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No hot water if recirculating pump is shut off

Nickrnm
Nickrnm Member Posts: 13
Hi, I'm a newbie to the site and saw some familiar posts but they did not actually match my issue. Hopefully this is not a duplicate issue.

I have a 3-year-old recirculating hot water loop that was installed as part of the new house. It appears to be a fairly typical installation. I have a TurboMax 45 Indirect hot water heater with a hot water recirculating loop. The circulator pump is a Taco 006-BC4 and it was hooked up to a simple mechanical timer to shut off for only a few early morning hours. I decided to eliminate the timer and installed a Honeywell L6006C strap-on aquastat to control the hot water recirculating loop pump. I strapped the aquastat to the hot water outlet line and I set it up to turn the pump on when the hot water temperature dropped. It appears to be working fine. It turns the pump on when the temp drops (temp setting minus differential) and shuts the pump off when it rises to the set temperature. Also, there’s a check valve installed between the circulator pump and the cold water inlet to the hot water tank. (photos below) The Aquastat and circulator pump appear to work correctly being I get plenty of hot water to any faucet and get it quickly. I think it also indicates that the check valve is installed correctly being the hot water recirculating return pipe coming from the pump and into the cold water inlet pipe at the hot water tank is hot when the pump is running.

Sounds all good but here is the problem I stumbled across. Whenever the pump is off and you pull hot water, it immediately allows cold water from the cold water inlet pipe to come back into the hot water recirculating return pipe right through the check valve and through the circulator pump. The hot water recirculating return pipe becomes cold and continues to stay cold if the circulator pump is off and you are pulling hot water. When in this state, the master bathroom, which is the furthest away and the end of the hot water recirculating loop quickly has no hot water. The kitchen and other bathrooms still have hot water being there is plenty of hot water in the tank and it’s being replenished.

Also, once the system is in this state, the aquastat does not turn the pump back on being the water coming through the hot water outlet is hotter than the aquastat set point. With the circulator pump not running, the master bathroom quickly has no hot water and stays that way until you manually set the aquastat to a higher set point temperature which then turns on the circulator pump. As soon as the pump turns back on the master bathroom immediately has plenty of hot water.

I have already replaced the check valve located between the pump and the cold water inlet even though it appeared to be working. I did inspect the one I took out and as I expected it was in good working order. Also, I tested the new check valve after installing it by opening the shutoff valve that is installed between it and the cold water inlet. No water came out of the check valve end that the pump is attached to.

I can replicate the issue at any time by shutting off the circulator pump and pulling hot water from anywhere in the house. Also, if I isolate the recirculating loop pump but turning off the pump and closing the shutoff valves in front and in the back of the pump, there is plenty of hot water everywhere including the master bathroom. However, it takes longer to get hot water to where you are.

I believe this issue may have been here all along, being the circulator pump was actually never shut off when it was hooked up to the timer, except for the few early morning hours when no one was pulling hot water.

Photos: https://photos.app.goo.gl/cWiYoxCePMN5UAoR9 https://photos.app.goo.gl/gA6fvyWZfnS4d8fP8

Any advice or suggestions on why this may be occurring is greatly appreciated. Thanks.

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 15,742
    Piping diagram? Is this recirculating system connected only to the master bath, and not any of the other hot water faucets?

    To be sure I have this straight.

    If the recirculation pump is running, you have good hot water everywhere.

    If the recirculation pump is off, and you open a hot water faucet anywhere in the house, the master bath, and only the master bath, quickly gets cold water, but all the other faucets are hot and stay hot.

    Correct?

    Among other things, the check valve can't be seating properly if you are getting back flow through the recirculation return. However, there are other possibilities -- such as a bad or improperly piped mixing valve in the master bath.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,129
    Hello, In addition to what Jamie says, there is a possibility that the recirc is masking a cross connection problem. Try shutting water off to the tank, to prevent any cold from entering. Now open a hot tap and see if flow quickly drops off it if it keeps running. If it runs, there is a cross connection to find and fix.

    Yours, Larry
  • Nickrnm
    Nickrnm Member Posts: 13
    -Yes, if the pump is running I have good hot water everywhere. Kitchen, powder room, guest bathroom, and master bathroom.

    -Whenever the recirculation pump is off, and I open a hot water faucet anywhere in the house, the master bath quickly gets cold water, but all the other faucets are hot and stay hot for an extended amount of time. They do start to become warm if you let them all run at the same time for an extended amount of time but they never become actually cold. I thought that would be normal due to the hot water recovery time.

    I agree that I should not be getting backflow through the check valve. However, I did test it when I replaced it being I had everything apart and there was no water coming out of it when I opened the shutoff valve in front it.

