Takagi T-H3S-DV-P stops heating even at 1.3GPM flow with no error codes

[punaman]

This has been a problem since we got the unit over 2 years ago.

Seems like it happens whether or not it is a mixer valve or separate. Some days the water pressure is higher and it's not an issue, but for basically every single faucuet, or shower that doesn't have the flow regulator literally drilled out it will stop heating. Somehow the dishwasher can pull hot water, I have no idea why though.

Usually it will start heating for a bit, but then the in use light will just go off. With Kitchen faucet I checked and it was at 1.3 GPM the entire time, but just shuts off after 15 seconds or so. Extremely frustrating. I have heard cleaning the flow and/or flame sensor might help but I have no idea what I am doing and finding someone to do maintenance here is a nightmare or I would just pay someone to do it.

Having the temp down to 100F helps, but doesn't totally alleviate the problem.

 

[Breplum]

Descaling is always the first thing we tell people. though it may not be relevant. There are troubleshooting flow charts for almost everything. I quit servicing Takagi...doesn't the unit have a smart diagnostics, with error codes, like Navien and Noritz?
Call Takagi tech desk, but of course they'll want you to have a manometer and multimeter. It should be under parts warranty so they will send you anything that can be determined to be defective. Southwest Airlines

 

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[punaman]

It does have smart error codes, that's the thing. That's why it is so weird. It seems to be related to water pressure though.

The water here has near zero TDS, but I will certainly try the descale if what I'm about to try doesn't work.

We live at the bottom of a huge hill and the water pressure here should be really high, so it always confused me how it would get low sometimes. However, I just discovered today there is a flow control valve, it's not a regulator, just a valve right where the water enters my house's plumbing system. It's rusted, so I bought some rust remover stuff and sprayed it tonight. I will try adjusting this morning.

I am wondering if I shouldn't get a PSI guage first though to make sure I don't blow out my ice maker or anything though.

 

[Reach4]

Water pressure gauges are cheap and easy. You can temporarily mount a garden hose thread gauge on a garden hose spigot, laundry tap, or the drain for a tank water heater.

When you have no flow, you get no pressure drop due to friction. If you see low pressure only when flowing water, there is a restriction, such as a clogged whole-house filter.

A flow control valve that is not a pressure reducing valve (PRV) sounds odd.

This comment is not relevant to your water heater. But still, checking water pressure can be useful.

 

[punaman]

Actually it is a pressure regulator. It's just not the kind I'm used to, like with a sprinkler system to keep it a constant PSI. This doesn't keep it constant it just seems to control the max. Then again I am not very well educated on this sort of thing. Maybe that's what all pressure regulators do.

I bought a gauge, and tightening the adjustment on the regulator increased the static pressure a *little* (like 5psi maybe for a TON of tightening), but the pressure when the water is being used has increased a lot. The lowest it seems to go now is 50PSI when before it would drop below 30 in use sometimes.

I think this should fix my issues, I will keep an eye on the gauge to make sure it doesn't go over 100 or anything. About how high is too high?

 

[Reach4]

Is this for the whole house? Some PRVs have a screen, and if it has one, clean the screen.

If it behaves badly in the future, replace or rebuild that PRV.

 

[punaman]

It's for the whole house. It's also possible the pressure in the neighborhood was dropping as I was adjusting things. It tends to around this time of day for whatever reason.

I would have to take this thing apart to clean anything. I think it is very similar to this one: https://www.amazon.com/Zurn-Wilkins-1-NR3XL-Pressure-Reducing/dp/B004NHOPUW

I am going to keep an eye on the gauge today and just make sure it doesn't go over 100 or something. I will check before bed too.

 

[Fitter30]

You have flow but look at temp readings in and out might have a sensor way out. Post #2 clean the heater. Use cleaning vinegar.

 

[punaman]

One thing interesting is, if the water pressure is high it seems to activate at 0.5GPM. If the pressure isn't at the max of the day it will take 1.3GPM+ to keep it active. At 1.2 it will come on and the "in use" light will shut off after only seconds.

Even with my adjustments it is having trouble with bathroom faucets at 1.2GPM. However now the kitchen faucet runs at 1.5-1.6GPM and it never cuts out.

The water coming into the house is 80F btw. I think the guy who installed it for us overpowered us for the climate. I kept asking him to give us a smaller unit, but he kept telling us it would be underpowered. It says three showers for warmer climates, and we indeed have three showers in this house, however I bet this thing could run four no problem here.

The manual says 0.5GPM to activate, so all of this is very weird. A sensor malfunctioning does indeed make sense. The installer originally said to clean the sensors with a scrubby sponge if I had issues, but I am honestly scared to take the thing apart. I might try after the guests I have visiting leave at the end of the month. I may be able to find someone here to service it if I call around enough too.

Is there a good tutorial for taking this thing apart?

PS. I have a plumber coming in a few months to do some work on the house, I will ask him to replace that PRV while he's here.

Thanks for the help.

 

[Fitter30]

Look at youtube there's all kinds. Just search brand and model#