Besides from it looking sloppy the pexs is just hanging in the breeze there's no support especially by the recirculating pump it's just hanging there whoever installed this did not install valves or hose bibs for future servicing of the system IE Flushing. I can't tell from the picture but if I wanted to take that unit out and install a brand new unit how would I do that without a union on the gas line after the shut-off? Also gas line just flapping in the breeze. And lastly probably not the person who installed the unit but whoever did that spray foam job should be shot if I paid all that money to have that tankless unit installed and some jackass got spray foam all over it there would be hell to pay.
Tankless water heater and Circulator pump
- Thread starter jparker371
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Jamesplumbing06
Well-Known Member
It’s got a service install kit. Pump is a waste anyways. Could use a few more straps. Can’t control the foam guy. I caught where he said it’s not even getting to 120. So temp setting isn’t it. Check the condensation tube it’s the white pvc coming from rear center. If it’s clogged and water has built inside reservoir it will cause the unit to slow down. After that you need a company to check pressure from gas. I agree that your main supply isn’t big enough and in right sequence. But it must have worked at some point for someone to get that gas bill with circ pump on. To decide to unplug it. So check that condensate drain. Use a shop vac on end of pvc to suck it dry. Then test the temp on a 2 handle fixture hot side only.
Can you get the pump to work? Plug it in and see if it will recirc the water. Grundfos makes an aqua stat that you can install so the unit doesn’t constantly run or you can set up a timer. First I would put a ball valve on each side of the pump so that you could isolate the pump and return line and just run the tankless as a “standard” unit to see how it works without the pump and return line.
Diehard
In Remembrance
Well based on the OP's statements, "the faucets arent far from the tankless unit. the unit is right under the master bath and it takes a solid minute for the water to heat up. additionally, the unit is set at 120F and the water doesnt even come close to reaching that temp, as you can stand under the shower head with it on full hot." That would circulation has nothing to do with the problem.
Jamesplumbing06
Well-Known Member
O the return does have a check valve before tying into cold. So the circulation pump might send water in correct direction. If check is leaking backward. Like most checks ever used in a circ system. They stick open. Causing cold to mix with hot. It’s all a stab in the dark till we get op to respond
@Diehard. If it is plumbed with a true loop, the bathroom could be close to the heater but be on the end of the loop. Making it the farthest fixture from the heater. A six degree change(colder) is a 5% drop in water temp, this very well could be cold water mixing backward through the return line. Once again, isolate the pump and you will find out what’s happening.
jparker371
Member
thank you for all the information, its great that there is this forum for those who do not have any expertise but are willing to learn and try to do things for themselves. it sounds like
jparker371
Member
im not sure how i go about isolating the pump. the pump and the water heater are directly beneath the master bathroom. any suggestions on how to move forward besides raising the temp are appreciated. we are going to try and raise the temp and see if that fixes the time it takes to heat up as well as the lack of higher temps of hot water. as is, the shower is run on full hot and its not hot enough.
120 is code. Setback to 110 at the showers. Every degree hotter can burn you quickly. Cutting in 2 pex ball valves would be easy. One above, one below. There’s a stop above that pump. You could connect a hose to that and let it run. It will take a bit, but it should get hot. When it does check the temp there. See if it gets to 120(or whatever you have the tankless set to). If it does, you know the tankless is producing correctly. Also, check your house for any other cross connection points. Mixer valves, hot and cold hose bibs, etc. anywhere hot and cold come together. I just went to a house last week with your exact problem. He had a mixer valve in the garage that was on with a hose connected. We disconnected the hose and turned off the mixer and bam problem solved.
wood4d
Well-Known Member
There is temperature control in your shower so if you turn the water temp up on the rinnai the shower diverter controls how hot the water is. Your water temperature for the house is supposed to be hotter at the kitchen sink and dishwasher than in your shower. I see foam insulation so I assume the house isnt very old. It looks like they are recirculating the hot water and feeding it back into the hot water heater supply. You have endless hot water but no one said it was instant hot water. In nj 120 is the max for a shower and bathtub but you cant use the hot water heater to control that temperature. You can use something similar to a meat thermometer to measure the temp. If you post a photo of your shower diverters someone will tell you how to adjust the temperatures.
Diehard
In Remembrance
Pump was not plugged in. I have to assume he knows where the warmest water is. And it's taking too long and not barely warm. What he needs is someone to look at the unit it trouble shoot it properly.
That CSST gas line is bad for gas volume also. We were told to up size if running CSST because the corrugation disrupts gas flow. It may not be feeding enough gas to the burner.
Diehard
In Remembrance
So true but the gas pipe sizing charts include sizes vs flow capacity for CSST as well as steel.
Diehard
In Remembrance
Interesting!
I know the question came up before but is the GPM typically controlled by the unit?
Or perhaps depending on which unit you have?
Do they have a built in flow control based on temperature?
Yes most work off temp rise. I am not sure they are smart enough to know exactly though. It is usually x GPM at x rise. It may kick the GPM down but the burner still might not be able to meet the rise if it is starving for fuel.
I am just guessing here. You may want to contact a Rinnai certified repair company to look at it.
I am just guessing here. You may want to contact a Rinnai certified repair company to look at it.
Diehard
In Remembrance
x GPM at x rise is the typical rating for both tankless and tank type water heaters. In other words, that's what it's rated to do, as a maximum.
During my recent research, what I found was, "Most tankless water heaters do not feature true thermostatic temperature controls and accordingly, they cannot maintain a precise output temperature when the flow rate of water changes."
I suppose when you think about it, the user would typically reduce the flow rate if the hot water supply was diminishing in temperature. I know that's what I do on my tankless(heat exchanger) equipped heating boiler. They're commonly rated at about 3 gpm at about a 60 degree temp rise. Until they get dirty of course.
Again i am just guessing. If that burner is not able to rise 60 its still going to put out 3 GPM and that GPM may not be that warm but your still getting it. Again it is a complete stab in the dark. For all i know it could be a dirty sensor. I have never been trained by Rinnai on there products, i have just installed them.
It’s all GPM on a curve based on incoming temp. The unit has to “slowdown” the cold water going through it to heat it up. The colder the water the slower(lower GPM) it goes. The newer units actually “overheat” the water and then temper it to the set temp. That is suppose to help handle the fluctuation issue. I live in an area with as low as 37 degree water in the wintertime. It gives tankless heaters hernias trying to keep up on big houses. And don’t get me going about sizing, most 3 bath houses should have 2 units installed for winter demand. A dirty sensor would throw an error code.
