I want to add a Bock 40gal indirect tank to my oil fired boiler and eliminate the coil for domestic hot water. It seems like a pretty straightforward installation but I have concerns about the boiler controls. The way it is set up right now, it seems the boiler is set to run until it reaches the temp on the high limit on the aquastat, which is set to 180. When a thermostat calls for heat, the circulator comes on and then when the boiler temp drops below 180 the aquastat will fire the burner until it gets back to 180. The low limit on the aquastat is currently not hooked up to anything. Once I add the indirect tank, I don’t think I need this boiler maintaining 180 degrees all the time, correct? What are my options here? Can I make this a cold start system? Or can I set this up so it maintains a minimum temp and then will only fire when there is a call for either heat or domestic hot water? I’m not sure how to do this.

I tried looking up the aquastat that I have – Honeywell L4010B and I can’t find anything on it. Inside the cover it says “Circulator- Close on temperature increase”, “High Limit – Open on temperature increase.”

 

You need to change the control to make this a cold start boiler. The coil plate gasket could leak when converted to cold start.
How high does the differential go?
You can max out the differential which deducts from high setting so the boiler will drop 20º -25º depending how high the differential goes. I would change the control.
Do not cap the coil pipes and maybe think about a new gasket. My guess if you contact Peerless they may have a coil plate cover and mew gasket. Than hope the bolts come out.

 

Can you recommend a controller? I was thinking of using a tekmar outdoor reset. Would that work for this application?

 

Deuce, the control that rbeck is talking about is the 4010 ... that's your 'aquastat' and it controls the boiler firing based on the water temperature.

You would probably want an L8148A in place of that one... but beware, it may or may not fit in/on the 'well' that the 4010 is currently on... so that's one of the first things to consider ... if the 8148 will work with your existing well, you won't have to drain the boiler. If you have to change the well, you will.

Additionally, the existing wiring needs to be looked at ... because the 8148 won't be a 'plug and play' ... some re-wiring will need to be done.

Any 'outdoor reset' control that you might add would be in addition to any other control changes you make, so don't concern yourself with that until the other work is done. One thing at a time ...

On your boiler ... I don't see an ASME rated pressure relief valve. You DO have a relief valve (next to your feedwater regulator), but it really isn't rated for the job it might be called on to do ... it will relieve pressure, but may not be able to relieve pressure FAST ENOUGH to properly protect ... that's the way they did it back then, when they didn't know better.

You should plan on adding the proper relief valve.

When you add the indirect, if you leave the domestic coil in the boiler, do NOT cap the pipes. Leave them open ... or, for a finished look, drill a hole in the caps before you install them. There has to be a pressure relief on that now unused coil. If you cap them yer taking a chance...

 

So will switching to the L8148A make this a "cold start" system?

And where should the pressure relief valve be added?

Thanks for the help guys.

 

There might actually be a way to re-wire the existing setup to go to cold start ... those old controls pre-date me though, so I don't know for sure ...

For some information on what your control is SIMILAR to in function, see Honeywell L6081A control. You can use that to replace yours in need be.

In the close up picture, the settings look like 120 and 140 ... but you are saying that the boiler is going to 180 ? Are you sure the temperature gauge on the boiler is accurate ?

Yes, the 8148 is a high limit only control. Will only fire the burner in response to a heat call.

What is the model # of the two relay boxes on the side of the boiler ? (RA89 ?)

As close to the boiler as possible.

What size is the tapping that the automatic air vent is in ? Is it reduced down from a 3/4" to fit the vent ?

Otherwise, on the supply pipe close to where it leaves the boiler.

Can you get another pic or two ? Get a view of the piping coming off the top of the boiler ...

 

The setting on the hi limit is currently 180. That is an old pic. I had turned it down in the summer.

The two relay boxes are RA89a and RA832A.

The air vent looks like it goes to a maybe a 3/8" pipe size. I'm not sure, but it def looks smaller than 3/4".

