Indirect Water Heater running out of hot water

AmatGonzi

I have a 2 year old new install of a Navien NHB-150 boiler and a 40 gallon indirect peerless water heater. I run out of hot water sooner than in the first year. Not sure if it's a mechanical problem, an issue due to the extremely cold weather in NJ in January/February, purge issue, or possibly because I haven't drained the boiler and cleaned it. Can someone offer several suggestions as to what it can be, or what I can investigate?

Thanks,
Amado

Larry Weingarten

Hello @AmatGonzi , There are various things that could be happening, but if you could post some photos of the setup, that would help us to do a better job of getting to the bottom of it. Thanks!

Yours, Larry

mattmia2

What was it like last winter? typically municipal water supplies are colder in winter.

AmatGonzi

Here are some pics of the setup Larry. Appreciate any insight. Thanks, Amado

AmatGonzi

yes, the municipal water in NJ at this time of the year is freezing. From what I read this can cause issues with heating up the water fast enough.

mattmia2

@Larry Weingarten is the peerless partner just a rebranded htp superstore?

The amount of heat needed to raise the temp of a given amount of water, say the amount of water you use in a shower from say 55 degrees to 95 degrees, to raise the temp 40 degrees is a fixed amount.

If the incoming temp of the water is 35 degrees and you add that same amount of energy to that same amount of water it will only be 75 degrees.

The boiler may not be big enough to add the amount of additional energy to make it 95 degrees in that second case with winter water temps.

There are a couple ways to fix this. one option is a low flow shower head that doesn't consume more water than the system can produce. Another option is to add a mixing valve to the water heater and store the water at a higher temp so you have more energy stored in the tank at the start of a demand for hot water.

The other thing to check is to look at the firing rate of the boiler during a big draw, if that boiler will display it, see if it is firing at 100%. If it is firing at 100% and is set up for hot water priority, it is transferring as much heat as it can to the hot water tank, the flow and the transfer of the coil are good enough.

iPipefitter

Sounds like the boiler may be undersized, I do see that issue where I live quite frequently as well as it gets below zero quite often.

mattmia2

Another option would be a bigger or second indirect tank or even a buffer tank. A bigger boiler would also work, but then it may need a bigger gas supply and wouldn't match the load of the building as well on a mild day and isn't a practical solution now anyhow. Unless you need a continuous supply or are really tight on space, a bigger tank is a better solution.

AmatGonzi

What's the difference between a second indirect tank and a buffer tank?

AmatGonzi

Is there anyway to preheat the incoming municipal water before it hits the indirect tank for further heating?

mattmia2

A buffer tank stores heating system water so there is more heat in the heating system that would get transferred to the indirect tank on a heat call, the second indirect tank would store more heated domestic hot water.

You could preheat it with an electric water heater or a passive tank that just stores water that slowly is heated by the ambient air to ambient temp.

SuperTech

I second the recommendation to add a thermostatic mixing valve and raise the temperature setting on the indirect tank,  that would be the easiest and least expensive option to try first.  In my opinion every water heater should have one anyway. 

Also you can see if you can setup that indirect tank as a priority zone on the boiler.  

JohnNY

That looks like a Taco 007 pump feeding the indirect water heater. There's a lot of restriction through the heat exchanger of that little boiler, and also through the coil in the indirect water heater which could be something like 6 feet or head (resistance to flow) on its own. Looking at the Taco 00 series pump curve chart, I'd go with another pump. To get the most out of that boiler, you want to move about 12 GPM through it against something like 10 feet of head. You gotta resize and replace that pump, man.

AmatGonzi

Here's a closeup of the circulator for the indirect. (attached). It's not 007 but 0015-MSF3-IFC, the other two on the space heating side are 007's. I do see a speed setting for this 0015, was wondering if it would make any difference to adjust to the "3" setting, as it's currently set at "2".

Dave H_2

Yes, turn that 0015 to high as the quick and easy for the moment. As @JohnNY said, there is a lot of restriction in that boiler and coil of the indirect. I would have to dive thru the manuals on each in order to size the circ properly. Each manual should discuss this or at least recommend a circ size for the application.

I do have one question though as it worked last winter and not now, has anything whatsoever changed?

Dave H.

AmatGonzi

The only things that have changed, is a change out of the shower heads, which I must admit do have more flow than the previous ones. And to re-iterate this issue really only happens in the winter months, when it's really cold outside. It could be the higher output shower heads and the cold weather in combination are just overtaxing the system. If that's case, it seems the cheapest things I can do are 1) Currently increase the speed of the current IFC circulator into the indirect, 2) Increase the size of the indirect circulator 3) Increase the overall size of the indirect and/or have some type of buffer tank, 4) Add in a mixing valve.

One question on the mixing valve, would the mixing valve be installed at the boiler/indirect location, or at each shower? I assume the mixing value would take some of the boiler water and temper the incoming cold supply water before enter the indirect?

Dave H_2

The mixing valve would control the water temp on the Hot water delivery to the home. They are default to 120F and you would increase the the tank setting to about 145F. That would give you a tempered increase in capacity. No boiler water passes through the mix valve

Dave H.