Under sized circulator?

foven

I have a 4 zone hot water baseboard system with a single Taco 007 circulator. Here in the North East when the temperature drops towards 0F we can't make enough heat for the first floor. Over 20 years at the property I've asked our service (oil heating) technicians about the problem but got nowhere. I have believed that when a 16 x 16 extension was added, the extra footage of baseboard tacked on is the cause of the problem. In the winter it never reaches temperature. Finally I traced out the system and I don't think it's a lack of BTUs. The boiler is 26 years old but it's still 82% efficient and rated at 112,000 BTU/hr. I think there are imbalance issues but first I want to make sure the heat is getting delivered properly.

Zones:
- The first floor zone has 73 feet of fins and a total loop length of about 280 feet of 3/4 copper pipe including the heaters.
- The second floor seems poorly designed. It has about 53 feet of fins and about 350 feet of total loop length (3/4 copper pipe). The loop returns to the basement three times to connect different rooms on the second floor.
- The basement zone has 26 feet of fins and a 121 foot loop length. Also 3/4 copper pipe.
- The indirect water heater is on a 1 inch zone and just a few feet.

The Taco 007 circulator is on the return and common to all zones. From my calculations, it only has enough power for the basement and water heater zones. I am guessing the water is just drifting around by convection when the zone valves open, encouraged gently by the pump! With such a range of zone sizes, I'm not convinced a more powerful common circulator is the answer. Any advice for what would help?

HomerJSmith

No Monoflo tees?

The way it works is that the flow goes thru the loop with the lowest pressure drop. What strikes me as weird is that so many installers don't use circuit balancing valves to provide a balanced flow to all the load.

A Taco 007 at a flow of 2-4 gal/min will put out about 9-10' of head energy. Every thing in the circuit from the boiler to the return including fittings etc. will use up that head energy. To have flow you must have more head energy than the system removes.

If the second floor get sufficient heat and the first floor doesn't and the first floor is the only zone operating then I would look for some restriction in that loop. I would check to see if it is air bound as a circulator can't push water thru an air pocket.

If the first floor is more restrictive than the other zones and doesn't put out heat when the other zones are on, but puts out heat when it is operating alone, I would put on balancing valves on the heating zones and balance the system. You may need to increase the head energy and replace your old circulator with another circulator. I would suggest a Grundfos UPS 15-58 with three speeds.

Jamie Hall

What @HomerJSmith says, plus... figure out some way to measure the pressure at the inlet to that poor little pump. Unless that is also where the expansion tank is, you may find that under some conditions the pressure at the inlet drops very low -- at which point the pump becomes very unhappy and won't pump well, if at all.

Zman

Are your lengths equivalent feet (including 90's) or is that the length of actual pipe?
If it is equivalent feet, this is what your flows look like with and without the domestic calling.
You could probably make what you have work if you prioritize the DHW and throttle the short zone. Both Taco and Calleffi make simple zone valve controllers for that.
If those are not equivalent feet, you should go with a bigger circ.

HomerJSmith

There is a big difference if a problem just began and had worked ok earlier and a problem that was there from the beginning.

Can't tell much without seeing the system setup.

foven

Thanks for these great responses. Here's a few more details to hopefully answer your questions.

The system is 26 years old. At some point the original owner added the 16 x 16 extension and added 17 extra feet of fins in a straight pipe length (including fins) of about 50 feet. That room never reaches temperature and I know there are some imbalance problems to solve but first I want to make sure the water is flowing properly.

We have had imbalance problems over the 20 years we have been there and problems in the winter teens. At one time I shifted the high temperature up to 190+ and the low temp to 170 or 180 which helped get the first floor close to 70F when it was single digits outside. Only repairs have been made during our tenure. Leaking relief valves, failed zone valves, replacement expansion tank. I'm about to replace the 40 gal superstor hot water tank because we have well water and it takes forever (an hour plus in the winter) to recover. My belief is the element is heavily scaled and I wonder if it starves the first floor.

All the zone lengths I gave are straight lengths; I didn't try to count the elbows but there are many of course. I am using 4 head feet per 100 feet of pipe and it might have been on this site that I found a good estimate is to add 50% for elbows and valves. I was worried most about the first floor because of the addition until I found the second floor makes so many transitions that it's 350 straight feet of pipe. So, by my calcs that's a load of 21 head feet but obviously there's a big variation between all the zones.

