Hot Water Faster

Paul_M

Hi all-
I received good feedback from this forum on another DIY project (hydronic toe-kick heat), so I'm now looking for some more guidance. This time, I'd like to get hot water faster to my kitchen and/or bathroom, with minimal water waste and expense.

Current setup: I have a reasonably-efficient oil-fired boiler with a domestic hot water coil (Weil-McLain WTGO series 3- installed 2004). I'm not looking to replace the boiler. The total piping distance from the boiler to each location is ~40 ft of 3/4" copper pipe. The first 20 ft of those distances is shared. Most piping is accessible in an unfinished basement.

I'm considering these options: 1) Unheated Storage Tank, 2) Heated Storage Tank, 3) Circulator Loop

Option 1 - Unheated Storage Tank
I could position a well-insulated tank so that it is 15 ft from the kitchen and 20 ft from the bath, thus reducing the distance for hot water to both delivery locations. Concern: Even though insulated, the water temp will slowly drop in the tank. When this happens, even though "warm" water would be delivered quickly, it may take even longer for "hot" water to be delivered. The larger the tank, the longer for water to go from warm to hot, wasting water in the process.

Option 2 - Heated Storage Tank
Same location as option 1, but make it a smaller electrically heated tank. This would mitigate the warm-to-hot issue with the unheated tank, but will require greater up-front expense and operating cost. If this makes sense, what size tank would be appropriate.

Option 3 - Circulator Loop
I have not seen this described anywhere, but it seems do-able. Create a well-insulated, low-flow circulator loop with a controlled valve just before the kitchen. When hot water is called for, or if the water temp at the valve is at or above x-degrees, do not circulate, but allow water to be delivered. When hot water is not called for, if the water temp at the valve falls below x-degrees, circulate water through the loop back to the boiler inlet point until target temp is achieved. This should deliver the hottest water fastest to one location. If the other location is branched off the loop anywhere, it will still benefit somewhat. One concern- even with insulated pipe, the heat loss will probably be faster than with either storage approach, and the boiler may fire more often.

Any feedback or alternate recommendations would be appreciated.
Paul M

Bob Bona_4

To save energy I would pipe an indirect water off the boiler and abandon the tankless, convert the maintaining aquastat control to an on demand type. To save water, and for hot water right at the tap, I would look into the Grundfos Comfort System.

SWEI

What are your costs for oil and electricity like? How hard is your water? I would suggest different solutions depending on the answers to those two questions.

Dave H_2

Take a look here for different options when looking at DHW Recirculation. There are alot of ways to get it done based upon the application.

http://www.taco-hvac.com/products/systems/instant_hot_water/index.html

Dave H.

JUGHNE

I have about 65' of 3/4 copper from my indirect to mas bath. Took a long time to get hot water.

Have an article from an old PLBG magazine that is a reprint from an older PLBG publication. "The forgotten method of hot water recirculation". So I have done this for my mas bath and a customer's kitchen wing. It works....2 seconds at the lav....3 seconds at the shower.

I went under the mas bath lav, which is next to the shower, and added a gravity return line. I put a ball valve on the hot supply, for service, it is always open, and installed 1/2" OD (because I had it on the rack) all the way back to the storage tank bottom drain valve. There a swing check valve is installed and a ball valve for throttling flow. The entire line has a slope down towards the tank.....(10" drop between the joists.......10" drop paralleling the duct work and then a 7' drop to the tank drain valve.) It is all insulated except for the 7' cooling leg drop.....I actually just run out of insulation.

I figured I didn't want another pump in the basement, ($$brass or SS) already have 6 there for heating.

Yes, I have a continuous heating loop going on at all times. I will insulate the "cooling leg" drop and monitor performance. The throttling valve is about half closed.

But the cost of running a pump, replacing a pump, more controls etc. It is nice to have something simple with no moving parts other than water and a check valve. It always works.

