Navien boiler short cycling

E5_Farmer

I have a dual fuel Navien NHB-150 connected to an indirect water heater for domestic hot water with an electric boiler running off peak.  

When the electric side runs all is normal including DHW.  When the propane side kicks on it fires for about a minute or two then kicks off will not push hot water to my three zones for heat but still seems to make DHW.  

E271 come up “temperature differential limit”.  

I am wondering if some way some how a simple setting got messed up?  I was suggested to clean flame sensor but since it’s making DHW does that make sense?  I have read through the manual enough to get to menus to see what things are set at but I don’t quite understand the language of setting parameters.  

Thank you

Ironman

How about posting some pics from about 6-8 feet back that will show the entire setup?

And no, it’s not the flame rod.

E5_Farmer

Jamie Hall

lost circulation through the unit?

E5_Farmer

Jamie Hall said:

lost circulation through the unit?

I don’t think so.  It works fine when running on electric 

Jon_blaney

It is a circulation issue with pumps or controller.

E5_Farmer

Jon_blaney said:

It is a circulation issue with pumps or controller.

I just don’t get why it’s work on the electric side and not the propane side

Jamie Hall

Hard to determine just what goes where, but do I seem to see two separate pumps, one for the electric boiler and one for the Navien? And if I do, is the one for the Navien running? All the valves which should be open are open?

E5_Farmer

Jamie Hall said:

Hard to determine just what goes where, but do I seem to see two separate pumps, one for the electric boiler and one for the Navien? And if I do, is the one for the Navien running? All the valves which should be open are open?

Yes.  The three red pumps are for Navien boiler.  There’s one on top left for circulating water through zones.  One directly under the Navien boiler, I believe that is for pulling water from circulation to boiler.  Then there’s a pump on the indirect hot water inlet.  The blue circulation pump in the picture is for pumping hot water across our house to the kitchen do it doesn’t take so long to get hot water in kitchen.  That was an add on after wards

E5_Farmer

Jamie Hall said:

Hard to determine just what goes where, but do I seem to see two separate pumps, one for the electric boiler and one for the Navien? And if I do, is the one for the Navien running? All the valves which should be open are open?

Also yes I believe all valves that should be open are open.  

Jon_blaney

I don't see and zone lights on the controller.

Jamie Hall

It's the one directly under the Navien which I'm interested in. Is it running when the Navien is trying to run? What controls it? If it isn't running, why not?

Ironman

You’re not getting flow through the Navien on a space heating call.

More than likely it’s because the circulator below it is not pumping. What’s controlling that?

E5_Farmer

Jon_blaney said:

I don't see and zone lights on the controller.

I don’t think it was calling for heat.  

E5_Farmer

Jamie Hall said:

It's the one directly under the Navien which I'm interested in. Is it running when the Navien is trying to run? What controls it? If it isn't running, why not?

Ok.  I believe it’s running but hard to tell with the other pump for DHW right there vibrating pipes.  It is definitely not vibrating as much as the DHW pump is though.  

E5_Farmer

Ironman said:

You’re not getting flow through the Navien on a space heating call.

More than likely it’s because the circulator below it is not pumping. What’s controlling that?

The wires from the pump under the Navien go over to a circuit board.  I’m not sure what exactly controls it

E5_Farmer

I switched it over to straight gas and turned up thermostat.  It seems to be running exactly how it should right now.  But the last two nights when we get “rippled” and it switched to gas and it won’t work correctly.  

How do you test or make sure those pumps are working?

E5_Farmer

I have been looking online.  Supposedly those grundfos pumps have a pretty simple screw on back.  Mine is covered with this black plate?   Does that plate pry off of am I stuck taking this thing apart?

PC7060

E5_Farmer said:

I have been looking online.  Supposedly those grundfos pumps have a pretty simple screw on back.  Mine is covered with this black plate?   Does that plate pry off of am I stuck taking this thing apart?

I wouldn’t take the plate off.  What are you wanting to accomplish with the pump? 

If you put the tip of a screw driver in the center of the label you can hear the pump running if you put your ear to the handle end. 

psb75

Sometimes you can tell whether a pump is running (or not) by manipulating a shut-off valve on one of the pump flanges. You can feel and/or hear the flow 'stop and start-up'--IF the pump is running and moving fluid properly. Be aware of possibility of a circulator being 'air-bound" and cavitating.

mikeg2015

Make sure all the dip switches and configuration in the Navien are configured correctly. I the Navien boiler pump wired to the zone panel or the boiler? I’d prefer it’s wired to the boiler as well a the DHW pump. That way you can use Outdoor reset for space heat and different temperature for the DHW. Also you can adjust the Ramp rates on the boiler so help DHW economy. You want it to ramp up slowly and down overpump. DHW indirects are usually over pumped and return water comes back well over 135F so efficiency is under 90%.

E5_Farmer

FIXED.  THE INLET WATER STRAINER WAS PLUGGED.  Simple fixes are the best fixes.  Thank you to everyone for commenting