Relocating Navien tankless

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bennecc

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I'll try to be brief. My family has outgrown our existing heat pump water heater which currently sits in my unfinished basement/shop area roughly under the middle of the home. We wait to get hot water at each fixture, but it is not much of a bother and the wait is never too long.

I have a Navien NPE 240-A which I had planned to install in the same location as the existing HPWH. However the only reasonably straightforward way to vent the tankless is through a side wall about 35' away. The required pitch of the vent pipe means that it will be fairly low when it passes across the "shop" area of my basement and I believe it will be a nuisance. Venting up and out the roof is not something I am willing to do.

As an alternative I thought of putting the unit all the way on that sidewall where it will vent. This would free up some wall space in the shop and make the venting simple. However this will add an additional 35' of 3/4" pipe to empty when any of the fixtures in the bathrooms or laundry calls for hot water. The basement ceiling is finished in the half of the house with the bathrooms & laundry, so running a dedicated recirculation line is not something I am able to do.

As a novice I don't know what that extra 35' of 3/4 pipe means in terms of added wait time when calling for hot water from a lavatory faucet (or shower). Plus whatever delay is added by changing from a tank to a tankless. If its a few seconds then I can live with that. If its a couple minutes then that would be an issue.

So my questions are:
1. Can anyone give me an idea of how much additional time and water I would waste waiting on hot water if the heater were installed an additional 35' away?

2. Would using one of the Navicirc (or other similar) valves be a simple way to reduce that delay? I'm concerned about the inefficiency of repeatedly firing the burner to heat water that is unlikely to be needed before it cools off and has to be reheated again. I believe I may can set programs if I have a Navien remote and/or Navilink?

3. Would there be any value in a partial recirculation line leading back from the point of the existing heater (the furthest point to which I have access to the pipes)? Basically my thought is would that then provide approximately the same delay that I currently have?

I'm not interested in any of the "hot buttons" as I just don't want to overcomplicate this.

Existing:

as-is.png

Proposed:
proposed no recirc.png


Proposed with partial recirculation line:
proposed partial recirc.png
 

Bannerman

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My family has outgrown our existing heat pump water heater
What is meant by that statement?

Is the wait time that is too long, although tolerable? If so, a recirculation pump maybe utilized with your existing HPWH. Since it would be difficult to install a dedicated return line from the MB, a NaviCirc or similar crossover valve could be installed to utilize the cold water line as the hot water return loop back to the WH.

If you mean the HPWH is no longer providing a sufficient amount of hot water to satisfy an increased demand, have you attempted to increase the WH's temperature setting?

Hotter water from the WH will typically require additional cold water to be mixed with the hot to reduce the temperature to the usual desired temperature, where someone is in direct contact with the hot water exiting a faucet.

To prevent scalding, hot water exceeding 120°F, should be reduced to a safe temperature prior to the fixture. This is commonly achieved using a thermostatically controlled mixing valve after the WH outlet, which will automatically mix in the appropriate amount of additional cold water so the hot water supplied to faucets will not exceed a specific temperature, typically 120°F.

Because cold water will be mixed with the higher temperature water exiting the WH, the gallons of hot water supplied by the WH will be reduced, which will often allow the same WH to satisfy increased hot water demand.
 
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bennecc

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@Bannerman What I mean is that the 50gal HPWH does not supply a sufficient volume of hot water (at least when utilizing the heat pump) for 5 people to take a shower within a 1 hour timeframe. The water is already turned up to 140.
 
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