The old article called for an 1/8" hole drilled in the swing flapper of the check valve. I did do that for the customer's kitchen but not for my bath. There is enough flow by gravity to just swing the check for water return. The check valve is to keep your recir line from becoming a cold supply and having a H-C cross connection.

I know it is old school, low tech and most people don't think you can do this without a pump. But we and the kitchen customer are happy.

BobC

Simple solutions are always the best solutions.

Bob

Paul_M

Thanks for all the input. I'm researching the links provided and I'm most interested in seeing if JUGHNE's gravity loop would work for me. I've enclosed a diagram and have some starter questions. What's the purpose of the 1/8" hole in the swing flapper valve? Where should it be located (A or B )? Does the 'yellow' return run from B-to-C need more than 2" drop over a 30' run? I can't lose anymore head room than that. Would copper or PEX be better for the return?

JUGHNE

The 1/8" drilled hole is to maintain minimum gravity flow in the system. I don't have the hole in my check and it works, maybe because I have good slope and plenty of drop at the indirect tank.

The check is located at your point A, easy to service area.

As far as slope, my guess is that is there as long as there are no "hump up and back down" (roller coaster ride) areas in the pipe then the gravity would make the flow. This might make rigid copper the best choice. I mentioned I did use some 1/2" OD (3/8" nominal ID), but standard 1/2 nominal is less money.

There are people with baseboard HW heat who have "Phantom water flow" simply because of the gravity effect. BB water piping is pretty well installed level under floor joists and this still occurs. Flow check valves are installed to prevent this.

But any "heat trap" piping may stop the flow, (up and then back down).

My recirc line is connected under the mas bath vanity with the service valve and is always accessible.

Coming from the tank drain is first a ball valve to drain the tank, then tee with another ball valve to recir line, tee with boiler drain valve, then swing check valve, then throttling valve. I use a ball valve for this, can't imagine this flow will harm a half closed valve.

The boiler drain valve is to establish initial flow and get any air out of the recirc line.

As I look again, most of the vertical drop at the tank is insulated.

I don't know how well this will flow thru your boiler DHW coil, thinking friction loss.

I have a 120 gal tank with homemade heat exchanger connected to ModCon boiler. The tank & HE are over 20 years old.

2nd floors sometimes get recir water within the HW supply pipe.
This works because the hotter water rises up in the center of the pipe and as the water at the outer walls of the pipe cools then it travels down. Hydraulic chimney effect. There is a proper term for it but it escapes me at the moment. So if your hot supply to the kitchen is maintained at a higher temp than previous you may get that migration, at least overnight anyway.

This happens in old gravity piped HW heat. The riser will get hot even with the 2nd floor pipes capped.

I would insulate as heavy as possible as there is heat loss all year long. It would take a lot of bean counting to see if this method is waste full and not as green as possible. The way I look at it is that I pay money to get cold water into the house, I pay more money to get some of that as hot water, I will pay a little more to get it quicker. All the water I used to run to get hot water at the shower used to be hot water and it lost that heat sitting in the pipe. So there is some balance to the green equation somewhere?

Hope this helps, let us all know what works out. In my case I figured I would try the gravity method and if it didn't work out I would have to install another damn pump! Kinda of where you would be I guess.

P.S. If you do this, I would try it without drilling the hole in the check flapper..........Also found the article could scan and post if needed, it is written in Engineerese.

hot_rod

As Jughne mentioned, insulation is critical on any DHW piping. You basically have a 24-7 hydronic loop running when you install a recirc pump.

Another option is the self regulating, quality heat tape, for a short run it might pencil out better for install and operation cost. I think they run a few watts per foot on recirc tape is adequate, so less than 100 watts to keep the supply side warm.

Paul_M

JUGHNE- I re-looked at my basement and cannot route the return without having one 12" hump in the line, and your caution about friction loss through the coil is also noted. If not showstoppers for the gravity approach, am I understanding your design properly per the enclosed photo? If it's not too much trouble, I'd like to review your engineerese article.

