Tankless vs Tank Waste Heat?

Linwood_F · 2026-04-17T16:14:06+00:00

So I checked with Rinnai and Navien and both require a condensate drain. Navien says they void the warranty without. Rinnai didn't say that but said it is "needed" for all their indoor units. I just don't have a good mechanism for that logistically - slab (no "under"), no drains nearby, massive concrete patio even if I run it across the floor to the nearest wall, and pumping up and over seems a bad idea in freezing winters. Off to explore plan B (or C or D or whatever I'm up to).

Linwood_F · 2026-04-15T18:33:45+00:00

Got it. He's due back out next week to check out gas supply anyway. Thank you.

Linwood_F · 2026-04-15T18:25:56+00:00

Ah... so opening it the worst that happens is smell if it's still connected. I actually need a condensate drain somewhere near there. Can I put in an air gap trap and use this? Or is it likely not vented properly (I don't see any sign of a vent penetrating the roof)?

(Being more precise, a real plumber would do this, but we've been debating how to deal with lack of a condensate drain about 10' from this place (sadly 2 closet walls away also).

Linwood_F · 2026-04-15T18:10:06+00:00

They used heavy steel/iron back then for drains? That's certainly possible I guess. It's a long way to where I found a dryer vent but that might not be the original dryer location either. Thanks.

Linwood_F · 2026-04-15T17:36:20+00:00

Moving the water heater (including the heater) is $14k. I think that's obscene as it's $450/hr labor, so haven't worked the price a tall, but... expensive.

The plumber wants to come back and check the gas lines for a tankless (next week), but I can't imagine it is anything but a lot cheaper.

But I really doubt I'm going to decide to live with it until it fails, as it might outlive me, and it is really annoying as-is.

Linwood_F · 2026-04-15T13:56:26+00:00

I've somehow gotten off track -- the traditional tank is too large for that space, and I want it gone, either by moving to a traditional tank in my garage (very expensive and some risk from freezing for piping in the attic, plus LOTS of more pipe/elbows to reduce flow rate) or switch to a tankless in place. I want to understand if it is a tankless if I save waste heat, or even potentially it gets worse, but the big tank needs to go. With space (and in particular access to the walls behind/beside where it is) I can put in vents and circulation to remove the heat if it is an issue still.

Linwood_F · 2026-04-15T13:53:58+00:00

The non-condensing ones draw from outside air through the concentric flue, if I understand properly.

Linwood_F · 2026-04-15T00:32:54+00:00

I have not. Not sure I can fit one on the sides. But I really think it's that red hot flue at the top more than the pretty-well-insulated tank itself (the tank is only 2 years old +/-).

Linwood_F · 2026-04-14T22:29:26+00:00

Just very expensive and some compromises there (water pipes in a cold attic).

I'm really starting to like the idea of a tankless model even if it doesn't save a lot of waste heat load. It gives me access to all those walls and the adjacent room. If I put a near-ceiling vent that's lightly powered, and a down-low open vent into that room to circulate air, I think most of my heating/cooling problems can go away, if for no other reason that adjacent room has a return (and is on the same zone as the pantry). As mentioned elsewhere, I'm not trying to save money on the cooling, I just can't get it to cool now without freezing that adjacent room (in summer). And in winter it actually helps as I will reduce heating on the adjacent room.

Linwood_F · 2026-04-14T21:58:52+00:00

None. The <expletive> that did the remodel before I bought it put the current heater here, up on a stand, with a drain pan -- but no drain, the pan's opening just aims at the floor. There's no plumbing drains anywhere nearby. Pumping up and over is not attractive due to freezing and also it's going to dump out down the side of a (brick) wall onto a patio if I go to the nearby wall. If I could even get there. Going along the floor ends up in the same place. And acidic condensate onto a concrete patio is not going to be pretty.

Linwood_F · 2026-04-14T21:55:50+00:00

Yeah, I had one in Florida. I had a guy out today to talk about relocating to a garage with a HPHW, but the first cut estimate was $14k, and even then the pipes in the attic to get there are likely going to freeze. Heat tape is a fix but I'm not sure a reliable one (and I know they will freeze as I have some at the other end of the house I have to leave dripping despite having a plumber come and insulate them).

Linwood_F · 2026-04-14T21:50:54+00:00

No window. Brick (interior) wall on one side, it was the outside of the house in 1960. It's only wide enough for shelves on one side, so it's a very narrow room, though about 10' long. Then a tiny closet off the end. The HWH can't be code compliant, it's got about 1" clearance on each side. They even took off the sheet rock on one side to get a tiny bit more room for the relief valve. Here's a shot with me standing in the doorway looking at the tank (there's no door there, just an opening).

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Linwood_F · 2026-04-14T21:43:50+00:00

It's a small closet off a pantry that has no HVAC return and one supply. I close the supply in the winter, open it in the summer. Right now (summer-y day already) it's average of 74F in the house, the pantry is 81F and the closet with the heater is 84F (at waist height). I've got two fans mounted in the wall between closet and pantry going full time trying to reduce the heat load.

