Lowering Burner Temp in Summer.

Mitragorz

I’ve asked this question on Reddit, asked it on Facebook, and got literally zero answers. So you guys are my last effort. 

Peerless WBV-04-W boiler with Hydrostat 3250-Plus. 

My oil burner typically sits around 200F, bc in addition to the regular hot water it also has to run the baseboard heat for two stories. 

Summertime now, obviously I’m not running the heat. Can I lower the temp to something like 120F for regular hot water use? Right now the “Low” temp on the unit is set at 180, and the “High” temp is around 200. 

Side note: Economy is “off”.  I understand that since we have a three-zone home (one zone upstairs, two downstairs) this should be set at 3 or 2. Any reason why it would be off?


Thank you guys. 

Derheatmeister

Do you have Rads or Baseboards?
Do not know this boiler but it is a none condensing boiler that does not like temperatures below 140 f..
If you set your low temp to 120 F it could cause damage to you boiler and venting system.

Mitragorz

Thanks. 

We have baseboard heat. No radiators. 

Derheatmeister

if you have baseboard you may try setting you lower temp to 140F and your high temp to 180F

SuperTech

Your high limit should be 180⁰ for baseboards and your low limit should be 150-160⁰. Economy should be set for the number of zones, 3. Your Hydrostat is setup all wrong as it is. It's almost like it's set to burn as much fuel as possible.  

As stated above you don't want it set too low to avoid condensation in the venting and on the cast iron boiler itself.  Ideally you would have a thermostatic mixing valve on the hot water coil to keep the hot water for showers and faucets at 120⁰. 

This site should have been the first place you looked for an answer.  You should see noticeable fuel savings with the Hydrostat setup as I described. 

Mitragorz

@SuperTech Great info there. We seem to burn oil like crazy with the way it's setup now. 180/160 should be a good year-round setting?

I don't know anything about a thermostatic mixing valve. Either we don't have it, or it's not setup correctly because the hot water for faucets and showers is scorching... Definitely way more than the 120 it should be. When we shower, adjusting the temp is super senstive. I basically have the hot water cranked 100% and adjust to cold to comfortable temp. But microscopic changes in the cold knob translate to big changes in temp. I always just chalked that up to the hot being so hot out of the boiler. I can turn the hot knob almost all the way closed and still get a comfortable temp out of the shower (as long as I adjust the cold to compensate) and still get good water pressure. The whole system is just too hot but I always considered it a necessary evil bc of the baseboard heat.

When I get home in a few days I'll snap some photos of the whole setup and hopefully you can tell me what's what.

This burner was installed in 2020 after the old one caught fire. We didn't own the home at the time, we moved in in 2021. Hydrostat settings are as they were when we moved in, I've never touched them.

HVACNUT

I don't think we know exactly what makes the domestic hot water. Is it a tankless coil? An indirect? 
If it's a tankless coil, then economy needs to be off. If it's an indirect, then set the economy to 3 for starters and see how it does on the Coldest days. If it has trouble keeping temperature in the house, then lower it to 2.
If you have the manual for the 3250 Plus, read it for important settings. If you don't have it, download it. It has a built in circulator hold off option to prevent condensing of the flue gasses, which you definitely don't want with a cast iron boiler. The wiring is a little atypical with this control so if you have an indirect and 3 heat zones using circulators in a 4 zone relay panel it must be wired correctly to take advantage of all the options the control offers. 

Mitragorz

Here are a few pictures of the burner. I'm a pilot, not a plumber/HVAC so I'm not really sure what components I'm looking at here. But I don't see anything that resembles a mixing valve.

EdTheHeaterMan

From those pictures it appears that you do hot have a mixing valve or at least a tempering valve (not recommended). That mixing valve is in the instructions that come with the boiler... How long ago was the boiler installed?

You will know why you need a mixing valve that has an ASSE 1070 rating. once you understand how your boiler makes hot water. This will insure that you will not get scalding water at the tap.

bburd

There is a closed ball valve on a bypass between the hot and cold pipes just above the tankless coil on the front of the boiler. It is not thermostatic.

