Not enough hot water--need help!

Zman

The boiler should not be cycling on and off during call for hot water. Turn on 2 showers, go to the boiler and watch. What is going on? Which pipes are getting hot? Are the heating pipes hot or just the DHW? As you run out of hot water is the hot pipe going into the mixing valve still hot?
Only someone who is actually in the boiler room while you are running out of hot water is going to figure this out.

Zman

You should also go ahead and measure the flow at your shower head. Get the water to a comfortable temp and time how long it takes to fill a 5 gallon bucket.

Eastman

kunisk said:

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.

That's not what I am asking about. If the hot water tank is cold, the boiler should never even get up to 180. One would expect a boiler to cycle on and off if the hot water tank is already pretty hot. But... if the tank is depleted, like after two showers have been running for awhile, the boiler shouldn't cycle on and off any more. The "on" cycles should get longer and longer as the tank gets colder and colder --until it just stays on.

When you say the boiler is turning on and off between 180 and 160ish, we want to now when you have observed this. Does it do this even when the hot water tank is depleted?

Rich_49

See if this helps

kunisk

I understand now. The boiler fires and stays on when hw runs. It doesnt shut off as we call for hot water. I raised the temp on boiler to 210 degrees from 180. Lets see if that helps.
Regarding check valves - if the boiler return and supply are scorching hot, is not having a check valve an issue?

HomerJSmith

Yes, because some flow will go thru the indirect circuit when there is a call for space heating. In some cases you can get reverse flow of BTU's from the tank water to the HX water. Heat energy travels in a straight line to what ever is colder. It all depends upon resistance. If there is more resistance in the space heating circuit, more flow will go thru the indirect circuit.

flat_twin

Like Zman said, feel all the pipes. When the boiler is heating the house, are the supply and return pipes to the indirect getting hot also? They shouldn't be. And vice versa, when the boiler is making dhw are the pipes for the heating circuit getting hot?

HomerJSmith

I don't like your setup. Heat-Flo says to put the circulator on the indirect supply near the tank and they also say to put a check valve there too.

Based upon what Rich said and his link, you should raise your tank storage from 140 deg to 165 deg.

Rich_49

HomerJSmith said:

I don't like your setup. Heat-Flo says to put the circulator on the indirect supply near the tank and they also say to put a check valve there too.

Based upon what Rich said and his link, you should raise your tank storage from 140 deg to 165 deg.

Circulator placement has very little to do with performance in this instance .

Did you actually read this discussion ? Is this tank not storing at 160* already ?

HomerJSmith

Oh ya, it's the sixth paragraph into this post. 3 pages of posts is getting me dizzy.

SeymourCates

kunisk said:

I understand now. The boiler fires and stays on when hw runs. It doesnt shut off as we call for hot water. I raised the temp on boiler to 210 degrees from 180. Lets see if that helps.

If the boiler runs continuously on a DHW call, increasing the high limit to 210F will, unfortunately, have no effect on the outcome.

Your previous statements regarding the operation of the boiler contradicted this information.

My suggestion to increase the high limit to 200F should be dismissed and the boiler should be returned to 180F.

Back to @Zman recommendation. Get a bucket and measure the time to fill a five gallons. If it is anything less than two minutes, the shower heads need to go.

HomerJSmith

Zman sez, "The boiler should not be cycling on and off during call for hot water." Yup, If the boiler's operating limit is 180 deg and the boiler is cycling, what does that mean? It means that the boiler water reached 180 deg, the boiler shuts down till the differential turn the boiler on again to recycle again and again.

Ideally, you want the boiler water to reach 179 deg and never 180 deg when there is a call for hot water so the boiler never shuts down. It just keeps pumping the maximum BTU's in to the Indirect tank. This scenario is base upon two things. 1) The HX in the tank is capable of transferring the BTU's that the boiler supplies to the domestic water in the tank . 2) That there is enough water flow to carry the BTU's to the HX to be released in to the domestic water. If there isn't enough flow, the boiler will reach operating limit and shut down, whereupon the pump will continue to run and the HX reduces the heat energy in the boiler circuit to the point where the differential turns the boiler back on and the cycle repeats, again and again until the tank aquastat shuts the boiler down.

