Indirect hot water temps vary wildly

gilead1234

I'm posting in steam because a plumber is suggesting my boiler may be to blame for this problem. As the title suggests, the temperatures of the hot water coming out of my faucets vary wildly. We have an indirect tank coming from a steam boiler.

The baseline hot water temp is around 130 degrees, in line with what I understand to be safe and normal, and close to what the setting is on whatever that dial is on the tank. But other times, the water will come out much hotter—as hot as a scalding 155 degrees. Not great for anyone. Even worse with two very young children in the house. (I suspect this is a wintertime-only problem, i.e. a heating-season problem, though it's possible I'm wrong.)

I had guessed—just a guess—that whatever sensor/aquastat on the tank that is meant to tell it when to draw hot water from the boiler is defective. But a heat/plumbing professional I called in about this is seems to be under the impression that the culprit is stratification of hot water, and that I need something that will mix the water.

I'm struggling to understand how that would work, which I acknowledge might say more about me than the plumber.

Does his theory make sense?

mattmia2

First of all, the manufacturer of the tank recommends it be installed with a thermostatic mixing valve that gives it a consistent output.

That being said, my bet is on a flow check in the loop off the boiler that is stuck open so you are getting gravity circulation when the circulator for the indirect is off. Pictures would help a lot.

yellowdog

You need a mixing valve on the hot water outlet. Not only is it code almost everywhere, but you mentioned young children. Not something to let go for much longer before one of them gets scalded. Get someone there now to install the mixing valve.

gilead1234

Many thanks, @mattmia2 and @yellowdog. Matt, I'll post photos when I'm back at home. What/where would I look for to see if there's a mixing valve currently installed?

SuperTech

Check the pipes coming in and out of the water heater. A mixing valve would be located between the cold water pipe going into the water heater and the hot water pipe coming out of the water heater. 

gilead1234

Do these photos tell you anything about whether there's a mixing valve, or if a flow check might be stuck open?

@mattmia2 @yellowdog @SuperTech






As an aside, the plumber also mentioned that drips of water coming out of cut off pipe in the picture (temperature and pressure relief valve) is caused by a pressure reducing valve installed above the water meter, which is causing back pressure -- and that this can be harmful to the longevity of the indirect tank.

kcopp

You are too close to everything. A pix from further back is needed.
Yes you prob need a Potable water expansion tank.

mattmia2

This is a flow check but it is for presumably some hot water domestic heating.




Is there another one we can't see? it could be integral to the circulator too.

We don't see the domestic hot water and cold water pipes in your picture, if there is a mixing valve it would be on those.

clammy

Aside from a thermostatic mixing valve if you have a house pressure reducing valve then to still have a warranty on that indirect your installer should have installed a portable domestic expansion tank aside from the code required mixing valve . I would say that either your plumber is lazy or has never learned the codes required to ensure his customers safety . If he s an old guy maybe but any young buck should know this it’s code and it’s his job to ensure you and your families safety . If he states he doesn’t know I would sugggest to find some one else who will do the job as it should be done . A lot of guys are afraid to add these as they say extras to the job in fear of too high a price and not getting the job that’s a sad reason also that everyone there pricing against is pulling the same stuff. Personally I take the high road and price it like it was my own house own family and the customer can chose which they see value in . That being said it’s always cheaper and correct to do it all when it’s installed being there’s no way anyone is going to install them latter for less then when it was easy and should have been done .
Being your using a steam boiler to make your portable I would suggest flushing the tank and flushing the boiler well . Usually most decent contractor would use a 3 piece bronze pump for water side of steam boilers due to it being a open system and a cast pump will ended up being destroyed or burn out over a few years. Also your installed should have installed a check valve as Stated by others and a decent wye strainer to protect the impeller of the pump . If your installer is unable or unwilling to correct you should find a better plumber who possibly is concerned about code compliance over the cost being getting sued for damages will be quite more then a mixing valve and expansion tank . Ps I hope he had a p/t safety on the coil if not you really need a new plumber . The price of a 3 piece bronze pump is about 10 fold one of those taco 007 pumps so you get a idea of what exactly it is you have ,which is about less then half a properly done job . I highly doubt when faced w the truth that any plumber will be fixing ,updating or making it proper without a bill being connected to it and a big bill at that . In closing this is really totally beyond common cause everybody wants a deal and that is what you a deal and a bunch of junk which at least every two years or so will be a issue and a expense unless your getting a real water side flushing,wanding and boiler cleaning but again this swings on the boiler bein installed so it can be done other wise just wait till it’s full of mud and done then replace. Again only the truth according to the clam ,got zero reason to lie being this is what I do and I see garbage all the time so much I was thinking of changing careers and becoming one it would be less complicated and still doing the same being junk to the curb .
Not picking just say what I see and what’s not on the up and up
Peace and good luck clammy

gilead1234

@mattmia2 There is another flow check on the other side of the boiler. This connects to a pipe that leads to the indirect tank.

clammy

There is nothing to prevent heat transfer from the return of the boiler common to the equilizer to the return outlet of your indirect when the boiler is firing to make steam . Having the check valve on the return side of your pump from what it looks like ain’t to kosher either . Unless there’s a plug or nipple cap on the other return I can’t see how the block can be flushed of mud . Your installer should be capable of correcting your issue or find one that can . Have you attempted to flush the boiler side of your indirect Peace and good luck clammy

hot_rod

Here is an example of a tank mixer kit, this model is accurate at low flow rates, and is able to stop flow if the cold side fails. A handy feature for tanks running at scalding temperatures.

https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Caleffi-520510AX-Brochure.pdf