How to calculate GPM for this system head loss?

ced48

One thing that is for sure, it certainly doesn't mean it's the right circulator for your application.

Gordy

And many of those 007's end up in the installers inventory. Just because it came with the boiler does not mean it is correct for the system, or you have to use it.

bmwpowere36m3

If I had installed the Grundfos 15-58 that came with my Lochinvar boiler it'd never condensate... WAY over-pumped.

bob_46

hydronic design has changed over the years. For many years residential systems were designed around a B&G 100 pump, we matched the system to the pump not the pump to the system.Today we have many more options.

HeatingQc

@bmwpowere36m3

This is a common mistake. Overpumping the boiler itself won't make it condensate less. This type of boiler should normally be installed in a primary-secondary system. And your boiler efficiency (level of condensation) will be affected by the system return temp, which is independant from your boiler flow. The only thing is to make sure to have more flow in the system than in the boiler so you don't recirculate hot water at the succion of the pump.

The system flow should be reduced to have higher deltaT and colder returns. At the opposite, for a constant return temperature, having more flow in you boiler will reduce deltaT, lower the average temperature of the boiler's exchanger, and this can make it condensate even more!

Zman

HeatingQc said:

@bmwpowere36m3



This is a common mistake. Overpumping the boiler itself won't make it condensate less. This type of boiler should normally be installed in a primary-secondary system. And your boiler efficiency (level of condensation) will be affected by the system return temp, which is independant from your boiler flow. The only thing is to make sure to have more flow in the system than in the boiler so you don't recirculate hot water at the succion of the pump.



The system flow should be reduced to have higher deltaT and colder returns. At the opposite, for a constant return temperature, having more flow in you boiler will reduce deltaT, lower the average temperature of the boiler's exchanger, and this can make it condensate even more!

I am going to have to go ahead and disagree with you on that one...
Over pumping the boiler will in fact reduce condensing and efficiency. Over pumping the system side can also contribute.
Read Idronics 1 http://www.caleffi.com/usa/en-us/technical-magazine

Gordy

So you want to have a wide delta on system side which depending on emitter type is not always a good idea. Say radiant. Also wider deltas usually require lower flow rates. Depending on the system this could easily throw you into a lower flow rate than the primary loop.

Also many instances do not require primary secondary if mod/con selection has a low pressure drop fire tube HX. So long as the minimum flow rate can be maintained at the HX.

With the coming of higher TDR boilers 10:1, 7:1 see
HTP UFT, Lochinvar KHN direct piping is a higher possibility. Along with flow rates that can match the low end modulation. There will,always be a place for P/S, but boiler advances in the high efficiency arena are changing the scope.

hot_rod

There is still a need for P/S in many boiler applications, although a hydro-sep is sometimes a better 4 in 1 choice.

The new UPXML pumps from Grundfos will add to the selection of PWM and 0-10VDC for the smaller sized fire tube boilers.

HeatingQc

I totally agree that if the boiler flow is higher than system flow, you will recirculate, and then kill your efficiency and condensation. This was stated in my original comment. I also totally agree that with fire tube boilers not in P/S, you don't want to overpump, since you would overpump your system too.

But on many systems, primary/secondary, where big flow/low head system pumps have been replaced with random pumps, often way to strong for the system. As long as your boiler flow doesn't exceed the system flow on a P/S, you still are more efficient with a 25F deltaT than a 40F deltaT, and having more chance to condense. As I stated before, on a P/S, your system supply temp and return temp won't change if the boiler is running at full fire and boiler flow is kept smaller than the system flow.

Let's say your return is 110F. Supply 130F

Option #1 : 40F boiler delta T, the water leaving the boiler will be 150F @100%.

Option #2 : 25F boiler delta T, the water leaving the boiler will be 135F @100%.

The mix will be the same temperature, but we did many testings, and option #2 is more efficient by a few %. Simple to understand : colder average temperature in the heat exchanger. Sermenta (Giannoni at the time) tested it too, with the same results.

Zoning, variable pumps, all those variables may affect all of this. Yes the best option is to modulate the boiler pump AND the system pump.

But in a simple all open system, no a 15-58 on #1 speed won't be too big for any Lochinvar boiler, even the WHN055. I hear often that boiler deltaT must absolutely be as high as possible, which is not true!

MikeSpeed6030

Slightly different issue. For my older, relatively large, mono-flo system, I want to keep flow rate relatively high to help the diverter tees do their thing. A B&G HV pump was originally installed 60 years ago, and worked fine -- when I replaced it, I went with a Taco 0012, which has a comparable head-flow curve. This is for a fire-tube, high-mass boiler and system - non-condensing, of course.

HeatingQc

In that case it will work just fine. What's the deltaT of the system? Those big old systems are not too restrictive.

MikeSpeed6030

delta T is typically about 35 deg, but it varies. The boiler return temp is never below about 140 deg. The boiler gauge drops to about 160 (from 180 deg - for a warm-start boiler) during a long run. Cast iron baseboards and a steel fire-tube boiler, maybe 45-gal boiler volume? The boiler, piping, and the rest of the system is 60 years old, but I've replaced many of the valves and other components.