I did a rudimentary guesstimate of the pressure losses of the piping to and from the boiler to the indirect with HydronicPro. I can't vouch for its accuracy as the measurement were guesses and the picture of the setup didn't show the complete piping arrangement. I did it with a flow of 11gpm. I got a 1" pipe equivalent of about 92' of type 'L' copper, which is a pressure loss of about 6.5' hd. It looked like on the photo, type 'L' copper.

SeymourCates sez, "The pressure drop though the coil is 3.5' @11 GPM. " Sounds reasonable. So, we have a total of 10' hd pressure loss. The Taco pump at 11gpm is 9' hd and I didn't even include the pressure drop thru the boiler, the B&G IAS, or the black iron pipe and black iron fittings.

These calculations are a guesstimate, so don't nail me to a cross for it. A real pressure loss must be done, a flow indicator installed or if your lucky a sonic flow indicator reading taken.

It seems to me that the boiler is cycling because of inadequate flow which would impede performance.

Eastman

Visualize image of Captain Picard face palm here.

SeymourCates

@HomerJSmith

EL of 92'?

You have about 30' of piping between the two pieces of equipment. Add 50% for the fittings. EL is 45 max. 3.62' @ 11 GPM. Add another 3.5' through the coil. Add another 2' for the boiler. Total: 9.12'

Inadequate flow is only possible if there is 3/4" piping in the system.

A quick DT measurement would confirm.

HomerJSmith

I don't mind being wrong about this. My wife says, I'm wrong all the time. So, confirm it, I'm an easy sell when it comes to the truth.

SeymourCates

@ Eastman

Yes.

SeymourCates

@HomerJSmith

There is also a misconception that flow rates that are not per the spec of the manufacturer of the indirect will cause the boiler to shutdown on limit (which is currently confirmed to be not the situation).

If we make the assumption that the coil will dissipate a fixed about of energy at a given temperature, the only thing that can happen with a lower flow rate is an increased DT. The boiler really doesn't care if you supply 10 GPM at a DT of 20 or 14 GPM at a DT of 14.2. It's going to add the same amount of energy in either scenario and won't shutdown on limit.

The issue with the lower flow rate is the fact that the AVERAGE water temperature in the coil is a bit lower and the heat transfer is of course a bit less. So, in the case of the 10 GPM scenario, the DT will be slightly lower than 20 due to the reduction in AWT in the coil. This is the only reason to pump faster.

It all becomes moot unless the boiler is closely matched (or a bit larger) than the coil specification. In the case of the OP the boiler is 20K below the spec so flow rate is most definitely not a consideration.

The OP has proven this by confirming that the boiler runs continuously for the entire time of the call.

kunisk

Sounds like everyone is concerned about the flow rate. What info can I provide to help us determine if that is the cause? Its the only thing left, unless that check valve was an issue. I have attached a bunch more pics.

kunisk

Yes, the boiler runs continuously during the call for hot water.

kunisk

ignore the last pic. i tried to do a panoramic.

HomerJSmith

I was going thru the posts to see where short cycling came up. So, if there is no short cycling and the boiler fires during the whole call for hot water, then raising the boiler operating limit from 180 deg to 210 deg would be beneficial. That boiler may not have a temperature for space heating and one for DHW like the Mod/Cons. I would want to be careful about that and definitely raise sys pressure.

I'm not talking about flow rates, I'm talking about flow, itself.
Close a ball valve on the the output and you will see how fast the boiler reaches its operating limit and shuts down, turn off the pump same thing.

I gave a possible reason for short cycling, it there isn't any short cycling, my efforts were wasted.

Has Kunisk provided a temperature for the return and supply for the boiler or the return and supply for the indirect in the DHW mode?

SeymourCates

@HomerJSmith

Raising the HL to 210F can have no effect.

Why?

