Is this zone underpumped?

D107

Just checked the system again today. When I moved the porch thermostat-- which is kept at 60 degrees--up to 70 I immediately heard expansion noises from the supply water, so that seems to indicate--as per subcooler, brad and others that deficient flow is not the problem. It would seem to rule out an air problem as well. Baseboard got warm quickly.

The old honeywell chronotherm --the clock function of which is dead--somehow turned off the call for heat when temp reached 64, so something is up with that. By jacking t-stat all the way up, got temp to 67-8 degrees. I checked supply and return temps at boiler and got about 110 deg out, 100 deg return. It was probably 48 degrees outside. Not sure how to interpret the 10 degree delta T except to say it's low and maybe not shedding enough heat. (I put black tape on copper piping and measured with fairly inexpensive digital thermometer that rose gradually to those temps.)

Subcooler's software figured 9.3ft head. To figure flow he used the Taco 007 IFC curve but the actual circ is the plain 007. On that curve it looks like at 9.3ft head I get about 6+gpm. Now that might be too MUCH flow, and account for the low delta T? So either that or the lower temp in porch is due to baseboard emitters requiring hotter temp than convectors.

Thanks,

David

D107

3/4\" supply, baseboard, 176 ft total circuit with Taco 007

This is 2nd zone for porch on slab. Zone Heat loss 7500K Btu; gain is 26KBtu. Element is 2.5"square fin in 10"H Embassy housing, 44ft run. Other zone is 1" monoflo with box convectors, heats fine to 70 with t-stat-run Logamatic 2107. Zone 2 barely gets to 66 or lower. Zone 1 has no air problems due to EAS separator, assume same for zone 2. Using Dan's rule of thumb I get 11 ft head, @ 4gpm.

Taco 007s also used on zone 1 and DHW. Former zone 2 circ was Grundfos UPS 20-42 speed 3, which at 11 ft head gave about 3.5gpm. (Of course that was with old 154K firing boiler. this is Buderus G115/21 firing at 84K.) I know baseboard requires a higher temperature than convectors, but porch load to loss ratio is quite high: 3:1. Looking at Taco 007 curve, at 11ft head--if that's indeed the head-- appears to give half a gpm. Can't see how that's enough.

The 20-42 has been discontinued. Its replacement, the Grundfos 15-42 speed 2 gives about 4gpm at 11ft head; or Superbrute 15-58 FRC speed 2 gives 4gpm at 12ft head.

Sound good?

Thanks,

David

Empire_2

Hi Dave

You are a little short as far as pump goes and I mean real close to the point of no flow. I came up with the same Numbers and I would bump up to Taco 008 which will give more than enough head to deliver the heat. GPM should be OK with the 3/4". 4 gpm with the 008 gives you 14 ft head, which will be your answer.

Mike T.

Rich Corcoran_43

Dave

You're on the right track with either Grundfos. You'll get the pumping capacity you need as well as the ability to tune your system by trying low, medium, or high speed.

subcooler

(1) 007 could easily heat most homes.

According to your heat loss?? you need less than 1 gpm to heat the space. 2-3 gpm for air elimination. What is you supply and return temp going to that zone?? This will show you what is going on. It is not the circulators fault.

Empire_2

Subcooler

It's not a flow issue, it a head issue. The loop specs out to 11 Ft head the pump only can deliver 10 @4 gpm....DO the math.

Mike T.

subcooler

I wish you would

do the math. How big of circ. does it take to move 1 to 2 gpm in a 3/4" pipe? Obvious that you don't know! Did you miss the btu's part of the question? This industry will never learn.

Empire_2

Easy big guy:

I didn't mean to come off cocky. I am looking at the head in this case. With the length of that run, and I don't care if it's 2 gpm or 1 or 4,...The 007 cannot produce the head to get it through the total length. Yea, even if he only needs 2 gpm which I think you meant, I can see that on the curve and it would do it, But the 3/4" line with the 007 will try to convey the 4 gpm!!! Yea 4 gpm and 40Kbtu/Hr. The pump doesn't care if the Heat loss is only 20K or so. Even if the 2 gpm would be OK, the head needed is still border line in my opinion with the 007.

And to answer your question, how big of circ to move 2/3 gpm through 3/4" line. If it's real SHORT, I could use a 003, but not at 176 ft total length. I think you walked out on the Head Vs GPM part of training that's when I walked in. OK were eeven Deal? :-)

Mike T.

subcooler

Cocky no.

Try this, it's some free software a guy sent me.

D107

re: Taco 008

Thanks Mike and the others. This hydraulics is quite a field all by itself. If the Taco 008 would give 4gpm at 14ft head, doesn't that mean in actuality at the 11ft head it would give 7-8 gpm which is twice recommended gpm for 3/4" pipe? Don't the Grundfos units match more closely? (Of course I know 11ft head is only an estimate; could vary either way.)

Curious what you'd say about subcooler's diagram.

Thanks,

David

Empire_2

Subcooler....:-)

Upon further review, the ruling on the field is I should have shut my mouth...:-) I looked and looked again, and I see where you are coming from. He could actually use 1 1/4" pipe and would still have enough pump to get the 1 to 2 gpm that he needs....sorry. I apologize. I do think that there could be a Q with the total run though. I see that 11 Ft head at 1 and2 gpm will work.....but do you think it would be better to up size just a little? Boy do I feel foolish......:-(

Mike T.

