TT Prestige Solo 110 Re-Piped P/S - Improving Operation

JustinS

I've finally had my Prestige Solo 110 re-piped so that it's Primary/Secondary - now that this is done, I'd like to discuss how to improve upon its operation but before I get into that, I'd like to take a moment to thank everyone here for their help and patience as I tried to understand all of this stuff...

I've attached a couple of pictures of the new P/S piping...

One thing that the new installer and I noticed is that the delta-T between the supply and return is pretty small (seems to range from 2 to 8 degrees, depending on # of zones calling)... we decided to measure the delta-T (using a UEI DT302 - Apollo II Digital Temperature Logger with clamps on the piping) of each zone and found that it was similarly small... we also measured the delta-T between the common supply (before Exp Tank) and the common return - it was also pretty small...

I have the following radiation (Haydon Heat-Base 750, I believe) on my three zones for my 2200 sq ft home...

1st floor - ~39 ft plus kickspace heater => ~26600 BTU/hr
Master BD - ~25 ft for ~45% of upstairs => ~14500 BTU/hr
2nd floor balance - ~25ft for ~55% of upstairs => ~14500 BTU/hr

Each of my zones is using a Taco 0015 set to LO and the boiler's internal circulator is set to 2... my next step with the new installer is to have him do a heat loss but for now, based on the below, I suspect that my flow rates are too high...

1st Floor - In Progress
2nd Floor - 246 ft equivalent => ~4.4 gpm @ ~9.75 ft of head loss on LO => ~2.9 ft/sec (0.785" ID)
Master - 213 ft equivalent => ~4.8 gpm @ ~9.8 ft of head loss on LO => ~3.15 ft/sec (0.785" ID)

Thoughts? Thanks again!

SWEI

Smaller pumps?

ced48

I don't understand how you get that kind of head with such small amounts of baseboard?

Gordy

That's like 00 buckshot for pigeons. No wonder the dt is so narrow.

Paul48

Show us how you came up with those heads.

JustinS

I used the equation HL = k x c x L x (f1.75), where k = 0.00295 and c = 1.0 for 140F water

Please see attached for a screenshot of my Excel spreadsheet - it has my 0015 pump curve on LO (and two others I'm looking at) plus the system curve for my two upstairs zones @ 213 and 246 equivalent feet...

I then saw where each crosses the 0015 pump curve... did I do something wrong?

unclejohn

That boiler only turns down to 30K. You need a buffer tank.

JustinS

unclejohn said:

That boiler only turns down to 30K. You need a buffer tank.

Yeah, that's on highly likely to have to do list...

BTW, not sure if this means anything but just now while the house was warming up from nighttime setback (4 deg), the boiler was reporting approximately 8-10 degrees delta-T... this occurred throughout its warmup and mostly once it was maintaining setpoint, although the delta-T did tighten a bit to 6-8 degrees or so...

SWEI

Was the boiler firing at 100% during that recovery?

You should be looking at smaller pumps.

unclejohn

Your delta t will be low when your putting more heat into the water then your getting rid of to the house. As the house warms the delta t will close. More people on the train then are getting off.

JustinS

SWEI said:

Was the boiler firing at 100% during that recovery?

You should be looking at smaller pumps.

It may have gone to 100% briefly but as I recall, it was mostly around 30%...

Regarding smaller pumps, any recommendations? I believe folks have recommendation Taco 007s for baseboard applications but I think that there are two versions (one single speed and one multiple speed)? I have both the curve for the 007 single speed and the 007 multiple on LO in my spreadsheet above - seems like the 007 multiple speed on LO would be better since it would lower flow? Or should I be considering an even smaller pump?

JustinS

ced48 said:

I don't understand how you get that kind of head with such small amounts of baseboard?

Did my spreadsheet look right? Are you thinking that the head was too high?

SWEI

JustinS said:

SWEI said:

Was the boiler firing at 100% during that recovery?

It may have gone to 100% briefly but as I recall, it was mostly around 30%...

You want to shoot for maximum useable ΔT at full fire.

You should be looking at smaller pumps.

Regarding smaller pumps, any recommendations? I believe folks have recommendation Taco 007s for baseboard applications but I think that there are two versions (one single speed and one multiple speed)? I have both the curve for the 007 single speed and the 007 multiple on LO in my spreadsheet above - seems like the 007 multiple speed on LO would be better since it would lower flow? Or should I be considering an even smaller pump?

