Secondary Circulator Problem

D_Clark

I have a grundfos up26-64f that has been in my system for 12 years. It is a secondary pump in radiant system with 5 zones all controlled by Taco zone valve controller. Last weekend I cleaned and flushed and added protector. Water was clean and there was no air in the system. Weird thing happened after the fact though, seems the temp coming from primary side to secondary was really low 110f, but in the primary the was 130f to 150f. The only way I could seem to get hot primary water to secondary was to throttle valve to secondary pump about half way closed and you could physically feel the temp raise to about 120f but that is it. When you did this you could hear turbulence increase the more you shut it. I took the pump off and checked to see if impeller was toast but seemed to look ok and no obstructions where apparent. Any ideas?????

hot_rod

Got a drawing or pics on how it is piped. What pump on the primary circuit?

D_Clark

I will get those for you tonight and the pump is a Taco but will check model as well.
Thanks

D_Clark

I took some pics of the install. Little background, I am a retired plumber and have been working on this on and off for 13 years. Adding and changing etc. The secondary pump is a Taco is a 0011 - F4

hot_rod

It's hard to tell exactly where all that piping goes/ What type of boiler, is there an indirect DHW tank also?

You really don't want to run more then 10 minutes or so with that temperature return to the boiler if it is a gas fired standard boiler.

There will always be some temperature blending at those closely spaced tees.

Is this drawing about right? proper flow direction?

D_Clark

Hi Bob,
The boiler is an NTI Trinity Ti150C Combination Heat/Hot Water Boiler with DHW hooked up but not used at present and running on propane, 50-145 MBH Modulating,
92.7% Efficiency. The drawing has the correct flow.

hot_rod

Was this immediately after a cold start, did the return increase after running for a time? The return from the distribution will be cool, possibly ambient room temperature or cooler depending on where the piping runs.

As the distribution warms up, that return temperature will also, it may take time depending on the type of heat emitters and the load on the system.

Did you get all the air purged out after the pump removal and reinstallation?

You should not need to choke down those ball valves like that.

I assume it worked in the past? How long did you observe the operation for?

It is a bit of math, but it's possible to calculate those temperatures under different conditions.

The 0011 is the circulator they suggest, and it looks like it is piped correctly.
The pumps are installed in the correct direction?

D_Clark

the system was cleaned and purged and protector was added and ran for about a week until I noticed a temp drop on the secondary side and started to investigate by first removing pump and testing flow on either side of pump...that was good. I then cycled the boiler to see if the impeller ran and it did. Bolted it back on and then backed screws off a bit to purge. Turned on again and then started working on valves and found that when I started restricting the flow it got hotter and return did also after a bit. But if I opened it full it would go back to what it was doing before, which was the temp drop. last year I was getting full temp from boiler at 130 - 140 depending on how cold it was
When I started to restrict the flow you can hear turbulence in the line. I must be missing something for sure! Checked rotation on secondary and that is right. I can't really see it being a blockage because I don't think I would get that much turbulence for the line being restricted. I know the system quite well but this I have never seen in the field and never from this system.
Thanks
Doug C.

hot_rod

Are you sure the gauge isn't lying? Is it keeping the home warm?

D_Clark

No I have 2 digital gauges as well and they say 110. The boiler is not keeping up supplemental heat has come on numerous times. In the last photo u will see a tee that is capped off.........could it be that causing some sort of flow problem with the inlet and outlet secondary tees?

hot_rod

So the system has function adequately in the past? The only change is you flushed and added an inhibitor, no other changes?

I'd first suspect that it was not purged completely and you are not getting adequate flow. Primary secondary piping can be tricky to purge depending on how it was valved.

The boiler comes up to temperature and shuts off? But the heat emitters never warm up sufficiently? What type of heat emitters?

D_Clark

Yes it has run well, as far as the purging goes I have a valve on the feed and return of each zone and a sed faucet to allow purging.
the boiler cycles from about 110 to about 155 and shuts off, rinse and repeat but the radiant (tube and fin) this time only gets to about 115 and returns drop about 10 or 12 degrees. to me the return temp is about normal but the feed was always about 130 to 140 depending what was coming out of the primary loop.

Paul48

Reducing flow on the secondary helps your problem. It's not possible that your secondary is somehow flowing more than before. It's more likely that while "cleaning" you dislodge things, partially blocked the HX, and have reduced that flow. That's my hypothesis.

Gordy

Fin tube emitters? Or tube, and plates?

I suspect air. May take some time to work its way to air eliminator. Have one?

D_Clark

Hi Gordy,
I have both actually but 80 % is tube and plates. I have air eliminators on all the runs and a spiro on the boiler plus a couple of eliminators on the high spots around the boiler.

Thanks
Doug C.

D_Clark

I see what your saying Paul48. So start over the purge again and then reverse flow to HX to see if I can get whatever is in there out. Also I think your saying there not enough water flow for secondary?
Thanks
Doug C.

Paul48

Say the primary and secondary both flow 8 gpm. If you reduce the flow in the primary to 4, the secondary will get the other 4 gpm from it's own return, reversing the flow in the close tees.

This seems like the most plausible explanation, based on what you've said.

hot_rod

What Paul is saying is it may be a restriction in flow rate through the boiler, either it is somewhat air bound, not allowing 100% flow, or something has reduced/blocked the passage way.

Here is what it looks like on paper. Since you know the temperatures on all sides you could guesstimate some flow rates and see where the flows match your temperatures. Someone better at math could determine the boiler flow based on your temperatures

You have too much blending of the return, not enough flow from the boiler.

Some of those mod con boilers will lockout when the delta t through them gets too large. My Lochinvar does, sends an error code but resets itself when the delta T temperature drops. So the boiler may not be reaching the higher setpoint as it previously did because the control is locking out on high delta.

D_Clark

Thanks guys,
That makes a lot of sense! Never thought of that. Was always looking at the distribution side of things! The primary will be nice to work on as I can isolate that from the rest of the system and see what I can find. got lots of valves and sed faucets on that side! Along those lines can I take apart the SpiroVent to clean it or does it not come apart? I tried once with a couple of 18" pipe wrenches but she wouldn't come apart so thought better leave alone. There is also a 3 way valve for DHW. The DHW is not in use but check anyway? I will also back flush the boiler and see if anything comes out. Think of anything else to do let me know

Thanks again

Doug C.

hot_rod

That would be a good place to look for a partial blockage inside the Spiro, all brands can sludge or plug up. That would reduce flow on your primary circuit.

Does the boiler circulator have a check in the discharge side? I've seen those clog up also.

Yes they do split at the belly seam, some easier than others This one in my vice with a pipe wrench and cheater!

D_Clark

No I have just valves on either side of that pump. But I will go through it with a fine tooth comb as they say!
Also would like to send a thanks to anybody who responded with your incites and the diagrams were very helpful.
Will comment on how it went over the weekend.

Merry X-mas!!

Doug C.

D_Clark

It's been awhile since my last post, But finally got it fixed!!!
1. Flushed the system again and did a reverse flow through the boiler side. (Got a bit of dirt out of that experiment)
2. Took the circulator apart and cleaned (was some blockage)
3. The big one was the 2 way valve for instant HW, I took it out of the system and disassembled it. I found that there was a rubber ball in the body of it that had partially broke off and was restricting the flow from the heat exchanger. I don't use the HW so just took the ball out and put the valve back in and started it up and.......problem solved!! Thanks for all your help guys!

Doug C.