Heat not working like it should

jonathandaponte

I have a Navien NCB 240. When it was installed we ran the piping for 6 zones ( each room on its own zone) and hooked up zones as the rooms were completed. As I have added more zones, the baseboards aren’t putting out the heat like they should be. I’ve bled the system a few times, no avail. The zones that were working before are struggling. Baseboard was over done as in a little more than the heat lid required but still under the systems max output. Any help is appreciated

kcopp

How is it piped? Posting a pix will help us see possible flow issues.

jonathandaponte

All zone circulators forgive the drawing, I’m not currently home but 1 inch all around except for the manifold which feed the circulators at 3/4. one zone is split because it was over the delta drop of 15-20 degrees so that’s why there are 6 zones but 7 returns.

Ironman

One thing that's not readily understood about combi boilers is this: just because the burner can produce 199k btus doesn't mean that much heat can be delivered to the emitters.
The onboard circulator is rated for about 4.5-5.5 gpm. It's sized for the domestic plate heat exchanger, which at that gpm and a 77* temp rise (delta T) through it, will give about 5 gpm domestic hot water.
The problem lies on the space heating side: at 5 gpm, you're only gonna get about 50k btus delivered to the house for space heating .Btus = (gpmx500) x Delta T.
High temp BBs are generally sized for 180* SWT and a 20* delta Tee. At 5 gpm, that translates to 50k btus.
Think of it this way: at train is is being loaded at the station (the boiler). The station has 199 tons of cargo (btus) to be delivered, but the train (the circulator and piping) can only carry 50 tons of cargo at a time to the depot (the emitters).
Unless you oversize your BBs so that they can operate at a lower SWT which would allow for a wider delta T, you're not gonna be able to get enough btus to them.

jonathandaponte

I should also mention 4 of those zones have a rise of 20 feet or so.

jonathandaponte

Iron man, when I put the BB in i oversized the amount of them. Meaning like if the room called for 10 feet I put in the max amount I could without having to split it. That does make sense though, meaning the train thing. I debated on putting in bigger pipping to hold more volume of water, this way the system would not have low heat but I don’t think that’s the answer. When I only had 2 zones calling for less than the 50k btus it worked. Maybe I should simply not use the combi. Really stinks that they advertise 100k but it appears as if that’s the problem, just simply not getting enough BTUs....

Jolly Bodger

A picture of the boiler and piping would help. It's not entirely clear (to me) if you have correct primary secondary piping.

Might be able to add and extra pump in the boiler loop to increase the GPM when heating? I'm not sure how much flow that unit can take.

jonathandaponte

Here it is

hot_rod

Looks like the boiler is good for about 120,000 on the heating side. Do you know what the heat load of the home is? The manual is pretty clear on how it needs to be piped, primary secondary. Doesn't look like your system is?

SuperTech

I don't think that is proper primary/secondary piping. What's with the shark bite ball valve on the boiler loop that is shut off?

Ironman

Jolly Bodger said:

A picture of the boiler and piping would help. It's not entirely clear (to me) if you have correct primary secondary piping.

Might be able to add and extra pump in the boiler loop to increase the GPM when heating? I'm not sure how much flow that unit can take.

Putting another circ in series will increase the head, not the gpm. It would have to be in parallel to increase the gpm.

That's not proper p/s piping in the pic. That could be part of the problem.

Also, with oversized radiation, he should be able to get by with a lower SWT in the secondary loop. That would allow more btus to be transferred from the primary loop.

Ironman

Proper p/s piping:



The boiler would connect to the bull of the Tees (the part that's marked secondary).

Compare this and hot rod's diagram to see how the closely spaced Tees are configured to create p/s piping.

Here's another to show the house loops in parallel so they all receive the same SWT.

Jolly Bodger

@Ironman pumps have curves. If you increase the head supplied by the pump(s) the GPM will go up. This assumes that one selects a pump with the right head and GMP curve for the application. Pumps in parallel will increase GPM until they hit the head curve.

One could also just replace the internal pump with a stronger pump, but space may make that hard.

@jonathandaponte the ball valves in the system may not be full port and adding restriction to you piping. A 1" full port valve will be 1" ID. Cheaper valves can be highly restricted being 3/4" ID or less.

Zman

Do your circulators have check valves in them?

jonathandaponte

The ball valve is there because I realized after adding the additional zones the circulators were sucking up return water ( not 180 water and it also make it easier to purge the system of air. When I turn the valve to open the system is installed to the manual. There maybe check valves in the circulators so I’ll swap em out one by one with a spare one I have ( I doubt that’s the case though just because the the primary loop gets hot and the “secondary loops get warm”. I oversized each zone, knowing that I needed a 70 ish temp raise on the usual coldest day, but put in like 85ish , but still stood with the acceptable standards for the temp drop at the end of the loop. I’ve purchased electric heaters to supplement and the rooms are warm. I really feel like this a flow problem in some way. I shut off every zone except for one ( my kitchen zone ) and the toe kicks don’t fire up. I’m beginning to suspect the thermometer is all sorts of goofed up. If it is reading 180 but really pushing 130 through baseboards, that’s a BIG PROBLEM... undortunatey I think I’ll need to bring in a contractor to test that out.

DZoro

Need to do a re-pipe, in order to get the proper performance of that boiler. The guys have all provided proper piping techniques. Follow them exactly. It will be some work, but it's the right thing to do to take care of the issues you are having. Maintain proper pipe sizing's in the design. Step by step with the O/M.
D

Zman

If you don't have checks in the circs, you end up pulling water back through the zone that are turned off rather than from the boiler.
You can tell a lot from just feeling the pipes. What is getting warm and when?

jonathandaponte

> @Zman said:
> If you don't have checks in the circs, you end up pulling water back through the zone that are turned off rather than from the boiler.
> You can tell a lot from just feeling the pipes. What is getting warm and when?

