Help - Pump Sizing

adamt

Greetings Experts, I was hoping someone might be able to give some advice. My parents heat their house with hot-water baseboard, and they're having trouble maintaining a comfortable temperature (68-70 degrees) when the outside temperature drops below 30 degrees.

Here are some of the specs for their heating configuration:
- Their house is a remodeled farmhouse with okay insulation.
- The boiler is Weil Mclain CGi-5 (87,000 BTU output) running at 180 degrees.
- There is a total of 102' of baseboard (30 years old). If I assume we can get 500BTU/ft/hour, we can get 52,500 BTU an hour.
- There is a single pump (Taco007)
- 3 basboard zones.
- 1 zone is connected to a Modine HC-18 heater for the basement area (maximum 18,000 BTU/hour. I'm not sure how to determine the head loss on the heating element. (https://www.ecomfort.com/manuals/1719095ebeeec50fdc0d0b5f87de40a2.pdf)

I think the pump that was installed can probably only handle 1GPM through each zone. My parents have minimal appetite for adding additional baseboard in each room. I think a few things could be done to help add more heat.

Solution 1:
Put a much larger pump on the system to increase the GPM to each zone.

Solution 2:
Put a much larger pump on the system to increase the GPM to each zone and add balancing valves to regulate each zone to 4 GPM each.

Solution 3:
Put a much larger pump on the system to increase the GPM to each zone and add balancing valves to regulate each zone to 4 GPM each.

Add a water to air heat exchanger to the air conditioning air handler to add additional heat on cold days.
I'm attaching a picture of the manifold and a photo of the head loss calculations I did. Any help/advice would be much appreciated.

I tried to do head loss calculations. The first section is at a 1 GPM and the second section is at 4 GPM. The numbers don't seem accurate to me and I'm not sure what I'm doing wrong.

Manifold


Head Loss Calculations


Attached is the spreadsheet that I used for the calculations.

Gordy

First questions

Is baseboard getting hot on heat calls in all zones?
Are baseboards clean, and not blocked?
Type of baseboard?
Air purged from system?

Gordy

The 007e should produce over 8 gpm@10’of head

I don’t care for the flex connections to the piping. That’s a Little Kentucky windage for head calculations.....

hot_rod

Is this a new problem, has it worked previously? Has any work been done on the system recently?

adamt

@Gordy - the baseboard does get hot on heat calls to all zones. The baseboard is clean and the air is purged. I don't know the manufacturer of the baseboard.

Zman

@adamt
When did this problem start?
What type of boiler and how is it piped?
A picture from farther back would help.

adamt

@hot_rod - this is a new boiler. They use to supplement on cold days with a forced-air furnace. It's been replaced with an air handler (no-heat) that is used just for air conditioning.

Zman

The 007 looks to be an appropriate selection for the distribution side. I suspect the issue is in the boiler piping. Can you provide more details on that?

adamt

@Gordy - I don't have software for calculating head loss, so my numbers might not be accurate. I tried to use formulas I found off of the internet/youtube.

The flex connections would add some head loss as opposed to smoothe wall copper. But, on such a short distance and at 1-1/4 diameter, I wouldn't think it would add enough to be significant.

adamt

@Zman - The supply and return flex lines connect directly into the boiler via 1-1/4 copper. I'll upload the only photo I have. I can try to swing by their house and grab another shot from a different angle.

Zman

It looks like it is a cast iron boiler. There should not be that much resistance there.
Your spreadsheet shows copper, I see some kind of plastic pipe in the pictures. That can change the flows considerably.
Here is a quick model of your flows with the info provided. The 007 should be getting the job done. What kind of delta t numbers are you seeing at the zones?

adamt

@Zman - thank you so much for working up the zone math for me. There's about an average 12 foot of 3/4 pex connecting the manifold to the copper baseboard runs. If you look at my spreadsheet, I added 0.09587025 of head @ 1GPM to each zone in my calculations. At 4 GMP it would be 1.084648062 of head added to each zone. The fourth zone is 1/2 pex to the Modine HC-18 which is rarely in use and ads quite a bit of resistance to the system.

hot_rod

To the right if the zone valves, what is that zone with just a ball valve for?

adamt

@hot_rod - that's an extra for an additional zone and It's not currently in use. I thought I might be able to add a water to air heat exchanger off of that zone.

Gordy

Could you do a photo of the boiler piping?

adamt

@Gordy - here you go.

Jamie Hall

A simple minded question. On what basis was the potential heat output of the baseboard figured? Is this based on the baseboard itself, or on the flow through it? And at what delta T

adamt

@Jamie Hall - I used this chart from this website.

adamt

@Gordy - I updated my previous comment with photos...

Jamie Hall

Thank you, @adamt . It's worth keeping in mind that those figures are for the average of the inlet and outlet temperatures.

Now... we have a reasonable heat output for your baseboard. The next question is... what is the heat loss of the house they are trying to heat? There is a very good on-line calculator for heat loss put out by Slant/Fin. Easy to use. It would be worth it to try it to find out if that much baseboard can even be expected to heat the house.

