Direct Connection

Alan (California Radiant) Forbes

I'm just about to start a job to replace a boiler in a 3,000 [] Eichler home; all on a single thermostat. The distribution piping is 3/8" copper tubing and because of the high pressure drop, I plan to use a Grundfos 26-99 circulator, piped directly, i.e. no primary-secondary configuration. In addition, there's an on-board circulator on the IBC HC boiler, so there will be two circulators in series, increasing the head pressure.

Other facts:

• 1" supply and return
  
• Two manifolds, both with butterfly valves on the 3/8" tubing. Some of the valves have been turned off. All the valves are frozen.
  
• The interior is all original. Minimal insulation and single-glazed windows.
  
• The previous boiler and circulator were gone by the time I got there, so I have no idea what was used before.
  

I plan to put pressure gauges on the suction and discharge sides of the circulator to find the duty point of the system.

Any comments?

EBEBRATT-Ed

Don't know where to start:

Finding valves shut off make me think leaks. I am assuming in your area there is no freezing potential.

I think i would start with pressure testing and flushing.

are you doing a heat loss to size the new boiler?

hot_rod

Some if those 3/8 copper tube jobs were only 100’, the length of the coil. You may not need so much circulator?

Alan (California Radiant) Forbes

Finding valves shut off make me think leaks.

The old, site-built copper manifolds are only return manifolds, so the tubing would still be pressurized.

I am assuming in your area there is no freezing potential.

Correct.

I think i would start with pressure testing and flushing.

A leak locating company was hired to test the system. They noticed a very small leak, but said it was too small to find.

are you doing a heat loss to size the new boiler?

Yes - 27 BTU/[]

Some if those 3/8 copper tube jobs were only 100’, the length of the coil. You may not need so much circulator?

There aren't that many loops on the manifolds, so I think they are longer.

hot_rod

With some loops isolated, can you still cover the load?

Alan (California Radiant) Forbes

With some loops isolated, can you still cover the load?

Those old butterfly valves are porous. Even though they are turned off, I think the loops still heat.

mattmia2

Are those actual butterfly valves like with a plate that the stem turns like a throttle or choke plate in a carb or are they something like little 3/8" gas cocks? If the latter, might be able to loosen the nut and wiggle them out and free them.

You know you can't post this without pictures

Alan (California Radiant) Forbes

Yes, the plate kind. Pictures coming.

Jamie Hall

Be very careful of two pumps in series. If their flow characteristics don't match -- maximum flow, not maximum head -- they may not play nice with each other.

GroundUp

Why not pipe it P/S like the MFG requires? Odds are slim you're going to get any more umph from those two incredibly different circs in series than you would with the 26-99 alone, and I already think the 26-99 is gross overkill. I'd talk to IBC before you get too carried away and verify minimum flow requirements are being met and that they'll still honor warranty if piped direct/in series

EBEBRATT-Ed

This is a spot for doing something I always wanted to try and never did.

With an unknown concealed system. Hook a garden hose to it with a flow meter and pressure gages on the system supply and return. Turn the water on and get some flow, read the flow meter and get the PD off the gauges. Then go to the B&G wheel and find the PD/ft of head at the desired flow.

will it work? I don't know

mattmia2

Just the pressure and flow from the supply will let you figure out the rest. Should be able to figure out resistance from that and equivalent length given the size of the tubing from that.

kcopp

I did a very similar job a couple years back.
IBC HC 125
Radiant in the walls and ceilings w/ 3/8" soft copper.
I did a LLH w/ a Caleffi unit.
the 2699 worked fine.

Alan (California Radiant) Forbes

What flow meter would you suggest?

hot_rod

You have a load of 27 btu/ sq. ft?
If so for 3000 sq. ft you need 81,000 at design.
Then determine how many gpm you need at the delta you want to run. Simple math shows at 20∆, 8.1 gpm. Although you might want a tighter 12- 15 ∆?

Now you need to figure out how to move that gpm in the tube you have, that being your biggest unknown.

27 BTU/ ft sounds high, lots of glass, poor insulation?

For accurate flow meters, do you want to install and leave it? if so the Caleffi 132 is a good option.
For a temporary reading you can rent or borrow a clamp on type ultrasonic. Go to www.onicom.com, search for local rep. Badger meter is another brand.

Or I could lend you my Caleffi Conteca, an energy meter that uses a basic rotary water meter and two temperature sensors to give you flow rate, ∆T, and BTU/ hr readout.

Or here is a basic 13 gpm rotary water meter I use for getting accurate flow rates, two garden hose connections. I use it mainly for filling systems to get an accurate fluid capacity. Pipe one in temporarily to show actual flow with your different pump options.

Alan (California Radiant) Forbes

Thanks, GroundUp. I contacted IBC and they said don't do it in no uncertain terms.

I don't have the equipment for measuring flow, nor the time to procure it. I'll let you know the outcome.

Alan (California Radiant) Forbes

Three thousand [] house, 13 loops of mostly 3/8" tubing. If the loop spacing is 12", that's 230 feet per loop, a bit too long for such small tubing. Maybe that's how they made Eichler's so affordable.

hot_rod

It looks like different OD tube on the various loops? is the 3/8 the OD size or ID?
200' at a .3 flows what is suggested for 3/8 pex. I have seen 3/8 rubber tube run at 250' lengths, and it was a rougher inside compared to pex or copper. It took a bit more circulator to make it happen
The old copper around my area was 18" on center, maybe the copper being a much better conductor than pex allowed it to work ok?
Or the owners never noticed the wide temperature striping with 18" space.

Just seem 13 loops for a 81K design load is way off, if most are 3/8 flowing .3 GPM?
It must have worked all these years? Any sign of backup heat sources?