Triangle Tube CC125 Boiler not reaching thermostat set temperature

petec88

Hi,

I have a Triangle tube cc125 boiler on the 2nd and 3rd floor of a 2 family home located in Boston. The combined living area is about 1,200 - 1,300 sq ft. There is about 200 linear feet of baseboard radiator running on a single loop through the 2nd and 3rd floor house.

The problem I am having is the thermostat never reaching it's set temperature. The thermostat (Nest) is located near the end of the loop. It was set to 66F but the temperature hovers around 62-64F (when the outside temperature the last two days has been around 20F). The parameter on the boiler is set to: Set Point Temp: 190F; Min Supply Temp: 120F; Min Outside Temp: 20F; Max Outside Temp 64F. As it is not reaching the T-stat temperature, this results in the boiler burning almost 24 hours per day.

I set the pump to the lowest speed in hopes of dissipating more heat from the system before it returns to the boiler but not sure what else I can do here. Any help or insight into the setting is greatly appreciated.

P.S. this is different than the short-cycling problem I am experiencing with my other TT boiler.

Gordy

200 feet of baseboard on one loop is way to much. Your experiencing a considerable temperature drop near the end of the loop.

Also slowing the circ down will compound the issue.

Jamie Hall

Reducing the flow rate is not going to help. What it will do is reduce the water temperature in the radiation near the end of the loop, which will reduce the heat output of that radiation -- which is exactly what you don't want. Keep in mind that the heat output of the radiation is a function of the radiation's temperature; the hotter the radiator, the more heat it puts out.

That said, you say that your boiler is actually burning almost 24 hours per day. That's a modulating boiler, and it is quite possible that it is not firing at full power. That would be a control problem.

Gordy

How are the other areas from the beginning of the loop?
Are they over heating?

petec88

> @Gordy said:
> How are the other areas from the beginning of the loop?
> Are they over heating?

The beginning of the loop is warmer. I closed some of the dampers in the beginning of the loop so that some of the heat can be transferred downstream to the other radiators. From Jamie's comment, I might try moving the pump speed setting to Med and see if it might help with the end of the loop.

smithfan

I second what hatterasguy said, you may even want to raise your
Min temp more. I'd be curious as to what the boiler target water temp is. Also, consider lowering your min outdoor temp as well. Depending on what type of baseboards you have, the lower water temps provided by having a mod/con may not being desired. I have my triangle tube curve set pretty agressive, I run it hot and short because it's also oversized. If I where to run the same curve you are it would take forever to reach my stat temp and I'd be short cycling like crazy.

Gordy

Solve the real problem...

petec88

Hatterasguy said:

First of all, set the pump on the highest speed for that lo
Slower speeds do not dissipate more heat. They just make the end rooms more uncomfortable.

Second, raise the minimum supply temp from 120F to 130F.

See what it does with the new setting.

BTW, you WANT the boiler to run forever and never shutdown on limit. That is the benefit of a mod-con. It never lets the boiler and the system cool down if setup properly.

Actually, I had the pump set on the highest speed in the beginning and it was worst in terms of the room temperature. The lowest speed I got about 62-64F in the room but on the highest it was struggling to even get to 60F. That was why I thought lower speed would allow more heat to dissipate.

The system right now is not experiencing any temp limit (like my other one in the other post) and it is firing the entire time. Will upping the minimum supply temperature actually make any difference since it's already running at 188-190F now? I will still try it to make the heat curve more aggressive.

smithfan

Hatterasguy said:

smithfan said:

Also, consider lowering your min outdoor temp as well.

That will lower the curve..........exactly what he doesn't need.

Right now he should get 190F at 20F ambient. If you lower the min outdoor to 0F, you'll get something around 170F at 20F. ambient.

good catch, I meant to say raise the min outdoor temp.

petec88

@Gordy i might have misspoken about the footage. I just went to remeasure it and it's actually more around 100'. Sorry for the confusion and misinformation there.

petec88

@smithfan Yes thank you. I can raise the minimum outdoor temperature (perhaps to 32F?) so it's running at 100% all the time. But the temperature in Boston was around 20F and under this past weekend and it was still having trouble. But I am sure it will help when the temperature is in the low to mid 30s. It's more of those cold nights when temp is in the teens or single digits that it's struggling.

smithfan

petec88 said:

@smithfan Yes thank you. I can raise the minimum outdoor temperature (perhaps to 32F?) so it's running at 100% all the time. But the temperature in Boston was around 20F and under this past weekend and it was still having trouble. But I am sure it will help when the temperature is in the low to mid 30s. It's more of those cold nights when temp is in the teens or single digits that it's struggling.

