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Old 02-20-2019, 02:16 PM   #1
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Excel over pressurizing?

Hi everyone,

Thanks in advance for your help.

We have the Excel tankless ventless hot water heater in our skoolie and have been experiencing some issues I'm hoping someone out there can help us trouble-shoot.

1. The water heater occasionally shoots out super heated water from the water drain. About 1/2 c. to 1 c. comes out when it does this.
2. Sporadically the flame doesn't turn off when we turn the water off. I believe this is why the water is getting super heated.
3. Yesterday, the hot water pipe (PEX) coming out of the tank burst. When it burst i had been running the hot water in the sink and noticed it wasn't getting very hot. I probably ran 2 gallons of hot water before turning it off. I can't remember for sure whether I turned the water off and then the pipe burst or the pipe burst and then I turned the water off because it was basically at the same time.

other info: The pipes have not been exposed to freezing temperatures. the water heater has been in use for about 2 months now.

Any ideas?

is there something we should know about the set up that we could have done wrong?

Thanks so much for your help!
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Old 02-20-2019, 02:37 PM   #2
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My best advice is to send the heater back to the mfg for repair and don't risk a steam boiler explosion.
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Old 02-20-2019, 04:07 PM   #3
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Sounds like the thermostat or control board isn't working properly.
If it is still under warranty then try to get it replaced or repaired before using it again.
The P&T (pressure and temperature ) relief valve is doing its job if it's spitting extremely hot water. Any time it is doing its job then there is a problem somewhere. I haven't used a lot of PEX butThere is a red pex rated for hot water use.
In my thinking anything plastic is not going to handle 180-210degree water if the water heater mucks up.
If it's not under warranty then find the owners and parts manual for it and PM me.
Should be able to help fix it.
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Old 02-20-2019, 04:16 PM   #4
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Quote:
Originally Posted by Jolly Roger bus 223 View Post
Sounds like the thermostat or control board isn't working properly.
If it is still under warranty then try to get it replaced or repaired before using it again.
The P&T (pressure and temperature ) relief valve is doing its job if it's spitting extremely hot water. Any time it is doing its job then there is a problem somewhere. I haven't used a lot of PEX butThere is a red pex rated for hot water use.
In my thinking anything plastic is not going to handle 180-210degree water if the water heater mucks up.
If it's not under warranty then find the owners and parts manual for it and PM me.
Should be able to help fix it.
They are all rated for hot water use. The color of the Pex is to distinguish hot and cold. There is no difference between the Red, Blue, White, and Gray Pex. They are only rated to 200F.
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Old 02-20-2019, 04:33 PM   #5
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Thanks for the info. I didn't know the temp. And pressure rating of the material itself.
I have a few tools to repair some of it but have never ran it.
I have always worked as a commercial installer for the GOVT. so my minimum for domestic water is copper.
Thanks Marc.
For the OP. I don't know your brand of heater but I have worked on many other brands and they are not that complicated.
If you can't get a warranty fix then get us the info. And we can help.
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Old 02-20-2019, 05:00 PM   #6
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Quote:
Originally Posted by Jolly Roger bus 223 View Post
Thanks for the info. I didn't know the temp. And pressure rating of the material itself.
I have a few tools to repair some of it but have never ran it.
I have always worked as a commercial installer for the GOVT. so my minimum for domestic water is copper.
Thanks Marc.
For the OP. I don't know your brand of heater but I have worked on many other brands and they are not that complicated.
If you can't get a warranty fix then get us the info. And we can help.
One advantage of Pex over copper is the fact it can be radiused, so fewer sweat connections to possibly leak.

Here's some pressure/temp info;
Pressure ratings, testing and pressure drop
PEX Tubing Pressure Ratings Pressure testing - Hydronic & Radiant Heating Pressure testing - Hot & Cold Water Plumbing
200F at 80 psi
180F at 100 psi
74F at 160 psi 3 times the maximum working pressure or a minimum of 40 psi, but no greater than 100 psi.

Duration: 30 minutes minimum, 2 hours recommended 1.5 times the maximum working pressure but no greater than pipes pressure rating at given temperature.

Duration: 30 minutes minimum, 2 hours recommended
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Old 04-09-2020, 12:08 PM   #7
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I have had the same problem with my Excel 1.6 Gpm tankless heater. Blown out pex 2x now resulting in major flooding. Loud bang after turning off water - flame continues to burn superheating the water. Not good. Working with the company now to try to see what repair to the unit is possible to fix this. Makes me not want to use this type of heater anymore. If I do use again I think I'll install emergency propane and water shutoff valves next to the heater.

Here's my opinion: the super low flow magnetic flow sensor that they tout in their description is too sensitive and is malfunctioning. I don't really need the thing to work with only 2psi. I need it to NOT EXPLODE with normal use!
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Old 04-09-2020, 07:07 PM   #8
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following, have the heater in my amazon cart, just making sure I have all I need before hitting send. anybody else have experience with one
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