Coil for hot H2O vs Indirect Tank...not efficiency but performance?!

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Old 10-29-13, 09:00 AM
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Coil for hot H2O vs Indirect Tank...not efficiency but performance?!

Asking another way and appreciate opinions.

Have a 25 yr old Peerless boiler w/ coil. Appro. 1800sqft, poorly insulated Levitt house w/ 3 zones. The current plumbing is a nightmare of patched together zones, zone valves and circulators. When heat is on to a zone, how water drops terribly. When more than 1 shower head or shower plus anything (heat, dishwasher, etc), is running, hot water drops in a minute. Impossible to fill bathtub unless using the shower head which takes 1+ hours. Unfortunately very tight space so I have 2 proposals:
1. New Peerless WBV-03 with Buderus S120 (32 gallon) Indirect tank. 4 zones, correctly and efficiently plumbed. Advised the 32gal is all clearance will allow.
2. Create access panel and just add S120 indirect behind current boiler on separate zone.

I am not opposed to either plan and prices are great for both. ($5500 for plan 1, $1850 for plan 2). Reputable guy. Many references. Knows these houses and their unique issues. I do purchasing and know the going rates of the
equipment and think it's all fair and on the up and up. 2nd quote is in the same ballpark.

My biggest question is WILL I SEE IMPROVEMENT IN HOT WATER!?

I know recovery on coil (if new is 3-5 gals per min, my current one, who knows?). Recovery on tank is 260 gals per hour. Will the tank replenish continuously?

Hate to do this if no improvement in hot H2O. I know oil efficiency will be better due to not running as much during warm weather months. Unfortunately, gas is not an option and a larger tank not an option. 3 of us but we like long showers and unlimited hot water.

Sorry for the long winded question. Appreciate any answers. I need to pull the trigger asap. THANK YOU!!!
 
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Old 10-29-13, 10:15 AM
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WILL I SEE IMPROVEMENT IN HOT WATER!?
How can you NOT? The only way you could not see improvement is if you started heating your water in a kettle on a wood stove.

Recovery on tank is 260 gals per hour. Will the tank replenish continuously?
Study and understand water heater ratings.

I'm not sure what you mean by "...Recovery on tank..." Are you talking about the continuous rating that Buderus publishes for the S120? If so, that rating is presuming a stated BTU output of the boiler. If your BTU is less, so will the continuous rating.

So, 260 Gallons per hour equals 4.333 Gallons per minute.

No, you won't be able to run three showers at 2.5 GPM each continuously. Not even TWO. But, certainly ONE.
 
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Old 10-29-13, 10:44 AM
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Thanks Trooper. I'm not sure about the "How Can You Not" thing. If the coil does 4-5 gpm and the tank does 4.33 as you say, where is the big difference? In the age/wear of the coil?

I do not have the details in front of me but I am understanding the btu ratings of the propose equipment match so the 4.33 gpm # is probably accurate.

Unrelated, I am amazed at the spa shower setups (head, hand held and 4 jets) that are sold requiring 17+gpm. What does a residential system require to pump that much hot H2O?! Looks pretty but seems almost impossible to use as designed.
 
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Old 10-29-13, 11:45 AM
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If the coil does 4-5 gpm
I think the key word is " IF " and it obviously does not...

Perhaps a brand new coil might be able to do that, but once they get 'limed up', fuggedaboudit.

That and the fact that there is ZERO 'storage' for a coil, you are subject to the 'sandwich effect' of initial hot water, then cold, then hot when the boiler kicks back in again... etc...

With a storage tank, you are starting out with an ample supply of hot water, and the location of the aquastat on the indirect tank is going to sense the need to call the boiler well before you end up with a cold water sandwich.

I dunno about them fancy spas... never installed one, never been in position to use one.

How would one even flow 17 GPM of COLD water if they had to? That's a tremendous amount of water.

My guess is that there has to be dedicated plumbing to the shower, probably at least 1" 'home run' supply piping back to the service entrance.

