Delta T or Delta P Pump For My System

kgrant

I'm looking at replacing a Taco 007 circulation pump in my heating system. I included a crude drawing of my system. I want to replace circulation pump 4 (P4). In this situation would it be better to use a Delta P (Grundfos Alpha) or a Delta T pump (Taco Bumble Bee), or something else.

P4 circulates 24/7 to a separate building during the heating season. There is a small bypass line at the house.

The boiler is a Burnham PVG7. Its controlled by an aquastat with a 20 degree differential, strapped on to the supply line. I usually run around 180, sometimes 200 if it really cold.

What pump would you use for this application?

Thank You

hot_rod

I assume some components are missing in the drawing? Does the slab have a temperature mixing device?
Do you know the heat loads of the various circuits, or zones?

I believe delta p works best on systems that are zoned with valves. The concept has been used for many years on commercial jobs with VFD drives on pumps.

Here is some good reading on what it takes to properly size a circ, and also info on various delta P setting options.

Piping and pipe sizing is important when you connect multiple pumps to a header, you need generous pipe size to supply adequate flow to all the pumps.

http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_16_na_0.pdf

kgrant

The slab heat does have a manual mixing valve.

I don't know the heat loads.

The supply and return headers are large. It's 1.25" coming off the boiler and it looks like it is sized up to 2" at the headers.

I read that the expansion tank should be on the supply side. Not knowing this I added an expansion tank to the return because the tank on the supply wasn't big enough.

I'm sure there are many things wrong with this system and I am open to criticism.

I'm almost embarrassed to post these pictures of my supply and return headers, but here they are. I'm working on insulation.

This system was at the house when I bought it, and I'm slowly fixing problems. Maybe I'm creating more...

Thanks

SWEI

Looks like you have some corrosion issues there. Have you tried valving off the auto-fill to see if the system is holding pressure?

Also -- how big is the house?

kgrant

The pump on the right was leaking at the flanges for a while. The leak has been repaired. The system holds pressure.

Heating a 40x30 shop 16 foot ceilings, 10x40 two floor apartment, and around 1800sqft house.

SWEI

Also -- did you actually add a second expansion tank, or did you replace and relocate?

kgrant

I added the expansion tank to the return header 4-5 years ago. There is still an expansion tank on the supply. This year the expansion tank on the supply was flooded, had a busted bladder. Tank was only 4-5 years old.

Both expansion tanks are charged to 15 psi. From a cold start I end up with around 20 psi system pressure on my gauges with system at 180 degrees. My makeup regulator is set at 15 psi. I have the boiler shut down now and have make up water isolated. System is holding at 12 psi

hot_rod

How deep are you planning to get into the system? A complete re-pipe and upgrade would be a great option. You could clean up all the corroded components and upgrade old valves, flanges, connections etc.

The exp tank on the return is not a deal breaker with a cast boiler, ideally it would be installed just before all the pumps on that header.

Two tanks in different locations confuses the hydraulic balance somewhat, it probably works but not ideally.

It would be nice to start from the beginning, a heatload calculation, piping design, then repipe and update parts and pieces.

A pressure test also.

kgrant

I'm not sure how deep I want to go. I just need a reliable system. I'd like to improve efficiency as well, but I can't afford to put allot of money into the system.

This summer a fixed a few leaks in the system and flashed system. Then I'm cleaning the system with Sentinel X400 for four weeks then I will flush again and add inhibitors. The system was very dirty. The previous boiler had a cracked section and was limped along with stop leak for a few years before replacing. I believe I'm dealing with corrosion and build-up from that situation.

I need to replace the pump to the unit heater, it's making bad noises and is seized every fall when I start the system. I was planning on swapping the taco into its place and putting a more efficient pump to the house.

I can move the tank on the return to the supply. Or it would probably be better to remove the tank on return and replace tank on supply with a properly sized one.

What gains would I get from a repipe?

hot_rod

It seems like you might have some other issues going on. I am surprised an expansion tank would fail after only 4- 5 years That could be an undersizing, bad location, or dirty fluid.

The stop leak you added may be what is causing pumps to fail, hopefully you get it all flushed and leaks repaired.

If the system has, or had a lot of corrosion it is usually from O2 getting in somewhere, either through radiant tubing wall, or around the packings on all those valves.

When you flush again, take a magnet to the stuff that flushes out. If any sticks you could have corrosion still going on. A hydronic conditioner would help, but it would be nice to assure you do not have O2 ingress.

If you do add an ECM type circ pump, consider adding a magnetic separator to keep the fluid free from any crud still in the fluid.

kgrant

Yes,I have many issues going on.