Empire_2

I like the diagram

I jumped to conclusions on this one. (tail in between leg's):-) I figured that you only need x amount to btu to be carried to the area and even larger pipe would work although not needed. I was thinking that the head required was so close, but I was incorrect.

Mike T.:-)

Paul_44

software

where did you get the free software????

subcooler

From the guy

that made it.

Josh_10

It is no doubt the starter version of John Seigenthalers hydronics design suite that he gives away with his book or one of his seminars.

You can buy a full version at www.hydronicpros.com. Good software!

subcooler

No full version

Thanks

D107

possible that the 4 degree shortfall is due to logamatic

curve being set for the convectors and not for higher requirements of baseboard? Ref Temp is 167 supply temp at 14 deg outside temp. Old boiler always ran 180 so perhaps that's why there was no problem. Hate to have to up the curve--which I had to do temporarily--for just the baseboard.

Also perhaps I should look at baseboard and see if there's a valve I can bleed to check for air problem. This is the family house and not mine so I get out there when I can.

Thanks,

David

Tony_23

The Bbd

It may have been designed for 180 at DTD. If the convectors were designed for a lower temp water at DTD, then there's your problem.

Two choices. (1) Change the curve.
(2) Add more bbd.

D107

you may be right; dealing with this systematically

I would do this:

1-Make sure there's no air problem. I recall that at the end of the boiler installation it took about 40 minutes of run time to clear the air pockets that had existed for years with the old return-side pumping. Rads long cold were restored to heating. That main zone had been run by an 008 and now by 007. The longest circuit length though for that split zone is only 136ft (8ft head) so perhaps that's why the 007 handles it. Convectors may have been designed also for 180, but since the load is twice the loss, heats zone 1 nicely.

2-Since we kept the old grundfos UP 20-42 we can have that put back in and see if that changes anything. If not, yes I guess the curve will have to be raised. Pity since that porch is rarely used--kept at 60 mostly--but has to be ready for the occasional overnight guest and I wouldn't bother trying to teach any family members how to temporarily re-program the curve......

Thanks,

David

subcooler

The short answer is

No

Rob_32

pump

I've had mixed success with the rule of thumb for head; e.g., a zone in my house goes ~11 ft by rule of thumb but <9 doing a real calculation. Can you provide a summary of total lengths of straight pipe, elbows, valves and fittings?

D107

Out of 176 feet total loop (88ft each way)

> I've had mixed success with the rule of thumb for

> head; e.g., a zone in my house goes ~11 ft by

> rule of thumb but _9 doing a real calculation.

> Can you provide a summary of total lengths of

> straight pipe, elbows, valves and fittings?



There is 44ft baseboard
Not counting very near boiler, I'd say:

D107

Out of 176 feet total loop (88ft each way)

There is 44ft baseboard, 3/4" inch piping.
Not counting very near boiler, I'd say:
20 90deg elbows (You can subtract the length they may take up from 176ft 'straight' total run.
I think the baseboard might have one valve at its start;
by fittings you mean copper to copper joints? The straight runs--including supply and return, are 10,10, 15, 15, 15, 15, 20, 20, 15, 15, plus 30 around a door.
Starts at boiler in copper, changes to black pipe, then back to copper near baseboard.
At boiler, line tees off supply manifold, circ is isolated both sides, has flow check, return Ts into return manifold.

Also note that this line is about 40 years old.

There must be a gauge of some kind that could actually give you a reading of head pressure. That would be the best, yes?

Thanks,

David

Rob_32

flow

Assuming the 176 ft includes the 44ft of element, I get

gpm, head(ft);
3.5, 5.40;
4, 6.82;
4.5, 8.38;
5, 10.08;
6, 13.86;

If you have 176ft of straight pipe + 44ft of element, I get

gpm head(ft);
3.5, 6.48;
4, 8.19;
4.5, 10.06;
5, 12.10;
6, 16.65;

In either case, with a plain 007 you are around 4.5-5 gpm.

Maybe new stat fixes at least part of the problem?

D107

I'd guess that t-stat is probably a minor issue

since it can always be turned up all the way to get room temp up to 67 or so. Thanks for the figures; I've never seen each segment added up like that with corresponding flow. (element length is included in the 176ft.) I had assumed Subcooler's head calc was correct, it was just the specific pump curve used (should be plain 007 not ifc). Usually you don't want more than 4gpm with a 3/4" pipe.

Thanks,

David

subcooler

007..

Can you get close to these numbers? This is a different way to look at it..

D107

higher supply temp certainly would provide more heat

Thanks so much for the calculation. When I had temporarily altered the logamatic---raising ref temp and offset--heat was better. But hard to justify keeping such high temp supply water for a zone that's rarely used and almost always kept at 60. Main zone is set for logamatic outdoor reset default curve, so supply temp doesn't get to 180 until it hits around zero degrees.

This hydraulics aspect of hydronics is fascinating to me and I obviously have alot a steep learning curve.

Thanks,

David