It also would not surprise me if there would have to be instant hot water heaters added, or a 75-100 gallon commercial water heater, or both.

17 GPM is a LOT of water... talk about a 'human car wash!'

I bet the system needs upgraded drain plumbing too... at least 2" ... on a home run back to the building sewer connection.
 
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Old 10-29-13, 10:54 PM
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A standard tankless coil will never have the performance of a storage tank heater. If you want a large, and continuous flow of hot water then you want an instantaneous water heater.
 
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Old 10-30-13, 06:22 AM
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I think coils get a bad rap. This is my 2nd home with a tankless coil. Never an issue with any of them. We can shower, do laundry and run the dishwasher all day and never run out of hot water.

When you say the hot water drops, does the flow drop off or just the temperature? You could just have scale build up on the coil. It may have to be removed or just acid flushed to restore it's performance.

Coils may not be the most efficient way to heat DHW, but when they work correctly you get unlimited hot water from them.
 
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Old 10-30-13, 09:19 AM
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Tom, when heat is called to any zone the hot water loses temperature. When multiple items in use, loses temperature. Pressure drops slightly but not the bigger issue. It's the temp dropping. Too ritzy a showerhead? Temp drops. Even after last coil cleaning, temperature can be scalding (we like it very hot) but turn on another tap and it goes warm. I can live with the coil and unless I replace the boiler too (due to space issues, no way to get a tank in without removing the boiler) I will have to live with it.

Trooper: One repair guy says just correcting the plumbing and zone(s) mess will add efficiency that will help the whole system (and tank especially) even more. Based on a new boiler and indirect of course, not current system. Does that sound like a sales pitch to you or is their validity in it? Thanks.

Any opinion on new Peerless WBV-03 w/ Riello and Buderus S120 (32 gal) tank for 1800sq ft Levitt turned colonial (dormered) w/ 2 bathrooms, 3 people? The price is quite good.
 
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Old 10-30-13, 10:43 AM
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What are the aquastat settings, low, high and diff? Is there a mixing valve on the output of the coil?
When there's a call for heat that boiler should be running up to about 180, without a mixing valve, you should be able to make tea from your tap during a heat call. The fact that your losing temp during a heat call makes me think the boiler itself isn't coming up to temp correctly or isn't set up correctly. What does the actual temp gauge on the boiler say when the system is at idle, only using hot water? Then what does it go up to when there's a call for heat?

Another thing to look at is the BTU rating of the boiler and the nozzle size (firing rate) or input to the boiler. If the nozzle is to small, then your not getting enough BTU input to the boiler to overcome the heat loss of the system. That would cause a drop in the system temp when the demand is high.

When was the last time the boiler was tuned up and an efficiency test performed?
 
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Old 10-30-13, 12:06 PM
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Tuned, nozzle replaced, vacuum'd every year. Don't think we ever did an efficiency test (never heard of it). I believe boiler is 129k btu.

Winter temps set at 160/180. Summer lowered 20 degrees or so. Aquastat probably not spot on but not way off either.

There is a mixing valve that was installed later because water is crazy hot to start so we mix in a tiny bit of cold. Doesn't matter if we mix in zero cold, temps still drop (start scalding, drop to warm). Water is plenty hot to start. Drops if zone calls for heat or if other hot water source is used simultaneously.
 
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Old 10-30-13, 02:51 PM
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It really sounds like you have a few things going on. First off, the aquastat should give priority to the coil on a call for heat. Meaning if the boiler temp goes below 160, the circulator should stop providing heat until the boiler catches up. At 160, you should have plenty of HW, at 180 you can make tea.
Are you sure the mixing valve is working or installed correctly? Was the issue present before the mixing valve was installed? Do you know what the flow rate is on the coil? It should be on the plate, I think standard is 5GPM.

1800 Sq. Feet @ 129K BTU's is huge, which makes me think the boiler might be down fired incorrectly. I'm just under 2000 Sq. Feet, Cape with about 85K BTU's. I consider it over sized, but it's been down fired slightly. With a boiler that big, your DHW shouldn't be an issue if the right size coil is in there and it's fired correctly. You should have more heat and HW then you know what to do with.
 
