Oil Heat Tankless boiler coil disabled and replaced with Water Heater Changeover Questions
There are two aquastats Honey well L4006A (LOW) & 4006B (HIGH). Settings with coil 150/180.
The Switching Relay is SR-501 1 ZONE TACO with metal cover.
Question is what has to be changed as far a wiring,etc to make this a cold start boiler? I've read there are ways to do that but none yet that show it with this setup. Open for other suggestions as well.
Comments
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If the L4006A is the low limit just disconnect it. It is probably wired in parallel with your room thermostat.
What is the switching relay controlling and where are you getting your hot water from now?
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The switch relay is connected to the thermostat wires and also goes back to the circulator and burner. tt on the protectorelay is jumped. Get water from hot water heater now.
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The L4006B will prevent the circulator from operating until the boiler water temperature is above the set point. Take the two wires and connect them together with a wire nut. That way the circulator can operate when there is a call for heat.
Unless your L4006B has three wired connections. Then that is the operator control that controls the DHW minimum temperature. If the 4006B senses the temperature is below the minimum, then it powers the burner. If it is above the minimum then it sends power to the circulator through the SR 501. If the SR501 gets a call for heat from the thermostat it will complete the circuit to the circulatory and also operate the burner thru the L4006A high limit.
Does your system have three aquastats? Or are there only the two you mentioned?
PICTURES PLEASE
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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WOAH!!!
I just did a little research and DO NOT disconnect the L4006A. It may be the High Limit.
Here is the old school way we would install tankelss coil systems before the advent of triple aquastat relays. like the L8124 series.
Depending on the last 4 numbers of your L4006A control you may have only two terminals or three terminals. If it is a two terminal, then it may be the high limit the breaks on temperature rise and has only the R and B terminals. You can not remove that from the system.
It is important to know what the last 4 numbers of the L4006A and the L4006B controls are because each variation does things a little differently. Here is a cross reference of those aquastats:
If you want to send some Photos of your controls with the civers off thenI will give you a wiring diagram for a cold start system. BUT DO NOT UNDER ANY CIRCUMSTANCES REMOVE THE L4006A FROM THE SYSTEM as @EBEBRATT-Ed suggested. He did say "IF IT IS THE LOW LIMIT" and that is important to know if it actually is the LOW limit or if it is the HIGH LIMIT.
I'm sure Ed would agree.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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If you have three L4006 controls then will you have a L4006a for the high limit and another L4006A for the low limit the maintains a minimum boiler temperature and the third will be the L4006B reverse acting to disable the circulator on a call for heat in the boiler temperature drops below the minimum required for DHW. This would be the diagram for you and it would be just fine to remove the L4006A LOW limit as Instructed by @EBEBRATT-Ed
Just don't remove the HIGH limit
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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The A is High Limit. It has a differential. You need to replace the aquastat.
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ok..i will have to check the aquastats on the boiler…for more numbers….the covers don't have additional numbers on them..maybe there is a tag..there are two aquastats on the boiler…and the honeywell grey box on the burner. i am trying to post some pictures but had a problem with that due to program issues…,
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here is the pdf from honeywell regarding the two aquastats that are on the boiler.
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The L4006A is adjusted to 150…the low limit…and the L4006B is adjusted to 180…the high limit…this way the water which was produced by the tankless coil would be available for use when needed.
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Its backwards. An A control opens on temperature rise, and B control closes on temperature rise.
Unless the covers were swapped.
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Look on the actual control, not on the cover, for the part number with the additional 4 numbers
There are many versions of that control. There may be an older L4006A with SPDT switch action that would be used for a low limit. It is more likely that the covers may be wrong and you have a L4006C or L6006C that is being used as the low limit, and that you have a L4006A with SPST contacts that break on temperature rise as the High Limit. Once we know for sure what your controls actually are, then I can help to make it a cold start boiler.
Can you take a picture?
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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This is the wiring diagram you need. you must have a High limit between the #4 terminal of the Taco SR501 and the burner primary control. Other than that, you can just connect the circulator pump directly to the SR501 without going thru an aquastat.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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looks like these numbers:
A: 103773
B: 112826
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usually only 4 numbers after the letter. Do you have a camera on your phone that you can use to send pictures to heatinghelp.com It is very easy once you do it the first time.
