Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.
dP Bypass Valve with a Delta T pump?
Options
ldipierro
Member Posts: 10
Hello everyone. I am in the process of installing a new hydronic heating system in my home and have a question that I cannot find any specific info for online. I have already installed the boiler (mod con), primary loop, and a Caleffi SEP4 separator so that I could run the boiler for domestic hot water. I am now working on the secondary side throughout this summer. Later today I'll post a photo of the install so far. FYI I am a boiler technician and HVAC contractor but my area of expertise is mostly large industrial steam boilers and control systems. I am not a residential hydronic expert. On to my question:
The secondary loop I'm installing off of the separator is 1.25" pipe and will have 4 zone valves (Honeywells) with a single Taco 00e delta T circulator. My question is, is it necessary or would it be a good idea for me to pipe in a differential pressure bypass valve? I understand with a dP pump that it isn't necessary, but I would imagine a dT pump takes a while to ramp down when zones close since it is relying on temperature rather than pressure. I'm thinking the dP bypass might crack open for a short period of time immediately after zones close. But then again I don't know much about how those dT circs actually work, so maybe it just isn't necessary. Any feedback would be much appreciated. Thanks!
The secondary loop I'm installing off of the separator is 1.25" pipe and will have 4 zone valves (Honeywells) with a single Taco 00e delta T circulator. My question is, is it necessary or would it be a good idea for me to pipe in a differential pressure bypass valve? I understand with a dP pump that it isn't necessary, but I would imagine a dT pump takes a while to ramp down when zones close since it is relying on temperature rather than pressure. I'm thinking the dP bypass might crack open for a short period of time immediately after zones close. But then again I don't know much about how those dT circs actually work, so maybe it just isn't necessary. Any feedback would be much appreciated. Thanks!
0
Comments
-
The bypass is not necessary. As long as you only operate the circulator when there is at least one call for heat from a zone valve. You may want to use a bypass if the circulator is in constant operation, but I don't see any practical reason for that type of operation. Any Zone Control device can be wired to operate the system, circulator by way of the end switches on the 4 wire zone valve or any valve with an end switch for that matter. Just select the proper sequence of operation by selecting the appropriate zone control panel.
I can offer you a wiring diagram (if needed) for an idea of how to do the residential hydronic thing.
Best of luck with your home project!
Reminds me of my grandmother not letting my grandfather near the home coal boiler. He was a Commercial Steam boiler operator for the Philadelphia School District. If he were to stoke the tiny home boiler, there were some very high temperature evenings. The big ones and the little ones are very different in many ways! It's all in what you are used to!Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
2 -
Thank you for the feedback. I appreciate the offer but wiring is one thing I know very well. And more than that, I bought a Taco 4 zone controller for my house, so the wiring is pretty much idiot proof. And no I have no intention of running the circulator unless there is a call for heat. I was more asking this question because I don't know how long it takes for a dT pump to change speed. I know the dP pumps change speed in a fraction of a second, but thats only because the system pressure changes instantaneously when zone valves close. Thats not the case with temperature, it has to take at least several seconds if not more for the return temperature to start changing and the pump to change speed in response.
2 -
Good to know you have the control you selected. Only offered in case you needed it, since I don't know your background. As far as the delay you speak of, that will be inconsequential in the small system you are installing in your home. I could say that if you operated the pump for up to a minute or so, with all the valves closed there would be no significant damage to the pump. As long as you don't make a habit of operating with all valves closed by design, I have operated small residential pumps with the valves closed by accident several times over my career and have never found the pump to fail as a result. ( I don't recommend that you test this on purpose) But I did correct the closed valve issue as soon as I realized that the pump was operating extra hot. Those pumps went on to operate properly for years after the error was corrected.ldipierro said:Thank you for the feedback. I appreciate the offer but wiring is one thing I know very well. And more than that, I bought a Taco 4 zone controller for my house, so the wiring is pretty much idiot proof. And no I have no intention of running the circulator unless there is a call for heat. I was more asking this question because I don't know how long it takes for a dT pump to change speed. I know the dP pumps change speed in a fraction of a second, but thats only because the system pressure changes instantaneously when zone valves close. Thats not the case with temperature, it has to take at least several seconds if not more for the return temperature to start changing and the pump to change speed in response.
