Amtrol Boilermate 41G running out of hot water in winter

Raymodj

Hi,

We have a Amtrol Boilermate Clasic Series 41 Gallon water heater with a Honeywell am series r model mixing valve and a Slant Fin VSPH-90. Installed about 2006, 1500 square foot 110 year old house in city.

The problem. We sometimes run out of hot water after about 10 minutes. Only happens in (Minnesota) winter, and not every time. Shower is relatively low flow. Always more than enough hot water in summer.

Back in Jan 2017 my wife complained of running out of hot water so I cleaned the boilermate with phosphoric acid. It seemed to help a little, but not much. Before 2017 we rarely ran out of hot water, if ever.

This winter we seem to run out of hot water more often than we did in past winters. Not sure what to look for as cause.

Thanks for any help or advice,
Ray

EBEBRATT-Ed

Well your city water is a lot colder in the winter than the summer.

Coil in BM could be dirty?

Check the mixing valve it could be faulty or bleeding cold into the hot. Can you shut the cold off going in the mixing valve to try this or shut the hot water off coming out of the heater and see if cold comes out of a HW faucet?

Correct size pump and piping to the boiler mate?

Up the boiler water temp?

Some of these probably don't apply as it seems to work in the summer but that is all I can think of

rick in Alaska

Check the feel of the hot water pipe leaving the boilermate when your wife runs out of hot water and see if it feels hot or cold. If it is still hot, then it most likely is a mixing valve issue, but if it is cold, then somehow there is not enough heat transfer from the boiler going on, Maybe just a bad adjustment on the boiler itself, or since it is winter, maybe the boiler isn't keeping up.
Rick

sunlight33

Your boiler can only do 68k BTU, that could be the limiting factor.

hot_rod

It’s getting up there in years. They have a finned copper coil and in time the fins get plugged beyond what acid can dislodge.
How hard is your water? The mixing valve could also use an acid bath from time to time, and or a rebuild.

mattmia2

Did you change anything with the shower head or valve? How about how you use it? With my now much longer hair I now take a much longer shower than I did in the past.

Raymodj

Thanks for all the helpful responses, sorry I couldn't respond sooner. Life threw us a curve, but all good again. So I took a shower and let it run when I was done. It held steady at about 80 to 90 degrees with cold water turned completely off. Felt the pipe from the mixer, and it was about the same temp. So probably not the mixer?

Right after my first post,, I ran the shower and it was tap cold after 10 - 15 minutes. I need to pay attention to when we do laundry and dishes, that might be cause of very cold shower as opposed to lukewarm shower.

I have someone coming tomorrow to inspect and clean the slant fin on off chance that might help. Realized we didn't have annual inspection since summer of 2019.

I might clean the Boilermate again, but that didn't seem to help much when I did it 4 years ago. (We have filtered, treated city water.)

Otherwise it sounds like either the Slant Fin or the boiler mate were able to keep up when they were newer, but age has taken its toll.

On a side note, one of our thermostats gave out a few days ago. I noticed no heat in the kitchen. I tested then replaced the 10 year old thermostat and problem solved. Don't know how this could affect water temp, just wanted to throw it out there.

Thanks again, I will post after boiler inspection.

Larry Weingarten

Hi, I'm not sure if it will help, but doing a crossover test to see if cold water can leak into the hot side might just be useful.

Your, Larry

Raymodj

I forgot to mention that I tried that. Unfortunately the 15 year old valve wouldnt completely stop the hot water from the boilermate. So I still had some hot water flow after turning off that valve. Earlier, someone mentioned that you can also test by turning off cold, but I don't see a way to turn off cold to mixer without also turning it off to fill the boilermate.

mattmia2

feeling the pipes in and out of the indirect itself when it runs cold could give you some incite as well as pipes to the coil in the indirect. The dishwasher doesn't use much water, I wouldn't suspect that as making a difference. A conventional washer especially on the hot cycle will use a lot of hot water.

HVACNUT

Does the water heater take priority over the space heat zone(s)?

Raymodj

Good question. I didn't know, so had to read up on it. Its wired as a separate heating zone with its own zone valve. So no priority. That might be the answer. It would explain how it only happens sometimes and only in the winter.

I also did some experimenting. I ran the basement hot water at about 3 1/2 to 4 gpm. After about 5 minutes the hot came out cool, then maintained at about 70°. The boiler temp dropped from 145 to 125, and stayed there while the water was running. It took about 20 minutes to get back to 150 after I shut the hot water tap off.

I also notices the boiler temp gets down to at least 110° (maybe lower) with a high of 200. Seems it would be better with a low temp range of 150° or so?

I'm learning a lot here, thanks!

Raymodj

Took a closer look and my boiler has the cheap Honeywell 4080B hi limit aquastat. 100 - 200° so I can't set low limit.

We need to have the upstairs and downstairs put on seperate thermostats, which means replacing the old shared iron pipes. When I have that work done, they can do whatever else needs to be done. New aquastat? And prioritized Boilermate with its own circulation pump? Still figuring this all out.

EBEBRATT-Ed

@Raymodj

If your boiler temp is dropping that low you have a control or wiring problem......which is good because it can be fixed. If your boiler water is below 140 it won't heat the indirect much and with the boiler down to 100 forget it

When your service tech comes, run some hot water and show him the problem

mattmia2

Is the burner firing when the boiler drops that low?

Raymodj

It started up again at about 100 - 110 but that could have been thermostat calling for heat. I dont see anything in the manuals about what keeps the water above a specified low temp.