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Old 10-30-13, 03:41 PM
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I can make tea now, just can't make a whole lot of it! lol All the repair guys tell me the coil is probably doing 3gpm, maybe a little better after a cleaning and most houses in my area have the same issue w/ similar systems. Levitt houses are a bit of a unique animal but don't know how much that is an issue. Anyway, all the research has led to the possibility that I may be able to convert to gas after all but that will take some time. I appreciate everyone's answers and input.
 
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Old 10-30-13, 04:19 PM
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Tom, you give more credit than is due to t(h)ankless coils. I'm glad yours is working out for you but the jury has come back time and time again and declared them as a pitiful way to make domestic hot water for exactly the same reasons that the goose is talking about. The body of evidence says that you are LUCKY for some reason!

Meaning if the boiler temp goes below 160, the circulator should stop providing heat until the boiler catches up.
This isn't exactly accurate.

The LOW setting on a triple aquastat has TWO DIFFERNTIALS IN PLAY.

1. A BUILT-IN, NON-ADJUSTABLE negative/subtractive 10F differential. This is totally separate from the DIFF setting on the dial.

2. The ADJUSTABLE DIFF dial. This is a positive/additive DIFF.

What this means is that if the aquastat is set to 160 LOW, the boiler will not fire and the circulator will not be disabled until the boiler drops to 150 ( Low setting minus the fixed diff of 10).

The ADJUSTABLE DIFF dial is in the ADDITIVE (or positive) direction, and ADDS TO the FIXED diff.

Here's a couple easy formulas:

Burner will fire and circ will be disabled when:

LOW MINUS FIXED DIFF of 10 is reached.

Burner will continue to fire and circ remain disabled until:

(LOW - 10) PLUS ADJUSTABLE DIFF is reached.

Let's call the difference between these two temperatures the CONTROL RANGE, BOTTOM and TOP.

Some examples:

LOW of 160, (adjustable) DIFF of 10

160 - 10 = 150 = BOTTOM of control range.

(160 - 10) + 10 = 160 = TOP of control range.

With these settings in the absence of a heat call the boiler will cycle between 150 and 160.

another:

LOW of 150, (adjustable) DIFF of 25

150 - 10 = 140 = BOTTOM of control range.

(150 - 10) + 25 = 165 = TOP of control range.

With these settings in the absence of a heat call the boiler will cycle between 140 and 165.
 
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Old 10-30-13, 04:22 PM
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Goose, what are you setting on the ADJUSTABLE DIFF dial?

If you are on 10, try increasing it to 20 and see what happens.

This should give longer boiler firings when you are using hot water and will result in less of the 'sandwich effect'.
 
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Old 10-30-13, 04:39 PM
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Trooper, my wallet loves that train of thought but the aquastat only has two dials, lo and hi. I just set the high to 180 and the low to 160 ish. Too high?
 
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Old 10-30-13, 04:54 PM
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Ohhhhh... you've got an 'oldie'... I forgot!

I bet it's an L4081 , isn't it? The only thing in the box is the block with the two dials on it, right?

This probably also means that your circulator does NOT get disabled during a 'LOW' call... and explains why when there is a heat call during DHW call that your water cools.

Too high?
No, probably not. Lower it and you get cooler water... except when there is a heat call.

One repair guy says just correcting the plumbing and zone(s) mess will add efficiency that will help the whole system (and tank especially) even more. Based on a new boiler and indirect of course, not current system. Does that sound like a sales pitch to you or is their validity in it? Thanks.
Yeah, probably a little 'hype'. I mean, the water doesn't really care if the piping is 'organic' or not, as long as it can get through and does it's job of heating the home.

Where you would probably save is in the newer boiler which hopefully is designed a bit better with a higher AFUE rating.

Ask your guy how he feels about the Burnham MPO boiler instead of the Peerless...
 