EdTheHeaterMan

Here is a detailed description of how your water heater works.
If there is no call for heat
1. The boiler maintains a minimum temperature (usually 160°) so when there is a hot water tap opened there will be enough heat in the boiler to transfer to the cold water running through the coil in order to have a desired minimum hot water temperature.
2. If there is no need for Domestic Hot Water (DHW), then the non moving water in the coil will absorb the heat from the boiler and may be as hot as the boiler water temperature.
3. In condition #2 above, that hot water will exit the coil and proceed to any open tap. That water can be so hot that you could get burned.
4. Once a DHW tap is opened, the initial hot blast of water from the coil exits the coil en route to the tap. Then cold water running thru the coil will absorb heat from the boiler as stated in #2 above
5. At that point you may, but not necessarily get a reasonably stable flow of hot water, depending on the temperature control settings in the Hydrostat 3250-Plus.
If there is a call for heat
7. The boiler temperature will lower as the circulator pumps hot boiler water to the radiators.
8. This will cause the boiler water temperature around the coil to drop below the minimum needed to maintain adequate Domestic Hot Water (DHW) for a shower.
9. if that happens the Hydrostat 3250-Plus will shut off the circulator pump and operate the burner until the boiler water temperature is at or above the minimum in item #1 above.
10. During extreme cold weather the burner may operate for longer periods of time. This may cause the boiler water temperature to increase past the minimum needed for DHW
11. In this case the burner may operate until the boiler water temperature reaches the High Limit setting (Like 180°)
12. If there is no DHW usage during the heating cycle, the DHW water in the coil can absorb all that higher temperature heat from the boiler and be on standby at 180° as in condition #3 above

So during normal operation the boiler water can be as high as 180° and as low as 140° if the Hydrostat 3250-Plus is set at 160° low and 180° high. This happens automatically and is constantly changing as the boiler cycles thru a call for minimum DHW temperature and high limit temperature and varying calls for heat from the zones.

The only proven way to make sure that 180° DHW from the tankless coil never reaches your shower or sink is to have a tempering valve.

But to answer your question about turning down the low limit temperature on the Hydrostat 3250-Plus, the answer is YES. it will be trial and error as you select different lower temperatures. if you set it at 140° and you do not experience any problems with your hot water, then you are good to go. If you find that the hot water temperature is too cool, then Raise the Low Limit to 145°. Continue this process until there are no hot water complaints.

But MORE IMPORTANT...

Get a Mixing Valve installed ASAP


This is a diagram of what the mixing valve will do for your system. See how the valve will automatically adjust the amount of hot and the amount of cold to the outlet so it will stay at a safe temperature

HVACNUT

You have a tankless coil for domestic hot water so economy should be off.
You can set the temperatures to 160° Hi, 140° Lo with a 10° differential on each. It will only go to 160° with a heat call and will maintain 140° for domestic hot water. You should find a reliable oil tech for annual service that must be done, and get estimates for a thermostatic mixing valve, or (much more efficient) an indirect water heater. 

Mitragorz

bburd said:

There is a closed ball valve on a bypass between the hot and cold pipes just above the tankless coil on the front of the boiler. It is not thermostatic.

So can I crack that valve and experiment with it until I get non-scalding water at the taps? Or will that cause some kind of backflow problem? I realize that a proper mixing valve is the answer, but in the meantime...

Mitragorz

EdTheHeaterMan said:

