Navien CR240 and HeatBox KD-HBC100 No Heat this morning, DHW portion works great...

westbranch

HI, new here after searching for info on what has suddenly caused the Heat Box to stop providing and heat...

the center pic is exactly what we have:
https://us.v-cdn.net/5021738/uploads/posts/16431/Navien.jpg

To start I read this thread http://forum.heatinghelp.com/discussion/144463/navien-nr-240a-heating-issues?
and have had some similar issues over the period that this unit has been installed, with the combustion chamber being replaced under warranty. We do have hard water and a good (new) softener installed after the replacement... System has been in place ~ 4 years and though it is not perfect, it has worked well for us all considered.

Today's problem: the CR240 is providing ample hot water for showers and dishes, the internal circ. pump is sending HW at 140* as set, this is our winter temp setting to provide ample BTUs to the house. I used my inexpensive IR temp gun and the input pipe to the closed loop system is 121* F... so the circ pump on the CR240 is working, as well we have DHW all through the house...

When I throw the Circuit Breaker (CB) in the HeatBox I hear the 2 closed lop circ pumps kick on and run for ! 5 seconds and then stop, and the is an audible click from the area of the control board. I can repeat this on/off cycle every time I throw the CB... The copper pipes from the HeatBox get hotter.. so they are working. There is a very simple error message = HErr

Are there any ideas as to what is stopping the pumps from staying on?

thanks in advance.

RobG

I don't know much about those units except that they were cobbled together by Navien to try and compete early on in the combi market. They were mainly used in condos and small single family homes. If it were me I would replace it with a true combi boiler. Triangle tube and others make great combi boilers that will allow you to separate your heating water and your domestic hot water thus not allowing water to stagnate in the heating loop during the warmer months and creating a breeding ground for legionella.

kcopp

Is this the 1st time the heat was put on for the season? The circ may be seized...

westbranch

Thanks Rob, I am evaluating the replacement option, an expensive one for us... Ouch. Luckily This is a 2 loop unit so the heating loop and DHW do not meet...

westbranch

No we have had to have some heat for the last month ... temps have been down to freezing off and on...

westbranch

pic attached

RobG

westbranch said:

Thanks Rob, I am evaluating the replacement option, an expensive one for us... Ouch. Luckily This is a 2 loop unit so the heating loop and DHW do not meet...

Sorry about that I missed the FP heat exchanger in the middle of the unit. I would still consider replacement however it is possible that the FPHE may need to be descaled and you are not getting good heat transfer through it.

westbranch

FPHE may need to be descaled
thanks, good point, will suss that out.

westbranch

Just finished some basic testing, disconnected both circ motors, cycled them separately several times and both start and stop in the same few seconds so I can not envision a stuck rotor, ie occuring in both at the same time.... I did notice a brown stain under the conformal coating on the PCB, so this may be a hint that there has been overheating or an electronic component ??

westbranch

I also noticed there is a distinct pattern to 3 clicks when I power up the circuit, each coming from a different place on the PCB and after click #3 the motors stop.....??
No hits on the PCB model # either...

HDE_2

Sounds like the startup checks are happening if you power it up and the pumps operate and heat is created and transferred.

How about it being a control issue including the external wires and thermostat.
You wouldn't be the first one to have no heat because the batteries in your battery operated electro mechanical thermostat are dead.

westbranch

Well it gets worse I have to say... after getting phone help from Navien, suggested checking/cleaning the flow sensor, done , founmd a very small bit of ? in it that I blew out with my breath, so that vanes spin freely and then used cold water to flush... reinstalled and bled air out... Now no circ motor rotation plus....E038 code = circ motor not working...
Decided to replace heat box with a conventional NG furnace and now evaluating same for Navien boiler..

HDE

I believe E38 is a result of you not bleeding air out after removing and cleaning flow sensor.
Simple remedy, open hot water faucet and all purge valves

westbranch

sadly, been there, done that several times as well as turning on all taps in house to purge lines of air...