So I still believe there is no need for the bypass.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
1 -
Damaging the pump was never a concern of mine. I was thinking more about the potential for noise with zones being over pumped (even if only for a brief period of time before the pump slows down).
1 -
I did not think about that... Noise... I have had experience with some systems with noise after a Honeywell zone valve closed. but that was because the valve was installed backwards and the flow helped smash the valve ball against the valve orifice. Can there be some velocity noise as one zone closes leaving only one one left to carry the load of the pump impeller?... It may be possible.
The pump curve will determine that. If the pump curve is relatively flat across the GPM range then the answer is... not so much... If the pump curve is steep Then maybe the bypass is not such a bad idea. What 00e pump are you considering?Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
0 -
The model # of the pump is VT2218.0
-
I wonder think bypassing the hot supply back to boiler and circ would confuse the delta t function? The circ needs to see actual return temperature to makes its speed decision
Are you sure delta P isn’t a better choice? What are the heat emitters?Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream2 -
Bob - I've watched a bunch of your classes on youtube before I started this project and learned a lot. Thanks for posting those online for everyone to watch and thanks for responding here!hot_rod said:I wonder think bypassing the hot supply back to boiler and circ would confuse the delta t function? The circ needs to see actual return temperature to makes its speed decision
Are you sure delta P isn’t a better choice? What are the heat emitters?
The initial circ that I chose was the Grundfos Alpha1 but I switched to the VT2218 because I thought the delta T would be the better choice for my system (even more efficient) in the long run. The issue I had with the dP pumps is they can only change their speed so much but they still operate on fixed curves. Two of my four zones are relatively small and only require 1-2 GPM at low head (about 3 feet at the most). The Taco 006 is actually the ideal circ for both of those zones combined. The issue with all the dP pumps on the market is that none of them can really come close to that in their "automatic" modes whereas the VT2218 is infinitely variable all the way down to a curve similar to the 006. Given how my home heating tends to operate in the winter I think the VT2218 will be much more efficient in the long run. Again, my only concern is that brief period of time immediately after zone valves close. I know it isn't a major concern and PROBABLY won't cause any problems. But then again, I'd much rather install a dP bypass now then have to add one in after the fact. Although you are probably correct in that a bypass line will mess up the dT functionality.
FYI three of my zones are slantfin baseboard (3/4") and one of them is old school radiant floor with 1/2" copper tube in a concrete slab. All of my baseboard is significantly oversized for the spaces so I do not need high temperature supply water to keep the spaces warm. And the radiant floor does not require a mixing valve at the supply temperatures I run at.
Here is my installation so far, again I only piped up the primary side so we could use it for domestic hot water. I'm working on the secondary side throughout the summer, a little at a time. I'm going to be draining it back down and putting in the secondary supply/return headers in the next week or two...
2 -
Nice installation work, I like the hydrosep mount😁
If you have a mix
of fin tube and radiant what delta T will you run? The fin tube could run 20 or even 30 delta if you are over radiated. Radiant enjoys low delta,15 even10.