There was a unit heater at the house that wasn't using oxygen barrier tubing, it had heater hose, like you'd see supplying the heater on a truck. About a 40 foot run of it. . Last winter the hose burst under the house and wasn't found for a day. I'm glad my make up water worked! I found the hose nearly blocked off with hard rusty type corrosion. That hose has been removed from the system and will be replaced with proper tubing.

Is there a magnetic separator that you would recommend?

hot_rod

It's amazing how quickly non-barrier tube can take a toll on a system, especially high temperature systems. Good that you are running a cleaner and then flush and fill with a conditioner.

If you can, power flush each zone and loop with a pressure pump of some sort. You need a high velocity to move heavy sludge and metallic particles out of pipes, boilers and HX. If possible you want 6 fps velocity to "scrub" systems clean. Find an old swimming pool or spa pump, they move a lot of flow, low psi and really stir thing up. It's fairly easy to find used ones on Craigslist or want ads, maybe a pool supplier.

I'm partial to Caleffi stuff, I do work for them

If you do not have a good air purger, consider a combo unit. Or just the stand alone DirtMag. The suppliers up there Ferguson, & Frontier, should have it, or can get it. Mitch Mayo is our rep if you need more Caleffi help.
mitch@pacwestsalesinc.com

ECM pumps have strong permanent magnets in them, and can attract small metallic particles, if you go with one of those circs, add a mag separator of some sort.

kgrant

I'll see if I can come up with a pump. I just throttled city water when I flushed it. I flushed into a bucket outside and was collecting allot of heavy solids. I flushed each zone individually. The most junk was in the zone to the house.

I have a spirovent air purger installed.

I appreciate all the knowledge and experience, thank you.

hot_rod

here is an example of a cast iron boiler that slugged from non barrier tube use, thanks to Richard at Heatmeister in Colorado for the pic. Richard has been on a mission to find a pump setup to flush systems as there are many, many old non barrier PB and rubber systems in the intermountain west.

He flushed several drums full of sludge from this system.

I doubt water pressure from a home supply would provide enough pressure and flow to flush this out?

This table gives you an idea what it takes in GPM, to flush various size pipes. A cast iron boiler would need a lot of flow to provide the velocity to get heavy sludge out. Hopefully you can get yours cleaned.

The boiler will make a percolation sound if it is partially plugged. Sounds like a tea kettle that has limed up.

kgrant

I just watched the webanar from Caleffi by James Poehling on "water quality in hydronic systems". Excellent video! I'm excited to get my system cleaned up!

SWEI

As long as your meter and main can actually deliver that 16 GPM.

Commercial services are rather different. IIRC the flow test we did for a sprinkler job a few years back produced something like 700 GPM from the city mains (~95 PSI static in that part of town.) Five story building, 54' to the top floor heads, no fire pump required

hot_rod

Hard to say what flow you could actually get at the building without knowing the street psi, meter& yoke size, piping size and distance, and PVR size. If you have any or all of this? Maybe you are on a well, if so the pump size and capacity would determine available flow.

We used to design and install residential fire systems, typically 15 gpm through a residential meter set with 5/8 meter in a yoke with an integral BFD.

The nice thing about getting a pump to circulate is you can leave the chemicals in and just run it. If you can isolate the loops, a 1/2 hp transfer pump does fine on residential systems.

Some GEO loopers I know have old fire trucks to purge entire loop fields without isolation.

SWEI

hot rod said:

The nice thing about getting a pump to circulate is you can leave the chemicals in and just run it.

Definitely. Throw a 20µ filter on the return and you will see some amazing crud that gets caught. Which reminds me -- I need to buy a clear housing so the customers can see what's coming out.

kgrant

Man I'm having a great time watching these Coffee with Caleffi videos, I'll soon have many questions I'm sure. Just started watching hot rods pre season checks and maintenance!

kgrant

I'm a little confused on what water I should use to do my final flush and fill with. I have access to city water, softened water,RO water and DI water.

City ph is 8.3, dissolved hardness 140, conductivity 360
Soft ph is 8.7, dissolved hardness 0, conductivity 300
RO ph is 7.6, dissolved hardness 0, conductivity 4.6
DI ph is 6.9, dissolved hardness 0, conductivity .6

I don't know the TDS.

I'm not going to use glycol.

I'm looking at using a nitrite based inhibitor.

hot_rod

I think you could flush with the city water,as long as you don't run the boiler you should not precipitate out the hardness minerals.

Check with the manufacturer of the inhibitor that you plan on using, for their blend water suggestion. Is DI water available, or can you generate it at the job site? That is probably what the chemical supplier will suggest.

kgrant

I'll be hauling the water in a tank in my truck and pump it into the system.