New Navian and Faucet Hot Water Temps

addohm

We just converted to gas. Our only use of gas is hot water for baseboard heat fins and faucet water. We had a navian combi boiler 240E installed. Since the install our hot water at the shower just does not last. With our oil heat boiler, I had the output temp set to 155 which kept the entire 2200 sq ft house satisfied. The two settings I see in the menu are heat at 171 and faucet at 120. I've had the plumber that installed it come back to check it out and I'm not confident he knows anything about setting these up. Now I know 155 is supposed to be scalding but the output temp and/or flow as it is does not support the house like we were told.

What are some things we can look at and/or do to help this problem? We have low flow shower heads.

Suzook

^ Do you have an indirect for the HW?

addohm

@Suzook wcan you elaborate? Should I post a picture of the setup?

SeymourCates

@addohm

Raise the output temperature for the DHW to 130F and see if you find that acceptable.

page 55 in the installation manual:

http://navien-production-3.s3.amazonaws.com/2017/10/24/19/09/01/f680f67e-be09-456a-80e3-fbe52e67cd92/NCB_E_Installation_Operation_Manual_Eng_160307 (1).pdf

addohm

Here is a pic. Only baseboard heat is running at the moment.

addohm

@SeymourCates it doesn't adjust past 120. That was what I tried to change originally.

SeymourCates

The manual requires you to press and hold for two seconds to get above 120F. Presumably, to prevent you from going above 120F. However, it will absolutely go to 140F.

Suzook

No Indirect for HW. Hopefully the higher output temp satisfies your HW problem.

bob eck

Y

gschallert

addohm said:

Since the install our hot water at the shower just does not last.

I'm a little confused by this statement. Are you saying that you actually run out of hot water (meaning it's hot at first then cools and doesn't get hot again) in the shower or that the water doesn't ever get hot enough in the first place? The combi you have should have no problem supplying plenty of DHW if your demand doesn't exceed 4.5 gpm. An average family with 2 baths should be fine in this setup provided you're not trying to fill a whirlpool/walk-in tub at the same time someone else is showering. In addition to answering my first question please provide a little more info:

Water inlet temp (where are you located geographically if you don't know the temp offhand)

Municipal water supply or well water with pressure tank

bob eck

Y

addohm

@gschallert my wife says that the water is just not hot from the start. She says the team doesn't fluctuate.

We live on the Massachusetts coast. I do not know the water inlet temp, except to say that given the recent outdoor ambient temperatures it's probably friggen cold.

addohm

@Bob Eck. The incoming is 2". Originally they (the gas company) were going to do 1.5" but they decided to put in a larger line for future expansion.

addohm

@SeymourCates I will try bumping it up to 130.

Are there any recommendations for the baseboard heat supply? It seems the Navien is running 24/7 just to maintain 66 degrees in the house (we set our temps to 69). That particular setpoint seems to be maxed out at 180.

Is there any way I can see the water flow rate on the unit?

I will measure the water temp at the shower outlet after bumping it up to 130.

gschallert

Measure both the cold and hot water temps at a bathroom fixture while you're at it. A simple digital kitchen thermometer will work. Make sure for each you only have the one tap drawing, cold for cold and hot for hot with no mixing.

In the winter I have my in-laws bump up their DHW temp from 110 to 120 or 125 on their tankless combi to offset the colder inlet temps of the groundwater. At 110 the shower is what I would define as "hot", at 120 without mixing in some cold it's literally scalding and will deliver first degree burns in just a few minutes. Measure just the hot water in that bathroom at a sink tap as well as your shower.

addohm

@gschallert the faucet initial spike was 130, it dropped to about 115 and settled at 122.

The shower is known for taking bloody forever to heat up. I'm certain the shower hot water is not supplied by the same line as the sink. I just don't know how the shower is supplied though. I know where one line comes up to the sink, but can't find the second (unless it's in series with the downstairs bathtub).

The shower, is not even breaking 100 right now with the combi set to 130. So I doubt it's in series with the bathtub because the bathtub gets scalding.