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Old 10-30-13, 06:05 PM
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I dont own a gun but Im going to buy one so I can shoot my coil when I remove it.

Wait! I guess I really can't remove it when I get rid of it, but I'll think of something nasty to do to it.
 
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Old 10-31-13, 08:48 AM
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Trooper - Great explanation on how the a'stat works. Do you think his old style could be part of his issue? As you said, I guess I've been lucky with my coil, lets just hope it to work correctly for a few more years.
 
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Old 10-31-13, 09:40 AM
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Trooper, I think he recommends the peerless mostly due to small footprint, top flue (necessary) and they did amazingly well through hurricane sandy flooding compared to other models. Said they change the chamber and it's good to go while others had to go to the scrap heap.

Honestly, just called Nat. Grid and they can bring gas to the house no charge so is it a no-brainer to go to gas? Price wise it appears so. Would love to cook with it, too.

Unrelated (and last I'll ask in this thread since it's so off topic): Many options for boilers but Nat Grid offers crazy good rebates on Burnhams (not very high efficiency though). I am looking at a PVG5ANI-GS (or 6). Any reviews on Burnham gas boilers? It's hard to find reviews at all on line for any boilers.
 
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Old 10-31-13, 05:03 PM
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Do you think his old style [control] could be part of his issue?
Could be part of it.

More so I would think that the old coil is probably just really scaled up... perhaps not only on the inside, but maybe even on the outside as well, where acid flushing won't help.

they can bring gas to the house no charge so is it a no-brainer to go to gas?
Yes, absolutely.

It's hard to find reviews at all on line for any boilers.
I answered in other thread... I wouldn't trust any review on-line unless the reviewer's 'creds' were stated and meaningful. Even if you found a pant load of 'bad press' about a product, you should realize that the only people that are motivated to post their drivel are the ones that have an 'axe to grind' and that axe is usually handed to them by the jackazzes that messed their stuff up and NOT a defect in the product.

In other words, with boilers at least, if you read that a particular boiler is junk, 9 times out of 10 it is the fault of the installer doing a shoddy job.

There ARE exceptions. Every industry has them. I once owned a Chevy Vega.

There's nothing wrong with the WBV, I know lotsa folks with them.

There's nothing wrong with the PVG, I don't know that many, but as far as I can tell it's a good basic no-frills conventional boiler.

Is the PVG the ONLY one they are pushing? Check out the ESC from Burnham too... maybe they can get you one of those?

Burnham ESC boiler

One more thing... nothing wrong with the Buderus S120 indirect, but the Burnham Alliance SL is a nice one too.

Burnham Alliance SL

(now you watch, the flood gates are open... let the naysayers speak!)
 
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Old 10-31-13, 05:46 PM
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Thanks for the info Troop, and for the record a beat to s*it Chevy Vega got a friend and I all the way from Portland, ME to Caribou, ME and back (10+ hours each way) to a wild biker party one summer without batting an eye so it's got a place in my heart.

That said, the Burnham ESC's are on the list and also at insanely great price (lower than retail plus $700 gift card rebate + $400 energy rebate. That's a crazy good deal. Hard to pass up. No such deals on IWH's though so the Buderus is still the likely choice based on the footprint to quality factor.

Thanks for your help. Excited to upgrade and go to gas. Even my emergency generator is a tri-fuel (gasoline, propane and NG) so that's another benefit. No more sta-bil'ing and storing a dozen gas cans.
 
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Old 11-01-13, 11:47 AM
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Before I got silly a few posts ago and forgot what I was doing, I actually did want to add my negative experience with the coil. One more data point for those who read the thread.

My low limit on the astat is 155 and I can take one lukewarm shower. Its very hot (tea brewing) for 10 secs, then cools to warm, then barely warm. I know the temp gauge is good because I can compare it to the L7224 temp display (astat) and they are in agreement.

Former owners had their low limit on the astat set at 165. Now I know why. The water here is not hard but I guess liming of the coil still could be the cause, since I assume liming could still have occurred, but only at a slower rate than those with hard(er) water.
 
 

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