If you don’t constrain the delta it will move around as the load changes. Wide delta when coming on or out of a cold condition, delivering higher btu/ hr 500x flow x delta
As the room warms the delta will tighten Going to 0 delta when it shuts off 😂 Both the fin and radiant will seek and find thermal equilibrium
How will a fixed delta add to comfort or efficiency? Show your math😉
Take a look at the new Alpha 15-58. It has a lot more adjustability to dial it in. Maybe watch a you tube that explains all the new functions
Which ever pump you use, I would not install a a PAB, it will defeat the ability of the pump to modulate properly IMO
PABs are parasitic devices, taking you away from your goal of max efficiency
You are running with one foot on the accelerator and one on the brake petal!Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream2 -
I got the secondary side of my system in and got my two smaller zones connected (still have my two larger zones disconnected, I need to run new PEX for those). Bob, I took your advise and scrapped the dP bypass valve, but I did want to at least try the dT pump. Last night I filled those two zones, purged them, and ran the system in heating mode. Everything worked but unfortunately I got one of the VT2218s with a known electronics issue. So now I'm going to pull it, return it, and go with a dP pump. I actually have a question: does anyone know if a Taco circ can be replaced with a Grundfos? I checked the specs on them and the Grundfos circs are 4mm longer flange-to flange. I'm not sure if thats "close enough" that I'll be able to get it in or not. If not I'll just stick with Taco, probably a 0018e.
0 -
I think there is a small variance between many of the small wet rotor circs. They should all interchange.Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
So I went ahead and purchased a Taco 0018e to keep the swap out simple, since the standard Grundfos circs have flanges that are 90 degrees offset to the way I have mine. However, now I find out that the Taco app that is used to connect to the 0018e via bluetooth isn't compatible with my phone because it was made for an older version of android. They literally do not have a current app made for android, even though it clearly says right on the website (and box, and manual, etc) that they do. So now I can't get the data with this pump either. I want the flow and head indications so I can get an idea of what is going on in my system and with the zones. I'm really starting to lose confidence in Taco, to be honest. I'm going to contact Taco support about this and if I don't get a response I'm returning this and getting a Grundfos Alpha.0
-
@ldipierro I'm sorry you are experiencing an issue with your 0018e. I've reached out to Product Management and they have sent your request to IT to see if there is in fact a compatibility issue with newer software Android phones. Once I hear back I will let you know.
As for the issue with your VT2218, please see below:
Here is what happened with the VT2218 circulator production.
There was a display issue, not a performance issue. There is a circuit board internally between the display and the controller of the circ, basically the controller for the display.
After some exhaustive digging around, some sleuthing, testing and more testing this is what we found.
This control board did not have its software correctly installed so therefore it will not tell you the current watt draw, nor will it tell you the GPM. The circ will read "07 WATTS 00 GPM" whether it is running in Delta T mode, fixed speed mode, any mode or setting you choose. However, it will still operate in whatever mode you have it programmed. The buttons still operate as intended.
So, what is affected out there? If you have a date code that shows between 0422 and 0423, the display may be compromised. The date code represents a month and year; we predate these circs by 4 months to allow for the circulators warranty based upon the time it take to leave Taco, go to our reps warehouse, get to the wholesaler and then to the jobsite. So that means that these circs were built between December 2021 and December 2022.
If your circulator falls within the date code above, is installed and the display is working properly, there is nothing you need to do. It will not fail later. This is a right out of the box situation
What do you do about it if you have one that has the incorrect display? Contact your wholesaler and your local Taco Rep. They will help you out. This is a high priority for us here at Taco so getting replacements back out is important. We are working with supply chain to get new circuit boards and chips (these things are in such high demand; every business sector has a rough time getting them). There is no in the field fix or programming that can be done. If you have one that has not been used or installed, still contact your distributor and local Taco rep
1 -
No worries, Taco will not leave you hanging. I've been on the Wall from very early on, and Taco has always monitored the vibe at The Wall and took any issues head on. Not alot of manufacturers do this. Kudos to those that do! Mad Dog 🐕0
-
Thanks for the reply. Sorry about the delay, I haven't checked this forum in a while. Thats exactly what my 2218 was doing, displaying 07 watts, 00 GPM. I already returned it to supplyhouse and bought/installed the 0018e. I have no intention of going back to the 2218 until all of these issues are resolved and the pumps with the bad displays are no longer out there. I'm going to stick with the 0018e, but it really would be nice to be able to use the app.SteveSan said:@ldipierro I'm sorry you are experiencing an issue with your 0018e. I've reached out to Product Management and they have sent your request to IT to see if there is in fact a compatibility issue with newer software Android phones. Once I hear back I will let you know.