Fml @ the master bathroom sucking right now.

addohm

Well, I'm wrong. The supply water for the shower and the sink are the same. There is a shutoff valve in the basement that I used to confirm it.

Larry Weingarten

Hello, You might want to check to see if there is a cross connection in the plumbing. Cold getting into the hot could cause this sort of problem. To test, just shut off the cold supply to the heater, then run hot water. It should stop running in seconds.

Yours, Larry

gschallert

addohm said:

Well, I'm wrong. The supply water for the shower and the sink are the same. There is a shutoff valve in the basement that I used to confirm it.

If I were you I'd trace that shower supply line to see where it's feeding from but also take the shower valve apart and check the anti scald setting. The sink tap temps are totally reasonable for a tankless and should provide ample "hot" hot water. You just need to figure out why the shower is not reaching temp.

addohm

@gschallert you're the man. That was it. I had no idea these valves had anything other than physical limits.

Any ideas on the baseboard heat? The whole house is 66, and the combi is running all the time. We are set to 69.

gschallert

addohm said:

Any ideas on the baseboard heat? The whole house is 66, and the combi is running all the time. We are set to 69.

My guesses would be the ODR curve is wrong and your SWT is too low or you're pumping too fast or both. Did the install tech customize any of the settings or leave at defaults? You are using ODR correct? Break out your manual and start reading around page 57. Hopefully you have ODR and it's enabled. Make sure the heat load type is correctly set, finned tube, radiant, etc. You have baseboard you said right? Fin tube copper?

p.s. 130 degree DHW is a little dangerous so if you've adjusted the anti-scald setting for the shower you might want to drop the temp back down to 120-125 (or re-adjust after you've dropped it down)

njtommy

If you hit the mechanic button on the top left you can scroll through and see your boilers info. A is boiler supply water temp, b is boiler return. C is DHW supply D os DHW inlet. It will also tell you your GPM as well along with many others.

Your PVC flue is the problem most likely and the dip switch settings. You need to run schedule 80cpvc or other types of flue piping allowed by local code for higher exhaust temps. Boiler has an exhaust limit temp sensor controlled by return water sensor/ setting of 149max so you don’t melt your PVC venting.

addohm

@gschallert ODR? There is a round pick-shaped decide outside. I'd assumed that was for outside air temp.

Yes, I backed off the DHW to 125. I'll see if the wife has anything to say about it.

addohm

@gschallert I don't know what these acronyms are.

After checking all the parameters, the unit is completely default.

Also, I think you may be on to something with the flow. I don't know though, I'm clearly a novice. With only baseboard heat running, the outlet temp was 176. The return temp was 157. I feel like a 19 degree temperature drop is very low. Especially for my size home. Am I wrong? If not, what can I do to improve that delta?

addohm

@gschallert I'm also curious about info:D - cold water inlet temp. Mine reads 117. Now I'm assuming this means the water coming from outside the house. Would I be wrong to say that there is no way it is 117?

njtommy

Do you have DHW recirculation in the house by any chance chance?

addohm

@njtommy not that I know of. I'm not sure why they went schedule 40 pvc on the flue. Originally I thought the plan was to use the chimney to vent. I don't know why or how it changed. Here is the full info while baseboards is running:

A - 176
B - 157
C - 128
D - 117
E - 0
F - 12
G - 1
H - 0
I - 26.1

addohm

@njtommy

addohm

@njtommy the blue line at the top is the water supply. The blue line on the left that Ts into the supply is water from expansion tank getting recirculated into the supply right?

addohm

I tried shutting off every T from the main water supply to the navien. I also temporarily shut off the expansion tank recirc. The inlet temp still fluctuates 115-125 degrees.

The inlet pipe is cool to the touch though, which is more strange. Also, if I open up the expansion tank pressure relief valve to allow hot water back into the supply, the number rapidly raises as expected. So it's not like we are reading the temp from the wrong line. This gets more and more strange to me. If that D-temp was actually 120, that copper should be HOT.

addohm

Happy new year all

oceantrvlr

@addohm , did you ever figure this out? I have a 240e as well, with a slightly different problem, and I'm just trying to better understand the setpoints on the boiler.