Here is a detailed description of how your water heater works.
If there is no call for heat
1. The boiler maintains a minimum temperature (usually 160°) so when there is a hot water tap opened there will be enough heat in the boiler to transfer to the cold water running through the coil in order to have a desired minimum hot water temperature.
2. If there is no need for Domestic Hot Water (DHW), then the non moving water in the coil will absorb the heat from the boiler and may be as hot as the boiler water temperature.
3. In condition #2 above, that hot water will exit the coil and proceed to any open tap. That water can be so hot that you could get burned.
4. Once a DHW tap is opened, the initial hot blast of water from the coil exits the coil en route to the tap. Then cold water running thru the coil will absorb heat from the boiler as stated in #2 above
5. At that point you may, but not necessarily get a reasonably stable flow of hot water, depending on the temperature control settings in the Hydrostat 3250-Plus.
If there is a call for heat
7. The boiler temperature will lower as the circulator pumps hot boiler water to the radiators.
8. This will cause the boiler water temperature around the coil to drop below the minimum needed to maintain adequate Domestic Hot Water (DHW) for a shower.
9. if that happens the Hydrostat 3250-Plus will shut off the circulator pump and operate the burner until the boiler water temperature is at or above the minimum in item #1 above.
10. During extreme cold weather the burner may operate for longer periods of time. This may cause the boiler water temperature to increase past the minimum needed for DHW
11. In this case the burner may operate until the boiler water temperature reaches the High Limit setting (Like 180°)
12. If there is no DHW usage during the heating cycle, the DHW water in the coil can absorb all that higher temperature heat from the boiler and be on standby at 180° as in condition #3 above

So during normal operation the boiler water can be as high as 180° and as low as 140° if the Hydrostat 3250-Plus is set at 160° low and 180° high. This happens automatically and is constantly changing as the boiler cycles thru a call for minimum DHW temperature and high limit temperature and varying calls for heat from the zones.

The only proven way to make sure that 180° DHW from the tankless coil never reaches your shower or sink is to have a tempering valve.

But to answer your question about turning down the low limit temperature on the Hydrostat 3250-Plus, the answer is YES. it will be trial and error as you select different lower temperatures. if you set it at 140° and you do not experience any problems with your hot water, then you are good to go. If you find that the hot water temperature is too cool, then Raise the Low Limit to 145°. Continue this process until there are no hot water complaints.

But MORE IMPORTANT...

Get a Mixing Valve installed ASAP


This is a diagram of what the mixing valve will do for your system. See how the valve will automatically adjust the amount of hot and the amount of cold to the outlet so it will stay at a safe temperature

I had a basic idea of how water heaters work but jeez... Thanks for this!

bburd

Mitragorz said:

There is a closed ball valve on a bypass between the hot and cold pipes just above the tankless coil on the front of the boiler. It is not thermostatic.

So can I crack that valve and experiment with it until I get non-scalding water at the taps? Or will that cause some kind of backflow problem? I realize that a proper mixing valve is the answer, but in the meantime...

Exactly. That is why it was installed, but a code approved thermostatic valve is much better and safer.

HVACNUT

Mitragorz said:

There is a closed ball valve on a bypass between the hot and cold pipes just above the tankless coil on the front of the boiler. It is not thermostatic.

So can I crack that valve and experiment with it until I get non-scalding water at the taps? Or will that cause some kind of backflow problem? I realize that a proper mixing valve is the answer, but in the meantime...

Yes, you can crack it to mix in some cold. The problem is it's still a fixed position. If the boiler maintains 140° and you mix it to 120°, when the boiler temp drops to 130° before you burner comes on to reheat, the DHW temp likely also dropped. 

EdTheHeaterMan

Mitragorz said:

bburd said:

There is a closed ball valve on a bypass between the hot and cold pipes just above the tankless coil on the front of the boiler. It is not thermostatic.

So can I crack that valve and experiment with it until I get non-scalding water at the taps? Or will that cause some kind of backflow problem? I realize that a proper mixing valve is the answer, but in the meantime...

No, that is a useless valve installed by someone that has no idea what they were doing. It needs to be self adjusting like one of these. https://www.supplyhouse.com/Caleffi-521409A-1-2-Sweat-MIXCAL-3-Way-Thermostatic-Mixing-Valve-Lead-Free

Experiment with cracking that valve open will not provide the consistent water temperature because the boiler water temperature will constantly change thru the heating cycle. Also the standby temperature with all taps closed will eventually equal the boiler water temperature as stated in #2 in my last post. If you adjust that ball valve for that temperature, then you will always get much colder water during the rest of your shower. If you adjust it for the water that is moving thru the coil during a shower, then you will not be protected from scalding from that first blast of overheated water in the coil.

