Triangle Tube Challenger Solo CC50s boiler circulator

Voyager · November 2017

I have a Triangle Tube CC50s on order. I am contemplating which circulator to use in the boiler/primary loop of my primary/secondary design. The CC50s installation manual shows the Grundfos UPS15-58FC on speed 1 as being about the best fit to maintain around 30 degrees delta-T. However, I am interested in trying a delta-T circulator so I can vary the boiler delta-T to experiment a little with the operation of the boiler.

Taco provides a nice pump curve chart for the VT2218 showing both maximum and minimum curves. Unfortunately, this pump is rather large for the CC50s and I am looking at the 007 variable speed circulator instead. I have been unable to find a similar pump curve for this circulator.

The curve for the fixed speed 007 is readily available and the Taco installation documentation says to select the VDT as follows: "The circulator should be sized, using conventional sizing practices, based on the required head and flow for the system or zone on which the circulator is being installed." However, the head and flow requirements for the CC50s are well below the fixed speed 007 pump curve so I am wondering if anyone knows if the delta-T variable speed 007 will reliably run at say 5 gpm @ 4 ft of head, which seems to be a good operating point for this small boiler (delta T of about 30 degrees). Although, I do suspect the chart as it shows the same curve for both the CC50 and CC85 and the GPM vs delta-T values do not match my calculations using the universal hydronics formula, which suggests a flow closer to 3 GPM for the small 40,000 output boiler.

I submitted this question directly to Taco support, but the reply I got made no sense to me. The recommendation was to use the 007e, but this is not a delta-T circulator and its delta-P controlled curve is again well above what this small boiler needs.

Thoughts on using the 007 delta-T? Is it better to just keep it simple and go with the fixed speed Grundfos as listed in the Triangle Tube manual?

Leon82 · November 2017

The Delta pump will fight with the modulating gas valve unless you use p/s piping.

You can use the 1816 which is ecm and you can adjust the speed with a dial or run it n pressure mode

kcopp · November 2017

Nice Little boiler...
Don't over think this.
TT has a manifold that is supplied w/ the unit. Should be a 15-58.
You can play w/ the performance by adjusting the curve.

SeymourCates · November 2017

If you wish to use the VT2218 for the benefits that it offers in maintaining a fixed DT, don't be discouraged because of its size. Install a globe valve so you can throttle the loop and raise the head in the loop to enable the VT to perform in its operating range. Without the valve, it might overpump at the lowest speed and kill the DT. With the valve, you adjust it so that it needs to climb to speed 2 or higher to maintain the DT you desire. Under low load conditions, be careful that you don't end up with a flow rate below the minimum requirement for the boiler.

Voyager · November 2017

Leon82 said:
The Delta pump will fight with the modulating gas valve unless you use p/s piping.

You can use the 1816 which is ecm and you can adjust the speed with a dial or run it n pressure mode

Definitely using P/S.

Voyager · November 2017

kcopp said:
Nice Little boiler...
Don't over think this.
TT has a manifold that is supplied w/ the unit. Should be a 15-58.
You can play w/ the performance by adjusting the curve.

I admit I am "overthinking" it on purpose. This is my first hydronic design. I have always had forced air before, but this is in my 32x48 workshop and I wanted a warm slab to work on and don't plan to have AC. So in-slab hydronic looked like the way to go.

Also, I am retired after 32 years in the corporate engineering world and considering doing consulting HVAC engineering. This seemed like a good system to experiment with on things like delta T control, etc. My mistakes will hurt nobody but me and it is a fairly economical system so I can waste a little money and justify it on the educational value.

I wasn't sure if the near boiler manifold was still included. I read one place on the TT web site that said it was included with each Challenger, but then other places list the manifold as optional. I am waiting for the unit to arrive before buying the installation materials to see just what comes with it.

Voyager · November 2017

SeymourCates said:
If you wish to use the VT2218 for the benefits that it offers in maintaining a fixed DT, don't be discouraged because of its size. Install a globe valve so you can throttle the loop and raise the head in the loop to enable the VT to perform in its operating range. Without the valve, it might overpump at the lowest speed and kill the DT. With the valve, you adjust it so that it needs to climb to speed 2 or higher to maintain the DT you desire. Under low load conditions, be careful that you don't end up with a flow rate below the minimum requirement for the boiler.

Good thought. Part of my reasoning for using delta T, after watching many of the Taco university videos, was to ensure that the minimum 3 gpm was maintained or exceeded under full fire conditions. This boiler is almost perfectly sized according to my load calcs, so if the temp gets to the design conditions, this boiler should be running close to flat-out, assuming my assumptions for air infiltration and such are in the ballpark.