Anyway the wiring diagram you need is posted above on my previous post from 9:12 PM (after midnight is will just say Oct 19)
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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i've posted photos here showing aquastats and also sr501 wiring which is differently wired on diagram above as well as the name on the taco sheet describing wiring. the taco sheet wiring diagram i have shows that i have mine similar to typical wiring for cold start but not connected to terminal 6 and 5 to tt on protecto relay.
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Did you see this diagram? I believe you either have one more aquastat or your system has been operating inefficiently for many years. Regardless this diagram will get you the the cold start operation you desire.
The L4006A MUST be used as the high limit on your cold start up boiler wiring design.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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A photo of the entire heater far enough away to see all three of those controls in the same photo would be nice. the two controls you have L4006A and L4006B are the proper controls to operate a tankless coil boiler as shown below. the problem I have is that the two controls only account for the two at the bottom of the diagram. You are either missing the one at the top and your system has been operating inefficiently for many many years, or ther is an aquastat that hidden behind a panel somewhere.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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I cant help but see that your boiler looks like the Columbia Boiler that was in my childhood home on 4th street in Philadelphia from just the phots of the L4006A
This is the inefficient wiring design you probably have now.
- The boiler maintains the temperature based on the L4006A.
- The SR501 replaced an old Ra832 relay. that is the connection between the thermostat and the circulator.
- The L4006B is what shuts off the circulator pump if the boiler water temperature drops below that set point so you don't get a cold shower. the fact that it is set higher than the L4006A control just means the they are out of calibration, otherwise the boiler temperature might never get hot enough to allow the circulator to operate and heat the radiators.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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If my most recent diagram is correct, this is the easiest way to make it a cold start boiler.
- The red wire is all you need
- Remove the wires from the L4006B
- connect the circulator directly to the 4 N/O on the SR501
- Add a wire to connect from H on the SR501 to 6N/O on the SR501
- Remove the wire that goes from L1 power to the supply switch to the L4006A (maybe R or B)
- Connect a wire from 5 on the SR501 to the wire you removed from the L4006A limit (maybe R or B)
This should be easy and you may be able to use the wires you already have from the wires you removed from the L4006B
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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This should make it easier.
The covers on the L4006A & B may have been reversed. The L4006A is the one with the screw terminals close together. That is the high limit
Then use the #5 and 6N/O to operate the burner thru the High Limit.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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ok..so then that means the L4006a is on top and L4006b is on the bottom and the covers have been switched…but all things being the same with the tankless coil in the boiler as before..the L4006A top is set to 180 and the L4006B on bottom is set to 150 and the last instructions and diagram will change this to a cold start boiler?
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Ed, thanks for your help…wanted to mention that today I did the add air procedure to the compression tank that you mentioned before. Great stuff. Weird though with a 24 lb pressure on gauge at boiler there is a drip at the prv..so will look at that.
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Yes the last instruction will remove the B control so the circulator will run when ever there is a call for heat from the thermostat. and the burner will not maintain temperature because there are the 5 and 6 contacts in series with the L4006A control. That means the both the thermostat must call for heat and the boiler temperature must be below the L4006A set point
Adding air to the expansion tank must be completed with the expansion tank disconnected from the boiler pressure. And operating a boiler at 24 PSI cold will probably cause the water pressure to go near of above 30 PSI when heated. The relief valve is supposed to let water out when that happens. If you have a one or two story house you do not need to operate your boiler with any more than 12 PSI cold. If you added 24 PSI to the tank with the boiler pressure below 12 PSI, then that tank has too much pressure in it.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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the cold pressure after adding air to the tank was 12…after boiler on and water heating radiators and house the pressure on gauge was 24lbs hot and there was a leak at the dual valve prv side bell and gosset.
it means either the gauge is not accurate or the prv had a problem. looking to flush that and see what happens.
i have a compression tank in the rafters and not an expansion tank. if the circulator runs whenever there is a call for heat there has to be a temperature that the circulator won't run where the water wouldn't be hot enough correct? I guess what I'm asking is i see the circulator goes on at a call for heat but what is the temperature of the water…?
