At what point does a boiler need a larger circulator?

Steve Garson_2

I am adding a 16,000 BTU/hr load to my boiler for a new addition. My WM GV-4 Series-1 (115K net BTU) has a built-in circulator, that today moves water for four 3/4-inch zones and a 1-inch zone for the hot water heater. Total BTU load for the entire house with addition is 68,000 BTU/hr. The new zone will be another 3/4-inch pipe.

Is the present circulator fine? If not, do I measure the Delta-T at the boiler to do a calculation? My gut tells me I need faster water circulation since the Delta-T on the longest zone is 40* to 50* on a cold day.

Thanks!

Steve

EBEBRATT-Ed

40-50 is way too much delta. Most CI boilers want you not to exceed 30 if I recall correctly. Big TD across the sections could damage or crack the sections.

Post a sketch of what you have pipe sizes and draw it out show baseboard footages and myself or someone else will figure it out

Steve Garson_2

Will do. The boiler has a bypass so that hot water always mixes with the return water, Will gather the info.

pedmec

weil mclain recommends that you switch to a primary secondary piping arrangement

mattmia2

So i'm guessing this is a gravity conversion?

HomerJSmith

At what point does a boiler need a larger circulator?

You know when you've gone to far when you blow the fittings off the pipe.

Other than that, you add up the pressure losses in the circuit and add 10%. I know what you're thinking, "That's not easy to do." Agreed. A variable speed pump will give you some leeway as to Delta T. Use a Caleffi boiler by-pass valve that will regulate the by-pass.

Steve Garson_2

Feet of baseboard by zone (does not include length of copper feed pipes:
1: 36 Feet (this room has big delta T) plus 4900 BTU/hour Runtal flat panel radiator
2: 12 Feet
3: 22 Feet
4: 22 Feet
Indirect HW: 41 gallon
5: New zone: 14,000 BTU/hr from Manual J Calculation. Fed by 30 feet of 3/4 PX each supply/return.

The Manual-J for the main house is 34,000 BTU equipment load. The addition is 14,000 for a total of 48,000 BTU/hr. Boiler is twice the size needed.

The circulator in the boiler is a WM GV-4 Series one. Old, but works fine after new circulator, blower and ignitor. Kompak baseboard specs for different temps below. Assuming 170* it's 530 BTU/foot and 56 feet of radiators, that's 34,580 BTU/hour load, then 49,000 BTU for the whole load.

Thanks for your assistance.

JUGHNE

I had a GV-4 Series 2 until I went to a Mod Con.

Great boiler, still resting in the basement corner. Working when removed, control module updated and spare parts....waiting for you to come and get it....SS venting included.

Those had a internal mixing valve to keep the return water above condensing temp for the boiler.

This mixing valve usually failed and no replacement is available.
There is a tech service bulletin SB0401R1, 2-25-2004 on how to correct the situation.

I plumbed mine originally as PS with another circulator.
Advice from the supplier to do so.

Steve Garson_2

JUGHNE, do you recall how much your gas usage dropped with the modcon?

EBEBRATT-Ed

Looks like you need around 13gpm. I allowed 6 gpm for the indirect so that gobbles up a ;lot of flow when it is on. You may want to recheck the TD when it is on then off to see if there is any difference.

zone #1 2.47 gpm, #2 .66gpm, #3 & #4 1.21 gpm each, indirect 6gpm and addition 1.4 gpm.

A typical Taco 007 will do 13 gpm against a 6' head (about 2.6 psi across the pump)

If you could get gauges across the pump that would tell something . Probably get one on the boiler drain for instance. Unless you have some restriction I can't see why the TD would be so high. Weil uses a TACO 007 or = with that boiler so it should be large enough unless you have some restriction

EBEBRATT-Ed

Unless your gas pressure is off and is down a bit that would give you a larger TD.

Steve Garson_2

So it sounds like the Taco 007 on the boiler is all I need, including for the indirect HW heating, which is on priority over the other zones. I was going to add a circulator dedicated to the hot water, but I guess it's not necessary.

EBEBRATT-Ed

@Steve Garson_2

Unless you have something unusual going on the Taco 007 looks light the right circulator. but that does not explain you high TD

Robert_25

1: 36 Feet (this room has big delta T) plus 4900 BTU/hour Runtal flat panel radiator

I would not expect a large delta T across that load unless the flow is very restricted.