I made a drawing of the wiring that I have now. I also took some pics of the top of the boiler. The last pic is of the well for the aquastat.

 

Pull back some ... tryin' to see where a relief valve could mount on the pipe ...

The top of the well looks right, but you can't really tell how deep it is ...

You don't have any destination drawn for the LO LIMIT switch?

Where does that go ? anywhere ?

The way that thing is wired, man, you are burnin' some fuel ! wow ...

 

The lo limit is not hooked to anything. The purple and red wires run into the junction box and are just cut off. I'm guessing this was disconnected at some point prior to me living here. The aquastat cover says “Lo Limit/Circulator- Close on temperature increase”, “High Limit – Open on temperature increase.” So I'm not sure what the lo limit would do in this setup anyway.

And yeah, the oil company loves me!

Is there a way I can set this up so that the thermostats will tell the burner when to start and then the lo-limit would tell the circulators to start running? And then the hi-limit would turn the burner off. If that would work then I wouldn't have to change the aquastat, right? Or is that a bad idea?

 

I think I might just get 3 of these RA845A relays. One for each zone and one for the indirect tank. My only other question would be how to tie them all in to each other. Do I just wire terminals 5 & 6 on each relay to the burner control so that if any zone calls for heat it will turn on the burner? I'm not sure if this is right or if there is a better way to do this?

 

Yes, 5 and 6 would all be wired in parallel to the T T terminals on the (new) boiler aquastat.

I need to think about this some more before I give you my final answer Regis, but ...

The L7224U aquastat could also be used as a replacement ... and the advantage to this would be the fact that it has a LOW LIMIT control that you can turn OFF ... so, you could use it now with your existing system, and then later when you go to the indirect, you can just turn off the Low Limit feature. With the 7224 you probably won't have to change the well either ... see:

L7224 Aquastat
click for possible source

Too bad both relays aren't the 832 variety ... those X X terminals in the 832 can be used to fire the boiler with the new aquastat, but the 89 would need an external relay ... or just replace the 89 with an 8845 ... (not the 845 ... not a typo) see:

R8845U1003
click for possible source

If for some reason you wanted to get rid of all the relays, rather than replace/add new ones, you should consider something like the Taco SR units ... 1 box, as many 'channels' as you need. It also has a function that will allow the water heater to operate on 'priority'. see:

Taco Switching Relays
click for possible source

 

OK, thought about it some ...

Refer to fig 9 in this PDF:

7224 install info

You could replace the 89 relay with an 8845 and wire as shown in that illustration. This would be the least $$ approach.

Your 832 relay can still be used ...

Then, when you get the indirect installed, add another 8845 for that.

The expenditure this way could be spread out ... three relay boxes, and you are at the price of the Taco panel ...

A few ways to go ... you choose ...

What would I do ? I'd rip it out and go with the 7224 and the Taco panel ...

 

Interesting...What is the advantage of the 8845 over the 845? Just curious. That taco unit is very cool...tempting. I might be able to get a hold of a few more 832's for free...I have to check into that first. But otherwise I might just go with the Taco just to de-clutter everything.

Also, with the L7224U aquastat, it looks like the aquastat itself will control 1 zone. Then I would just need the 832 I have and then one more relay when I get the indirect, right?

This is looking pretty do-able for me. The part that concerns me the most is how the aquastat is going to mount. None of these really look exactly like what I have now. Thanks for your help.

 

There actually IS a slight problem using the 832s to zone with ... but only if you are using the LOW LIMIT function.

When using the low limit, because the 845 relay does NOT have an internal connection to L1 (HOT), you are able to prevent the circs from running when the low limit is active.

Since the 832 DOES have that internal connection, you can't 'segregate' the pump operation in order that the pumps do not run if there is a heat call that occurs during a low limit call.

Not a show stopper... but if you should be showering when there is a heat call ... well, you might get some 'shrinkage'.

