New Navien combi boiler hot water heater - one zone loses heat?

mentos

Hi, I'm new here and this page was recommended to me. We just bought a home in the Boston area and replaced the 40 year old boiler as recommended by Mass Save. We actually left for a 2.5 week vacation with the heat on at 60 and came back to a cold house. The old boiler turned off for some reason, so I'm kinda glad that we got a new one.

The house is a 1980 2,000SF contemporary with high ceilings and 3 heating zones: main (living room/foyer, formal dining room, guest bed, 1st floor bathroom, front door), upstairs (3 bedrooms and 1.75 bath) and kitchen (kitchen, laundry/mud room, half bath, informal dining area). It's gas heat with baseboards. The windows are new. According to Mass Save, our walls should have insulation since it was built in 1980.

The new system is a Navien 210E high efficiency (95% rating) combi boiler/hot water heater with indirect storage tank SSU-30. The plumber noted that upon start up, combustion sequence was 0.17 for test and then tapered down to 0.09. I also installed 3 Nest E thermostats.

I set the temp to 70 when home and 68 when away. When first installed, the boiler took a long time to heat up the house but I found out that is normal. It would take hours to go from 60 to 70 degrees. But once it's at 70 degrees, the main and upstairs zones are great. However the kitchen is always heating up. It would be stuck at 68 or 69 and take all day to reach 70. I have eco mode set to 68 so it should never dip below that. I believe the plumber set the temperature to 155 degrees (default is 140) to try to help the kitchen heat up.

Usage for the past 4 days:
Main: No usage, 30min, no usage, 6 hours
Upstairs: 2 hours, 15min, no usage, 5.5 hours
Kitchen: 13.5 hours, 16 hours, 19.75 hours, 22 hours

I expect the kitchen to be the coldest area, since it connects to the mud room and garage. The garage is not insulated and the door actually leaves a half inch gap from the ground, so it's basically wide open. The door from the garage to the mud room is just wood with metal sheet on the back. I can feel drafts coming from that door and another exterior door in the mud room. This is the coldest room in the house, however with the old boiler it would still be piping hot when we walked into the house. I do feel a bit of heat coming out of the baseboard in this room, but the room remains cold most of the time - I'm actually glad we're not wasting much heat in this room though. The half bath that connects to this room is nice and warm, we keep its door closed.

On the other side of the kitchen zone is a sliding glass door. There is a metal grate with baseboard heat in the floor near the sliding glass door. I know this is a source of heat loss, but the living room has sliding glass doors as well and does not have an issue. With the old boiler, the kitchen tile floors would be warm but now they are cold. There are not many baseboards in the kitchen area with the cabinets and appliances are.

Does this sound like just a matter of poor insulation in the kitchen area? I don't understand how the rest of the house can have no gas usage on the same day that the kitchen burns gas for 19.75 hours. With the old boiler, the kitchen area would be very hot and toasty. Now it struggles to maintain 70 degrees.

Our first heating bill with the old boiler was almost $500 and nearly gave me a heart attack. Hoping it's significantly lower next month.

Jamie Hall

Something is truly bizarre there -- and I'm suspecting that it's a control problem. Your figures appear to indicate that two of your three zones used no heat at all to speak of, and the third ran all the time. I suspect that information came from the Nests, not from actual observation of the boiler, the zone valves, and the pumps -- and, bluntly, I don't believe it.

What I suspect is that somehow things are miswired, and that the kitchen Nest is actually not controlling the kitchen zone at all -- and that, in fact, either one of the other thermostats is, or nothing is -- since you are getting very little heat in there. That heat from the boiler is going somewhere (like the rest of the house), though.

You are going to need to go through the controls for this system and find out what it's really doing, rather than what the whiz-bang on the wall says. Turn all three thermostats down. Then turn one of them -- any one -- way up and see which zone or zones get heat. Repeat for all three zones, and let us know the results.

Also it would help to know whether this system uses zone valves or zone pumps, and how the new boiler and old manifolds are piped.

mentos

Hi, each zone has a circulating pump - is that what you mean by zone pumps? The Nests were installed with the same wiring as the old school thermostats, using just the red and white wires. They are wired correctly. When I turn on one zone, the circulating pump turns on and the supply line gets hot for that respective zone. I then feel heat coming out of the correct zone.

Some more things about the kitchen zone that I didn't mention: The thermostat is on an exterior wall for some reason (I suspect this is the main reason it keeps calling for heat). There is a fireplace with a draft, and also a 3 seasons room with a draft. I think the combination of the garage, laundry room with exterior door, sliding glass doors, fireplace, 3 seasons room and thermostat installed on the exterior wall are all to blame.

I think getting an insulated garage door and insulated exterior doors would be best?

Jamie Hall

Well, certainly any insulating and draught stopping you can do will help -- probably a lot, and be worth every penny. Definitely a damper on the fireplace!