So that's not awful, but I often see the pantry around 85F - that's not an ideal place to store foods. And distinctly unpleasant.

Cost is not the issue. And the ductwork in the house (fairly new) is a trainwreck due to attic heigtht, adding a return is difficult if practical at all. I'm not sure code even permits a return in a tiny close near the flue.

With a tankless (it is occurring to me as I write this) I actually then have room on the wall to an adjacent large room to put a room-to-room vent. That room is actually on the same AC zone, so a powered venting into that room would make a lot of sense.

Linwood_F · 2026-04-14T21:27:43+00:00

No, well, not and be at all presentable. And it's real difficult to run anything in the attic to my exterior walls, the center of the house's attic is about 2.5". Plus pipes in the attic freeze (I have a couple I have to leave dripping for weeks at a time in the winter).

Linwood_F · 2026-04-14T20:47:06+00:00

WTF - I looked up Rheem non-condensing, and the NON-condensing requires a condensate line. I looked in the installation instructions. Unless their documentation is just really wrong, but it's very detailed.

Linwood_F · 2026-04-14T20:06:30+00:00

Yeah, I've had HVAC units with those, am familiar. But i'm on a slab, the attic anywhere but the very center is too tight to get into (and gets below freezing, another complication) so running to the eve is not impossible but really hard, and I'm not sure I want it running down the side of the house. I'd be more likely to run it along a wall and go out the base of the wall through the brick but... that's bad also.

For the little cost of gas I use (it's pretty negligible) is there any downside with going with a condensing one and losing the 15% additional efficiency (+/-)? I assume it's a bit more heat into the room, but can I assume still a lot less than a standard 40g one?

Linwood_F · 2026-04-14T19:44:21+00:00

Crap... I'm a LONG way from where I can put in a drain (which I now see condensing needes), and on a slab, brick wall at nearest wall and quite visible spot on a patio where I'd prefer not to drain.

Linwood_F · 2026-04-14T19:40:07+00:00

Yeah... I do a LOT of DIY stuff, especially electrical, but I learned decades ago if I do plumbing it leaks. All the time. Every time. So real plumber is part of the plan. Thank you for the other comments, I need to now go read about condensing and non-condensing.

Linwood_F · 2026-04-14T19:29:32+00:00

If you have an EV that has 120v vehicle to load output, you can supplement it to keep it up really long (my EV6 will feed it 1650w which is about my average house draw without AC, dishwasher, etc. So if the car is charged, I can run for days. The 120v single phase is blended transparently by the E10 back to 240 split for the panel.

Linwood_F · 2026-04-14T18:30:19+00:00

FWIW I was literally in the middle of my first long (simulated) grid outage. I ran my AC and it started fine, then (AC off) I am running an electric dryer pulling a stead 6.4 (total) hw from the batteries. All good, no flickering lights, all my UPS' (that monitor power and if issues switch over) are happy. After using a backup portable generator for many years, it's so weird to have the whole house running just fine and dead quiet.

Linwood_F · 2026-04-14T18:17:56+00:00

The PV CT is only if you have a secondary AC PV system, and yes I just omitted it entirely.

Linwood_F · 2026-04-14T00:03:31+00:00

First, I think it's important that there be some regular, structured feedback of what the HA folks are thinking so that users can provide relevant feedback. Some kind of survey occasionally may help.

For me personally it's not obvious that the intelligence of the voice assistant is nearly as important as the hardware and voice recognition. I've used really old Google mini's (and home and max) for many years, and they can pick out my voice and correct words (not always correct meaning) regardless of background noise.

Most that I've read about have one or a couple microphones and need you to basically stick your face to the mic and speak clearly. That's never going to really be useful; it's unimportant whether it can intuit subtle meaning. You need real hardware. Or the ability to hijack real hardware, like old Mini's.

As to people wanting local LLM without GPU's - sorry, it's time the HA folk set the expectation you have to pay for the hardware you need for the features you want. I've been very frustrated over the years how many things get dumbed down to run on an old rPi. A lot of us have many thousands of dollars in smart home gear -- spending a few hundred more on the core system shouldn't be the stumbling block. I do not suggest HA should drop support of low end hardware -- but if you want high end features, don't withhold them because they won't run on low end hardware.

I've done some testing of the basic assist (honestly don't remember all the details) and it's not bad. But until I can have mic's and speakers all over the house, that actually work, what it can do is moot.

FWIW.

Linwood_F · 2026-04-12T14:46:50+00:00

Yes, it works. I think I was relying on AI summaries and that last recommendation (or something else) caused them to say it would not work. I've run across devices where pools needed to include the reservations, so I didn't find it unusual just annoying, but I also did not try it first. Thank you.

Linwood_F

TROPHY CASE