SeymourCates · November 2017

The setup will be perfect for maximum load conditions. The danger with the DT pump under very small loads is that it will likely reduce the flow rate below the minimum requirement for the boiler. If you set a DT of 20 and have a load of 13.5K BTUH, the flow rate through the boiler would be 1.35 GPM. You'd need to ask TT whether the boiler would accept that flow rate as it is not specified in the manual. Generally, the mod-cons have difficulty with low flow rates under conditions that are not steady state. The mass flow is too low for the control to effectively modulate. Check out the pressure loss curves for the CC-50. TT shows DT's between 4 and 8 (nothng higher) which indicates they desire high flow rates at the expense of efficiency.

If you can manage to get the VT2218 to perform on the primary loop, the efficiency improvement will be significant. Most typically use a relatively large pump with a resulting tiny DT, thereby putting the RWT much higher than desired for efficiency.

Voyager · November 2017

SeymourCates said:
The setup will be perfect for maximum load conditions. The danger with the DT pump under very small loads is that it will likely reduce the flow rate below the minimum requirement for the boiler. If you set a DT of 20 and have a load of 13.5K BTUH, the flow rate through the boiler would be 1.35 GPM. You'd need to ask TT whether the boiler would accept that flow rate as it is not specified in the manual. Generally, the mod-cons have difficulty with low flow rates under conditions that are not steady state. The mass flow is too low for the control to effectively modulate. Check out the pressure loss curves for the CC-50. TT shows DT's between 4 and 8 (nothng higher) which indicates they desire high flow rates at the expense of efficiency.

If you can manage to get the VT2218 to perform on the primary loop, the efficiency improvement will be significant. Most typically use a relatively large pump with a resulting tiny DT, thereby putting the RWT much higher than desired for efficiency.

The TT manual leaves a little to be desired. It appears to me that the boiler flow vs head vs delta T graph is for the CC85s with no real adjustment for the smaller 50s. Even though the graph says both 50 & 85, there is no way the delta T values can be the same for both at a given flow rate so I think data is missing. As you said, the graph shows flows down to 4 gpm, which matches the note below for minimum flow at full fire for the 85. However, the noted minimum 3 gpm for the 50 at full fire isn't even on the graph.

I also did not see an absolute minimum flow, just the full fire minimum. I assumed the flow could be lower at the full turn-down, but that may be a risky assumption as you say.

I should have the unit in a couple weeks, so I will see if the included documentation is more current than the web site files. If not, I will give TT a call.

Voyager · November 2017

kcopp said:
Nice Little boiler...
Don't over think this.
TT has a manifold that is supplied w/ the unit. Should be a 15-58.
You can play w/ the performance by adjusting the curve.

My 50s arrived today. It did not come with the manifold. That is now apparently sold as an optional kit.

kcopp · November 2017

IF you bought it from a plumbing supplyhouse it would have come w/ the manifold kit. If you got it from dot-com place online I'm sure it would be an extra....

Voyager · November 2017

kcopp said:
IF you bought it from a plumbing supplyhouse it would have come w/ the manifold kit. If you got it from dot-com place online I'm sure it would be an extra....

Yes, purchased from supplyhouse.com. I plan to order the manifold, but they first have to confirm it works with the 50 as TT literature only mentions the 85. From reading the TT literature, it appears the 50 was introduced more recently and the documentation has yet to catch up. The fitting sizes and spacing look identical so no reason it shouldn't work, but I want to be sure before ordering as does Supplyhouse before selling. I also may try to get them to swap the 15-58 for an Alpha save operating cost over time and have the flow rate readout.

One reason I believe the literature is not yet fully updated is the pressure loss curve charts which are the same for the 50 and 85, which makes sense as the heat exchanger appears to be the same in both units. However, the delta T on the flow axis is also the same and that can't be. At the same flow, the delta T can't be the same for a 50,000 BTUH unit as for an 85,000. And the chart ends at 4 GPM, even though the footnote states that 3 GPM is the minimum flow for the 50 rather than 4 as for the 85.

It is a nice looking unit and very light. It shipped freight, but even UPS could have handled it. I told the trucker I would meet him with my hand truck and pickup so would could roll it off his semi into my truck. He basically said "why don't I just hand it to you." Sure enough, it is easily handled by one man. I don't know why the shipping weight was listed as 130 lbs as I am not sure it weighs 80. I took it out of my pickup as easily as a bag of cement.

Voyager · November 2017

Yes, Supplyhouse.com. I will order the manifold, but Supplyhouse needs to first confirm with TT as the TT literature does not list the 50 only the 85 and larger.

It appears much of the documentation has yet to be fully updated for the small unit.

It is a nice looking unit and very light. It shipped freight, but a UPS driver could have easily handled it. When the trucker called, I offered to meet him with my pickup and hand truck to roll it off his truck into mine as the shipping weight was listed as 130 lbs. He basically said, "why don't I just hand it to you." Sure enough, it was easily handled by one man. I took it out of my pickup as easily as a bag of cement. I don't think it weighs even 80 lbs. Hopefully, it isn't too light to be durable. It does look like a nice design with the water path completely in copper so little worry about needing aluminum safe antifreeze, if I decide to use antifreeze and I am leaning against it.