Note that this ONLY matters as long as you continue to use the low limit for the DHW coil ... the 832s will work fine if you don't need the low limit circulator control. I'd say grab the free relays... ya never know!

Here's what's _supposed_ to happen ...

When there is no heat calling, the boiler will maintain the LOW limit setting, and the circulators will be prevented from running at this time.

A heat call will fire the boiler up to high limit ... and the circs will obviously be running, but not until the low limit is 'satisfied'.

This guarantees that the full power of the boiler will go into recovering the domestic hot water system. BUT< you don't have that now ! Keeping the boiler at 180 24/7 kinda guarantees that you'll have hot water, but yer spending a FORTUNE doing that!

Advantage? price mainly... the 8845 is a bit cheaper than the 845.

From what I can see of the head on your well, it appears that there is a concentric groove around the top, no ? That _looks_ right ... there is a clamp mechanism with a single screw that clamps onto that groove. There is a 'flush mount' version available too... mounts on a flush surface, temperature sensor is on a lead wire, and inserts into the well.

The Taco panels are available with less channels than the 504 model that I linked to. It's a good idea to buy one more channel than you need. If one channel craps out on ya a few years down the road, you just move the wires to the next channel.

Yes, the 7224 controls one zone, just as would almost any of the aquastats. Extra zones by adding relays as required, though there's probably a limit as to how many circs you cold power off of the ZR[C] terminal on the aquastat. [not true, the circs are not powered through the 7224, they are powered by L1 ... - ed.]

 

No one will ever know why that Low limit control was disconnected. Maybe that part of the control is defective ? Maybe when they hooked up the second relay they couldn't figure out how to wire it ? and just said "Arghhhhh ... just cut it outta there! Oil is cheap! who cares! Just GITTER DUN!"

I DO have an idea how you could wire it ... if you replaced the 89 with one of the free 832s ... and fire the burner on a heat call ... and the high limit would be only a high limit ... but I can't yet visualize how to get that low control back in there ... (IF it even works still!). [ I have an idea how it was originally wired, when there was just one zone... but how to make it work easily with multiple zones is eluding me ... might not be possible. - ed.]

 

Replace the first elbow out of the boiler on top with a TEE ... re-connect side port of tee to supply line ... on the top of the tee, provide 3/4" threaded fitting ... into that fitting, install 30 PSI ASME rated pressure relief valve ... run 3/4" piping off valve and elbow down to within 6" of the floor ... pipe to where anyone in vicinity won't get blasted with superheated steam if it opens ... and also to where you can place a container underneath if necessary ...

 

I could check the lo-limit switch with a continuity tester. Could it be used to supply the neutral leg to each circulator? Instead of the neutral wire going from the relay directly to the circulator, it could pass through the lo-limit switch first. That would keep the circulators off until the lo-limit temp is met?

There is a groove towards the end of the well. I guess the diagrams of the bracket look different on Honeywells site and maybe that is throwing me off.

As for the relief valve, I found documentation on my boiler and there appears to be a cap on the back that is designated for pressure relief. Should I install the valve there or just do it the way you described? See pic below. Thanks!

 

No... don't do it. One should never, ever put any kind of switch in a neutral wire. It's dangerous! I believe it _may_ be permissible to switch the neutral ONLY if that switch is a 2 pole, and ALSO switches the hot...

What you MIGHT could do is use the low limit to fire ANOTHER relay ... that would disable the circs when the boiler is running at LL ... not saying it's possible, or a good idea, just thinking out loud...

Yeah, see if you can determine if that switch is functional.

I'm sure the bracket is different than the one on the 4010 ... but I think it will work with that well. Theres a 'clamp' with a U-shaped piece of metal that is drawn into the groove as the screw is tightened, securing the device to the well.

Are you sure there's not a valve already installed there? I don't think that side was visible in the pics? I guess you've looked already though.

