Navien Combi System NCB-210E - Temperature Issue

[Jessica857]

Hello,
I'm new to the forum and hopefully someone will be able to help me.
I recently bought a new house that was converted to gas. A new Navien combi boiler was put in to replace the old furnace.
I've moved in for 3 weeks, everything was fine until this past week when the temperature dropped.
I have 3 zones in the house, basement, 1st floor and 2nd floor. I have no problem in basement or the 1st floor at all. Hot water is also fine. But I have trouble heating up the 2nd floor. I tried cranking the thermostat up to the max and I still don't feel any heat from the baseboards.
I tried changing the space heating temperature on the boiler from 140 to 150 and it still doesn't work.
Basically my 2nd floor where all the bedrooms are have no heat at night, the temperature stays at around 60 degrees and would not go up any higher.
Hopefully someone is familiar with the combi boiler here and can provide some assistance.
If not then I'll have to reach out to a local HVAC technician.

 

[Dana]

This sounds more like a system problem than a combi-boiler problem. If the plumbing to the second floor zone is stone-cold it means you're getting no flow, but could be multiple reasons why.

Were you there when the old boiler (which is NOT furnace, BTW) was still there? If yes were all zones working?

Are the zones pumped separately, or are there zone valves? If zone valves you can manually open the valve and should get flow to that zone if the pump is running.

What is the pressure on the system? If the boiler is in the basement it needs at least 8-9 psi to even get water up to the second floor, and should be set no lower than 12 psi.

Is it possible that there's a gate valve on the zone loop that was left closed after the installation, blocking flow to the second floor zone?

Is there an air bleeder on any of the upstairs baseboards or radiators, in case there is a big slug of air creating a vapor-lock condition preventing flow? whenever a system is drained to work on it air enters the system and needs to be purged to keep everything happy. If the installer didn't successfully purge the air for the second floor or other air in the system migrated to the second floor (bubbles do rise to the top, after all) this could be what's happening. Sometimes a large slug of air in the top of the system won't prevent flow entirely, but if it's just a trickle the pipes at the second floor may be pretty tepid. Bleeding the radiation (if there are air bleeders installed) will usually fix that pretty quickly.

If the boiler was installed in the past few months the installer should be on the hook for any gate valves left closed or any air purging that wasn't done right, but if the prior owner was the customer they might try to duck it, or they may be willing to support it (which they should.)

 

[Sponsor]

 

[Jessica857]

This sounds more like a system problem than a combi-boiler problem. If the plumbing to the second floor zone is stone-cold it means you're getting no flow, but could be multiple reasons why.

Were you there when the old boiler (which is NOT furnace, BTW) was still there? If yes were all zones working?

Are the zones pumped separately, or are there zone valves? If zone valves you can manually open the valve and should get flow to that zone if the pump is running.

What is the pressure on the system? If the boiler is in the basement it needs at least 8-9 psi to even get water up to the second floor, and should be set no lower than 12 psi.

Is it possible that there's a gate valve on the zone loop that was left closed after the installation, blocking flow to the second floor zone?

Is there an air bleeder on any of the upstairs baseboards or radiators, in case there is a big slug of air creating a vapor-lock condition preventing flow? whenever a system is drained to work on it air enters the system and needs to be purged to keep everything happy. If the installer didn't successfully purge the air for the second floor or other air in the system migrated to the second floor (bubbles do rise to the top, after all) this could be what's happening. Sometimes a large slug of air in the top of the system won't prevent flow entirely, but if it's just a trickle the pipes at the second floor may be pretty tepid. Bleeding the radiation (if there are air bleeders installed) will usually fix that pretty quickly.

If the boiler was installed in the past few months the installer should be on the hook for any gate valves left closed or any air purging that wasn't done right, but if the prior owner was the customer they might try to duck it, or they may be willing to support it (which they should.)

Thanks Dana!
The system was replaced before I moved in, but unfortunately after the inspection.
I did in fact tested out the heat on the 1st floor on the day of final walk through and it was working. I just assumed it worked for the entire house, boi I was wrong. It was still hot outside at that time and it was much quicker for the heat to work then.
I tried contacting the previous owner for the plumber's information and he's being non-responsive. I highly doubt he'll respond at this point.
This morning the temperature dropped to 25 degrees outside, I could only get up to 62 degrees even on my 1st floor now.
I looked at all the baseboards on the 2nd floor and didn't see an air bleeder.
I've decided to hire a HVAC tech to come take a look at it for me, since I have zero knowledge and I really don't want to mess up the system.

Thanks for your response and hopefully I'll get heat in my house soon! My kids and cats were freezing last night!

 

[Dana]

Thanks Dana!
The system was replaced before I moved in, but unfortunately after the inspection.
I did in fact tested out the heat on the 1st floor on the day of final walk through and it was working. I just assumed it worked for the entire house, boi I was wrong. It was still hot outside at that time and it was much quicker for the heat to work then.
I tried contacting the previous owner for the plumber's information and he's being non-responsive. I highly doubt he'll respond at this point.
This morning the temperature dropped to 25 degrees outside, I could only get up to 62 degrees even on my 1st floor now.
I looked at all the baseboards on the 2nd floor and didn't see an air bleeder.
I've decided to hire a HVAC tech to come take a look at it for me, since I have zero knowledge and I really don't want to mess up the system.

Thanks for your response and hopefully I'll get heat in my house soon! My kids and cats were freezing last night!

If all else fails or if they can't get to it for several days, for about $50 a 1500 watt oil filled radiator type space heater will heat a LOT of space even when it's 0F outside. The oil-filled radiator types are less of a fire hazard than anything with a fan or visible orange-glowing element. (Quieter than a fan type too.) The design heat load of a bedroom is typically less than 1000 watts (3412 BTU/hr) even for an uninsulated antique house, and less than half that for code-min new construction.