the boiler shower experience

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Old 12-18-11, 01:59 PM
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Unhappy the boiler shower experience

Good Afternoon folks,

I'm not sure if this is a boiler issue but I have a feeling that it wouldn't happen with a hot water heater.

The boiler seems to output a single temperature, just under 170 according to its dial.

When I take a shower the position of the temperature dial seems relative. It takes it awhile to get hot (normal), and once it's set at a comfortable temperature, it slowly gets hotter and hotter until it's scolding hot. This happens without moving the dial. At this point I have to turn the dial down, usually it doesn't change the temperature (still scolding as it moves to the cold direction) until it's well within the cold region. At this point there's a dip in water pressure and the water turns instantly lukewarm or coldish. I then have to turn the dial back up towards the warm side and this process is repeated several times until I'm done cleansing.

Is there a need for some kind of variable temperature controller on the boiler or does this happen because someone forgot to install a pressure stabilizing valve (I hear these exist)?

We will likely be remodeling the bathroom so I might get access to the pipes back there to fix this. Unless, is this normal operating procedure for boiler-heated homes?

Thanks for your help!
 
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Old 12-18-11, 02:38 PM
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When I take a shower the position of the temperature dial seems relative.
The 'temperature dial' ... you are talking about the position of the SHOWER valve, right? Not a dial on the boiler itself... just wanna make sure we're all on the same hymnal page here.

What make/model is your shower valve?

It sounds more to me like that may be the culprit.

How is the water from the lav sink? or the kitchen sink? they don't go hot/cold/hot, do they?
 
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Old 12-18-11, 06:12 PM
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Yes. I'm talking about the shower temperature control.

Other faucets don't go cold, but they do have narrow temperature er... settings. So while they don't alternate temperature they are finicky as far as setting them: get it hot, then millimeters over and it's lukewarm again. All are one-piece temperature selectors like the shower. I think the builder literally got the cheapest faucet hardware available.
head is different but this is what selector looks like (looks like, not sure if it's actual):
shower: Adler Chrome Posi-Temp® tub/shower - L82694

Not sure if water pressure to the bathrooms is marginal. One of the tubs upstairs doesn't fill with hot water. it has both a hot and cold lever and if you set just the hot water one to full blast, the flow alternates between hot and cold water. You can hear the boiler cycling while this happens.

So I assume that this isn't typical behavior even for a boiler based system. Is there a pressure balancing circuit we could use on faucets? Is there supposed to be a regulator on the boiler that alternates how much hot water gets sent at a given time?
 
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Old 12-18-11, 07:18 PM
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I dunno, if the valve IS actually a Moen, it's a pretty good valve.

First, let's talk about the boiler and how it makes your hot water. There's a 'coil' of copper tubing immersed inside the boiler water. As the cold water flows through it heats up... pretty basic idea.

But, the problem with these is that they can't actually STORE any quantity of hot water as a regular water heater would. And they never work well enough to actually provide any consistent quantity of hot water. The only worse way of making hot water for a home would be a kettle on a woodstove.

So what you are experiencing is pretty much 'typical' behavior for that type of water heating. What compounds the problem is that over the years, the performance is degraded by 'lime' (actually calcium and magnesium) buildup on the inside of the coil which reduces it's heat transfer ability. Each year you have less and less hot water available.

At best, you may be able to expect a couple GPM of hot water flow through them. You try to draw the water faster, as in filling a tub, and the water doesn't stay in contact with the coil long enough to get hot.

That said, if your shower valve IS a Moen or other temperature compensating type, there may be a problem with the 'spool' inside sticking and not reacting fast enough to the changes in temperature. You may have two problems... but it could just be that the coil can't produce enough hot water fast enough, and the valve just isn't designed to react that quickly.

What can you do? Well... you can have the inside of the coil cleaned by a plumber with a weak acid solution to dissolve the lime buildup. That will restore the capacity of the coil for a couple years. Then, you could have the plumber install a thermostatic tempering valve on the coil which would pre-mix the hot and cold to send a more consistent temperature to the home.

You might still have trouble with higher flows... not much you can do about that except turn the volume of water down when you shower, or fill the tub more slowly.

To summarize:

So I assume that this isn't typical behavior even for a boiler based system. Is there a pressure balancing circuit we could use on faucets? Is there supposed to be a regulator on the boiler that alternates how much hot water gets sent at a given time?
As above, yes, rather typical.