I am looking forward to installing it. Looks like a fun little project.

Voyager · November 2017

kcopp said:
IF you bought it from a plumbing supplyhouse it would have come w/ the manifold kit. If you got it from dot-com place online I'm sure it would be an extra....

Yes, purchased from supplyhouse.com. I plan to order the manifold, but they first have to confirm it works with the 50 as TT literature only mentions the 85. From reading the TT literature, it appears the 50 was introduced more recently and the documentation has yet to catch up. The fitting sizes and spacing look identical so no reason it shouldn't work, but I want to be sure before ordering as does Supplyhouse before selling. I also may try to get them to swap the 15-58 for an Alpha save operating cost over time and have the flow rate readout.

One reason I believe the literature is not yet fully updated is the pressure loss curve charts which are the same for the 50 and 85, which makes sense as the heat exchanger appears to be the same in both units. However, the delta T on the flow axis is also the same and that can't be. At the same flow, the delta T can't be the same for a 50,000 BTUH unit as for an 85,000. And the chart ends at 4 GPM, even though the footnote states that 3 GPM is the minimum flow for the 50 rather than 4 as for the 85.

It is a nice looking unit and very light. It shipped freight, but even UPS could have handled it. I told the trucker I would meet him with my hand truck and pickup so would could roll it off his semi into my truck. He basically said "why don't I just hand it to you." Sure enough, it is easily handled by one man. I don't know why the shipping weight was listed as 130 lbs as I am not sure it weighs 80. I took it out of my pickup as easily as a bag of cement.

Voyager · October 2018

I finally got back to this project. The installation is nearly complete, but I am wondering how best to connect the flexible condensate hose that came with the condensate trap to rigid PVC. I have yet to find a fitting that seems designed for this. I can use a barbed fitting with a clamp, but that seems a little cheesy. Is anyone aware of an adapter specifically made to connect this black flexible hose to rigid PVC?

DZoro · October 2018

My pet pev with TT , drain hose. I put their tube inside a 3/4" pvc coupling and hard pipe from there.

Voyager · October 2018

I was leaning that direction, but it seemed a little kludgy. I thought there might be some special connector for that odd-sized flexible hose.

I wish they had forgone the cheesy plastic trap and just provided a 3/4” threaded connection. It isn’t hard to make a trap in the drain...

DZoro · October 2018

The Lochinvar has the same trap system, but it comes with a pvc adapter...….

kcopp · October 2018

The condensate drain should not connected tightly. Loose in the top of a trap is fine. The downside of a really tight connection is that if the drain plugs downstream then you risk having the condensate back up into the boiler. JMO.

Voyager · October 2018

I used a 3/4” coupling as suggested and finished the condensate plumbing and vent installation and got the boiler into full operation yesterday. It took a while for all of the air to get out of the 1300+ feet of 3/4” pex, but after a while the Taco 0011 quieted down.

Now on to getting used to in-slab hydronic heat. My experience is entirely with forced air so this will be another learning opportunity. It was 34 F outside most of yesterday and the building was 49 inside when I fired up the boiler for the first time (not counting a couple of short test fires to ensure it worked). It ran flat out for 7 hours to raise the air temp from 49 to the initial 55 setpoint. The boiler temp (as displayed by the boiler) never got above about 96 and the analog gauges on the boiler supply and return lines stayed around 82 and 62, respectively. The boiler finally shut down the first time around 9:30. I didn’t go out in the cold rain again to see what the temps were at that time, probably a little higher than 82/62. Looks like the loops are too long to get to a 10 degree delta T as I was hoping for.

I checked the temp this morning and it is 57 so there was a little overshoot. I am using a Honeywell RTH6580WF thermostat so I can monitor the temps remotely. I am curious to see just how effective their “Smart Response Technology” will be in learning the characteristics of this very high mass system. It appears the boiler will need to shut down a degree or two before reaching setpoint and fire very quickly when the temp begins to drop. As I have learned more, I am thinking I probably should have bought a thermostat with a slab sensor, but time will tell. This is only heating a large workshop so a couple degrees of over or undershoot isn’t nearly as critical as in someone’s home.

This has been a fun learning experience for a retired engineer. I am curious now to get some really cold weather and see just how accurate my heat loss calculations are. The 46/40,000 BTU (depending on which rating you believe) boiler seems small, but the heat loss calcs said that ~38,000 was sufficient. It is always the assumptions that get you so I hope mine weren’t too far off.

kcopp · October 2018

To help the overshoot you could drop you water temps a bit to help that. 96F seems a bit high for a slab supply temp w/ an outside temp of 34F... You are using the outdoor reset feature?

