Propane tankless water heater

[Racer4]

inlet filter will help some. But as the water is heated, the minerals that are in the water will separate from the water and attach it's self to the water coil. You may have to flush the coil more than normal to prevent total blockage of the water coil.

I have attended several classes where they had cut aways of water coils completely blocked from mineral deposits. so I recommend a good flush depending on water quality

I use these as a treatment before the water enters the heater:

Amazon.com

The fitting that these cartridges screw into was purchased at the local plumbing supply house and is specifically for this purpose.

 

[HawkinsHollow]

Installed a tankless water heater for our addition/remodel. We just moved in and I am having a hard time dealing with the wait times for hot water. A hot water tap about 15 feet from the hot water heater takes 40 seconds to get hot water, that is unacceptable in my opinion. I am going to have the plumber back out to see if is a setting on the heater. With the old tank water heater we never waited more than 10 seconds at this same exact sink location. So I do not understand why there is such an issue with wait time in the new system. The house has completely new supply lines, so it could be something in the design. I plan on insulating the hot water pipes and probably in the end add a recirculation pump to drop the hot water wait times to acceptable levels. I think this is just the nature of the beast. Advice about putting it as centrally located as possible is good advice. Good luck.

 

[WinterDeere]

Instead of a circulation pump, I wonder if anyone has ever looked at just mounting one of those very small hot water heaters downstream of one of these, as a maintainer. Energy usage in the tank would be very low, as the initial heating is done by the tankless, and it's only maintaining a small amount of water. I'm thinking here of the type usually designed to go under a sink or under a bar, although even one of those old "Insta-Hot" under-sink faucet heaters could probably improve performance.

Theory here is that even a very tiny water heater downstream of the tankless system would ensure quick delivery of hot water, while feeding it from the tankless would ensure endless supply... which is the primary downside of the traditional water heater. Depending on how small the tank is on this system, 0.5 gallons versus maybe 5 gallons, there would be a slight dip in temperature due to initial cold water filling into the tank from the tankless, as it comes online.

Amazon.com

www.amazon.com

Of course a recirc system is instantly hot. But it also defeats a primary purpose of a tankless, in that the heater will be running very often when there's no demand, just keeping up with the losses of the recirc loop. I predict a substantial increase in operating costs, and a substantial decrease in component lifetime, when adding a recirc loop with no tank to a tankless system.

 

[kenmac]

Instead of a circulation pump, I wonder if anyone has ever looked at just mounting one of those very small hot water heaters downstream of one of these, the type usually designed to go under a sink or under a bar. Heck, even one of those old "Insta-Hot" faucet heaters, which I think run around 0.5 gallons, would totally resolve the problem.

Yes..... I installed a 5 gallon 110v electric WH in my crawl space just for that reason. The hot piping from the tankless goes to the inlet side of the 5 gallon elec. WH, and the out side is piped back into the hot water lines to my master bath. This way, about the time my 5 gallon 110v elect. is empty, the hot water from the tankless is there .

 

[HawkinsHollow]

Yes..... I installed a 5 gallon 110v electric WH in my crawl space just for that reason. The hot piping from the tankless goes to the inlet side of the 5 gallon elec. WH, and the out side is piped back into the hot water lines to my master bath. This way, about the time my 5 gallon 110v elect. is empty, the hot water from the tankless is there .

This sounds good, I would like to hear more about this. The main disadvantage about this over a recirc system is that it only works for the master bath, not at any of the rest of the taps.

Of course a recirc system is instantly hot. But it also defeats a primary purpose of a tankless, in that the heater will be running very often when there's no demand, just keeping up with the losses of the recirc loop. I predict a substantial increase in operating costs, and a substantial decrease in component lifetime, when adding a recirc loop with no tank to a tankless system.

This is the issue I fear with the recirc system. There are 2 types of recirc systems though. The one I would install is the bypass system. With this system you install a pump and valve at the furthest tap. The water gets pumped through the system and cold water is pumped back into the cold water side until the pump recognizes hot water in the system at which time it switches off. I think with good pipe insulation and a smart outlet or timer this system could be pretty efficient. Purging the cold water in the system during times of high demand (6am-10am and 5pm-11pm) with good insulation and hot water usage during this time the pump/heater would not have to run very much to keep up. That is what I am planning at this time.