A note on the Nests: they may or may not operate properly with only two wires; it depends a great deal on how much power they can steal. You will be much happier with them if you add a third wire, or the optional wall wart power supply. Also, you and your heating system and wallet will be much happier of you limit -- or turn off completely -- their effort to run setbacks. They are designed and intended for forced air heat, not hot water and certainly not steam.

mentos

For the setbacks, do you recommend keeping the temperature constant at 70 all the time? I set eco mode to 68 so it should only go down 2 degrees at most.

mentos

Also is this a normal amount of time for the gas to be running? The past few days for the kitchen zone have been slightly better, between 13.5-16 hours but that still seems very high to me.

DZoro

Insulate and tighten up, the only reason the thermostat tells the system to turn on is because its surroundings lost the heat.
Personally the nest doesn't belong in your application. They work good with forced air, not so much with hydronics.
D

oreo123

is this room, the kitchen radiant heat? Or baseboards? Kickheater? You mentioned that the boiler temp is at 140 or 155.

Was the old boiler located directly under the kitchen? Older ones are less efficient and will heat up their surrounding area (basement).

I agree with poster below for you to verify that the kitchen thermostat is calling. If you have a controller in the basement you might be able to see the appropriate led light illuminated. Shut off the other 2 zones and see if basement led is lit for kitch zone. Then check the circ pump to see if its running.

in the basement did the installer change circ pumps? are they all facing the same direction there is an arrow (hopefully on supply side)? I had a similar problem a couple of years ago where the installer put a different model pump in which threw off the gallons per minute and there was minimal heat in that one zone. Pix would be helpful.

In basement that zone - are the supply and return pipes way too hot to touch?

If the kitchen is radiant heat you need that room super well insulated. No drafts at all.

Jamie Hall

One thing I neglected to ask -- are your run times based on what the Nest is telling you, or on reality (actual boiler running time)? Could make quite a big difference...

mentos

When you guys say Nest is not good with my system - what difference does having a Nest vs regular thermostat make? I like the Nest because I can control the temp while I'm not home and see how many hours per day each zone uses. Lately I've kept the heat at 68 and haven't changed it - still uses 14 hours for the kitchen zone.

The heating is all baseboard. Yes the boiler is located directly below the kitchen zone where the fireplace is. The circulating pumps are new and all face the right direction. The kitchen zone does call for heat and the supply and return pipes are hot to touch, just like the other two zones when they call for heat. He kept the zones the same and the circulating pumps get warm when they call for heat. The difference with the new boiler is that the baseboards are slow to heat and feel warm but not piping hot like before. So I suspect it is due to heat loss.

I think the run times are accurate because anytime I'm in the kitchen I see the condensate blowing outside.

Peter_26

How much radiation in the kitchen and what's the SWT now compared to before?

mentos

Here is a photo of the whole system when it was first installed. The kitchen zone is the fourth circulating pump from the left.

I don't know what SWT is? The baseboards are the same as before.

neilc

you have to seal up those drafts.
that 1/2 inch gap under the door, ya might as well have the door open,
stand there barefoot and feel the draft,
get a cheap sweep from home depot and stop that draft.
now do the others.
caulk, tape,
is that fire place active ?
does it have a working damper ?
another big hole in the house.
I truly believe air sealing is more important than the insulation.

Jamie Hall

Let's step back here a moment.

First, the old boiler -- until it quit -- heated more or less adequately, no? What was its output BTUh? How does that compare with the new boiler?

Second, the new boiler runs most of the time apparently, but the kitchen zone does not heat up. Are the baseboards in the kitchen zone nice and hot? If the boiler is holding 150 plus, they certainly should be. If not, that zone isn't getting circulation.

But.

Third, if that zone isn't getting the circulation it needs, but the rest of the house stays nice and warm with no calls from the thermostats to speak of, the heat from the boiler running all the time has to be going somewhere. Which zone or zones is/are getting the heat?

Not that draught proofing and insulation isn't important. It is. But you are putting a lot of heat into that building, and it's not showing up in the one zone which is calling... so where is it going? And why? I still think there is a control problem here.

mentos

The garage already has one of those weatherstrip seals but the door still has a half inch opening. The concrete is uneven so I think I would need someone to level it with hydraulic cement or something before getting a new insulated door.

I don't think the fireplace has a damper. We do not use it. I'll look into getting one.

I don't know what the old boiler output was. The plumber said the temp was 180. It did heat the kitchen zone very well, I would feel plenty of heat coming out of the baseboards. The new boiler has heat coming out but it's not as strong.

The living room and upstairs stay warm. They call for heat when it's cold but the past few days they have called for minimal heat. I don't see any issues with the controls. When the living room and upstairs call for heat, their respective baseboards and supply/return lines get warm. The same with the kitchen except the kitchen continuously calls for heat.

