Superstore question

JimmyJam

We have just installed a Munchie 140M and a Superstore indirect SSU-45DW along with an HPS zone control panel with domestic water priority. The homeowner states they are running out of hot water. We have measured a 22 degree temperature drop across heat exchanger when calling for domestic water production, boiler cycles down on temp during production call. Is this delta t too great? The factory installed pump in the HPS panel is a UP15-42BUC7 and is plumbed with 1" supply and return lines.

Any ideas?

Thanks!

ScottMP

what

fixtures are in the house ? Are they trying to fill a tub ?
How about the shower valve, what kind of head ? Did they remove the flow restictor ?

I would'nt think a 22 degree drop would be that bad.

What temperature is the boiler going to on high fire ?


Scott

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Big Ed

Volume

Check the flow rate in the shower they run out in. Then do the math. Say it's a 5gpm shower head,you will only get a 8 min shower with a 45 gallon water storage....

With a 20*delta T you have heat transfer.

JimmyJam

boiler comes up to 180 then cycles down,(during call for domestic production)I don't know alot about fixtures but they seem to be running out of hot/warm water using shower in the morning. I forgot to mention that we do not have a Vision package installed and I believe that we need to do that to ramp up to high fire on indirect call.

Big Ed

flowrate

Take a 5 gallon bucket and a watch with a second hand to the shower . Turn the shower on full , let it run in the bucket for a min. Figure how much in that min for flow rate.

A rule of thumb ...........A 140K input boiler can produce about 2 gpm in recovery.

Unknown

I'm with you, Ed

The ratio I use is 50,000 of boiler OUTPUT per gpm at the faucet.

I think it works out about the same for older boilers.

Noel

JimmyJam

We will measure flow rate tomorrow. I know this is a pretty elementary question for most of you but what should a normal shower head flow? And lets say it flows 4gpm is there an average percentage of hot versus cold gpm? Yes, I know "some like it hot!"

Thanks for the input guys.

Unknown

Doesn't matter for the test

This formula isn't that close, it's for water that you can stand under, raised from street temperature in the winter.

To try to assume anything more specefic, you'll need to go to the manufacturer's charts.

You'll still need the flow rate.

Noel

J.C.A._3

I think you're right....

about the control being able to go to high fire immediately on a PRIORITY domestic call. I also think that it was the reason for the vision1 control.If you've got the older control, that is the way it worked. It started on high and worked its way to lower fire. With the Vision1 I believe on the call for domestic it goes to high fire and stays till completion.

Chuck, Jeff,Guy ? These folks will have a definate answer but I also believe the flow should be checked. I've seen tubs and showers dumping well over 4 GPM with no difficulty. This would be pushing the envelope HARD!! Chris

Big Ed

Hot water

None of us were born with this knowledge.. We all had to be taught, and we are all still learning.......I learned this usefull info from George L"FireDragon"hot water book.. Good tool to have when you have a house wife jumping up and down .

Not to kick you in the teeth ,but.............You really need to do the math before you figure what type-size water heater your putting in...As you are finding out (sorry) the hard way..

All shower heads being sold today, by code are no more then 2.5 gpm . Some need a resistor to pass... some of these resistors don't end up in the head. And they may have a old head , before the code . So you need to check flow rate.

I get a kick when you see someone install a row of body sprays with multiple shower heads and in the basement they sport a 30gal water heater. They run out before they can get in... "OK lady your flow rate is 15gpm so if you want a 10 min shower we need to install a 150 gallon hot water heater . Just move the pool table and we can put one out here"

Back to answer your question.......Average mix is 1 part cold -2 parts hot... But you must understand a hot water heater is about 80% eff and the last 20% is mix....So just figure straight hot water for the usage....

Hope this helps.....
From a near by basement,
Regards
Big Ed

Me_8

I have a t80 hooked up to a 40 gallon indirect without the vision package, it does take a good 5 minutes to get to high fire and stays there untill the call for domestic is done. Something is not right if the boiler is cycling off and there is still a call for domestic,,,,at worst would think it would slowly ramp down. Took a quick peek at the panel is that the only pump ? I was a bit surprised at how much pump my indirect needed and I have the boiler piped with its own pump.

hr

Personally...