As for the issue with your VT2218, please see below:
Here is what happened with the VT2218 circulator production.
There was a display issue, not a performance issue. There is a circuit board internally between the display and the controller of the circ, basically the controller for the display.
After some exhaustive digging around, some sleuthing, testing and more testing this is what we found.
This control board did not have its software correctly installed so therefore it will not tell you the current watt draw, nor will it tell you the GPM. The circ will read "07 WATTS 00 GPM" whether it is running in Delta T mode, fixed speed mode, any mode or setting you choose. However, it will still operate in whatever mode you have it programmed. The buttons still operate as intended.
So, what is affected out there? If you have a date code that shows between 0422 and 0423, the display may be compromised. The date code represents a month and year; we predate these circs by 4 months to allow for the circulators warranty based upon the time it take to leave Taco, go to our reps warehouse, get to the wholesaler and then to the jobsite. So that means that these circs were built between December 2021 and December 2022.
If your circulator falls within the date code above, is installed and the display is working properly, there is nothing you need to do. It will not fail later. This is a right out of the box situation
What do you do about it if you have one that has the incorrect display? Contact your wholesaler and your local Taco Rep. They will help you out. This is a high priority for us here at Taco so getting replacements back out is important. We are working with supply chain to get new circuit boards and chips (these things are in such high demand; every business sector has a rough time getting them). There is no in the field fix or programming that can be done. If you have one that has not been used or installed, still contact your distributor and local Taco rep0 -
@ldipierro The issue ( control board ) has been fixed and product with the new control board has been manufactured and in the field already.0
-
Mad Dog 2 - you were correct about Taco. Steve worked with tech support and determined that I was correct (their app is out of date) and apparently nobody at Taco knew about it. I believe that because I couldn't find a single bit of information about this when I googled it. Anyway Taco is now working on updating the app and have sent me an Amazon gift card for my troubles. Big time kudos to them, and thanks to Steve!Mad Dog_2 said:No worries, Taco will not leave you hanging. I've been on the Wall from very early on, and Taco has always monitored the vibe at The Wall and took any issues head on. Not alot of manufacturers do this. Kudos to those that do! Mad Dog 🐕
3 -
@ldipierro Thanks again for bringing this to our attention. Both Product Management & Product Engineers are working diligently to resolve this issue. Please, if you or anyone ever need assistance with any Taco product contact myself or please give Taco Technical Services a call during normal business hours Mon-Fri 8am-5pm EST 401-942-8000. Taco greatly appreciates your business.3
-
So I've had my new system up and running for the last 2 months now and its been incredibly effective. In fact I've had to dial back the settings 3 separate times because of short cycling. I now have the 0018e running on medium setting (auto ZV setting which maintains 5 ft head) and I've got the OAT reset at OAT 60F-0F/HWS 110F-170F. With these settings the boiler runs for long periods of time, but it still cycles off. I can't believe its so effective. I had to run my old CI boiler at 190F when it was less than 10F outside to keep temperature in the house. Granted it hasn't been that cold yet, but I don't think I'm going to need to even go to 180F to keep temp. The new 0018e must be moving a lot more water than my old pump did, which was a very old 009-F5.
Heres some photos of the fully completed system...
1
Categories
- All Categories
- 85.7K THE MAIN WALL
- 3K A-C, Heat Pumps & Refrigeration
- 49 Biomass
- 418 Carbon Monoxide Awareness
- 72 Chimneys & Flues
- 1.9K Domestic Hot Water
- 5.2K Gas Heating
- 92 Geothermal
- 160 Indoor-Air Quality
- 3.2K Oil Heating
- 59 Pipe Deterioration
- 847 Plumbing
- 5.8K Radiant Heating
- 371 Solar
- 14.5K Strictly Steam
- 3.2K Thermostats and Controls
- 50 Water Quality
- 39 Industry Classes
- 47 Job Opportunities
- 15 Recall Announcements