So the boiler water is getting hot! Why not put your hand on the baseboard and see if the baseboard is also getting hot, Are sections of baseboard hot and others sections not? At those water temps those baseboards should be VERY hot, if they are not, have you considered you may be air locked?

petec88

Hatterasguy said:

Is the actual SWT at 188-190 at the moment?

The reset curve definitely shows 190F at 20F ambient.

If the boiler won't satisfy the 'stat at that supply water temperature, you have a serious flow problem. 200' is quite a distance. What pump do you have?

Yes the actual SWT is 188-190F at the moment. I'm mistaken as it's more 100' rather than 200'. As for the flow problem, I was trying to play with the pump speed to compensate for it. The pump I have is a Grundfos ups 15-58 fc pump. I had it set on high speed originally but that was even worst in terms of room temperature.

smithfan said:

So the boiler water is getting hot! Why not put your hand on the baseboard and see if the baseboard is also getting hot, Are sections of baseboard hot and others sections not? At those water temps those baseboards should be VERY hot, if they are not, have you considered you may be air locked?

The baseboard is pretty warm when I put my hand on it. I will try to put a thermostat on the grill to measure the actual temp. what do you mean by air locked? There was air in the system at the beginning of the winter and I purged the air by draining and flushing the system so it should be good now (this was in December). I have not tried to open the drain valve to see if air got back into the system.

smithfan

Just to make sure we're on the same page here. You have baseboard and not radiators correct? By air locked, I mean you enough air in the pipes that they can't heat properly. At those boiler temps, the baseboard should be hot to the touch, not warm. It would be nice if you included some pics of the boiler and surrounding piping.

Zman

You need to stop chasing your tail on this one and provide the info needed to diagnose.
1. How is the boiler piped? A picture of the installation is mandatory at this point.
2. How many feet of actual baseboard fins do you really have? Not the lengths of the pipes or covers, just the parts with fins.
3. What is the difference between the supply and return temp for that loop? (buy a little IR gun for $50 put tape on the pipes and measure it)
4. A model number for the pump.
5. The approx total length of pipe in that loop.
There will likely be a few questions after that but these are the minimum to figure out what is going on.

NY_Rob

It would probably be a perfect fit if you could just use one of the TT125's for all three floors.

Seems like the OP owns the two family structure...
Was the home ever used with a single boiler setup?

petec88

Apologies for the late response. Please find the answer to the question you posed

1.) Boiler piped with a primary/secondary loop. The primary loop goes back to the return and the secondary loop goes into the house. The secondary loop branches into two loops, one is a short loop going to one radiator in the bathroom (about 5' of radiator fins) while the other loop goes throughout the house and has about 100' of radiator fins. Please see photo attached.
2.) It is 100' of radiator fins
3.) The beginning of the loop is about 144F and the end of the loop is about 130F
4.) Grundfos UPS 15-58fc
5.) Approximately 150' of piping

Thanks for all your help.

Gordy

That's not P/S piping.

petec88

Gordy said:

That's not P/S piping.

if that's not P/S piping, what's the purpose of running the small loop pipe back to the return from the supply? How would a P/S piping look like? Is it because the T in installed incorrectly?

FYI...the right side of that pipe coming down from the supply leads to a water spigot and not connected to anything else.

Gordy

From the manual

kcopp

As I thought... not piped right.
They Actually make it Super easy as you can get a kit that has all on the P/S piping done.
Most suppliers add it in to the boiler price and provide it for "no charge".

http://www.supplyhouse.com/Triangle-Tube-CCRKIT202-Timesaver-Primary-Secondary-Piping-Manifold-1-25-SWT-for-Challenger-Solo-Boilers

kcopp

Here is an example...

Gordy

The reason for P/S piping is so the boiler can have the flow rate it needs, and the system flow can be what it needs. The two different flow rates do not conflict with each other.

The challenger has a higher head HX than a fire tube. So trying to pump direct through the boiler, and system creates more pressure drop. The higher the flow the worse it gets. I suspect this is your problem in both threads.