Unless you want to actually sit there and adjust the valve for the whole time your wife it taking her shower. You don't have Teenaged Daughters do you? I can see you sitting by the boiler watching the temperature of the hot water leaving the boiler and adding just the right amount of cold to keep her from screaming... IT'S TOO HOT... NOW IT'S TOO COLD... DADDY JUST BUY THE FREEKING MIXING VALVE!

Mitragorz

Thank a lot guys. Much appreciated! 

exqheat

e set the DHW supply at 140. The remaining cooling comes during the way up to the outlet faucet. Is your outdoor reset attached. This will help with lower temps in the shoulder seasons. I prefer indoor reset. Are we heating the outdoors?

EdTheHeaterMan

exqheat said:

e set the DHW supply at 140. The remaining cooling comes during the way up to the outlet faucet. Is your outdoor reset attached. This will help with lower temps in the shoulder seasons. I prefer indoor reset. Are we heating the outdoors?

This is not very scientific in my opinion. Especially if you understand the way the L8124, L7224 or the HydroStat make sure a tankless coil in a boiler works. Outdoor reset, indoor reset and any other water temperature control design is not going to keep the water temperature in the coil at a safe enough temperature for ALL situations. I see that you thought the description above was "insightful" but did you understand it? Am I to assume by your statement "set the DHW supply at 140. The remaining cooling comes during the way up to the outlet faucet" that you believe the mixing valve is unnecessary? I hope I am wrong or misunderstood your intent.

Get the mixing valve installed @Mitragorz. It is important

Edit: once the water flowing thru the coil has started and is moving at 3 gallons per minute, there may not be enough heat (at 140° boiler water temperature) to generate 120° potable water temperature. My experience has been that you may need 160° with a 10° differential to keep the customer from calling with a "Not Enough Hot water" service call.

Every user is different, and maintenance is important. I have experienced some tankless coils that have not been flushed in 20 years. This causes the tankless coil to have substantial scale build up inside the tubing, reducing the heat transfer little by little over the years. At that point the boiler low limit setting is 180° with a 10° differential and the high limit set at 200° in order to combat the reduced heat transfer. At that point many homeowners choose to get a 40 gallon electric water heater and leave the boiler settings at those inefficient high temperatures.

All they needed was a little maintenance and they would have saved tons of $$$ on a new water heater and wasted fuel over the years leading up to the decision to get a new water heater.

ethicalpaul

Or they could have bought a dedicated water heater years ago, avoided the wasted fuel all those years and always had plentiful hot water.

EdTheHeaterMan

ethicalpaul said:

Or they could have bought a dedicated water heater years ago, avoided the wasted fuel all those years and always had plentiful hot water. And I would add that they could have has maintenance all those years and saved money also

Do you have a time machine Paul? You could have also made different decisions years ago that would have reduced your cost also. But you waited until you did. And there were no heat pump water heaters back then were there?

I like to look at what is there NOW and make suggestions based on that information. And I certainly would spend YOUR money Paul to resolve your suggestions for others. But I'm not going to spend MY money to help those put in expensive ideas of yours in there homes.

But there are lots of different opinions on what should have been done and what could be done. I believe that a Mixing Valve in an important part for tankless coil water heaters. Any professional who does not include one should have his license revoked. Do you disagree?

exqheat

mixing valves are excellent. I should be more complete in my explanation. When I control Domestic Hot water temps from an unmixed tankless coil, I place the dhw temperature sensor on the exit pipe from the coil. The Low temp on that sensor will trigger the boiler at 140 up to 150. This can be adjusted if supply problems occur. This feature is activate if there is no call for heat for more than one hour. ( like summer or shoulder seasons.) During the heating season the boiler temps are adjusted automatically. On smaller houses the boiler temps stay near 150-160. The heat loss from the boiler to faucets increases due to cool chases. If there are children in the house we require a mixing valve, to prevent scalding. If needed we recommend a mixing valve. We cover this added need up front.