Not enough hot water--need help!

HomerJSmith

NOTE the mis-use of prepositions, to and from, in the supply and return to the heat source. It should read, I think, "Supply From Heat Source" and "Return To Heat Source".

nicholas bonham-carter

That shows the importance of paying attention in English class!—NBC

HomerJSmith

I stand by my earlier posts, the tank is not piped correctly.

SeymourCates

It might be piped correctly.

From the Installation manual:

flat_twin

HomerJ which model is that diagram for? It doesn't match this one from Heat Flo website. See page 4, For standard and HO models...

https://www.heat-flo.com/pdfs/Indirect Water Heaters - I+O Manual.pdf

The cold water inlet and hot water out are reversed between these two diagrams. The OP's photos look like the page 4 diagram.

EDIT
Sorry I didn't see this was already covered.

Dave H_2

I also see that the circ may be slightly undersized. Not enough to really jump at but the tank requires 14 gpm and the coil has a pressure drop of 6.2'
That land right on the performance curve of the 0015 set on hi. However, that does not take into account the extra pressure drop of the associated piping from the boiler to the tank. It also doesnt account for the extra pressure drop of 1" pipe rather than 1-1/4".
So with that being said, you are looking at a 0010 or a 0012

Dave H.

HomerJSmith

SeymourCates, interesting, I went to Heat-Flo site and looked at the indirect manual and your representation is correct.
I stand corrected. Startpage gave me the storage tank link instead of the indirect link. It should have been obvious to me, duh.

It looks to be a cupro-nickel HX in their brochure. I guess I should ask what the model # the tank is. HF-60?

From the Manual: Trouble shooting

"Insufficient/ runs out of hot water at the faucet.

•Thermostat (aquastat) setting too low.
•Undersized boiler with no priority to domestic water heating.
•Peak draw of hot water is greater than the tank storage.
•Sediment and/or scale buildup
•Faulty water heater thermostat" (aquastat)-- I might add low flow thru the HX in the tank--

"Mount the water heater circulator as close to the
water heater as possible, and make sure the flow arrow points toward the water heater. " Pumping into the tank HX (greatest pressure loss).

"The use of a check valve is required to prevent back flow through the water heater during operation of the space heating system." An IFC Taco pump and what model ?

Is the Taco pump correct in terms of flow, is it big enough? What is the pressure loss in the Indirect system? Low flow-low heat output. The flow rate thru the boiler and indirect should be about 13 gpm. 1" copper pipe at that flow has a velocity of about 5'/sec and that's ok.

I would concentrate my attention on flow and pressure losses.

Is the Nibco white handle valve 'fully ported' and why is there a red handled valve above it? I hope it isn't a globe valve.

SeymourCates

@Dave H

There really is no magic to the 14 GPM rating. This manufacturer specifies 14 GPM for boiler outputs ranging from 131K to 273K. So, clearly, he accepts a widely varying DT depending on the specific model. One could make a good argument that since the manufacturer allows a DT of 39 for the largest unit, allowing a flow rate of 10 GPM with a DT of 22 for the HF-30 should be perfectly acceptable. Of course, the performance will be improved with a higher AWT with the faster flow rate, but this is not the issue for the OP.

The OP will have an issue with cycling when attempting to store at 160F. With a DT of only 20 as the indirect approaches limit, the capability of the coil to accept the boiler output rating is not present and the boiler will likely cycle on limit near the end of the call. The solution, if he desires to store at 160, is to utilize 200F SWT to the indirect.

HomerJSmith

On closer inspection the red handled valve appears to be a hose bibb?

HomerJSmith

The way I learned it is based upon the BTU capacity of 1 gal of water which is rounded off to 10,000 BTU's. 10,000 BTU's into 140K=14 gpm. Is this the right concept?

Zman

This all comes from the universal hydronic formula.
Btu/hr= GPM x 500 x delta T.
It just works out nicely that 1 gpm x 500 x 20 delta = 10,000 btu/ hr. There is no saying that you have to use a delta of 20.
If you are are trying to make 160 degree domestic and you are starting with 180 degree boiler supply, you need to have a delta of less than 20 or you will never get there. The boiler would cycle as the tank temp approaches target.

To the OP. Has anyone considered a faulty or incorrectly piped mixing valve.
Next time you run out of hot water, feel the hot pipe going into the mixing valve. You can also turn the adjuster on the tank aquastat and it will click at the the actual tank temp.

kunisk

I had the piping triple checked. Everything is in the right spot out of the water heater. Two things stand out from all the comments so far: 1. the size of my boiler not being strong enough and 2)
possible gunk in the circulator that could slow the flow. I still need to check the temps on the pipes going to/from boiler to see differential.

kunisk

Also thank you to everyone for input.
Regarding faulty mixing valve, I changed the mixing valve already to confirm that is not the issue.
Here is a pic close up of circulator. Is this my issue? Is the "check" valve you mention there? Could that be the cause if its not there? The green circulator is the one that pipes into the boi
ler return on top.