I note that your are thinking of possibly putting a heating coil in the A/C system. That would probably help -- and you have the extra capacity in your boiler. But before we go there, let's look at the heat loss we are trying to keep up with.

Gordy

I believe the point is that the baseboard is supplemental to the forced air. Whether this was the initial design of baseboard sizing, or something adapted to a new design, I’m still at a loss.


If the baseboard, as is heated the dwelling with same given parameters it should still be able to.

I don’t think it’s a circulator issue. I’d be willing to bet the original was a 007.

Also different baseboard designs have different outputs at different flow rates. cI, fintube etc.. Not huge differences.

So question now is this.

Does the baseboard heat primarily, and forced air supplemental, or vice verse?

adamt

First off, Merry Christmas, and thank you all for the responses.

@Gordy - The original house was heated with forced air. When I was young, my parents put an addition on their house and added the boiler. After the addition was complete, they added baseboard to the rest of the house. The baseboard heat is and has been the primary source of heat for the past 25+ years. The original forced-air furnace would kick on when the temps dropped into the teens. I think there might be a few things happening now:

The forced air furnace is now gone and has been replaced with an air handler for AC only.
There is a new boiler, so the temp might be lower than it was in the past, and the pump might be smaller - less total BTU/hour.
All of the windows/doors have aged, and they're not as air-tight as they once were.
My parents are older now, and their tolerance for a colder house has decreased.
Adding baseboard isn't much of an option. Potentially, I could replace the existing baseboard with a higher BTU version that would have a similar form factor. I was hoping to do some "easy" additions like a larger pump, balancing valves, water to air heat exchanger. I also plan on adding some spray foam, and windows seal to help eliminate cold air infiltration.

Undoubtedly, the existing configuration can only maintain 66 degrees on sub 30 degree days with the boiler running non-stop. Anything above 30 degrees and the house will stay at 70 degrees+

Thanks again for the help!

Gordy

Ah so it’s two different systems for different areas ?

Jamie Hall

The water to air heat exchanger is really your only hope if you can't change the baseboard or add to it much. There is only just so much heat the baseboard can put out, and putting more water through it isn't going to help -- and you are already pretty much at the maximum practical temperature.

You might consider adding such things as panel radiators, though.

Gordy

What is the boiler temp set at?

Quite possible 190-195 was used on the old boiler.maybe even 200

That gets AWT 180-185 verses 170 if a 20 delta is what you are seeing.

Steamhead

@adamt , @Jamie Hall is right. Do the heat-loss calculation for each room in the house. Only then will you know if the rooms have enough baseboard or if the boiler is big enough.

Also, where are you located?

Gman66

That fifth "future zone" is off in one picture and open in another picture. If open it is just a system bypass and you will get very low flow to other zones.

Check your delta T to see if flow is good; greater than 20 degrees suggests higher flow needed.

Gordy

Based on the information provided by the OP the baseboard was primary heat source for whole house, and forced air secondary when temps dropped in the teens.

Now there is an issue for the baseboard to keep up below 30.

Base board has not changed so.

Replacement Boiler temp is possibly lower than original Boiler.

Flow rate is reduced.

As been said check deltas. If less than 20 circulator is good.

EBEBRATT-Ed

@adamt

You said 102' of baseboard. It it all finned? You may have a bunch of dummy covers that do not have actual baseboard element in them.

I agree with the other posters above. Start from scratch and do an accurate heat loss.

Then check to see if you have enough baseboard in each zone to handle the heat loss at a reasonable water temperature.

Then you can work on the flow rates needed

adamt

Thank you for all of the replies. I'll try to do a heat loss this week and check the delta T's. There's no thermostat on any of the return zones or manifold. Could I use an infrared thermometer? Do infrared thermometer work on manifolds where there are closely spaced pipes?

@Steamhead - The house is located in western PA.

@Gman66 - the future zone is closed. The first photo with the zone open was taken after I bled the system hoping I would find air in the pipes.

@EBEBRATT-Ed - there are fins everywhere. No dummy covers.

@Gordy - The boiler temp is set at 180. There's a single boiler for the entire house.

Dave H_2

Close the two valves circled. All you are doing is bypassing the heat to the zones. It looks like this is the "future zone"
Dave H.

adamt

@dave h_2 - they are closed. Sorry for the confusion but good catch.

Dave H_2

I would also look to see how the circulator is wired/controlled. I see the wire heading to the boiler and not the ZVC controller. Make sure the circ stays running when the boiler shuts off (look at light on circ).

Dave H.

KennethGoetz

Did you verify the actual boiler feed water temperature... ?? With a accurate thermistor type probe on the boiler feed pipe 3- feet away from the boiler while it is running and pumping .

adamt

@Dave H2 - The circulator does continue to run when the boiler is off.

@KennethGoetz - I've only verified temps at the TP gauge.