The boiler high temperature is 180F. The circulator is right on the common 1" return to the boiler for all 4 zones. The expansion tank is on the common flow side of the boiler. Each zone has a taco 570 zone valve. There's no mono flow tees and no load balancing valves.

Is there some way to measure the pressure at the pump inlet? The boiler pressure gauge registers roughly 20 psi. Several years ago it used to be more like 15 psi.

mikeg2015

Does the boiler reach setpoint and cycle on and off? How how does it get?

What are the return and supply temperatures?

Is all the baseboard getting hot? What is the temp at the start and end of each branch of baseboard.

Low flow would result in a high delta T (25f or more).

You issue might be more balance and undersized main header that made worse by a marginal pump.

Zman

I would absolutely do the zone controller with priority so that the DHW call is not competing with heat from a flow point of view. https://www.supplyhouse.com/Taco-ZVC404-4-4-Zone-Valve-Control-Module-with-Priority?gclid=Cj0KCQjw9fntBRCGARIsAGjFq5HznGK6RThNABqIAB3jD9fIR9FFMoF4PSjRj9C0AL54xev_sjQLz6UaAohTEALw_wcB

The Grundfos 26-99 on speed 2 would be a good fit. You can turn it up to speed 3 if needed. It has the same flange to flange dimensions as your 007 so should bolt right up.
https://www.supplyhouse.com/Grundfos-52722512-UPS26-99FC-3-Speed-Circulator-Pump-1-6-HP-115-volt-5587000-p

Here is the before and after using 1.5 multiplier.
You should probably do a heat loss calc on the spaces to see if you have enough radiation.

mikeg2015

Ideally you want around 10-12gpm for 112k BTU (not sure if that’s input or output). You can get there with abut 4ft pressure drop. Which is possible if you have well laid out 1-1/4” header.

Zman

mikeg2015 said:

Ideally you want around 10-12gpm for 112k BTU (not sure if that’s input or output). You can get there with abut 4ft pressure drop. Which is possible if you have well laid out 1-1/4” header.

I don't think the issue is at the header. Those long runs with lots of radiation are suffering due to low flow. The total radiation is < 80k

HomerJSmith

Having 12 gal thru the HX is nice (1 gal for every 10K of input), but conventional high mass boilers can deal with 5-6 gal/min or less thru it with no problem. Just might cycle more. High mass boilers usually have a pressure loss of about 1/2' of head energy, so the pump that came with the boiler, marginal as it is, can handle 3 zones. A 007 is typical.

So, you can bring the first floor up to temp if you raise the boiler aquastat to 190 deg. That means you have flow just not much of it. The thermo wax motor in the 570 if it is wired right is probably shot. Maybe calcified. I never liked those slow 570's. I would replace those zone valves with a cheap Honeywell. I use the Taco cartridge circulators, but in a well sys, they can clog up the cartridge. These are low torque pumps and anything can stop them from rotating. I would replace the pump with a Grundfos UPS 15-58, for sure, along with the zone valves. I would put on balancing valves, too.

Well water is sometimes very nasty, so I would clean the sys with a good cleaner that would remove carbonates and flush it real good before I make changes. Fill the sys with distilled or DI water.

Putting on a high head pump would certainly increase the flow in the first flr loop, but raise havoc in the other zones. Besides they are a lot more expensive.

These are some of the things that I would explore, especially the 570's.

You would replace a 40 gal superstor? What the Hey! Maybe the HX is calcified, clean it and put it on a priority mode with a Taco Zone Controller. That tank should heat up at 180 deg input in 10 minutes.
If you have a tempering valve maybe that's calcified, too.

What kind of expansion tank on your sys. If a bladder tank maybe the air charge is low. You are ok with a 15 psi and it should rise a few degrees with the sys up to temp. Any water dripping out of any pipes anywhere?

Ever hear of the saying, "A picture is worth a thousand words."? Hmmm.

