Navien NCB240 set up with Taco Viridian pump

[snowonweb]

Recently when the temp outside dropped to 10F, inside my home the temp couldn't get passed 60 while the thermostat was set at 70.
I have a 1952 brick house with plank and 1/4" cement board and 1/4" gypsum board. So there is really no 2x4 wall with space for insulation. Its 1172 square feet ranch with unfinished/unheated basement. House is heated by cast iron baseboards, 135 feet of them. It's 2 bedroom, living room, kitchen and a small office.
Initially it was heated by oil but now I have newly installed Navien NCB 240. professionally installed with navien manifold and taco viridian pumps. There are 2 zones but 2nd zone only runs breezeway's one cast iron radiator.
Initially my navien water temp was set to 140F and the pump was set to delta-t 20F which couldn't keep up with heating up the house. That was my initial setting. Then I lowered the delta on the pump to 10F and that didn't do anything. Then I switched the pump to manual mode and put it on the highest speed (which is 4) and that caused the temp int he house to raise to 63F except that the pump was noisy. If I remember correctly the return water temp was 127F.
Today i finally got fed up with cold house and noisy pump that I set the temperature from 140F to 160F and within 2 hours my home got to 70 degrees. Given that outside temp right now is about 25.
Now I am lost. I mean I am happy its warm but something tells me 160 is not right.
I am located in Connecticut btw.
BTW. Initially I had oil furnace that ran the water at 180 degrees and besides buying 200 gallons of oil every 6 weeks I had no issues with the heat. My issue was with the price of oil.
So my question is what mode should I run the pump and with what settings. Also what temp should I run the water at.

Also I dont know the heat loss calculation of my house but roughly its 100ft x 120ft x 8ft tall walls. I just bought the house and it's my second winter here.

Please advise,

Thank You,

Jack.

These are the links to my hardware.
TACO PUMP
NAVIEN NCB240
BASEBOARDS

 

[Terry]

In 1952 there was no insulation in the walls. I sometimes see people foaming those outers walls. A small hole near the top, allowing expanding foam to fill in the empty space between wall studs.

Since you have upped this to 160 degrees, does that mean the entire home, including the faucets, are now at 160?

 

[Sponsor]

 

[snowonweb]

This navien tankless boiler has 2 setting. One for heating water and one for domestic water which is still at 120F. Also now that it's dark and it's colder outside 14F. The temperature inside the home dropped to 66.

 

[Runs with Bison]

I've not dealt with home boilers so I don't know that I can help much. However, I noticed a few things about the information you provided.

If your set point is 140 and your return temp was 127 F at max pump rate, then it sounds like you are heat transfer limited in the baseboards. If the water was returning cold then I would look elsewhere for the bottleneck. But in this case it is going in hot and coming out only slightly colder. So it sounds like you need more baseboards to keep up with the heating load. Either that or you need to keep increasing the boiler outlet water temp.

Looking at the baseboard link it appears they might be sized for even higher temps than the 160 F that is making you nervous: table starts at 170 F average and goes up to 215 F.

What does your installer say your maximum operating temp should be?

 

[Zl700]

"BTW. Initially I had oil furnace that ran the water at 180 degrees"

The answer is right there-

It took 180 degree water to heat your house with the old boiler, why do you think 140 degrees will do it now?
I don't know which CI BB you have but in round figures the baseboard has different heat outputs at different water temps.
If you had 550 BTU's per foot at 180 degrees (550 x 135') = 74,250 net BTU's to heat the house
At 140 degree water, the output may be around 340 BTU's per foot. 340 x 135' = 45,900 net BTU's available

That extra 40 degree water to get that 28,000 BTU's is what you need to get your house warm. The house you describe may easily need 60,000 BTU's to be 70 degrees inside when 0 outside (That's whats called the design degree difference)

BTW with less standby loss of boiler, you may need 185 degrees now as the boiler itself doesn't give off much ambient heat.
Bear in mind you only need the hottest water on the coldest days, that's why outdoor reset is so beneficial to use and set up properly.

 

[snowonweb]

Ok to clarify.
The 127F return water was when my navien was set up for 140F . Now that it's setup at 160F the return water is 147F (just checked while its 20F outside and thermostat is set at 70 with heat on)
My installer says i have AIR in the system which I already bled numerous of times so there is no air.
I have my pump set at Delta-T 20F and it says S-147F on bottom left and R-129F on bottom right. Seems whatever is the return water temp on the boiler is always the Supply temp on the pump. Now if my boiler just kicked in and is adding 160F water to the mix, shouldn't the S water on the pump slowly go up to 160 and where the hell is the pump getting R 129F from. Does R stand for RETURN and S for Supply.

Either way it seems I solved my own problem by bumping the temp from 140 to 160 but can someone please confirm that running the pump at delta-t 20F is the right mode for the tankless system. There are few other modes to choose from. I just want to make sure I am getting the most of out of the system and I will look into getting a OUTDOOR RESET SWITCH.

 

[Runs with Bison]

Without seeing your layout and controls and looking for the location of the sensors I can't say what those are exactly. However, if the boiler and pump system are separate they could very well have different readings for the supply temp. The Navien might be producing 160 F water while the pump measures 147 F to its supply. The supply might be a mix from the boiler and a recycle which is fairly normal for process plant tempered water systems. If it is then one would expect the pump's supply to be lower than the boiler's outlet temp. (Locations of thermocouples and such can dramatically impact sensed vs. actual temperatures as well.) As long as you can increase the boiler output temperature and see a rise in the supply temp you still have some excess capacity in your system.