Because the boiler is currently not limited in operation with the HL set to 180F. You can set the HL to whatever you want (above 180F) and the boiler won't reach 180F. We know this because the boiler doesn't shutdown on limit (currently set to 180F).

We have no need for the temperature of the supply and the return because...............the boiler doesn't cycle on limit.

kunisk

@SeymourCates i think raising the temp will help me. Why? Because the boiler goes on quicker now. Once i turn on hot water, boiler starts going on and will cycle hotter water sooner than before (starting when it hits 160-170). In other words arent I getting hotter water cycled to hw heater sooner and longer?

neilc

it's a twisted thread.
in the beginning we were cycling 180 - 170 / 160,
were we not?
Now we're not shutting off,
What is the boiler temp during recovery, while we're not shutting off?

HomerJSmith

Ya, but the temperature of the water going to the tank HX is hotter and I would suspect that the transfer rate of BTU's from the water in the HX to the water in the tank would be greater because of the temperature differential, so there would be a faster recovery time as the hot water draw lessens, but is it worth the added energy cost?

I understand what you're saying. The return from the tank temperature is low so that the boiler can't produce enough heat energy to raise the boiler water to 180 deg (operating limit) while there is hot water draw so raising the operating limit to 210 deg achieves nothing.

So, there is no short cycling of the boiler at 180 deg, that the boiler fires continuously during the hot water draw, that's a fact.

I still want to know what the boiler output and input temperatures are. The tridicator can tell me the output.

Options as I see it boils down to three things: Increase the BTU source, increase the storage volume and temperature, and limit the hot water draw. So...

Buy a new and larger capacity boiler.

Raise the storage temperature of the tank or add a 50 gal gas fired water heater in series with the HF-60 with a recirc between the two tanks that turns the recirc on when the gas fired unit temperature falls. The vent from the previous 75 gal W/H can be used.

Lower the domestic cold water pressure to 50 or 45 psi.

Add low flow shower heads or flow restrictors.

Sell the girls to a band of roving gypsies, wait, forget I said that. I love my girls. Why, I'd even let them take 30 min showers. It's my frugal wife that makes them get out of the shower afer 3 minutes--soaped up or not.

SeymourCates

@kunisk

Raising the limit to 210F will help you in one way...........but it is miniscule:

The boiler begins the DHW call 30 degrees hotter than the previous setpoint. You have about 2500 extra BTU to utilize for the call before the boiler falls to the previous setpoint of 180F (considering 10 gallons in the boiler). This offers an extra 4.3 gallons of HW.

Have at it but it won't make much of a difference in your situation. (maybe 1 minute). Will the girls accept 21 minutes?

Zman

None of this makes sense. If he heated with a 75 gallon stand alone before and it kept up, it should work even better now.

He needs a pro to check all the components, measure water flow and clock the meter.

hot_rod

Zman said:

None of this makes sense. If he heated with a 75 gallon stand alone before and it kept up, it should work even better now.

He needs a pro to check all the components, measure water flow and clock the meter.

I agree, this set up, other than the initial dump capacity should provide plenty of DHW.

It could be the tank is performing as predicted but the usage has gone up?

Unless you confirm the actual amount of DHW used with a water meter, or 5 gallon bucket seem like we are all guessing.

We need some actual, hard data.

neilc

ok, so, right,
now I would be curious to know the boiler temp as the showers go cold
@kunisk

SeymourCates

@Zman

Let's say the 75 had a net output of 55 (considering it's a water heater). And let's also assume that about 60 gallons are usable.

How could it possibly keep up with a 5 GPM draw for more than 20 minutes?

There is a flawed assumption here.

SeymourCates

@Zman

Here's another thought:

If the indirect is truly at 160F and we assume full stratification for the entire call, we have the full 60G available. The flow rate to achieve 115F (with 40 supply) is 3.125 GPM. 60G lasts 19.2 minutes WITHOUT any boiler input.

So, if the OP only gets 20 minutes, the only possibility is that the tank is nowhere near 160F as claimed OR the flow rate at the showerheads is much greater than 5 GPM. (requires confirmation).