    Rough piping diagram: https://photos.app.goo.gl/xoyfu45SHJTiZz5JA
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,129
    Hi, What brand of shower valve do you have? Some allow a cross connection to happen.

    Yours, Larry
  • Nickrnm
    Nickrnm Member Posts: 13
    In the master bath its a Moen 3330 M-Pact. Yes I believe they do but this problem will happen even when not using the master bath shower or sinks.
  • Jamie Hall
    Jamie Hall Member Posts: 15,742
    Now let's think about it quickly here... based on all you say, it almost has to be a problem in the master bath, and most likely in that mixing valve. Otherwise, when you opened a hot water tap anywhere else, you would get the same cooling as in the master bath, but perhaps not as quickly. I don't think it's a problem with the recirculation.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,129
    Hi @Nickrnm , This may be too obvious, but you don't have a shut off valve on the showerhead and leave the mixing valve set to just the right temperature do you? o:) I've seen it!

    Yours, Larry
    JUGHNE
  • Nickrnm
    Nickrnm Member Posts: 13
    Larry, no shut off at the showerhead. :)

    Jamie, I thought the same thing when I first came across the problem. But after all the testing it came back to, no matter which faucet I pulled hot water from, somehow I get cold water backflow through the check valve, even though the master bath shower and faucets are closed. I would think if the shower is closed then it could not be able to mix cold water back into the recirculating loop. Just very strange..

    I believe the reason I get no hot water in the master bath first is that its last bathroom on the loop but the closest to the pump.

    Example and some additional detail: Let's say we pull hot water in the kitchen and everything else is off. If you go feel the recirculating return pipe between the check valve and the cold water inlet it will be hot from the cold water tee, through the check valve, through the pump, and all the way through where it enters into the wall. However, within about 20 seconds or so, you can start to feel the return pipe between the check valve and the cold water inlet start to get cold. Then you can feel the cold water continue to creep through the check valve, through the pump and within another 15 seconds so, the return pipe is cold all the way till it enters the wall. Being the return pipe starts turning cold at the cold water inlet side of the check valve and then continues to creep through the pump and through to the wall entry, is why I do not think it's an actual issue coming from the master bath.

    The strange thing it somehow comes back to the check valve and why it's opening? Do you think it could be a pressure-related issue?

    Quickly thinking, maybe far fetched, but have you ever seen the recirculating return teed at the hot water output? Would that work?

    Btw, I could just back to the mechanical timer and shut the pump down for only a few hours in the early morning! ;) lol

    All kidding aside, I want to thank you Guys for taking the time to discuss and talk through this strange situation. Thanks!
  • Jamie Hall
    Jamie Hall Member Posts: 15,742
    That check valve can't be closing then. It should be a spring check -- not a swing. Is it?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    rick in Alaska
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,129
    Hi, In the photo, it looked like a swing check to me. It seems time to replace it with a spring check. Also, It couldn't hurt to do the cross-connection test, just to make sure that isn't another source of trouble. >:)

    Yours, Larry
  • rick in Alaska
    rick in Alaska Member Posts: 1,178
    The only way cold water can go backward through a check valve is if it is not working. Change it to a spring check, and the problems will go away. And get a good one.
    Rick
  • "Quickly thinking, maybe far fetched, but have you ever seen the recirculating return teed at the hot water output? Would that work?"

    I did that by mistake recently. Over time, it just gets cooler and cooler.

    I agree: a spring check should solve the problem.

    Question: Why place the aquastat on the hot water outlet. That will turn off the pump almost immediately, no?
    Often wrong, never in doubt.
    BillyO
  • BillyO
    BillyO Member Posts: 264
    aqua stat should be on return piping , agreed
    JUGHNE
  • Nickrnm
    Nickrnm Member Posts: 13
    I replaced the check valve with what was originally installed and it was a swing one. I just replaced like for like. The spring check valve sounds good. I will do a little research and will replace it with a spring check.

    Agree and plan on getting a good quality one. I have not used a sping check before and I will do a little research to understand it better prior to buying one. I understand the concept but are there any specifications I should be looking for like the spring tension amount?

    Thanks all! I will try to get one quickly and carve out some time to install asap. I will keep everyone posted!
  • If you can find one, Caleffi check valves are excellent. Look back to hot rod's post in this thread:

    https://forum.heatinghelp.com/discussion/comment/1565307#Comment_1565307
    Often wrong, never in doubt.
    SuperTech
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,129
    Hello, I'd look for one with a soft seat, so you don't get any chattering noise when the pump is running. Some spring checks are named, indicating they are meant to be quiet... like silent-check.