Yeah, put it there ... you might have some fun getting that plug out ... if it's plugged ... I would recommend starting to put some PB BLASTER on there a couple weeks before you plan to do the job. Then, ever day or two, put a few more drops on there. Use that stuff SPARINGLY! IT STINKS! worse than fuel oil ... use a SOCKET wrench ... with an 8 point socket (not the 16 point) ... 1/2" drive, 3/8" drive may be too wimpy ... it may come right out ... but it may be stubborn ... prepare for stubborn.

Mount the valve vertically if possible. It's tempting to screw the valve in the side of the boiler and just point the pipe straight down, but I believe the valves last longer if mounted vertically. You don't get boiler crud building up in them as much ... so, elbow out and up, use a close nipple if needed for clearance... install valve, and elbow down to the floor ... if the valve is in an inaccessible location, you could also raise the valve a bit on a nipple ... keep the valve as close to the boiler as possible ... and still be able to get to it for service ... you can run the discharge line to where you can put a container under it, but no more than one elbow on the discharge... keep the discharge pipe as short as possible ... and away from where persons could be hit with discharge ...

 

Okay I won't do it that way. I checked the lo-limit switch and interestingly enough it works--but it does the opposite of what it says. It actually closes on temperature decrease and opens on temperature increase. Unless I am misunderstanding. But the continuity tester beeps when I turn the temp down, and stops beeping when I turn it up.

There is a cap on the back of the boiler and there seems to be enough room for the relief valve and pipe so I will start working it with the pb blaster.

 

By the way, do the relief valve in black pipe ... stronger ... easier ... cheaper ... than copper.

Cut the threads off the bottom of the down pipe to the floor so nobody will be tempted to put a cap on the bottom when it starts dripping ... B O O M ! ...

Ya know, it's been this way a long time ... I would do it soon, but don't be hasty ... make sure you feel comfortable that you can get it done and get the heat back on in a few hours ... gettin' cold here this weekend ...

 

It is confusing ... seems to defy logic ... but, those contacts should MAKE (beep) when the bulb temperature is above the setpoint. By turning the setpoint down, to a setting BELOW the bulb temperature, the contacts make.

Remember that when the control is in operation, it's the bulb temperature that's moving and the setting is fixed. You are doing the opposite by having a fixed bulb temp, and a moving setpoint, so the action appears to be reversed.

 

Okay now I get it...about the continuity tester. Thanks for explaining. I'm leaning towards the Taco SR504 and the L7224U. I just have to start getting all the parts together. I hope to do this soon. The semi-warm showers are not fun.

When we first moved into the house about 5 years ago my father in-law changed the thermostat for us. It had a line voltage thermostat and we put in a 24v. I think the original thermostat probably wired into that lo-limit control and he took it off then and added the R832 relay. That is my best guess.

NJ Trooper: Thanks for walking me through this so far. You have been a great help! My father in-law (who was a plumber, architect & carpenter) passed away in October. He was my go-to-guy for all things home-related.

 

I'm more inclined to think that it was when the second zone was added ... cuz it would be real easy to add the circ control back onto only one pump ...

Thing is though... that Low Limit control appears to only have 2 terminals ... probably labeled R W ? To do the burner control properly for the LL, you need that 'other' terminal labeled B ...

I was looking at the 7224 install sheet ... they recommend a 3" deep well ... I have to think that the old well is probably deep enough, but at some point you might want to verify that it is in fact at least 3" deep...

My condolences to you and your family. If we can in any way help to fill his shoes (maybe a tall order!), just ask...

 

Can you maybe take a broomstraw and stick it down that well to get an idea of how deep it is? POWER OFF TO BOILER! 120 VAC!

Where's yer oil tank located?

Me personally would be uncomfortable with the location of your oil line ... and a bit concerned that it appears to be buried in concrete back toward the wall? I don't like that...