Jamie Hall

Part of the problem with the kitchen may be that it really does need that 180 temperature water. Consider: if your boiler is running at 140 instead of 180, you are getting less than two thirds as much heat out of those baseboards as you used to, and no amount of changing the flow rate will help that. Have you tried to see what happens if you kick the boiler up to 180?

mentos

Not yet, currently it is set at 155. I can try going up more. Would that negate the high efficiency?

mentos

Yesterday the kitchen saw a significant drop in heat, from 14 hours Friday to 8.5 hours Saturday. It was 50 degrees both days.

psb75

If you can't get a damper put in the fireplace right away...stuff a batt of fiberglass insulation in the flue to block it. AND put an obvious note/reminder of it on the fireplace. Like: WARNING. FLUE BLOCKED WITH FIBERGLASS INSULATION.
If that flue is truly open, that is a crazy heat loss.

mentos

So I stuck my head in the fireplace and there is a damper, but there's a huge opening even when closed. Guess I'll have to call someone to repair or replace this. I stuck a piece of insulation in the opening and it helped with the draft. I still feel a draft but it's not as big as before. Perhaps we can get the top capped too.

DZoro

The boiler is not properly piped. It should be piped primary/secondary (P21 in manual). The way it is piped now the boiler will not function properly.

Yes raising the water temp will loose efficiency, but the problem zone may need a higher water temp until better sealed/insulated.
D

mentos

> @DZoro said:
> The boiler is not properly piped. It should be piped primary/secondary (P21 in manual). The way it is piped now the boiler will not function properly.
>
> Yes raising the water temp will loose efficiency, but the problem zone may need a higher water temp until better sealed/insulated.
> D

Hmm that doesn't sound good. Would this be a major issue to fix? I doubt the plumber is willing to come back and do it for free.

EzzyT

It’s not just a major issue it needs to repiped otherwise your always going to have issues. I don’t get what was the logic to install a combi unit along with a indirect tank being used as a storage tank when the best app would’ve been to install a boiler only with the indirect tank.

neilc

psb75 said:

If you can't get a damper put in the fireplace right away...stuff a batt of fiberglass insulation in the flue to block it. AND put an obvious note/reminder of it on the fireplace. Like: WARNING. FLUE BLOCKED WITH FIBERGLASS INSULATION.
If that flue is truly open, that is a crazy heat loss.

I would go one further,
stuff the insulation into a large flexible garbage bag, insulation by itself will pass a surprising amount or air thru it, the bag will be my air seal, tuck it into the corners well, or supplement small bags in the corners,,
and yeah, hang a sign there so no one forgets if they try and light a fire.

mentos

The plumber recommended the indirect storage tank for extra hot water in case our family gets bigger or we lose power.

Is this repiping something that can be done in the spring or do I have to do it now and lose heat for a couple days? I'm guessing the plumber won't come back and do it for free. Are we talking thousands to pay for this?

EzzyT

The indirect tank is ok just make no sense to go with a combi.
Plus there’s a missing pump on the indirect tank which is acting as a storage tank. Pressure drop in that flat plate heat exchanger are pretty high so it’s gonna be hard to maintain temperature in that tank.
The Repipe should only take a days worth of work. We don’t discuss pricing here.

DZoro

I would think they would want to make it right. There is a reason for the installation manual, it is not just a suggestion it is the correct/proper way. Really wouldn't be that hard a couple tee's and 90's and it's done.
When they are there they should plumb the safety relief, that is not good the way it is. The relief is on the upper left of the boiler, and it should be piped down to within 6" of the floor. That way if it does open up you will be safe from scalding hot water.
I can't tell but there should be another one on the domestic hot water piping coming out of the boiler bottom right.
No matter what the safety issues need to be corrected, no charge. The piping should be the same IMO.
D

mentos

> @EzzyT said:
> The indirect tank is ok just make no sense to go with a combi.
> Plus there’s a missing pump on the indirect tank which is acting as a storage tank. Pressure drop in that flat plate heat exchanger are pretty high so it’s gonna be hard to maintain temperature in that tank.
> The Repipe should only take a days worth of work. We don’t discuss pricing here.

Is the missing pump supposed to go in-between the boiler and storage tank?

The first pump on the left pumps water from the tank too the rest of the zones.

EzzyT

That isn’t a storage tank it’s a indirect tank. Is that pump wired into a relay and set up as priority? If so or not it’s going to creat issues on how the boiler operates. You definitely need to get that near boiler piping addressed ASAP.

mentos

I don't know I'm kinda clueless about this stuff.

So is this what I should tell my plumber?

1) The boiler should be piped primary/secondary
2) The safety relief should be piped down to within 6" of the floor.

DZoro

You and your plumber should get familiar with the installation manual p 24-31 and steps on p 76-77 must also be done and results printed off and left with the boiler to insure proper set up and operation of the boiler.
D