Bradford White new unit not holding consistent temp

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Hogan

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As the title says, my new BW 75 gal gas Powervent has much more variability in temps than I think it should?

Started on the Middle setting which should have been around 120 and found it was more like 135. Turned down to the next line and it came down over time to like 115. Trying to get around 125 so set it in the middle of those 2 settings. It got close so I thought I was golden but then WITHOUT THE DIAL MOVING AT ALL last night the water was super hot and I measured it at the tap at almost 140.

Alarmed at how the temp can just move from 125 to 140 when the dial didn't change? It had been fine for a few weeks and I never changed the dial and it juiced up to almost 140

I turned the dial back down a tiny bit (like a millimeter or something) to see if it will bring it back down

Why is it so sensitive and also why would the temp fluctuate like that?

Surprised that for a unit that costs 2000 bucks or something that they dont have a digital control and the temp is just changed through a tiny wire that you turn back and forth with a red plastic dial attached to it

Any advice appreciated thank you
 

GReynolds929

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Do you have a recirculation loop? You could have stacking happening.
 

John Gayewski

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A water heater can't give you a consistent temp. The thermostat is near the gas valve so you're measuring temp near the coldest water in the tank. If you really care about have a consistent temp you'd need a tempering valve after the water heater.
 

Hogan

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A water heater can't give you a consistent temp. The thermostat is near the gas valve so you're measuring temp near the coldest water in the tank. If you really care about have a consistent temp you'd need a tempering valve after the water heater.

Hmmm that is interesting. Why would the tank change that much though. I'm not talking about changes while running a tank. I'm talking about a tank sitting basically full and lightly used...why would it only go to 120-125 for a while and then one day it goes up to almost 140.
 

John Gayewski

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Hmmm that is interesting. Why would the tank change that much though. I'm not talking about changes while running a tank. I'm talking about a tank sitting basically full and lightly used...why would it only go to 120-125 for a while and then one day it goes up to almost 140.
Different conditions cause the thermostat to tell the burner to fire. You have cool return water trickling into the bottom of the tank near the thermostat. It will probably depend on usage and what not. I bet if you kept a chart over time with different usage scenarios clearly charted you'd see a pattern, but the temperature control on a water heater is not considered a reliable control to outlet temperature.
 

Hogan

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Different conditions cause the thermostat to tell the burner to fire. You have cool return water trickling into the bottom of the tank near the thermostat. It will probably depend on usage and what not. I bet if you kept a chart over time with different usage scenarios clearly charted you'd see a pattern, but the temperature control on a water heater is not considered a reliable control to outlet temperature.

Interesting I guess I never thought of it like that but yeah I guess if you had a slow steady trickle of cold that kept the burner kicking on then maybe it would overcompensate and end up heating the water more and overshoot.

I guess I will just watch it

I was trying to dial it into a nice range without really using the tempering valve I have on it but I guess I can turn that one up a little if this thing is gonna move up and down that much. I guess good news is kids are all teens now so less likely to scald themselves by mistake
 

Tuttles Revenge

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This is the example of why we're not allowed to use the water heater control itself to regulate the safe temperature of hot water at the end point. A thermostatic mixing valve at the water heater or at each point of use better guarantees consistent temps.
 

Hogan

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This is the example of why we're not allowed to use the water heater control itself to regulate the safe temperature of hot water at the end point. A thermostatic mixing valve at the water heater or at each point of use better guarantees consistent temps.

Yes BUT I'm not sure how those valves work in practice in terms of actual temp vs just 'banding' a relative temp from the heater output

What I'm trying to say is that the valve has 1 thru 7 on it let's say where 7 is Max. At Max I believe it basically just is wide open so whatever temp your heater is at it will pass it through. So if I am 125 it passes thru 125 or same with 135. And middle numbers are just sort of setting a quasi percentage mix so let's say you set it on 5 out of 7, well that will mix in a small amount of cold which will have the effect of Modulating the temp. But are the mixing valves actually set to a temperature range on an absolute basis in degrees? Like does "5" correspond to "130 degrees" where if the tank is running 150 then the valve will blend to get no higher than 130, but yet if the tank is at 120 then the valve will just pass that thru because it is already lower than the set limit on the tempering valve? If that is the case then I agree I can just find the valve setting for 120 or whatever I want to output and not worry whether the tank is doing some fluctuating in the background. My assumption and worry was that 5 on the valve would fluctuate up and down some with the tank temperature and if the tank went to 120 then I didn't want the valve to down mix even more just because on 5 it thinks it is supposed to be adding some cold.
 

Jeff H Young

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I never thought it was that complex if you leave the knob on number 5 the water when used temp will drop main burner comes on and warms it up for kicks lets call that 120 well every time you use enough water for the burner should come on and heat the water up to about 120 degrees and turn off to just pilot. Maybe 118 degrees maybe 123 degrees but if its 100 or 140 something is wrong. But whatever you are saying above isnt making sence to me Do you still have a question or something dosent seem right?
 

John Gayewski

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Yes BUT I'm not sure how those valves work in practice in terms of actual temp vs just 'banding' a relative temp from the heater output

What I'm trying to say is that the valve has 1 thru 7 on it let's say where 7 is Max. At Max I believe it basically just is wide open so whatever temp your heater is at it will pass it through. So if I am 125 it passes thru 125 or same with 135. And middle numbers are just sort of setting a quasi percentage mix so let's say you set it on 5 out of 7, well that will mix in a small amount of cold which will have the effect of Modulating the temp. But are the mixing valves actually set to a temperature range on an absolute basis in degrees? Like does "5" correspond to "130 degrees" where if the tank is running 150 then the valve will blend to get no higher than 130, but yet if the tank is at 120 then the valve will just pass that thru because it is already lower than the set limit on the tempering valve? If that is the case then I agree I can just find the valve setting for 120 or whatever I want to output and not worry whether the tank is doing some fluctuating in the background. My assumption and worry was that 5 on the valve would fluctuate up and down some with the tank temperature and if the tank went to 120 then I didn't want the valve to down mix even more just because on 5 it thinks it is supposed to be adding some cold.
Yes mixing valves for water heaters come in different types. There are types that are compliant with one standard which is more like a paddle type mixing valve that only let's so much of hot or cold go by. Then there are mixing valves they are compliant with another standard, those have wax (or bi metal) elements in them that swell or shrink based on temp. Those will only let one temp or cooler come out of them.
 

Hogan

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Yes mixing valves for water heaters come in different types. There are types that are compliant with one standard which is more like a paddle type mixing valve that only let's so much of hot or cold go by. Then there are mixing valves they are compliant with another standard, those have wax (or bi metal) elements in them that swell or shrink based on temp. Those will only let one temp or cooler come out of them.

I believe mine is the latter
 
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