor/finished floor; in a real sense, the entire first floor or 2nd floor becomes a giant radiator; others install PEX sub-floor in the cellar between the floor joists (where there is access, on floor 1, for example); others even include the side walls; rarely, the ceilings.
Last edited by Pelton; 08-05-2014 at 10:55 AM.