Zman

There is no check valve in the picture. Some of those circulators have an internal one in the throat. Usually there will be a sticker on the motor indicating it is.

Do you have the specs on the old HWH? Usually those are < 40k btu

kunisk

Just to be clear, the circulator in the pic is the one for the hot water going back into the boiler.

Zman

The water does not care about arrows on the pumps or where you want it to go. If you don't have check valves on both circs, the water will flow backwards through one circ when you are trying to satisfy the load on the other. On occasion the mixing valve can backflow as well.

What area are you in. Your system should be performing better that the old system. Maybe a fresh set of eyes would help.

kunisk

I am in ny on long island.

kunisk

Plumber says there is a check valve.

kunisk

Is this a check valve? If so its ln the pipe that is labeled boiler return.

SeymourCates

kunisk said:

Dennis- the priority is on for the hot water circulator. I have two circulators. One for my heat circulator (which has three zone control valves) and one for my hot water circulator. The priority is set for my hot water circulator and i have tested this.

The boiler goes between 170-180. As the boiler drops to 170 it turns on till reaching 180 again.

I read this as the boiler is cycling during a DHW call. If correct, you certainly cannot get 100K BTUH from a boiler that is not running!! Raise the high limit to 190F and see if that solves your problem. The boiler must run CONTINUOUSLY for the entire DHW call. If it won't run CONTINUOUSLY with the high limit set to 190F, raise it to 200F. This is certainly not ideal for CH but you have few options with dual showers that exceed 20 minutes.

Although it may sound counterproductive, you might also experiment by reducing the indirect tank temperature to 150F and simultaneously raising the high limit to 190F. This will certainly allow the boiler to run continuously.

Zman

kunisk said:

Is this a check valve? If so its ln the pipe that is labeled boiler return.

Nope,
That would be a pressure reducing fill valve.
You may have one in the circulator.
Quite a few of the guys on here are from your area. You might try the find a contractor tab at the top of the page.

HomerJSmith

I can't see from your photos where the supply from the boiler to the tank takes off. Is it after the B&G IAS on the manifold after the zone valves?

Zman is right, water moves from high pressure to low pressure and you have to have check valves to direct the flow where you have bifurcated runs. That means a check valve for the black pump and one for the green pump. If the green pump is a newer pump, the output of the volute probably is channeled for a plastic check valve if it doesn't already have one. If it has one, the installer should have put a IFC (Internal Flow Check) sticker on the back of the pump. Your pump is a Taco 0015 MSF-IFC so it should have a IFC. Caleffi make an inline flow check with a high CV (low flow resistance) that can be mounted vertically or horizontally and that can added before the black pump. If you have indirect tank priority over space heating, I would expect that the Honeywell zone valves would stop the dynamic flow but without a check valve on the black pump allow thermo-syphoning to the heat emitters on the upper floors, but that may not be a big deal.

BOTTOM LINE--You ain't got the flow, babe. You have a Taco 0015 MSF-IFC pump, did anyone look at the pump curve for speed 3? At 14 gpm it has 6' hd. Damn, your HX has 6.2' hd + boiler and piping pressure losses. When you don't have the heat I always think of flow, first. Flow is the conveyor belt that transfers heat energy. Measuring the temperature differential between the boiler supply and the return at the HX would have told you that. It would have been a wide differential.

Kunisk, you have a convoluted piping arrangement, it could have been done a lot better and if you had chosen a tank with boiler ports on the side rather than on the top, you could have shortened your pipe runs by 2/3.

You are going to figure out your pressure losses on the indirect circuit and choose a pump that would give you 14 gpm at that head loss.

HomerJSmith

No, that's a picture of a pressure reducing valve. It sets system pressure. I think it is connected to the bottom of the B&G IAS.

SeymourCates

The boiler has a net of 113K. A flow rate of 11 GPM is more than sufficient and would yield a DT of 20. Sure, if you force 14 GPM through the coil, you reduce the DT to 16, but the effort and cost is not worth the four degree benefit.

The key to performance is the difference between the tank setpoint and the boiler HL. That needs to be 40 to keep the boiler running throughout the call. It's only 20 at the present time.

Don't take the manufacturer's magic flow rate as gospel.

HomerJSmith

Kunisk, let us know what changes you make to solve your
dilemma. Inquiring minds want to know.

HomerJSmith

I haven't seen a pressure loss vs flow chart on that tank HX, but at 11gpm you have 9' hd with that pump. The HX pressure loss would drop to maybe 5' hd which leaves 4' hd for all the other pressure losses in the system. I think with that pump and sys losses you have a lot less flow than 11 gpm.

SeymourCates

.03 psi/foot on 1" @11 GPM

Figure 30 feet of pipe down and back.

