Hot water below 120

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  #1  
Old 05-18-16, 06:13 AM
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Hot water below 120

A cleaning tech. told my wife he adjusted something down to improve efficiency. We can't get a consistently hot shower since. I have tweaked the furnace set points, but that doesn't seem to be the issue. Due for a new cleaning, I had the same company come in.

A different tech showed up, and as soon as I began explaining, he began cursing about the last guy. In the end he didn't fix anything. He started saying the water is bad, I pointed out its filtered. He blamed the extrol and the vents, but I had changed them myself. He told me I didn't know how to adjust the mixing valve, but when he saw my model he was mistaken. He then claimed it must be a bad mixing valve, but he couldn't change it then. Having lost all faith, I am searching for a new company for next year, and went about changing my mixing valve.

That isn't it either. Here is what I can assess. The new thermometer strip that came with the mixing valve says at full hot I am getting 110F. The pipe leaving the boiler, is only slightly warmer to the touch. The tech changed the set points back to 160/180 and 10. This produces 160/190 on the furnace gauge. I have tweaked them to 170/190. Which adjusts things pretty much as expected. There is not blow-off at these temps. That was recently replaced as well.

Please help. If the suggestion is to change the coil, please tell me how the domestic water coil can be soaked in 170--200F water for hours without coming up to 120?

Thanks in advance.
 
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  #2  
Old 05-18-16, 06:24 AM
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What hot water tank &/or boiler do you have?
 
  #3  
Old 05-18-16, 06:43 AM
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Your domestic coil will hold, at best, two gallons of water. Yes, sitting in a boiler full of 170 degree water that one or two gallons will heat to nearly the same as the boiler water but as soon as you open the hot water tap it is on its merry way and being replaced with 40 or 50 degree water. The heat transfer through the coil to the moving water is impeded by any calcium (lime) deposits on either side of the coil and THAT may have a severe bearing on how fast (gallons per minute) the water may flow while still maintaining a usable hot temperature at the point of use.

It may be a problem with the mixing valve allowing too much cold water to mix with the hot. This could be from maladjustment to actually having a faulty mixing valve. You can close down on the cold water supply to the mixing valve to test if the mixing valve itself is the problem. Do NOT consider this test to be a cure as it could lead to scalding hot water being discharged from your hot water faucets.

It DOES sound like it is past time to get a different company to service your boiler.
 
  #4  
Old 05-18-16, 06:49 AM
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If it's an indirect system, eliminate the boiler from the loop. I'm about to do that for a friend. If you shut the boiler completely, the hot water tank should take care of it.
 
  #5  
Old 05-18-16, 07:39 AM
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Avalanche -

...He started saying the water is bad, I pointed out its filtered. ...
I bet he meant he suspects your water is hard, which would lime up the coil over time, which in turn would cause poor heat transfer to the domestic water in the coil as Furd points out. I don’t think filtering would change the hardness. I think you would need a softener if your water is hard. There are procedures to clean the mineral buildup in the coil which you can find online, and I pretty sure (not 100%) boiler service people can also do it for you.
..He blamed the extrol and the vents, ...
If I understand correctly I don’t think that would have anything to do with the coil efficiency. I can’t imagine what he meant by that.

I have the coil also and the hot water productivity is pretty poor – although I never directly measured things as you have. I found those low flow shower heads help a lot, but I don’t know whether you would be interested in something like that. It’s just me in the house so I can get by with the inefficient coil, but if it’s just not good enough for your demand you may have no other choice but to try either a coil cleaning or a new coil or an alternative DHW source.

A lot of posts on this forum in the past have complained about these coils, although I remember one guy defended them. Very inefficient way to heat water. I hate mine - lol.

But good luck - hope you get it straightened out.
 

Last edited by zoesdad; 05-18-16 at 07:58 AM. Reason: added coil cleaning
  #6  
Old 05-25-16, 05:19 AM
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Thanks for replies

There is no hot water tank, and for other reasons I don't want to add one. I can live with this if I need and don't want to add the equipment in the basement due to other plans.

I meant filter system - sediment filter + softener that removes trace levels of arsenic and hardness. Water feels quite soft. This is my second house with a softener so I feel that is okay. Aside from the old vent ports, there is minimal sign of scale on my appliances, etc.

The coil exit line does not get that much warmer than 110F, estimated by my hand vs. the mixing valve line with a thermo strip, even when hot water has just started flowing. I wouldn't think the new cold water entering the coil could affect this too much, and we could at least get an initial hot blast.

Instead, we get pretty consistent hot water. Only when running three showers or the Jacuzzi wide open do we over-draw and it runs cool. It just doesn't get hot enough for a steamy shower or good dish washing. I am used to restaurant water.

My question, is there anything flame related that the first tech could have lowered in the name of using less oil that would lower the domestic hot water? That's the best I can piece together.

The reasons I am not interested in a tank at this time include upcoming basement renovation, space competes with future alternative heating, other complaint is hot water takes long to reach faucets - I will consider faucet heaters if the products mature...

Did I miss any questions?
 
  #7  
Old 05-25-16, 06:21 AM
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If you put a smaller flame under a pot of boiling water it takes longer to boil. Could of down sized your nozzle. Don't know what brand of tempering value you got but the insert in some go bad. Could need a acid flush,not many do that any more.Rare times it's the outside of coil,was a product that took care of that in place,maybe there still is.Could need a new coil. Lot of guesses. Good luck.
 
  #8  
Old 05-25-16, 07:39 AM
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The low limit setpoint would definitely affect the temperature of the domestic hot water. But since you have it set very high, 170, that shouldn’t be the problem.

The only thing I can think of is that possibly before the tech came, your low limit was set crazy high, say 180 or something like that. Now that your low limit is 170 you would notice the difference in terms of domestic hot water.

Maybe the previous tech had set the low limit really high (180) to satisfy the homeowners request for hotter DHW, and the new tech saw that, cursed a little, and then dialed it back to 160.
 
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