Voyager · October 2018

kcopp said:
To help the overshoot you could drop you water temps a bit to help that. 96F seems a bit high for a slab supply temp w/ an outside temp of 34F... You are using the outdoor reset feature?

The supply temp to the pex manifold was 82. The boiler displayed a temp in the low 90s, but the water exiting the boiler was low 80s. I am not sure where inside the boiler it is measuring the temp that it displays digitally. I am using a Grundfos Alpha2 15-55F primary loop circulator and leaving it in the AutoAdapt mode, it was delivering 8-9 gpm so I was somewhat surprised at the 14 degree difference between the digital temp displayed at the two mechanical gauges, one on the outlet pipe from the boiler and the other on the inlet to the pex manifold. They both agreed and stayed in the 80-82 range.

I have not yet installed the outside temp sensor. I wanted to see how the boiler operated without it, but that will be next on the list as it sounds like it is needed. I wasn’t sure it would be needed as the boiler never put out water above about 82 degrees even running flat out for several hours. My thought was that most of the year, the boiler is probably small enough that it will seldom short cycle, but I can see where higher outside temps might be a bigger issue. I likely will only keep the workshop at 60 degrees and will just turn off the heat when the outside temps approach that value.

However, I am interested in playing around with outdoor reset so probably will install that sensor soon. Just wasn’t sure if I needed to drill another hole through the wall.

kcopp · October 2018

With that modulating boiler and the slab radiant floor I wouldn't consider not using the sensor. Just remember north side.

DZoro · October 2018

Definitely use the outdoor sensor. Remember to allow 2-3 days to go through the radiant warm ups. 1st day overshoot, 2nd day recovery smaller overshoot, 3 day should begin more consistent floor temps. Need to be patient with the slab, when it has fully settled in then you can start to dial it in better. ODR will then help with some of the overshooting, slab/air thermostat set at a constant temp, with work wonders for your system

Voyager · October 2018

Thanks for the advice. Getting to the north wall is tricky, but not impossible. I went with the Honeywell t-stat as wifi was more important to me than slab temp as I want to be able to remotely heat up the workshop when I plan to use it and leave it cooler the rest of the time. I did not find any thermostats that had all three features: wifi, air temp and slab temp. Are there t-stats out there that I missed?

kcopp · October 2018

Slabs are not easy to heat up and cool like a forced air system
You will need LOTS of ramp up time.
Not sure what your schedule is like but traditionally w/ a radiant floor system and the outdoor sensor its "set it and forget it"... that goes Double for a Slab.
If you want the wifi monitor fine but playing the up and down set up is not recommended.

Voyager · October 2018

Yes, I understand. I am talking about working for a few days at a time and then not for several days. I travel a fair bit and tend to work in bursts and then be away for a week or so. With wifi, I can initiate heat a day before I need it so it is ready.

Voyager · November 2018

This will likely (hopefully) be my last post here, unless there is trouble with the Challenger at some point. I wanted to post a few final thoughts on this boiler.

I am pretty happy thus far with the CC50s. I have yet to have any real cold weather (27 F is the coldest to date) to test the boiler and my heat loss calculations, but so far it appears the boiler is well sized for my 32’x48’ workshop. It is running only a few hours a day to keep the shop at 60 F. I suspect that at 0 F, the design temp I used, it will probably have to run nearly flat-out, but then that is how it was designed. I used 68 F as the indoor design temp, so the boiler should be able to easily maintain 60 F when it is 0 F outside.

The installation of the boiler was straightforward. I really have only two complaints about the boiler.

1. I bought the concentric vent kit from TT and planned to just go straight through the wall on which the boiler was mounted. It turns out this was not possible as the vent 90 elbow would hit the plumbing for the pressure relief valve on top of the boiler (I used the fittings that came with the boiler installed per the diagram in the installation manual). When I contacted TT, I was told that maybe I could change the T&P valve plumbing and use an elbow to move it to the side. If this was required to use the vent kit, then TT should have showed this in their T&P plumbing diagram. I ended up buying a concentric pipe extension to raise the vent elbow enough to clear the plumbing. This pipe added $100 to the installation cost.

2. TT needs to hire an electrical engineer. The terminal block for the high voltage connections is hard to get to and barely large enough to hold 14 gauge wire. They should use larger and higher quality terminal blocks for the high voltage connections and locate them such that more room is available to make the connections. The low voltage connections use the same style terminal block and it worked fine for the smaller gauge wire needed for low voltage and the terminals are on the slide and tip-out shelf that allows easier access to make the connections.

Other than these two design flaws, the boiler seems to be well designed and well made and it came up and has operated flawlessly thus far. I would recommend it based on my experience to date.

Triangle Tube Challenger Solo CC50s boiler circulator

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