2'

You might have more flow than 11 gpm.

neilc

if the boiler is cycling on temp while doing the DHW, then there is enough boiler.
The flow isn't getting to the domestic tank.
The heating circ, or both circs, need backflow(s), to direct the boiler heat to the domestic tank.

HomerJSmith

I'd want to add it all up. I'm not good at guessing, I played roulette for 15 min, once, and walked away broke. I don't see where the take-off from the boiler to the tank is or how it is all piped or what the boiler pressure drop is at 11 gpm.

HomerJSmith

Kunisk, you can take 'hot rod's' advice and put in low flow shower heads or put restrictors in the existing shower heads. By the way, what is your domestic water pressure? You could lower that if it is too high.

SeymourCates

The pressure drop though the coil is 3.5' @11 GPM. The pressure drop though the piping is 2' @ 11 GPM.

This assumes 1" for the entire length from the boiler to the coil and back. Not confirmed.

More than enough circulator.

SeymourCates

Another interesting tidbit about the HF-60

It has a continuous rating of 208 GPH @140F with a 90F rise and a 200F supply. This precisely matches their stated boiler requirement of 155700 BTUH.

Contrast this with the continuous rating of 177 GPH @140F with a 90F rise and a 180F supply. This does not match their stated boiler requirement of 155700 BTUH.

In the former case, with a DT of 60F, the indirect can accept full output from the boiler. In the latter case, with a DT of 40F, the indirect cannot accept full output. The tank temperature would need to drop to attain a DT of 60F. Or, in the case of recovery, the boiler is going to cycle at the end of the call.

This is quite telling in the case of the OP who currently has a DT of 20. I suspect he will be OK with a DT of 40 and the indirect will accept the full 113K at that DT but it is not a certainty.

Zman

Heat exchanger sizing is heavily dependent on the delta t as well as the flow rate. It is really a moving target.

As the tank temp approaches the return water temp, the transfer rate will drop off.

It still does not explain why the new setup will not significantly outperform the original setup. He should be getting at least twice the output. Someone needs to measure the temperature of everything and figure out what is wrong. This is not a difficult task for a qualified troubleshooter.

Eastman

@SemourCates

Your DT of 20 occurs when the tank is full of hot water at 160 degrees. No one is complaining when the tank is full of hot water. We are concerned why the boiler is reportedly cycling when the tank is hypothetically luke-warm.

kunisk

Hi Guys--Wow I appreciate you all trying to solve my problem. Like having a team of experts here. Problem is I am not a plumber, just an homeowner and starting to get lost in a lot of the verbage here. Do any of you guys live on Long Island? Or can you explain things I should look at in layman's terms or what I need to ask my plumber about? Thanks!

neilc

looking back at your early pictures,
I do see zone valves on the heating circ loop,
are those zone valves closing when you get your domestic heating priority?
or is the "scorching hot" domestic heating water flowing back thru that heating zone and not direct to the boiler?

at the domestic tank,
is the "scorching hot" even in and out? can you feel or measure a difference in the heating supply and return at the tank?
(got 2 more strips of that temp tape?)

SeymourCates

@ Eastman

Agreed. However, the OP's stated DT of 20F at the beginning of the call is a long way from the manufacturer's stated requirement of 60F for full coil capability. I suggest that this could be part of the issue as the coil cannot accept the boiler output until the indirect drops to nearly 120F. At that point, it's game over.

@kunisk

Have the plumber raise the "high limit" to 200F. Ignore his complaints how it won't work. Take two showers at the same time and watch the boiler. See if it runs for the entire time the showers are running. Hopefully, you can get to 25 minutes (if the heads flow not more than 2.5 GPM) before the tank drops below 115F. That's about the best you are going to get with that setup.

flat_twin

When the dhw has finished cycling, feel the piping on the inlet side of the dhw pump for temperature changes when the heating cycle begins. If you sense a change of temperature, there's no check valve in the pump. Same for the heating circuit.
As was mentioned already, both circuits need check valves.
Suppose the installer didn't add a check valve to the heating circuit. Cross flow between heating and dhw may be responsible for lack of flow in the boiler and indirect tank resulting in the short cycling and slow recovery.

Our 38 gallon indirect makes hot water faster than we can use it. I found out quickly when I installed it that my heating circulator had no flow check. 160 degree water in the cast iron rads was a good clue when 130 is the max on the heating cycle. I added a flow check to the heating circulator and the two circuits work exactly as they should.

Eastman

@kunisk

Ignore the check valve stuff for the time being.

The cycling boiler is a tell tale sign. When have you observed it cycling? Was it still cycling even after the hot water supply dropped off below 115 degrees?

kunisk

I believe you are asking when does the boiler fire as hot water is being used. If so, the boiler fires when the boiler drops to about 160 degrees and then turns off at 180 degrees.