First Winter with TT Solo 110

FPEngineer

Double checked the wiring

Everything appears to be correct.  I took some pictures just to make sure, but the DHW is definitely connected to the correct spot.  Nothing is wired to the Aux Boiler terminal.



One CH zone was just running and I have the valve on the DHWR shut.  Both the DHWS&R lines were cool to the touch.  As soon as I opened the valve, both lines got hot.  I will pay attention next time which direction the heat comes from.  With the checks in the circulator and the return line, I would expect it to flow from supply to return.

Gordan

No idea

Beyond what I've already suggested. The boiler and system circs shouldn't be able to circulate through this, since both the DHWR and DHWS are on the inlet side of the boiler circ and the system circ is off of closely spaced tees. So... check voltage/disconnect the DHW circ and see if it still happens. See if it happens with all circs off and the valves open. If the former, something is wonky with your prestige since it's turning on the DHW circ when it shouldn't. If the latter, you've got ghost flow and need to check your checks.

FPEngineer

Flow problem through indirect solved!!!

The installer left the thumbscrews on the DHWR check and the CHR check both open!!!



I closed them both to allow the flow check to operate and now I don't have reverse flow of return water cooling off my DHW tank!

BostonGTR

Success

Good job finally locating the problem!

FPEngineer

Hoping to now solve the issue with the return water temp

I'm leaning toward zone valves with the entire system running off the boiler circulator.  It seems to me that there is going to be mixing between the supply and return at the closely spaced tees unless the flow is perfectly balanced between the zone circulators and the boiler circulator.  When only 1 zone is running, the difference in flow in the zone and flow in the boiler is so large that the return water is mostly supply being recirculated back through the closely spaced tees.  The situation improves with multiple zones running, however, I'd prefer to keep each level of the house on separate zones.



What zone valves does everyone recommend if i make the change?

SWEI

changing to zone valves

I'd suggest replacing the internal pump with a pressure-dependent circulator (e.g. WIlo Stratos or Grundfos Alpha.)  Once you do this, you need to change the Demand Type setting from Switch & Setpoint to Constant & Outdoor Reset.

CMadatMe

Bumble Bee

I'd more inclined to use a Delta-T pump over "P"

In this case. Control delta you control flow rate. Can also

do set point with it.

FPEngineer

Thanks for all the help!

According to the TT manual, the flowrate through the heat exchanger needs to be a minimum of 5 GPM.  I have the internal Grundfos circulator set to LO. With 1 CH zone running I calculated the flowrate in the zone to be 1.4 GPM based on the delta T I measured across the zone and the heat load. I am struggling with figuring our a way to balance the flows in the zones to the flow in the boiler.  The flow in the zones is dependent on the # of zones running so this is a dynamic problem.  I notice a much longer delta T at the boiler when multiple zones are running. 



Would it make sense to install a buffer tank on this system?  The zones and the boiler would draw from the tank so the flows would not have to balance.

CMadatMe

Yes

Of course it is..

SWEI

Bumble Bee

I know it's a perfect fit for a boiler circ if he uses a buffer tank as a hydraulic separator.  Again, wish they offered more size options on the BumbleBee.



Will the ∆T algorithm respond properly to zones turning on and off?  I can envision a few scenarios where it might mis-read the conditions.  ∆P will change flow based on zone valves and not fight the ORC.

CMadatMe

SWEI

I've had 2 Beta's running for 2 years piped along with Alphas so we could run each one at periodic times to compare. The Bee kicks its ***. Not only in its ability to move more GPM but less electrical usage as well. Yes it will react to the zones opening and closing.

Gordan

How did you measure for the comparison?

Did you go by what the circs were reporting, or did you have external measurements of some sort? I ask because, judging by the specs for both, the Alpha should have a slight edge in terms of max head and max flow, with little difference in power usage. It's always good to get these first hand reports, especially as the circ is not widely available yet. I like that it has a more granular GPM gauge, as long as it's accurate!

SWEI

pump curves

Are significant here, though the manufacturers don't go out of their way to mention it.  Running an ECM circ in the bottom 30% of its range most of the time will result in very low hydraulic efficiency.  No matter how efficient the motor is, if the pump can only transfer 30% of that energy into pressure, annual energy use will be higher.



As soon as Taco offers some hydraulic options (003, 0010, etc.) for the BumbleBee, I'll start putting them on the majority of boilers.  Wilo offers a range of Stratos hydraulics, but nothing anywhere near as flat as a 0010 -- put the small one on a 399 and it never gets off the bottom of its curve.  That's ignoring completely the cost of actually making it work on ∆T (pump module, two sensors, and a controller.)  Same story for the Magna.

Gordan

Can you elaborate?

I'm not clear on how hydraulic efficiency relates to where on the curve you are, especially with ECM circs that vary their electrical consumption in order to meet lesser loads. Got any good links that explain this? Thanks in advance...

SWEI

hydraulic efficiency

Every pump has an efficiency curve as well as a pump curve.  They're not easily available for smaller circs, but if you look at something larger like http://www.taco-hvac.com/uploads/FileLibrary/KV,KS3007_1160.pdf you can see that there is a range near the middle of the hump in the curve where the pump works best.  Even with a VFD or an ECM, size matters!  Siggy covers this pretty well in MHH.

NRT_Rob

I have no idea

what chris is on about here. those are closely spaced tees. they do not have to hit the pipe from the same axis. the elbow a few inches away reduces their effectiveness, but the pressure drop between the two tees is practically zero. You are basically hydraulically separated and you do not have any piping problems i can see here.



even the expansion tank is not a problem. as long as you do not have a significant pressure drop between the suction of the pump and the expansion tank you are "pumping away". Such as in this case.



you are overpumped. this is why zone by pump systems are not as efficient as zone valve systems. end of story.

NRT_Rob

hold your horses

if you are going to direct pump this boiler to the zones, you better be sure your smallest zone will take at least 2 GPM, which is the bare minimum TT wants to see going through this boiler to avoid rampant short cycling. 30 dt on minimum fire.



usually you need a bypass. modulating pumps, not a good idea in this case, unless you are primary/secondary OR very sure your smallest zone has adequate minimum flow.

SWEI

good point

I'm used to modulating zone valves which we can use to enforce minimum flows.

CMadatMe

Based on Each

Pumps own readings. They are hooked into a hydro air zone.

Gordan

So...

Looking at the alpha, the fixed speed 3 curve is concave and not convex (although the other two are slightly convex.) What would one conclude on the basis of that?



I checked out what MHH had to say on the issue but there seems to be little in-depth discussion of variable speed ECM circs. I mean, hydraulic efficiency is what it is, but is it possible that with variable output wire-to-water efficiency could be good enough at lower outputs to make up for it?

SWEI

curves

Lowering speed with VFD generally shifts a pump curve towards the origin. The Alpha curves demonstrate that the relationship is a bit more complex than that, but starting in the sweet spot of the pump will improve things. A curve showing RPM versus hydraulic efficiency at differing system heads would likely prove interesting.