I would expect a system like this to be able to vary the boiler set point over a given range in order to achieve the desired home thermostat set point. However in this case it sounds like the boiler set point is being artificially constrained or fixed and you have to manually raise it when outdoor temps fall below some given range.

Did your installer tell you what the maximum safe/warranty operating temp is for the boiler, pump and baseboards is in this install? As long as you don't exceed this you still have capacity (assuming the boiler's burner capacity hasn't been exceeded, at which point increasing the temp will have no effect.) You will need to know this max if it hits -10 F outside.

 

[Dana]

In 1952 there was no insulation in the walls. I sometimes see people foaming those outers walls. A small hole near the top, allowing expanding foam to fill in the empty space between wall studs.

Since you have upped this to 160 degrees, does that mean the entire home, including the faucets, are now at 160?

Non-expanding injection foam as well as expanding foam pours are pretty risky, since it's impossible to get the stuff out or fill any voids that were formed during installation. In the expanding foam case blow-outs from over fills and voids from underfilling are common.

A less risky retrofit is to "dense-pack" the cavities with blown cellulose or blown fiberglass. While the result is a slightly lower thermal performance wall than with perfectly installed foam, the differences are pretty tiny. This is because in 16" o.c. framing about 25% of the total cross sectional aria of the wall is the studs, top & bottom plates, etc at about R1-R1.2 per inch of depth (a 3.5" 2x5 runs no more than R4.2 if hemlock, about R3.5 if douglas fir.) So even if the other 75% of the wall is R18 (say, for injection foam), more than half the heat transfer through the wall is via the 25% framing fraction. Bumping the center-cavity R to R-infinity with some magical insulation made of pure unobtanium doesn't bring the whole-wall R to even R17.

But he doesn't have wall cavities to fill, and is stuck with pretty much an R2-R3 wall, which is pathetically low performance for a cool-climate CT location.

Regarding the heating system, it's not uncommon to see a delta-T on the radiation of only 13F with 140F output water.127F return, which is the edge of condensing zone. That's an average water temp of about 133F, a temp at which the Snug cast iron delivers about 300 BTU/hr per running foot of baseboard (x 135'= ~40,000BTU/hr When you bump the temp to 160F the delta-T increases, since the average water temp increases, and the Snug emits the heat faster than at a lower temp. At an AWT of 150F (160F out, 140F return) it's delivering about 400BTU/ft (x 135' = 54,000 BTU/hr) into the zone. A 20F delta-T at high temp is fine, as is a 10F delta-T at low temp, but at delta-Ts below that it means you're probably spending too much on pumping power.

Clearly you don't have enough radiation to emit enough heat during the 99% outside design temp (the temperature bin at which only 88 hours/year on average are at that temp or lower), but you can still get condensing efficiency out of the beast at your AVERAGE mid-winter temp, if you set it up with outdoor reset, and take the time to dial in the reset curve.

It's very common to be able to heat a house with 140F water that was originally set up with a 180F system, but not always. The original systems were often already over designed for a barely insulated house with single pane windows/no-storms that leaked a ton of air per hour on cold windy days. The more thermal retrofits you've done to the house (air sealing, attic insulation, storm/replacement windows, basement insulation, retrofit wall insulation) the more likely it is you can get there. And those retrofits provide more comfort than just cranking up the temp or adding more radiation. So, while outdoor reset would cure the acute comfort shortfall and still get condensing efficiency, it's still going to be worth reducing the load where ever it's easy/cost-effective.

An apparent heat load of of 50-60,000 BTU/hr & higher @ single digits F (the likely 99% outside design condition is an indication of very low insulation levels, high air-infiltration, and an uninsulated foundation, and is extremely high for a 1172' rancher even at 0F outdoor temps. If you can air-seal & retrofit insulate the walls with rigid foam to at least R10 (1.5" of continuous foil-faced polyiso) and add something to the attic it'll drop the heat load at 0F to well under 50K, even if the windows are single pane double-hungs with clear glass storms. If you insulate the foundation you'll probably knock off at least another 8-10,000 BTU/hr of load. If you can't really gut the walls and do the rehab now, you can still insulate the basement (an inch of foam trapped to the concrete with a batt-insulated 2x4 studwall, or 3" of foam strapped to the foundation with furring does wonders- I've detailed that multiple times on the remodel forum of this site) and seal up any parasitic flues that extend from basement to attic & beyond (which includes the old flue & flue chase, plumbing stack chases, electrical chases, etc.) that suck air into the basement 24/365 you can still whack a big chunk of load off and raise the floor temperature.

Air leakage between the conditioned space and attic is also a big heat load, since it depressurizes the first floor, dragging cold air up from the basment or through window/door/wall leakage. If you have any recessed lights those are usually HUGE infiltration drivers. Even surface-mount fixures usually leak air, and it's w0rth air sealing the elecrical boxes to the finish ceiling, as well as any wire penetration/fastener points in an old steel elecrical box. If you have an open hearth fireplace those too really suck, even when the damper is closed, unless the flue liner is in really great shape AND you have a gasketed flue-top damper, not one o' them steel flaps in the firebox.

When you've fixed all of the obvious air leaks it may still be worth runing blower door tests to find & fix most of the other less-obvious leaks. You may have substantial wall leakage into the vent channels in the wall stackup. There may also be partition walls that leak copiously into the attic- you'd be amazed.