    Yours, Larry
  • Nickrnm
    Nickrnm Member Posts: 13
    I checked the post and will look into Caleffi. I was looking this afternoon and found proflo and webstone brands but did no their quality. The one I took out was a proflo brand. I will check into the Caleffi this evening and look or soft seat/silent-check attributes. Thank..
  • Nickrnm
    Nickrnm Member Posts: 13
    I ordered a Caleffi NA51249 1/2" Sweat Serviceable Flow Check Valve (Low Lead). It was out of stock but I should have it within a week or so. I will update all as soon as I install it.
    Alan (California Radiant) Forbes
  • Nickrnm
    Nickrnm Member Posts: 13
    Hi All, I received the Caleffi NA51249 1/2" spring-loaded check valve today and installed it this afternoon. Great news! -it fixed the cold water backflow into the hot water recirculating loop whenever pulling hot water. I tested it a few times with the pump shut off and all appears to be working as it should.

    I would like to "Thank" all of you for your recommendations and assistance! Greatly appreciated!

    I have one final wrap-up question regarding the recommended and/or best placing of the aquastat. Originally I had the aquastat mounted on the hot water outlet pipe from the tank. While troubleshooting the problem I moved the aquastat onto the return recirculating pipe by the pump. I believe mounting the aquastat in either location would work being it should sense a temperature drop at either location. However, are there any recommendations as to best practices or where it should be mounted for best efficiency?

    Again, thank you for all your help!
  • hot_rod
    hot_rod Member Posts: 14,753
    Nickrnm said:

    Hi All, I received the Caleffi NA51249 1/2" spring-loaded check valve today and installed it this afternoon. Great news! -it fixed the cold water backflow into the hot water recirculating loop whenever pulling hot water. I tested it a few times with the pump shut off and all appears to be working as it should.

    I would like to "Thank" all of you for your recommendations and assistance! Greatly appreciated!

    I have one final wrap-up question regarding the recommended and/or best placing of the aquastat. Originally I had the aquastat mounted on the hot water outlet pipe from the tank. While troubleshooting the problem I moved the aquastat onto the return recirculating pipe by the pump. I believe mounting the aquastat in either location would work being it should sense a temperature drop at either location. However, are there any recommendations as to best practices or where it should be mounted for best efficiency?

    Again, thank you for all your help!

    On the return

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • HVACNUT
    HVACNUT Member Posts: 3,908
    @Nickrnm

    I haven't been with this post since the beginning and was going to tell you the aquastat was in the wrong location.

    It also appears (and you always seem to see it on a Turbo Max) there is no domestic relief valve. It needs to be there as a temperature and pressure safety.
    It will take some re piping but its code everywhere.
  • Nickrnm
    Nickrnm Member Posts: 13
    Hi All, I received the Caleffi NA51249 1/2" spring-loaded check valve today and installed it this afternoon. Great news! -it fixed the cold water backflow into the hot water recirculating loop whenever pulling hot water. I tested it a few times with the pump shut off and all appears to be working as it should.

    I would like to "Thank" all of you for your recommendations and assistance! Greatly appreciated!

    I have one final wrap-up question regarding the recommended and/or best placing of the aquastat. Originally I had the aquastat mounted on the hot water outlet pipe from the tank. While troubleshooting the problem I moved the aquastat onto the return recirculating pipe by the pump. I believe mounting the aquastat in either location would work being it should sense a temperature drop at either location. However, are there any recommendations as to best practices or where it should be mounted for best efficiency?

    Again, thank you for all your help!
  • Nickrnm
    Nickrnm Member Posts: 13
    I appreciate the advice and followup. Yes, there is a domestic pressure relief valve installed. It just may not be able to be seen in the photo. Thank you for bringing it to my attention though.
    HVACNUTSuperTech
  • JUGHNE
    JUGHNE Member Posts: 8,264
    All install instructions I have seen for mixing/recir systems place the tstat on the return pipe.
    You want the return to stay hot, that insures almost instant hot at the faucet.
  • HVACNUT
    HVACNUT Member Posts: 3,908
    > @Nickrnm said:
    > I appreciate the advice and followup. Yes, there is a domestic pressure relief valve installed. It just may not be able to be seen in the photo. Thank you for bringing it to my attention though.

    THAT IS NOT A DOMESTIC RELIEF VALVE!

    That is a 30 psi pressure relief valve. Read the stamp on it. It is in the boiler water side, not the domestic.

    The domestic relief valve must be installed at the hot side.

    1 1/4 x 3/4 x 3/4 tee.
    3/4 F x street on the run so the probe goes down. Hot out from the bull to the mixing valve.
    SuperTech
  • Nickrnm
    Nickrnm Member Posts: 13
    I was away, sorry for the delayed reply. I greatly appreciate you pointing this out and clarifying it! I will now get a hold of the plumber that installed the system and request that he correct the situation. Thanks again!
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