JUGHNE

Is the 12" hump up and back down, what is in the way?
Maybe the flow would continue, I don't know. It might syphon?

I believe Icesailor used to describe storage tanks for in boiler DHW coils. He used a 50 gallon electric WH tank, with small pump perhaps to keep the 50 gallons hot. I use the ele T-stat in my 120gal to start the pump and fire the boiler. I believe he did that also. This also gives you a high limit protection. In my case if I have any lengthy boiler down time the electric element gets connected to keep mother happy.....because if.....

This would give you storage. If the gravity recir would work thru your coil it might produce a lot of short cycling. I don't know what calls your boiler to fire now. I'm thinking a long fire to heat 50 gallons would be more efficient than your present system, I'm not familiar with the method that you have now.

Here, hopefully, is the article. His text is actually easy to follow considering all, he seems to be a practical common sense type of 1998.

SWEI

Thanks for the article -- interesting approach.

SWEI said:

What are your costs for oil and electricity like? How hard is your water? I would suggest different solutions depending on the answers to those two questions.

There is no single solution. It really does depend.

Paul48

I know it's neither "here nor there", but the mixing valve in the picture doesn't look right.

Brewbeer

I've heard of systems where the recirc pump is controlled by a switch. You flip the switch a minute before you want the hot, and turn it back off again when you have it. It's not instant, but it helps prevent running a bunch of water down the drain while waiting.

JUGHNE

Don't know about the connections on the mixing valve, but the gravity return may not work connected there.

We have a large storage tank and no mixing valve as the tank gets heated to 140 HW and averages 130 output for the batch. The wife likes hot water, 50 gallons at a time.

The article stresses that the initial vertical rise out of the storage is important to establish flow. Our tank is so tall that we have only about 2' of riser pipe before going to the horizontal. But then the flow is actually thru 5' of tank also. He mentions this keeps the tank temp from "stacking" hot on the top, this helps for overall operation with the T-stat on the upper element location only.

The article mentions 3/4 supply & 3/4 return, we have 3/4 supply and 1/2 & 3/8 return ( about half & half).
Also the check valve needs to be in a horizontal pipe for this application. The hole in the flapper isn't mentioned here, maybe that idea came from another article. Leave it out unless you cannot establish flow.

Paul_M

SWEI- I live in southern CT, 2yrs in a 50yr old house. Electric is ~$0.20/KWH and last oil delivery was $2.60/gal. I don't know how to answer the hard/soft water question, other than to say I have well water with a whole-house filtration, water softener and radon removal system installed by the previous owner.

JUGHNE- Thanks for the article. The hump occurs because the return line would run under and perpendicular to the floor joists for 25', then turn 90-degrees and get past a dropped header to get back to the boiler. I can't leave the pipe below the dropped header for the final 10' to the boiler.

Paul48- What seems wrong about the mixer? Remember, I'm not a licensed plumber.

What do you folks think of this Rube Goldberg approach? (option 3 in attachment, and a variation on Brewbeer's note). Install a circulator pump at the boiler; and where the loop passes the kitchen sink, install an aquastat. Use a "push-button" switch to activate the pump, which will shut down when the aquatstat reaches the desired temp. I know there's a greater up-front cost, but this prevents hot water from circulating when not needed (e.g., all night long) and avoids water waste. Option 2, just a timer, might be just as effective without the need for the aquastat.

SWEI

Better to turn off the pump with an aquastat the moment the hot water arrives. You can also start it using an occupancy sensor or tie it to the bathroom light switch (which itself may be an occupancy sensor.)

http://www.gothotwater.com/ pioneered this approach, and has continued to refine it. They also licensed it to a few others, including Uponor.

spoon22

Grunfoss makes a kit with a circulator and a timer at the water heater and a bypass valve that goes between the hot and cold pipes under the sink no need for a return line the hot water travels up through the hot pipe and returns the cold pipe it the valve has a thermostat that closes when warm water reaches it

JUGHNE

You could do option 1, if the gravity does not work, add the pump at the boiler. An aquastat on the return line shuts the pump off when warm water gets back. I believe it was Grunfos who had a small time clock that mounted on the J-box of the pump, that in conjunction with the stat could limit operation when not needed. I for myself, like to have all these electrical/mechanicals in the basement/boiler room.