I’m going to repipe it with the baseboard returns a lot further away from the baseboard runs and very close to the boiler. With them being close on the primary loop it doesn’t appear to be helping my cause. For the time being I’m running to the plumbing supply store for a check valve to be put in the location I have my pex ball valve. That should solve the problem of “back feeding the return water”. General consensus is that it the piping is not productive for as many zones as I have VS what I had previously. I will go back to the manual as it was installed for 2 zones and now have 6. The heat loss is calculated in each zone and sized a little larger, but I NEVER did the calculations for the “tree” and it’s needed sizing to accommodate the entire heat load. I think with those corrections I’ll be able to get more BTUs to the circulators.

Jolly Bodger

@Ironman posted some nice pictures of what the near boiler piping should look like. using closely spaced tees to make true primary/secondary piping. The second one he posted also shows how your manifolds should be piped in. There should be no connection between the supply and return manifolds. Just leave the ball valve there and closed.

Another problem some people (installers) have with low mass high BTU boilers is they do not size the gas line for full fire. That is easy to run the numbers on and test with a manometer.

HomerJSmith

When ever there is a heat problem, the first thing I look at is the heat emitters. What is the temp of the first heat emitter and what is the temp of the last heat emitter on that circuit. The second thing that I look at is flow. No flow, no heat. The third thing is zoning and envelop heat loss.

I like balancing valves even on circulator zoning as there can be uneven flows. What do you mean the baseboards aren't putting out the heat they should be? And how do you determine that? Is it all the baseboard circuits or only one? If the offending circuit is one, with all the other circuits off, does the offending circuit produce enough heat?

The secondary boiler piping should be generous as well as the primary manifold piping. You can't allow the boiler output pipe size determine the piping sizes. I never do less than 1 1/4" pipe size.

Are those blue handled valves, gate or globe valves?

jonathandaponte

@HomerJSmith what I mean I know for sure the temp going through the baseboard is lower and less BTUs are coming out of them because my toe kick heater hasn’t turned on, my bathroom which is is like 100 sq feet and has about 15 ft of baseboard, doesn’t heat up in 10 minutes flat like it used to not do I hear the usual “expanding clanking” sounds. When Multiple zones are running, I am able to grab the primary feed after my expansion tank with my hand and it not be burning. When one zone is going I can’t touch that pipe, it’s hot! I have circulators each pushing at least 2 gpms but yet my broiler can’t only push out 5/6 tops. That’s certainly a problem.... those blue handled valves are gate valves. Each zone when running and being the only zone I have no issues. But when multiple zones are calling for heat, is the issue. As far as there not being enough gas pressure, I’m not being dismissive, but that doesn’t make sense to me because the unit cranks out hot water on demand for 2 showers and a dishwasher, no problem. So if it can crank up the 155-199k btus for on demand it should be able to come up to the 50-75k in broiler of the 120k advertised. So this feed has been great lots of information but there is also conflicting information. Should this system or all combi broilers have the primary loop end, where the water HAS to go through a circulator or should be able to continue though and circulate back into the boiler? The instal says through circulatory or nothing. Which works out when I have the ball valve closed, but I can feel the expansion tanks pipe and it isn’t hot at all that way, when it runs through the true loop it gets HOT!

Jolly Bodger

@jonathandaponte Just relaying other possibilities. I don't know that your DHW demands have driven full fire and that it performs there. This is an assumption given you have not had symptoms. Sometimes we get tunnel vision because we think we know what the problem is. Keep in mind that you are working on a system.

That said, I agree that the piping is most likely the cause of the issues.

To clarify, are you saying that when the ball valve between the supplies and returns is closed, the supply line at the expansion tank is not very hot. And if you open this valve the supply line gets hot?

But neither position meets the heating demand.

jonathandaponte

@Jolly Bodger correct in the closed position, the supply line doesn’t get as hot as when it is open, when it is open, the supply line is a lot warmer. I typically have that in the open position unless I’m bleeding the lines out of air.

hot_rod

looks like a DHW relief valve on the heating loop? Be sure you have a 30 psi, pressure only relief valve when you repipe.

mattmia2

The reason for the closely spaced tees in the primary loop is to isolate the action of one pump from the other. The way you have it now the pumps are interacting heavily. If/when you repipe, don't ignore the need for the takeoffs from the primary loop to be closely spaced.

jonathandaponte

@mattmia2 I’m not sure what you mean, when I repipe I’m going to use the same trunk design. I think I interpreted what you said incorrectly. On the left side of the broiler I’ll use that as the takeoffs and on the right side I’ll use that as the returns.

hot_rod

If you pipe it like the owners manual you will have no problems.

Know that with primary secondary piping there is always blending going on in those closely spaced tees. You may not ever see the boiler temperature to the zones depending on the flow rates of the various circulators.

Jolly Bodger

I've been making an assumption that all your pumps are pumping away form the copper manifold out to the PEX, given that this would be normal for the orientation of the motors.

With the orange handle valve open most of your zone pump circulation is going to flow from the return up through that valve and back to the pump. Given this would be the path of least resistance. That valve should be closed. Actually, that connection between the supply and return manifolds should not be there at all. With the orange handle valve open the supply pipe is hotter because it has very little flow. Thus you are not moving the heat out to the zones.