I feel a 40 gallon is too small for the average American household. Possibly if you could drive it, and pump it with 200,000 BTU/hr, but that's a rare combo.

Maybe a couple, or elderly homeowners could get by with a 40.

But a family, or teenagers, or DW and clothes washers loads in the same evening, no way Jose

The other wrench in the works is incoming water temperature. We all know how cold that can be in most areas of the NE mid west, mountain states, etc. That makes a big performance difference. Read the fine print.

When indirects first came into Vogue in the early 90's with radiant taking off, and boilers becoming more common (atleast in the western states) reps and manufactures tried to tell us they (40 gallon IDs) would supply water on the order of a 75 gas fired tank.

In their dreams maybe We went back to plenty jobs and doubled up or upsized at our expense.

It's the dump load!

And this may be the only country on the planet that won't be denied endless DHW Probably the only market for 250, 300,000 and larger instantanous units, also

Save yourself headaches and callbacks and size 60 or up, is my advise.

hot rod

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R. Swatton

What about increasing the hot water temp to 180 degrees and adding a mixing valve to reduce DHW temp.
Also most aquastats have a 15 degree differential, you can get them with a 5 degree differential.

EBEBRATT-Ed

What about a flow restrictor in the hot water pipe?

That would slow down the overdraw--Like we used to use on tanless coils

hr

High temperatures

really increases the mineral build up. Both on the coils and in the tank itself. Actually the minerals in suspension are attracted to the hotter surface temperatures. Just like an electric water heater element.

It also seems to increase the frequency of those mix valve tear down and repairs. They are real sensitive to scale build up. It could be done, but would be my last choice.

Check the water hardness going to that tank before you start cranking 'er up like that.

hot rod

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Paul Pollets

Agreed

We only put in 60g indirects or larger. There's very little price difference between the 45g and 60g SS. 45g is too small, except to feed one shower with a flow restrictor. Maybe in Europe, but not here. Most Americans take long showers and teenagers can double the HW usage.... plan for higher demand load, or twin in another tank. You can also run the tank to 140 deg. and temper the outlet back to 120. That will give a tad more capacity, but not much.

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Dave Stroman

I set up a boiler and SuperStore once. The plumber came in after me and ran all the water lines. He got the hot and cold reversed. Did not work very well.

Dave in Denver

ScottMP

HR

That goes against PAH's teachings about legionella.

We like the set up of a mixing valve and do it quite frequently. Its a good way to stretch out the hot water with out additional storage. I do agree, few homes are getting 40's anymore and we do the mixer on 60's much more often.

I installed my first Super-Stor about 15 years ago. Told the customer how great it would be. They could'nt take two showers. Found out he was showering and leaving it running while the wife stepped in. That coupled with the fact that he had changed the shower head to the old speakman with no restrictor he got from Uncle Charlies old farm house. Damn, that thing was flowing around 8 gallons a minute. Ya gotta get ut of the boiler room.

Scott

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Darin Cook_3

One thing to watch

We do alot of hw recirculation in our new construction homes. We started out by using T-mixing valves along with our recirc pumps. So we could stretch out the hot water. The problem being is that when the pump runs and no water is being run through a fixture, the thermostatic cannot temper the out going hot with cold water. So if you are running your indirect at say 160' although you have the thermostatic set at 120', you are sending out 160' into the hot line. The recirc pump just pulls it through. I just happened to be in one of our new homes and looked at the thermometer we always use in the outgoing hot line. 160' hot water blasting through the HW line and 2 small children in the home. If we do not use recirc then I do put a thermostatic on the tank. But if we are using recirc then we upsize the tank ( if they have a big hot water need). It is a toss up, scalding risk or legionella risk. I have seen alot of people scalded so I have to make that the first priority.









Darin

jerry scharf_3

going off on high limit seems wrong

First, I think that HTP recommends a good bit more flow than a 1542 can push through a munchkin and superstor. At 140 MBH, you should need a 14GPM flow to run a 20 degree deltaT. No way a 15-42 could do that. Looking at the 15-42 pump curve, it would need to have only 3' head to get 14GPM.