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The part that controls the circulator with temperature is the B control. The L4006B.
You wanted cold start, you got it. You want better control? Replace the aquastat with a modern aquastat from Hydrostat, Honeywell, Beckett…
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That is a different story. You do not have an Extrol type expansion tank. You have a tank that is connected to the system and the water and air are in contact with each other.
That makes more sense now.
That tank needs to start out empty of water (full of air) when there is no pressure on the boiler. When you add water to the system the air will compress at the top of that tank as the water pressure in the boiler. Then water will foll the tank compressing the air. At 12 PSI in the tank the tank will have about 1/3 air and 2/3 water. That 1/3 air in the tank should be enough to handle that expansion of the water in the system with about 3 or 4 PSI increase in boiler pressure. (Not 12 PSI more pressure)
So I have posted a trick I use to get the tank full of air in the past, let me see if I can find it.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Yes also open to other suggestions as i mentioned in first post. Is this cold start the best route to go on this boiler or some other way using existing aquastats at different temperatures,etc.
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Cold start will use the least amount of fuel
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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I wanted to do a few tests to see how the cold start boiler would work.
- i disconnected the two wires to the L4006B low limit aquastat and joined them together. I left the L4006A high limit alone.
- I then connected a voltmeter to the circulator motor and turned the burner switch on. Burner went on and so did the circulator…water was cold…
- The water went through the pipes evenly into all the radiators. The room temp was 70 and a call for heat at 75 degrees was set for the test.
- The thermostat was satisfied at 75, circulator stopped and the burner continued to run up to 170 degrees and went off. There has to be a wire connected somewhere that was mean for the original coil.
- On the honeywell protectorelay the TT was jumped which effectively takes away the thermostat from doing it's job.
- I took the jumper at TT off and connected the thermostat there and was able to control the burner going on and off but the circulator wasn't on. I wanted to see what happened and I'll say was very pleased with the test and think that this will be an efficient was to run this.
- Just have to make sure i totally understand where everything goes to follow the diagram in the post.
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- The thermostat needs to operate the SR501 so the circulator pump can operate.
- Removing the L4006B lets the circulator operate at any boiler temperature.
- Removing the jumper wire from the Primary control means the burner will not operate
- Connecting the thermostat to the primary control will make the burner operate but the circulator does not operate. because there is no call from the thermostat to the SR501
- Your next test should be
- Put the thermostat wires back on the SR501
- Put low voltage wires from 5 and 6N/O on the SR501 at one end and then put the other end to the primary control T T where you removed the jumper.
That will be easier than doing it on the line voltage side with all those old wires on these old controls with cracking insulation.
I should have thought of that earlier!
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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- Reconnected the thermostat to SR501
- Put low voltage wires from 5 and 6N/0 on SR501 at one end and put the other end to the primary control TT.
- I had to join the two wires removed from the L4006B Aquastat to turn on the circulator…if not connected circulator wouldn't go on.
- I set thermostat and room temp increased and water temperature on boiler was 100 degrees and it started at 50 degrees since it was off. I took some temperatures at radiators and range was 118 degrees to 103 degrees. I turned off the thermostat at that point.
- I guess the gauge on boiler may not be accurate.
- If the heat was left on would the burner have gone off when the differential temp was met?…high limit of Aquastat L4006A was 180 degrees…I read may be a 10 degree differential factory set?…and when would it turn on again?
- Circulator goes on as expected and even heat distributed throughout the house…I can see how this is more efficient now.
- Will do some more testing and get some thermostat wire to make connection from SR501 to TT terminals at Primary Control to replace the temporary hookup.
- I know you said the burner would not operate without a jumper at the TT on Primary Control. The thermostat would be on or off depending on call for heat,room temp..etc…and I tested all of that and agree…but if a jumper was there the burner would go on all the time. Just wondering where would the thermostat come in wth that setup…that jumper was always there with the coil in use making hot water from the boiler…it would seem that this jumper would override the thermostat.
- Seems like the bugs are being worked out here. Thanks for all your help and not only that I understand alot of this information now and how it all works thanks to your guidance!
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