Rinnai E110C

LBB

Had a Rinnai E110C Combo propane boiler/tankless hot water heater installed last November in a 100+ year old 2-family home to provide the 2nd floor apartment heat & water for both units. Heat works great. Hot water is very slow to arrive in both units. Water runs in kitchen or bathroom sink for 1.5+ minutes (wasting gallons and gallons of water) before it heats up. This is unacceptable to me and negates the environmental aspects of a tankless heater IMO.

My HVAC company suggested 3 options: 1. Electric on demand HW heater under kitchen sink (not ideal as it doesn't fix the issue in the 1st floor apt or the 2nd floor bathroom). 2. Shorten water pipes in basement for a more direct route
3. Recirc loop (not ideal as it requires the walls to be opened for access)

Options #1 & 3 are out and I am hesitant about the efficacy of option #2. At this point I'm considering having the tankless disconnected the from the boiler and going back to a separate 40 gallon gas water heater (tank).

I like the idea of a tankless but it doesn't seem to be a good fit for my situation. Does anyone have any suggestions?

Larry Weingarten

Hello, A tankless heater will add 7-15 seconds of wait time to the system as it heats up. Tank type heaters deliver hot water into the plumbing almost as soon as water is run. But my question is how long did it take to get hot water before the tankless was installed? If the wait time has increased more than about 15 seconds, the heater is misbehaving somehow.

Yours, Larry

LBB

The old system (regular HW heater, not tankless) was almost instantaneous. No problems.

Larry Weingarten

Hello, Were any other changes made to he plumbing, like adding a mixing valve? I'm wondering also if there is a cross connection. Test for this by shutting off water to the heater and then open a hot tap. If it doesn't stop running quickly, cold is getting into the hot side someplace.

Also, it occurs to me that with you old system, there likely was gravity flow going on, priming the hot lines, so you got hot quickly. That can't happen with tankless.

Yours, Larry

j a_2

That is a huge compliment from owners of the on demands...the e 110 c combi has like most a ,hot water priority...so a recirculation system won't work in a conventional installation..it's just the nature of the beast...u will hear of ways to do it but not without a lot of work and gadgets attached.....Better off moving the boiler to the floor it services...easy said from my chair..lol...
...there is a price to pay in comfort with on demands and such....but that's the direction we are going to....Mass has a plumbing code that says any hot water supply more than 100 liner ft..must have a recerc system..or at least they did....? do we waste water or energy...can't win...

rick in Alaska

I am with Larry. I will bet you were getting gravity circulation in the hot water line with the tank heater, which would give you instant hot water. You could put in one of the Grundfos D'mand systems, which would save you the problems of running a return line, but they also have some quirky issues.
I would wait until the water heater hasn't been used for a while, and then have some one turn on the water at one of the fixtures and see how long it takes for hot water to start leaving the water heater. My guess is you will notice it in about 10 seconds or so. This will at least tell you if it is a water heater problem.
Rick

LBB

Rick what do you mean "see how long it takes for hot water to start leaving the water heater" ? Is that different than how long it takes to feel hot water at the tap?

Larry, the system was installed with a propane conversion (from oil) no other changes.

J A - no way to move to the floor it services, unfortunately.

Thank you all!

rick in Alaska

By checking how long it takes for the water to get hot coming out of the tank, you can see if the water heater is heating it up right away, or if there is a significant delay. Then, knowing how long it takes for hot water to leave the water heater, and how long it takes to get it to the fixtures, you can verify it is a water heater problem or a system problem.
In other words, if it takes 10 seconds to get hot water coming out of the heater, but it still takes 1 1/2 minutes to get to the fixture, then it tells you the piping is where the heat is being lost, and not a water heater problem. Probably from a large hot water pipe size, or perhaps even some kind of cross connection in the piping.
Check out these if it is a piping issue.
https://www.taco-hvac.com/archives/102-153.pdf
http://us.grundfos.com/products/find-product/comfort-pumps-up-10.html
Rick

LBB

Thanks Rick, got it. So how do I check how long it takes for the water to get hot coming out of the tank?

kcopp

Is the location of the combi boiler the same location as the water heater was?

rick in Alaska

Just grab hold of the hot water pipe leaving the tankless after someone turns on the hot water upstairs, then just time how long it takes for the pipe to get hot.
Rick

Jack

In the Parameters menu on the boilers control, check and see what the setting is on Para. 36. If it is 00, change it to 10. That enables a "plate warming" function which will keep the hot water hx warm. If the setting is 00 the boiler has to fire and warm and then the hx gets hot.
In addition to this, as all ready noted, your system piping can play into this. Is your hot water piping to the kitchen accessible? What size is it? The reason I ask is that like you, I hate standing around tapping my foot at the kitchen sink waiting. I have solved that delay by running a small diameter line from the boiler/tankless direct to the kitchen sink. Cross sectional area on 1/2" pipe is .19", 3/4 is .44" & 1" is .77". Those numbers proportionately equate to volume. Decrease the volume of water, decrease the delay.

Solid_Fuel_Man

The small 120volt 1500watt electric water heaters work well if the plate warming setting doesn't fix the delay to tour satisfaction. Basically go with option #1. They use a surprisingly small amount of electricity. Put one in each apartment, or at least one half way between boiler and farthest fixture. Less energy waste than an uninsulated recirc line. Maybe even less waste than an insulated recirc line when pump power consumption is figured into equation. IMHO