After 60 years, it still runs fine. When I've opened up the system for service, the internal steel piping shows no sign of corrosion or build up of scale. Conventional steel expansion tank (not bladder type). City water that is softened at the main plant, but no chemicals have ever been added to the heating system.

Annual natural-gas fuel cost for heating is $1,000 per year - about 3,800 sq ft.

bmwpowere36m3

HeatingQc said:

But in a simple all open system, no a 15-58 on #1 speed won't be too big for any Lochinvar boiler, even the WHN055. I hear often that boiler deltaT must absolutely be as high as possible, which is not true!

Unfortunately that's not the case on my system (WHN055, P/S, panel radiators)… with an Alpha pump [boiler] on speed I… at best I achieved 10* delta, whereas the system side is always near 20-40* (depending on ODT). Per advice on the forum, I throttled the boiler pump (still on spd I) and now my boiler is running a 30* delta (system side hasn't changed).

Not only have my run times increased, but the amount of time in condensing have as well.

Ideally I'd have a boiler pump controlled by the boiler (function os there), just the cost of 0-10 pumps is $$$.

HeatingQc

Thanks. I understand much better now. 10 was too low indeed. I imagine you've also set ramp delays on the boiler? That really help to make cycles longer, reduce cycling, increase efficiency ... and make parts last much longer! That's one of my favorite features of the KBN/WHN.

bmwpowere36m3

Yup, ramp set to reduce cycling in 40+ temps and limited to 35% fire at the moment.

Heat_n_CT

mind if I thread-jack and ask how do you limit the fire %

bmwpowere36m3

Ramp setting 6, it won't modulate above it for the rest of a heat call. DWH is not affected. However I believe there's also a setting to limit fan speed (overall boiler fire rate) as well.

So basically I set the ramp from 20% to 35%, with step 6 being 35%.

Heat_n_CT

That simple? I'm embarrassed...I had it increase 20% per step...didn't know you could adjust the % in each step. Not a big deal since I've never seen this thing get over 30% for heating. Cool, more tinkering.

bmwpowere36m3

Yup, you can change it in 5% increments, I think (each step). However setting the first step at anything less than 20%, doesn't do anything. Boiler can only modulate down to 20%. For example I had it set to 10-15% and it simply went down to 20%. Now my first ramp setting is 20%.

Not only that, but you can adjust the time at each step as well. You can also repeat steps, i.e., 20% then 20% then 20% and so on.

I haven't tried ramping it up AND then down... Not sure if there be any point in that anyway. Grab the service manual and read it, then play with the settings. Write down where you started, so you can always go back. It's pretty intuitive and features a LOT of adjustibilty!

HeatingQc

Yup. 6 ramps, adjustable in time (1 to 45 mins i think) and %. Ramping it down, to me, is a none sense. It's no more available on the new controls. If you have less load, just shut the boiler down. The setting of 5-10 and 15% is available on the Knight, but only applicable when more than one boiler is connected in cascade. If you have 2 boilers, the ramp delay (set on the leader) will apply on the total % available. So if you set it at 10%, one boiler will fire at 20% (10% of 200%).

Heat_n_CT

Huh, there it was right there in black and white.

CMadatMe

HeatingQc said:

I totally agree that if the boiler flow is higher than system flow, you will recirculate, and then kill your efficiency and condensation. This was stated in my original comment. I also totally agree that with fire tube boilers not in P/S, you don't want to overpump, since you would overpump your system too.



But on many systems, primary/secondary, where big flow/low head system pumps have been replaced with random pumps, often way to strong for the system. As long as your boiler flow doesn't exceed the system flow on a P/S, you still are more efficient with a 25F deltaT than a 40F deltaT, and having more chance to condense. As I stated before, on a P/S, your system supply temp and return temp won't change if the boiler is running at full fire and boiler flow is kept smaller than the system flow.



Let's say your return is 110F. Supply 130F



Option #1 : 40F boiler delta T, the water leaving the boiler will be 150F @100%.



Option #2 : 25F boiler delta T, the water leaving the boiler will be 135F @100%.



The mix will be the same temperature, but we did many testings, and option #2 is more efficient by a few %. Simple to understand : colder average temperature in the heat exchanger. Sermenta (Giannoni at the time) tested it too, with the same results.



Zoning, variable pumps, all those variables may affect all of this. Yes the best option is to modulate the boiler pump AND the system pump.



But in a simple all open system, no a 15-58 on #1 speed won't be too big for any Lochinvar boiler, even the WHN055. I hear often that boiler deltaT must absolutely be as high as possible, which is not true!

I've been saying this for years now. I'll also stand by that the reason the majority won't give us a variable speed boiler pump option is they don't trust the trade as a whole. Don't want to end up with problems, tech calls, headaches.

Not only should the boiler control a boiler pump to match the modulation rate to the flow rate it should also be able to manager single and multiple zone pumps as well. Boiler needs to be the conductor of this orchestra not the Honeywell On/Off thermostat or other brand. Which comes to my next want. A boiler mfg to come out with a wireless communicating stat back to the boiler. Control the boiler room from the equipment. No reason I need a zone control when a boiler control could do the same thing or even better yet, start focusing on constant circulation systems with thermostatic's.

Zman

Chris said:

Well said.
And why would they? Even if you only sell a product to qualified and trained people. The owner will call some service company and let them screw it up.