Paul48

Paul_M........ I'm not familiar with that mixing valve, but generally you see hot to one side of a spool and cold to the other, with a "mix" coming out of the other. It just doesn't look like that is the case. I could be wrong. Is it marked "H", "C" and "Mix", by chance?

Paul48

What town in S. CT ? That sounds like UI's rate.

SWEI

spoon22 said:

Grunfoss makes a kit with a circulator and a timer at the water heater and a bypass valve that goes between the hot and cold pipes under the sink no need for a return line the hot water travels up through the hot pipe and returns the cold pipe it the valve has a thermostat that closes when warm water reaches it

Taco actually makes an improved version of that valve. Much larger port size and it's serviceable.

Marz

I'm not sure what the codes are in CT, but here in MA a 150PSI relief valve should be installed on the tankless. Usually a Watts 1/2" 53L in place of the draw off valve in the picture.

Paul_M

Thanks for all the suggestions. First- some answers to your questions: Madison, CT with Eversource (formerly CL&P) as electric provider; last bill was lower at $0.177/KWH. The mixing valve looks ok to me; it is marked: left 'hot', bottom 'cold', right 'mix'. There is a pressure relief valve at upper-left-front of the boiler.

So far, I've ruled out some approaches. 1) I'm not real interested in using the cold pipe for the return. Unless I'm missing something, it seems that once hot is at the tap, it will take longer to get cold water when wanted, wasting hot in the process. 2) Sticker-shock at the "gothotwater" site says I'm not paying over $600 for controls. So, I'm still researching.

SWEI

Price of oil there?

Water hardness?

Paul_M

SWEI- I'm not sure what you're driving at. I previously answered $2.60/gal for oil and that I don't know how to answer the hard/soft water question, other than to say I have well water with a whole-house filtration, water softener and radon removal system installed by the previous owner. What's behind your questions?

Marz

I see a 30Lb relief valve for the boiler. I don't see the 150 Lb relief for the tankless. It's code here in MA. Maybe not in CT.

SWEI

Sorry -- missed that earlier post with the oil price in it.

The fuel cost question was to see if a small tankless electric water heater closer to the point of use would make economic sense. In your case, that answer is a clear no (electric resistance heat is over twice as expensive on a per-BTU basis.) In our area, for customers on LPG, the difference is only about 6% right now.

The water hardness question was related. Even when the fuel costs do pencil out, tankless electric water heaters do not fare well with very hard water.

You can rig up your own demand-triggered recirc using a Taco 563-2 with the pump of your choice.

Paul48

Here's a different twist.... http://www.hotwaterlobster.com/

I have good friends that live in Madison. Horse Pond Rd.

Paul_M

Marz- You're right; there is no relief valve on the domestic circuit. If I'm reading the CT code properly, "Section 504.4 Relief valve" seems to apply only to storage water heaters. Does that make sense? I was unable to reference the MA code for comparison.
All- My current thinking is to install a return loop from the kitchen with a Grundfos UP10-16 PM BN5/LC, Comfort PM or similar pump on the return line at the boiler. The pump would be activated by a manual switch at either the kitchen or master bath. It will deactivate if the switch is off or if an aquastat (possibly a clip-on) somewhere on the loop indicates the desired temperature. I'll report back with my results if I go through with it.
A related question- I just noticed that in an accessory apartment with a separate electric HWH in an unheated crawl space, there is 20' of 1/2" HW pipe covered with rigid foam insulation sized for 3/4" pipe. Is it worth replacing with correct size insulation?
Thanks again for all your input-
Paul M