 

Thanks. The well appears to be at least 3 1/2" deep. I didn't see any letters on the terminals of the lo-limit control, but there are only 2 terminals.

The oil tank is about 12 feet away by the front wall of the house. The boiler is on the side wall. I too always thought it was a little strange that the oil line was buried in concrete. Doesn't concrete eat away at copper? The last time the oil company was here to do service, the guy recommended we think about getting a new tank installed as it appears to be original to the house.

 

I think the best plan is to change out the aquastat and the relays... cuz even though it _could_ be run with the old stuff, you would likely need a couple more relays, and a whole bunch of time wiring it all up. With the Taco panel, it couldn't be much easier to wire everything... and to add the indirect later, and be able to set priority on it.

3-1/2" ... You sould have no trouble installing the 7224 on that well then. Use the heat conductive compound that comes with the unit and make sure the sensing element is bedded into the blob of compound.

Tank above or under ground?

If it's underground, then get it outta there... and pray it ain't leaking.



If it's above ground and not all full of sludge and in good condition, why change it?

Yeah, as I understand it ... concrete will eat copper. Can you tell if there is any protective sleeving or even tape on the tubing where it enters the concrete?

I would think about at the very least perhaps doing something with the oil line, if it is indeed in contact with the concrete.

 

Yikes...Is that your house? My tank is above ground in the basement. It doesn't leak. The oil guy said to replace it because he thinks there is a lot of sediment on the bottom which is causing the burner to get clogged up somehow. It seems about once a year I need to call them in because the burner is putting out a lot of soot into the area.

I don't see anything protecting the copper oil line as it goes into the concrete.

I bought a L7224U relay off ebay the other day. Now I'm trying to figure out which water heater tank to get.

 

Let's just say that I'm intimately involved with the project... which by the way ... what you see is a very early stage photo ... it get's MUCH worse ... deeper, wider, longer... traffic diversion onto a temporary road across the front lawn of a residence while they open up the road to clean out the contamination from underneath it ... at about a 15' depth ...

Let this serve as a warning to anyone who is still maintaining an underground tank ... it CAN happen to you ! OK, enough...

Has anyone suggested a double filtration on the oil line?

Use a regular old felt filter at the tank, and a 10 micron spin on near the burner... an OSV (oil safety valve) on your system might not be a bad idea in view of the copper lines in the concrete. If you did happen to develop a leak in the line, the OSV would prevent a much bigger problem... optional ...

OK, the 7224 it is then... what did ya decide to do with the RA89 relay? If I wuz you, I'd scoff up them free 832s in a heartbeat, and swap out that 89 with one. Then, you wire the X X terminals in parallel, and back to the T T terminals on the 7224.

I'll 'mod' your drawing ...

 

This will work now... future add 832 to control indirect... or use Taco panel...

 

NJT thanks for the updated drawing. I went to my father in-law's house yesterday and I found one 832 relay, a Taco 007 F5 pump & flanges, two Honeywell L4006A aquastats, and a bunch of copper, brass and iron pipe and fittings. I think I'm still going to go for the Taco relay so I can have a priority zone for the hot water tank. I'm going to wait until after the holidays to tear into this. Maybe 2nd-3rd week in January.

Nobody ever suggested double filtration but that sounds like a great idea. That will be my next project.

If you could suggest anything regarding the design of the piping for the new tank that would be great.

Thanks.

 

The tank is in. I went with the Crown Boiler Megastor MS-40 (lifetime warranty), Argo ARM4P Relay (expandable for outdoor reset and more zones), and the L4006 aquastat. The L7224 wasn't really needed because I just need a hi-limit cutoff. I put in a new aquastat well and it was a good thing because the old well was "double wide" to accomodate 2 temp bulbs from the old 4010 aquastat. I don't think that would have worked with any new aquastat. I still need to finish the piping down to the floor for the relief valves. But it's working great and it's real nice to have hot water!