Trying to figure out my tankless unit out. I have it set up for a hydronic in floor system, closed loop. 3 loops under 270' ea, expansion tank and circ pump. I can get it up to 15psi and it initiates the circ pump but it never fires anymore, I had it running for 5 minutes initially, then intermittently for a couple hours and now, 2 weeks later, it doesn't do anything. Coded p1 and 11 and now 76, comm error, now I am at a loss.
Repost rheem tankless water heater
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Fitter30
Well-Known Member
Take a few pipes of the heater ,piping, pumps and expansion tank. Don't get to close. Brand and model of heater? 15 lbs of pressure is way to high.
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Bannerman
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I suspect he mean 'pics' (pictures).
Bannerman
Well-Known Member
Reduce each photo's resolution to less than 800 pixels.
Alternately, upload the photos to an online photo hosting site, then post only the links to the web page for each image.
Alternately, upload the photos to an online photo hosting site, then post only the links to the web page for each image.
Fitter30
Well-Known Member
270' 1/2" pex x 3 loops 8600 btu's you have a water heater not a boiler. 199k max btu 11k minimum, 22% oversized. That is why there is a 15 lb minimum water pressure. Max pressure 150 lb. Boiler max pressure 30/lbs most run 10-20lbs
290' 1/2 pex holds 2.84 gallons
290' 1/2 pex holds 2.84 gallons
Bannerman
Well-Known Member
Are you planning to use that condensing gas water heater in a closed loop, for hydronic heating only, just as a boiler would be utilized?
Assuming the 11,000 minimum BTU is the unit's gas input rate, a 93% efficiency factor will signify at minimum, 10,230 BTUs heat output into the water, although only 8600 BTUs will be radiated into the space.
While that model has the highest heating capacity in that Rheem series of tankless water heaters, the lower capacity models also have a minimum input of 11000 BTUs.
To maximize efficiency, condensing tankless units typically cause cool incoming water flow to pass through a secondary heat exchanger, to extract the maximum amount of heat from the combustion exhaust gases, to cause the moisture within the exhaust gases to condense into water droplets, which must be then eliminated to a suitable drain. The pre-heated water exiting the secondary heat exchanger, is then further heated to the desired temperature within the primary gas fired heat exchanger.
To extract sufficient heat from the exhaust gases to cause the exhaust gas moisture to condense, the incoming water temperature will typically need to be a maximum of 100°F, but an 80°F or lower incoming water temperature will be needed to achieve the unit's 93% efficiency rating.
Assuming the 11,000 minimum BTU is the unit's gas input rate, a 93% efficiency factor will signify at minimum, 10,230 BTUs heat output into the water, although only 8600 BTUs will be radiated into the space.
While that model has the highest heating capacity in that Rheem series of tankless water heaters, the lower capacity models also have a minimum input of 11000 BTUs.
To maximize efficiency, condensing tankless units typically cause cool incoming water flow to pass through a secondary heat exchanger, to extract the maximum amount of heat from the combustion exhaust gases, to cause the moisture within the exhaust gases to condense into water droplets, which must be then eliminated to a suitable drain. The pre-heated water exiting the secondary heat exchanger, is then further heated to the desired temperature within the primary gas fired heat exchanger.
To extract sufficient heat from the exhaust gases to cause the exhaust gas moisture to condense, the incoming water temperature will typically need to be a maximum of 100°F, but an 80°F or lower incoming water temperature will be needed to achieve the unit's 93% efficiency rating.
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That's right, only for the infloor heat and a closed loop. I do have the condensing outlet routed to the drain. Is it a thing to put a mixing valve in the loop, would this alleviate out and incoming pressure and temp differential? You said alot there and I am trying to keep up.
Bannerman
Well-Known Member
A mixing valve, mixes cold water with hot to provide a lower temperature than the heater is providing.
Since you are configuring a closed loop system, where would the additional water go since the closed loop system will be already filled with the maximum amount of water it can hold?
Is your home also equipped with a forced air heating system? If so, it maybe possible to install a small water coil within the forced air return plenum, thereby utilizing the WHs excess BTU capacity to provide continuously heated air, thereby requiring the fan to run continuously at low speed during the heating season.
Fitter30
Well-Known Member
What type of anti freeze? This is a service manual not on your heater but similar. Look up installer mode page 44 see if you can get into yours. Most manufacturers keep them pretty close to the same. Noticed that you can limit fan speed which will limit firing and also can vary off time.