It's not a problem of PRESSURE but of TEMPERATURE, and FLOW RATE

The 'regulator' is the mixing valve I described above. A help, but not a cure.
 
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Old 12-18-11, 07:26 PM
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You may be tempted to investigate the temperature settings on the boiler control... but what you want to be very careful of is turning the settings too high...

You might be able to make some adjustments that will improve, so let's have a look at what the temperatures are set at now.

On your boiler there should be a control box, most likely with a gray cover, a Honeywell, but could be another brand. The cover should slide straight off. There is probably one screw that you only have to loosen (not remove) to get the cover off.

TURN OFF THE POWER TO THE BOILER! and slide the cover off and read the three dials --- HIGH , LOW , DIFF and tell us what the settings are. Put the cover back on and turn the boiler back on.
 
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Old 12-19-11, 10:36 PM
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good evening,

Good call on the gray cover! it slid right off. The temperature control flashes 162 deg F. Followed by a 6 and something that looks like an E with the top line missing. I don't have a switch in this box but there look to be 3 buttons, an up arrow a down arrow and one with an "I" next to it. it is a crown shorty from 2005.

There's also a combined temperature needle and pressure needle. Temp reported here is in the 150s and pressure looks to be around 12psi.

some comments on your suggestions of cause:
-when filling the tub, the boiler cycles. it turns off and on, so to me it seems like it's supplying more water than needed, turns off, then turns on again, and this lag is what causes intermittent cold water. The hot water also comes on and off while filling the tub. Does this sound plausible?
 
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Old 12-19-11, 10:50 PM
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Here. This should be what you have. trooper is still on so possibly he is looking for this manual. Not sure about the cut off "E" thing. I have not read this manual through.

Ohh Thats a BT for boiler temperature.....

Try to go in and follow the instructions to get the HI/LO/Diff settings and post back.

http://www.forwardthinking.honeywell...ll/69_1720.pdf

Mike NJ
 
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Old 12-20-11, 09:09 PM
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settings

Hello,

I am amazed that you found the manual for that controller without having too many details!

High Limit: 180
Low Limit: 150
Low Diff: 10
local thermostat status: off
enviracom: off

deg F of course.

I'm abit sad that this manual says you should configure it to boiler's specifications. When I read "differential" I immediately dreamed that it would mean "heat up as much water as needed" and hence throttle my hot water needs at the boiler. alas, it doesn't seem to do that...

How often do you guys clean the coils? We have hardish well water here.

If this is "typical" could it be that the boiler is under-sized? 12psi doesn't seem like a lot to me to be driving flow thru the thing and then all the way upstairs after that... would a bigger water pump allow the boiler to heat more water?

I really don't feel that less flow to the shower can be achieved since we already have fairly marginal pressure. The shower that shares the room with the tub is not often used because it's pretty weak.

Thanks for your time and suggestions!
 
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Old 12-20-11, 10:18 PM
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I would leave the settings right where they are.


12psi doesn't seem like a lot to me to be driving flow thru the thing and then all the way upstairs after that... would a bigger water pump allow the boiler to heat more water?



Boiler pressure and the boiler water are seperate from you potable house water. 12 psi is what you boiler pressure is and what it should be.

Your house water is at the pressure your well pump produces. Say 40-60psi. This water travels in seperate piping in and out of a coil in the boiler. The two waters never touch. The boiler water heats the coil that contains the house water.

Got it????

Is there a mixing valve on the boiler for the hot water? It should have three pipes going to it and should be around the hot water coil.

If not one should be installed. They may help in getting a more constant temperature.

And when was the last time the coil was cleaned? No softner on your well water?

You can try cleaning it but possibly a new coil is a better route.

Mike NJ
 
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Old 12-21-11, 03:46 PM
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Originally Posted by bananapeal View Post
If this is "typical" could it be that the boiler is under-sized? 12psi doesn't seem like a lot to me to be driving flow thru the thing and then all the way upstairs after that... would a bigger water pump allow the boiler to heat more water?
You only need the pump to overcome the friction of the pipping. A bigger water pump will not help you.
 
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Old 12-21-11, 04:21 PM
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How often do you guys clean the coils? We have hardish well water here.
When they need it. Hard water compounds the problem...

Let us know about the mixing valve that Mike mentioned.

The pump size has nothing at all to do with your domestic water heating, nor does the pressure in the boiler.
 
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