Zman

@SeymourCates
It could be a whole lot of things. In your scenerio a faulty aquatstat or a sensor at incorrect depth could be the culprit...

DZoro

@kunisk , have you checked the water temp coming directly out of the tank pipe going to the mixing valve 90* elbow during a full run out of hot water?
Just checking many, many posts have happened since my last post........

SeymourCates

...........

Mark Eatherton

SeymourCates said:

@Zman

Here's another thought:

If the indirect is truly at 160F and we assume full stratification for the entire call, we have the full 60G available. The flow rate to achieve 115F (with 40 supply) is 3.125 GPM. 60G lasts 19.2 minutes WITHOUT any boiler input.

So, if the OP only gets 20 minutes, the only possibility is that the tank is nowhere near 160F as claimed OR the flow rate at the showerheads is much greater than 5 GPM. (requires confirmation).

You will NEVER get 100% of a storage tanks volume out in useable hot water. 80% is the best I've seen, and is the standard that most tank manufacturers defer to.

Regardless of input, he should be able to extract all output and convert it to useful DHW. As others have noted, it SHOULD be significantly better than the stand alone heater is displaces...

To the original poster, with the DHW pump running, try closing a 1/4 turn ball valve in the DHW boiler circuit as fast as you can to the off position, and listen for a hydraulic HISSssss indicating choked off flow. If you hear nothing, you have to little flow.

Another simple check is to turn the gas valve off, and turn all thermostats up to get rid of the boiler heat. Once cooled, activate the DHW circuit, which should also be as cold as possible. Then, take a torch and hold it with its flame against the wall of the boiler to DHW exchange loop for 5 seconds. Then, turn the torch off, and let the system continue to run for 5 seconds. Now, carefully place your hand where you had the flame. If the pipe is cool, you have SOME flow. If its still hot, you have no or little flow.

ME

hot_rod

I like that the coil in the HeatFlo goes from bottom to nearly 1/2 of the way up, so you should have a good transfer to the water.

1" coil and 8 square feet of surface, it should perform with the best of the tanks.

With the aqua stat down low, no dhw recirc, you should have a very hot tank (stratified) if it is set at 160 and the boiler is supplying 180F or more.

SeymourCates

@Mark Eatherton

If you use 80% (48 gallons), the situation starts to become bleak for the OP. The tank lasts 15.3 minutes. The boiler produces 28.8K in that time which can raise 46 gallons to 115F. Another 9 minutes (flowing 5 GPM now).

24 minutes total.

DZoro

Don't forget about the cold water being mixed in with the 160* tank water down to 115*.

hot_rod

Lochinvar has a nice simulator for elevated tank temperature operation

HomerJSmith

I just read all of Kunisk posts and there is no short cycling of the boiler. In fact he says that the boiler runs continuously when there is a hot water draw. I hope he means that the boiler firing is continuous and not that the pump is running.

SeymourCates is right. Moving the operating limit on the boiler to 210 deg from 180 deg won't change a thing. If you can't reach the 180 deg limit you sure aren't going to reach a 210 deg limit.
The limit just tells the boiler when to shut off. It doesn't add any more BTU's to the firing rate.

What continuous operation, when there is a hot water draw, tells us is that there isn't a flow problem as the boiler doesn't reach the operating limit (180 deg). My erroneous assumption was that there was short cycling during the hot water draw, there's not.
Everything I said about flow you can throw in the dust bin. The flow is adequate for the boiler output. Had there been short cycling, it would have indicated a flow problem. So, where do we stand?

The tank aquastat is a Honeywell L4080B1352 with a fixed differential of 8 deg, I assume? Kunisk can verify the Honeywell model #. (8 deg, that's tight.) Minimal improvement there.

hot rod--low flow shower heads or restrictors.

Homer--lower the domestic cold water pressure to 45-50 psi.

Others--get a new boiler with higher capacity or take shorter showers.

Increase the hot water storage capacity. Add another heat source, like a 50 gal gas w/h in series with the HF-60 with a recirc system between the two tanks. The 50 gal tank would rarely turn on except in extreme water draw.