Zman

@HomerJSmith
He has equivalent pipe lengths of over 500'. One of those has 73 lin feet of fins. The delta t of that loop at the 2 gpm or so that the 007 can move is 32 degrees plus un-insulated pipe loss. This is starving the last radiators in the loop of energy.
I do not believe that the 007 is the correct circ in this case.

foven

@HomerJSmith

I'm working on getting some temperature readings. I just got a contact thermometer but I'm learning how to use it. This morning, at the boiler I finally got measurements that are closer to belief, but not very scientific; 140-ish out, 112-ish return. This is in line though with @Zman's predictions. Is it expected to see big temp drops on the outside of the copper pipe a couple of feet from the boiler?

The reason for changing out the hot water tank is it's age ~ 25 yrs, the slow heating and the other alterations that are needed. I like the idea of replacing the valves. I remembered that the head has been changed 2 or three times and they seem very constricting even when open. I was unsuccessful at convincing our service tech to replace the body last year.

I like the idea of the bigger pump and some load balancing.

Later on I'm thinking about cutting out about 70 feet of weird piping on the second floor. The circuit (on it's first trip to the second floor) visits the master bathroom, returns back to its point of entry in the basement, travels to the other end of the house and back up to the second floor to pass through less than 3 feet of fins in the master closet. If it passed behind the sink in the bathroom into the closet it would have been about 5 or 6 feet.

I'm also expecting that on the first floor, the family room is on the outward and return journey. On the outward trip there are 11' of fins along the exterior wall and 14' of fins on the opposite side when returning. The family room is open plan to the kitchen measuring about 13' x 17' for the room itself but 25' of fins at the opposite end of the floor from the thermostat might get rather toasty. I'm hoping to stage improvements and deal with imbalance once the flow is working properly.

@Zman I really appreciated the flow diagrams. It helped explain the problem. I'm actually more experienced in electronics so I could imagine the zones as resistors and the flow as current. The effect of the short 1-inch hw zone grabbing all the flow as the path of least resistance is obvious now.

Lots more planning to do now!

Zman

It is a lot like electricity!!

Zman

Why do you have supply temps of 140 degrees? Your first baseboard are probably at 50% output, the last in line is more like 20% at those numbers.
I have tried a few different techniques with those probes including the clamps. I like just using the thin wire sensors and sticking them to the pipe with foil tape. If I am logging for extended time, I put a little section of pipe insulation over it.

HomerJSmith

You could use a laser thermometer. Zman's right. Your supply temp should be at 180 deg to get the most out of your heat emitters and which would increase the return temp to the boiler.

On a conventional boiler the return temp must be high enough to prevent condensation in the boiler-flue sys, about 130-135 deg.

Yes, you can run out of heat energy at the last heat emitter and the way to solve that is to increase the supply temp and or increase the flow.

140 deg out? Where was the measurement taken? What does the boiler gauge (tridicator) temp read? If you have 140 deg at the first heat emitter and 112 deg at the output of the last heat emitter then I would suspect that you have a flow problem especially if the boiler output is 180 deg.

"Is it expected to see big temp drops on the outside of the copper pipe a couple of feet from the boiler?" Ahhh, no. If the boiler is hotter than the pipe, where is that heat energy going to?
Is it possible it never got out of the boiler? Boiler short cycling with a tridicator temp reading of 180 deg? That would be a flow problem. Excessive carbonate build up on the inside of the pipe, narrowing the opening? A bound circulator? It's easy to take a Taco circulator apart and inspect the rotor and inspect the inside of the volute for carbonate. The hard part is draining down the sys. I would replace the Taco with a Grundfos 15-58. If the cartridge is bound a new cartridge cost the same as a new 15-58.

A 15-58 @ 3 gal/min has a head energy of about 17' on high speed. A 007 @ 3 gal/min has a head energy of about 8'. There is practicably no loss thru the boiler, so what's eating your flow? 570's, bound circulator, carbonate, pumping onto an expansion tank, etc.

I think you probably have a flow problem, you have a lot of solutions from these great professionals. It is up to you to decide what solution will solve your problem.

Remember, flow is the conveyor belt the move heat energy around the heating system.

1 mm of carbonate in the inside of a pipe or HX drops the heat transfer about 10%.

foven

The boiler high temp reads 180F. I'm not convinced my temp readings are right yet but I think the flow problems are more evident now. I was holding the probes by hand to the copper pipe right above the circulator on the return and 2 feet above the flow side on the boiler. I'll see if the results are different with foil taping later. I'll also check the low temp and short cycle issue. Thanks for lots of great pointers!