Assuming your curves are correct, you need a tad over 4' of head at 3 GPM. That 007 on low will work, but I'd lean towards something like the new VR1816 instead. Probably 75% less power consumption at low speeds, and a full range of control.

ced48

JustinS said:

ced48 said:

I don't understand how you get that kind of head with such small amounts of baseboard?

Did my spreadsheet look right? Are you thinking that the head was too high?

All I know is that even with a lot of piping, I would expect to see head well under what you are coming up with, something under 4-. maybe less. I would think that a Taco 005 might even be to large, a 003 might be enough pump.

The new Taco Viridian 1816 would be the perfect pump, she is a sweetheart.

wmtandson

use the bumble bee

Eastman

@SWEI What controls the modulation rate on these TT units? I don't see a differential high/low limit parameter in the manual. Does it really fire to the ODR target and then cut out? How does it know when to cut back in?

SWEI

Fairly basic PID control of supply water temp to setpoint. ODR manages setpoint, DHW calls override that.

Eastman

If the demand is below min mod, how does it manage on/off cycling?

Harvey Ramer

TT handles that with a minimum off time adjustable setting.
HTP handles it with an adjustable differential setting. They both have PRO's and Cons. It is best to be able to remove the Btu's from the boiler as fast as it produces them.

Depending on system configuration, sometimes you have no other choice but to add a buffer tank. Kind of sucks but "it is what it is" .

It is always important to adhere to the manufacturer's minimum flow rates through the boiler. I have personally seen cracked TT hx's because somebody had to small of a pump on the boiler. It happens, it's not just theory.

JustinS

ced48 said:

All I know is that even with a lot of piping, I would expect to see head well under what you are coming up with, something under 4-. maybe less. I would think that a Taco 005 might even be to large, a 003 might be enough pump.

I don't know - I looked at my calculations again, comparing them to the sample calcs in http://www.taco-hvac.com/uploads/FileLibrary/SelectingCirculators.pdf and I get the same...

Maybe I'm not getting it but looking at the 0015 pump curve, it would produce a head of ~4 ft around 10 gpm, right? I'd need about 25 ft of length to get that kind of head loss and flow on 3/4" piping, right?

Am I misunderstanding something?

ced48 said:

The new Taco Viridian 1816 would be the perfect pump, she is a sweetheart.

What mode would you run the Viridian in?

JustinS

wmtandson said:

use the bumble bee

So you would use a Bumblebee to replace each zone circulator and maintain a specific delta-T across each zone?

JustinS

JustinS said:

wmtandson said:

use the bumble bee

So you would use a Bumblebee to replace each zone circulator and maintain a specific delta-T across each zone?

As I understand it, the flow rate through 3/4" piping should remain above 3GPM or so in order to maintain a minimum velocity of 2 fps, right?

If this is the case, the highest delta-T that I can expect to see on my smaller zones with 15k BTU/hr @ 180F would be 10F, right? This is based on 15k BTU/hr = 3GPM * 500 * 10F...

As the boiler uses cooler water as the outside warms, my baseboard output and delta-T will drop, assuming my flow remains at 3GPM... if I were to use the Bumblebee to maintain a specific delta-T, wouldn't it cause the flow to drop below 3GPM and 2fps in order to maintain the delta-T?

Seems like this wouldn't be something I'd want to do?

Snowmelt

Justin the 0015 is way to big your not looking at the chart correctly. Your head is small. Try the 007 pump. The best pump would be a variable speed pump like the bumble bee.
It's going to sound crazy but your over thinking the job. Also you want to size the pipe for the job or should I say the job should dictate the pipe size not the pipe size dictate the size of pipe.

JustinS

Snowmelt said:

Justin the 0015 is way to big your not looking at the chart correctly. Your head is small. Try the 007 pump. The best pump would be a variable speed pump like the bumble bee.
It's going to sound crazy but your over thinking the job. Also you want to size the pipe for the job or should I say the job should dictate the pipe size not the pipe size dictate the size of pipe.

Could you clarify how I am not looking at the chart correctly? By chart, do you mean the pump curve or the baseboard heat output?

If something like the bumblebee would be best, are you saying that I am wrong about my concerns with dropping below 3GPM?

Definitely understand that the job should dictate the pipe size but unfortunately, that ship has sailed as the pipe is already installed... out of curiosity, though - would 1/2" pipe been a more appropriate choice for my smaller zones given their low heat output? Or does a delta-T of 20 not really matter that much?