Second, HTP has a small box that you can add that gives you a contact point. If you close this, it automatically turns the system to max firing.

Which gets to the bigger problem. You're seeing the return water temperature climb disproportionally to the tank water temperature. This says that the coils are not transferring enough heat to cool the return water. Perhaps your coils have goten covered with something (maybe "lime") that is preventing the heat from going to the water quickly. The boiler will then modulate for 20F delta T and it climbs to temp and cycles. If the tank has a good sized inspection port, I'd open it up and look inside.

This is also consistent with the narrower than expected deltaT for that small pump's expected flow rate and 140MBH input. All this is also consistent with low recovery rates and unhappy occupants.

best of luck,
jerry

Boilerpro_3

You guys using the Triangle Tube indirects?

I've got several single 40 gallon models in and no complaints about hot water. They can eat up about 140,000 btu/hr of boiler output continuously and have almost no pressure drop at full flow on the boiler side. One is on a 75,000 input condensor and the boiler almost never gets above 140F outlet temp when charging the tank. I have another serving 4 apartments with a 245,000 input Weil CG that also gives them no trouble.

From what I have seen, most indirects have relatively little heat transfer capacity and need big, high head, power sucking pumps. Really need to watch those spec's. I'll stick with the Triangle Tube units, they don't have these limitations.

Boilerpro

JimmyJam

Superstore

We found that the shower head is producing 2.5 GPM, Installed a Vision 1 package and tank is doing a better job now, however while running shower the supply temp out of Superstore dropped to 88 degrees after 16 minutes of continuous flow (mixed). Now if I have approximately a 2part hot to 1 part cold mixture on average I would be drawing out 1.65 gallons of cold water correct? If I use the "rule of thumb" that 50K output per GPM of boiler capacity shouldn't this be keeping up better? We had measured a delta T of 32 degrees across heat exchanger when supply temp was 88 degrees. (195/160) What is even more complexing to me is that I have an HM150 "Completeheap" in my own home which only stores 30 gallons with a Speakman head lacking orifice and can not run that baby out of hot water. I don't know alot about first hour recovery but the 140m with Superstore should produce 253 which is very comparable to the Completeheap. To say the least this kind of confuses me.

Unknown

First hour or first 16 minutes

Your example of 2.5 GPM for 16 minutes is 40 gallons of water straight down the drain. If you want to heat the water up extra hot and mix cold with it to deliver it at a temperature that you can stand under, the 50,000 is still good.

Enlarge your picture for a minute.

Look at the 2.5 GPM at the cold water inlet to the building. Flow some through the water heater and some up the cold pipe to the shower head. Flow 2.5 GPM out the shower head.

The temperature rise is between the street and the shower head. It really doesn't matter how much cold and how much hot, the net effect is it takes 50,000 BTUs for every GPM at the shower head, at the temperature you can stand under it.

Whether it all goes through the tank, or a little goes through the tank and mixes with cold, the delta T of the street water to the shower water doesn't change. You use 50,000ish for each GPM the showerhead passes at a comfortable temperature.

You can't get more BTUHs per hour by raising the tank temp and mixing with cold. You CAN run it for a longer time and STORE more btuh, but you can only MAKE (recover) what the boiler puts out.

Another thing, the first HOUR rating is not very useful if you are only using it for 16 minutes. If you look at the second hour rating and divide it by four (for a quarter hour) that's how much hot water it will actually make in 15 minutes, above what is already stored in the tank.

Noel

hr

BoilerPro

That is my tank of choice, although I buy it under the Weil Mclain or AquaTherm badge. Same "Made in Belgium" tank, I believe?

What I find happens in apartments and rental units is the tenants get use to the hw that is provided.

"You take a shower with the capacity you have, not the capacity you wish you had"! in their case

Not often that a owner or property managment company will up the dhw ante for a DHW guzzler tenant.

Custom homes are a different animal. They feel they should get what they pay for! Which often means endless DHW.

I have never, ever, had a customer complain that I gave them too much DHW.

Knowing and agreeing on the customers expectations is the key. Sometimes it may be wise to put it in writing, like the heat design "assumption reports" that good design software spits out.

hot rod

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