HomerJSmith

So, you are pumping into the boiler. The expansion tank is probably hanging on to the air eliminator on the supply side of the boiler. If so, you are pumping into the XTank, a no no.

foven

Hmm, that's right. I was aware about pumping away from the expansion tank and now I do vaguely remember that pumping through the boiler into the tank is the same thing. This is good! When the pump is replaced it can be repositioned after the tank.

The foil tape trick enabled me to get good temperature readings. The supply side reading maxed just above 193F. The boiler cut out just above 180F and back on just above 170F which are the controller temperature settings. On the return side, the temperature maxed out about 176F. These are obviously out of phase. When the supply side hit 193F the return side was at 158F and when the return side hit 176F, the supply side was roughly 170F. The supply side low temp was about 166F and the return side got down to 93F.

Taking the difference between the supply and return high temps I get 17F, and the difference in the low temps was 73F.

This has taught me that I need to find out how the 20F circuit drop is calculated!

HomerJSmith

Some aquastats have a separate setting for the delta T differential and some of them have it built in. Mostly a 15 deg temp differential.

I'm a little confused about the last post. The return temp will vary based upon how many zones are operating. The supply temp will vary depending on where the boiler is in the firing cycle. There can be a little overshoot when the boiler shut off at high limit as the heat exchanger still transfers heat to the water.

I'm less concerned about the supply and return temp unless there is flashing. I'm more concerned about getting your heat emitters delivering the heat.

Zman

You want to be measuring the supply and return of the zone you are having trouble with not at the boiler itself.
The 20 degree delta design is a unicorn. It sounds great but I have never seen one
Seriously, it is just a common design basis. It comes from the universal hydronic formula, btu/hr = gpm x delta t x 500. I honestly think it became popular because you just need to move the decimal if you use 20 for a delta T. 10,000 btu/hr = 1 gpm x 20 deg x 500

Big Ed_4

One of the common mistakes when installing a parallel system , which you have is the placement of the supply and return connections of the manifold .. It makes sense to keep track of the heating loops and most connect supply and return in order . When doing this without "Reverse Return"to the manifold, the first on the line will have the greatest pressure drop and the last will have the least . You can search here on Dan's site for "Reverse Return" to explain better then I could ...

mattmia2

You can calculate hydraulic resistance of your loops and develop and solve a system of equations the same way you do it for an electrical circuit.

foven

Reverse return is interesting. What I get from that is that ideally the loop planning would match the resistance in each zone, except the DHW. I actually think the second floor loop could be reduced to be closer to the first floor length. The basement loop is so much shorter (160 feet less) that I think it will need a balancing valve for it. The other thing is repositioning the circulator. Given it's pumping through the boiler into the expansion tank, there needs to be rearrangement. Currently the circulator is vertical on the return feed and the expansion tank is hanging off the common supply side feed.

foven

The 70 feet of 2nd floor pipe that runs from the master bathroom to the master closet could be cut down if the pipe from the bathroom baseboard continued under the sink through the wall to the closet baseboard. A distance of 7 feet. To do that the pipe would obviously have to pass the hot and cold water supplies for the sink. Is that allowed?

Zman

I am confused as to why you are talking about repiping your house. The circ should be pumping away from the expansion tank so that move makes sense. Beyond that, I think you should size the circ for the longest run and then install balancing valves on the shorter runs. Reverse return distribution has its place. I don't think your home is one of them.

foven

Here's the theory. I agree the reverse return option isn't viable. However, the 70 foot loop, with probably 8 elbows, could be replaced with a 7 foot straight connection and lower the second floor resistance to roughly the same as the first floor. The rest of the work is around the boiler. Then only the basement would need balancing. Overall it should be more efficient for a little more work.

Paul Pollets

The first floor uses 73' of baseboard, which is 38K Btu's. That should be 1" pipe and hopefully run with a separate supply and return. If all the BB is run in series, it's gonna be a continuing problem. Moving the correct sized pump to the supply will help the performance. You have "choke points" in the piping that diminish the efficiency.

EBEBRATT-Ed

You have 98,000 btu worth of baseboard thhat needs 10 gpm plusl the indirect. I would seperate it into 2 seperate zones and add another pump