Raymodj

So after reading a lot about aquastats and cold starts vs warm starts with indirect water heaters, I think I have the wrong type of aquastat for our needs. What I have is more energy efficient, apparently, but as not good for heating my boilermate. There is no low temp setting.

EBEBRATT-Ed

@Raymodj

Most boiler with an indirect do not have an aquastat with a low limit setting.

Hot water temp should be maintained in the indirect not in the boiler (the indirect is better insulated)

You have a temperature control on the indirect. When that control (which closes on a temp drop) makes contact it does one of two things depending on your system:

1. turns on the boiler & turns on the indirect circ pump (with this system each zone and indirect have their own pump)

OR

2. Opens a zone valve for the indirect and the zone valve signals the boiler and circ pump to run. (with this system there is usually one pump and each zone has a zone valve

HVACNUT

The L4080B has a fixed differential. Not sure if its 20 or 30 degrees. 
If the burners aren't firing until the temperature gets down to 110° then that would be a concern. 
It could be what others mentioned as far as build up on the HX and mixing valve. What is the tank temperature set to? 
What is the mix temperature set to?
Large heating pipes in this old house? With a high water volume and heat and domestic calls at the same time, boiler temperature drops pretty quick and has a hard time catching up. 

Raymodj

The more I read about this subject, the more conflicting information i find. But it's interesting.

@HVACNUT
I'm not positive its the L4080B, but that's what it looks like. I can't find any identifying markings on the aquastat. Tank temp is set to 119 and the mixing valve is at 4 / 16. When they installed this, they emphasized never having water heater temp over 120, but didn't mention the mixing valve.

Yes, large cast iron heating pipes and radiators. There were electric radiators in kitchen and half bath, those were replaced with baseboards with some kind of flex piping on its own heating zone.

I will look to see if theres a way to test the aquastat. The high limit is working, I saw it break at about 195, but if it has a fixed differential, that's not working. I took some photos to get a better look, but markings don't pull up anything on google.

@EBEBRATT-Ed

I have 2. Seperate zone valves all sharing one pump. The problem with maintaining water temp in the indirect is that the boiler can't heat the water fast enough during a shower, especially if the boiler water temp is under 140. But there is a problem other than just boiler water temp, because even at boiler temp of 180 the shower was better, but wasn't what it should be.

rick in Alaska

The tank temperature should be higher than the mixing valve output. I would set the tank temperature about 140 and then mix it down to 120. That will make the mixing valve work better, and give you more hot water,
Rick

Raymodj

More questions. I just checked the hot water temp from the tap and it's 120 to 121 on two different food thermometers. Indirect set to 120, so no mixing? I don't understand what the markings on the mixer dial indicate (4 16), and now I'm not even confident that they screwed the handle back on with correct markings at arrow or that it has the correct sticker.

Because I just took a look at the Honeywell am series install info. The one on my indirect is an R model, which is for baseboard and radiant heat applications, with no temperature lock. For domestic hot water, Honeywell says use only the C model set to max 120 or STD model set to 120.

Long story short, not sure if this is actually an R model, or if I can use it to get 140 indirect temp mixed to 120. The R model has a range of 80 to 180, but that "no temperature lock" concerns me.

Raymodj

Thought I would experiment, but handwheel will not budge...

Raymodj

I found what the markings mean, so I will take the mixer off tonight when everyone is done with hot water, clean it up and see why it won't adjust. (I did loosen the screw and turn on a faucet)

mattmia2

Does the circulator com on with a DHW call? I assume the zone valve opens on the aquastat on the indirect then the end switch on the zone valve makes a heat call to the boiler, probably paralelled with the end switch for the zone valve for the heating zone?

Jon_blaney

Is there a zone controller on this system?

Raymodj

Well, I should have checked the mixer as soon as you guys mentioned it. I got the chance to take the mixing valve off, and WOW!! I'm surprised there was any water flow at all, and the cold was probably completely blocked. Inside was packed with yellow sludge and hardened thick deposits. I'm giving it a soak, but I may need a new one.

Raymodj

After soaking in vinegar and baking soda for a couple hours, I wasn't able to get the mixer lower assembly out. Is there a more effective solution to soak this in, or need a new mixer?

Raymodj

Thanks for the help everyone! I finally got the mixing valve cleaned, soaked it overnight. Hooked up, turned water heater to 140, mixing valve at 120 and we are back to having plenty of hot water.

After learning so much, I might be back with questions about replacing cast iron radiator pipes with the appropriate pex pipe.

Raymodj

Forgot to share the photos of what the mixing valve looked like when I took it off. 15 years worth. Unfortunately I don't have any after photos, my wife was worried that we may never have hot water again.

mattmia2

How were you getting any water through that one port?

Raymodj

That was the cold in, and we had our wh set to 119, so I guess there wasn't any need for cold into the mixing valve, or very little. I definitely wasnt expecting to see all that.

Long story, but we did foster care years ago, and they made us set the wh to 119. One of the rules. I was thinking it was the installers, but wife says it was the county. I had no idea about the mixing valve or what it did, so... a couple years before that when we bought this place the first thing we did was new Boiler and water heater, so I just never thought about it except getting boiler serviced. Had so many other broken down things to replace or restore in our old house so I just never paid attention to the "new" thing until it went bad.

Raymodj

I cleaned the tank in 2017, and flushed some gunk out. Maybe what couldn't flush out wound up in the mixing valve.

hot_rod

Raymodj said:

Forgot to share the photos of what the mixing valve looked like when I took it off. 15 years worth. Unfortunately I don't have any after photos, my wife was worried that we may never have hot water again.

Can I use the pic of that plugged mixer for my training webinars?

Raymodj

Yes, you can use them.