Will the tankless aquastar work in a RFH system? I have a Bradford White 40’000 btu that has had its last problem this year . I don’t need a WH that needs to be worked on twice in three months. 5times in three years.
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Fine Homebuilding is excited to be the official media partner of the 2024 Building Science Symposium series! This event offers builders, tradesmen, architects, designers and suppliers to discuss topics ranging…
Featured Video
How to Install Exterior Window TrimHighlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
A tankless can (may) work with RFH if the minimum BTU/hour of the tankless is within the range of what your RFH calls for. But if only one zone (3 gpm?) calls for heat and the tempering valve is set for 95F and the water returns for at 75F then the BTUs going to the RFH is (3 x 8.3 x 60 x 20F) = 29,880 BTU/hour. If that is less than the tankless can produce, than colder and colder water will circulate until the tankless kicks on for a little while and then shuts off. Or no heat might be produced until another zone demands heat or the return water gets colder.
Definitely a tougher install for a pro and a lot tougher for a DIY than a tanked HWH. In most cases, I like a reasonably efficient non-electric gas HWH (like for about $180). Polaris and other brands claim 94% but use electric fans to get that efficiency. Which means the kwh's cost more and they don't work in a power failure.
My "Bradford White 40'000 btu" and similar units last 10-15 years at a time. Maybe look at your water chemistry and/or maintenance. Running them cold can make them rust prematurely.
David, when you say your water heaters last 10-15 years, are they failing from tank leakage? I change my anode every 6 years, and still have wh after 20.
Also, have you heard of a Bock water heater? I had not until recently.
Don't know if good or not.
Polaris have had some problems over the years with ignition, but I am told a major change this year has fixed the problem. They went to a Honeywell burner, and igniters that can handle higher voltages with out burnout. Do you have any input on these?
Tks, PaulEnergy Consultant and author of Practical Energy Cost Reduction for the Home
I ought change the anode every couple of years. I ought to take a baby aspirin each day. I ought to lose another 10 pounds. And so it goes.David Thomas Overlooking Cook Inlet in Kenai, Alaska
Not trying to add to your shoulda, coulda, woulda, list,I was just wondering if WH failure was tank life or burner failure.
You had no comment on Bock water heaters, so I take it that they are not in your area. They appear to be somewhere between a Polaris and a convential gas WH. One model that caught my eye holds 32 gal, has 104,000 Btu burner (blower), finned flue, and dual anodes. Don't know its efficiency.
Appreciate your comment on tankless heater. Have a friend who is building a house who thinks they are the way to go.
He stayed in a condo on vacation that had them. I told him to go ahead as long as he is disciplined enough to not run any two of the following at the same time; dishwasher, take a shower, fill bathtub, fill clothes washer, use heating coil in forced air, run hot water in kitchen sink etc. For his family and lifestyle, he only needs four to get the gpm.
He is now rethinking water heaters.Energy Consultant and author of Practical Energy Cost Reduction for the Home
Once saw something on a modulating tankless water heater combined with a buffer tank. Had a circulator on it, which kept the tank warm, and drove the recirc for the pipes.
Idea was to get the combustion efficiency of the tankless, and the 'spike' capacity of a tank. Setup was cheaper than a Polaris or equiv.
Similar in concept to using a tankless with buffer for space heating.
Interesting idea. IMHO, the standing losses are not as big a problem with tanks as folks tend to believe. Tank insulation is quite effective these days. Standard gas water heaters are notoriously inefficient.
Of course, I can't find this article now...
Thanks, it's that first 30 gal that needs to be on hand. I would like to find a WH in the high 80's eff, that was not too critical to pressures, quality of gas, iffy igniters, narrow range of settings, and at a reasonable price. We can certainly add enough insulation to slow the standing losses.Energy Consultant and author of Practical Energy Cost Reduction for the Home
Starting with a tankless, rigging up somthing like that from Home Depot Parts would be easy:
1) Electric HWH ($180)
2) Circulation pump (on the large size), and ($140)
3) even more insulation for the HWH, if you want. ($15
Wire the circ pump through the upper thermostat on the HWH (using 120 instead of 240, duh.) When the tank cools off, it will cause the tankless to fire up. Then a single loop of RFH, or low-flow hand washing would work fine. The HWH is not powered. Only functioning as a surge/storage tank. And as a switch for the circ pump.
Endless showers would still work just fine and if someone did the dishes or laundry during that endless shower, there'd be the peak flow of hot water to allow it.
You would avoid the standby losses of a gas HWH. Without a flue going through the middle of all that hot water then into the great outdoors (i.e. gas HWH), electric HWHs have pretty low standby losses. And you would never be heating water with electrons, only with gas in the tankless. And the tankless should come on less often since small uses would just draw a few gallons from the unplugged HWH. That should lengthen the life of the tankless.David Thomas Overlooking Cook Inlet in Kenai, Alaska
Thanks for the input David. I have a hotsurface igniter 84% power vent Bradford White now most of the trouble has been switches and electical sensers. But the tank has been rusting from day one. Water temp has been in the 140 - 120 out about 80 in. I don't think that is too cold to promote tank rusting. My AOSmith 25year old WH is not rusting yet and still making water hot . In fact the second person gets a hotter shower than the first. I have it set a 120.
That is what I was wondering about the tankless , If the cool incoming water would triger the heater. That and the water flow . I heard that a low water flow would not fire up the burner on a tankless.
I think it is time for another standing pilot AOSmith This was the first power vent water heater I ever had and it has been nothing but trouble , And noisy.
The incoming flow rate is enough (3 gpm versus 1 or 1.5 gpm to trip the tankless.) BUT the output of the tankless will be 75F returning water temp plus 80F temp rise = 155F and your RFH doesn't want to see 155F. So it won't really take 3 gpm. 2 or 2.5 gpm will come from the return loop through the tempering valve. Until the floor cools down some more or another zone comes on.
Tankless are really good at what they do well (provide endless showers for one user) and RFH are really good at what they do (provide uniform temps given a supply of 90-110F water at 1 to 6 gpm. They two do not necessarily play well together.
David Thomas Overlooking Cook Inlet in Kenai, Alaska