 

[WinterDeere]

This is the issue I fear with the recirc system. There are 2 types of recirc systems though. The one I would install is the bypass system. With this system you install a pump and valve at the furthest tap. The water gets pumped through the system and cold water is pumped back into the cold water side until the pump recognizes hot water in the system at which time it switches off. I think with good pipe insulation and a smart outlet or timer this system could be pretty efficient. Purging the cold water in the system during times of high demand (6am-10am and 5pm-11pm) with good insulation and hot water usage during this time the pump/heater would not have to run very much to keep up. That is what I am planning at this time.

The only type I've ever seen deployed is this second type, and I predict problems, namely because the power output of the tankless heater is way too large to be an efficient maintainer of the relatively small but constant load that is this recirc loop. Think of it as starting a semi truck to drive 100 feet, then shutting it down, over and over all day long.

If you can adjust the hysteresis in the system to be very wide, then you might minimize the problems with this. But then your shower comfort goes way down, as the water temperature drifts and you need to constantly re-adjust the knobs. I also wonder where you're going to sense temperature in the recirc loop, to drive the firing circuit in the tankless system.

I'll admit I've never owned one of these, but on the surface, it really appears to me that a small water heater downstream of the tankless must be a much better solution. Simpler to plumb, as well.

 

[2manyrocks]

Recirculation systems used to be considered pretty high end stuff for residential homes.

 

[HawkinsHollow]

The only type I've ever seen deployed is this second type, and I predict problems, namely because the power output of the tankless heater is way too large to be an efficient maintainer of the relatively small but constant load that is this recirc loop. Think of it as starting a semi truck to drive 100 feet, then shutting it down, over and over all day long.

If you can adjust the hysteresis in the system to be very wide, then you might minimize the problems with this. But then your shower comfort goes way down, as the water temperature drifts and you need to constantly re-adjust the knobs. I also wonder where you're going to sense temperature in the recirc loop, to drive the firing circuit in the tankless system.

I'll admit I've never owned one of these, but on the surface, it really appears to me that a small water heater downstream of the tankless must be a much better solution. Simpler to plumb, as well.

I mean this system is no different than turning the hot water tap on and sitting there for 50 seconds until the hot water gets to that tap, washing your hands and then shutting it off. I do that 20 times a day already, how is this different? Sometimes I turn on the hot water tap to wash my hands and I shut it off before I even get hot water because I am sick of waiting.


Your tank only takes care of the issue at that one tap and nowhere else.

 

[WinterDeere]

I mean this system is no different than turning the hot water tap on and sitting there for 50 seconds until the hot water gets to that tap, washing your hands and then shutting it off. I do that 20 times a day already, how is this different? Sometimes I turn on the hot water tap to wash my hands and I shut it off before I even get hot water because I am sick of waiting.

Good point, on the runtime. But how are you sensing the temperature in the loop? Are you teeing it back into the inlet side of the tankless system, and just counting on the pressure differential created by the recirc pump to minimize mixing? I still see this as creating more short-cycling, than normal usage.

Your tank only takes care of the issue at that one tap and nowhere else.

Not if tank is installed before first tee, or separate tanks for the branch to each floor, etc. Still resolves issue of differential time, waiting for tankless to heat up, as compared to former tanked system.

 

[HawkinsHollow]

Good point, on the runtime. But how are you sensing the temperature in the loop? Are you teeing it back into the inlet side of the tankless system, and installing a check valve upstream of that in cold supply to minimize mixing?


Not if tank is installed before first tee, or separate tanks for the branch to each floor, etc. Still resolves issue of differential time, waiting for tankless to heat up, as compared to former tanked system.

There is a valve in the pump that senses temperature in the line. The pump turns on at 85 deg and turns off at 105 degrees. The excess water is pumped back into cold supply line.

Yes, that is what I was thinking, if the tank/tanks were centralized this would help that.

I have to figure out some solution because waiting 50-60 seconds is unacceptable in my opinion. Lots of wasted water and time.