How to Wire My Oil Boiler Circulators to My Coal Boiler

bowman
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Post Mon. Mar. 17, 2008 9:48 pm

I have my coal boiler plumbed as stand alone boiler with my oil boiler on standby. as it stands right now the circulators are getting power from the oil boiler but they won't run when the house calls for heat unless the oil boiler temp is up to at least to the lower limit temp stetting. Can I disable this temp control? Some pictures of my relay and junction box.
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stoker-man
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Post Tue. Mar. 18, 2008 11:29 am

What are you using the current aquastat on your coal boiler for now and what is the model of the aquastat? Your coal boiler must have some controls on it.

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Sting
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Post Tue. Mar. 18, 2008 2:05 pm

Sorry for the slow answer!

How did you pipe the Harmon?
I still have your oil boiler pipe pictures - but wiring will depend how you refurbished the system and how it stands today.

Can you show a picture of that piping and how your pumping the Harman -- into the oil boiler or ?

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1975gt750
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Post Tue. Mar. 18, 2008 3:14 pm

i had the same problem had to build a relay box to seperate the controls. sting is right wee need some pics of the complete set up

bowman
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Post Tue. Mar. 18, 2008 7:00 pm

Thankyou for your responses and wanting to help. My boiler is Keystoker KAA-2 and the aquastat is used for over heat safety by-pass loop.
Here are some pictures of my system,I hope they help. If you need more please let me know.
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Sting
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Post Tue. Mar. 18, 2008 7:28 pm

OK - the triple aquastat on your oil boiler (maybe) is wired to allow the pumps to only run after the oil boiler reaches hi limit.

ImageI have been reminded in pm that my statement above is not correct - Please note: On a triple A, it would be Low limit. The circs continue to run after it reaches high limit, which it isn't supposed to reach, and continue until the temp goes 10 degrees below the low limit setting or the tstat is satisfied

Since the oil boiler is off its triple aquastat is also dead. -- well should be

Is there a similar triple aquastat on the coal boiler? (IF yes) simply connect c1 to c1 and c2 to c2 on each.

now the aquastat on the 'Live" appliance will control the circ pumps when either proof the c1 to c2 connection.

also connect the T terminals in the same way so the coal boiler sees a call for heat from the load.

but check this with a licensed electrician first. Thats my disclaimer.

This is the "least work" approach - I think there are better but I need to see what control you have on the coal boiler.

NICE PIPING by the way - did you do it?
Last edited by Sting on Tue. Mar. 18, 2008 9:14 pm, edited 2 times in total.

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Scottscoaled
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Post Tue. Mar. 18, 2008 8:23 pm

Boy, I'd hate to be a service tech and come in to work on the oil boiler and get a nice little tickle from the backfeed you just created from the coal boiler. Would really make his day. :x Scott.

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Sting
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Post Tue. Mar. 18, 2008 8:59 pm

yes - this is a "unique" wire arrangement - if you walked in on a pair of boilers in series like this - I would hope you would test for power before sticking pink parts into boxes.

As I mentioned - even with my poor description on the triple A operations - this is a very minimalism work around.

A far better arrangement with a couple of ice cube or fan relays tied to a dedicated circulation limiting aquastat
or a whole separate pumping circuit would be better. But I have been beat up in the past for making things too complicated. Guess now I can get flamed for making it too simple????
Image

Oh well - its a hobby.

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1975gt750
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Post Tue. Mar. 18, 2008 9:36 pm

on my system that I hooked up I put my kaa-2 in series with my oil burner but what I did was put another switch between the aquastat and oil burner. what this does it allows you to use all the controls on the oil boiler and not fire the oir burner when it calls for heat. I would also lower your aquastat temps on the oil boiler lower than the coal boiler. do you have a thermostat imput to the coal boiler from the oil burner? this is very critical. this will allow the coil boiler to start to stoke when heat is called for.as for your by-pass loop it was not neccasary keystoker claims if you put the coal boiler in series you are not reqires to put a by-pass loop. I installed the 4006b aquastat in the to port of the coal boiler and I ahve it dumping the heat into my boiler mate works great.let me know if you have any question possible we could talk on the phone ad get you squared away. it took me a good month of screwing around to get it right. but works great burns a bag evey 24 hours

chris

bowman
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Post Wed. Mar. 19, 2008 8:32 am

back to the question on what aquastat is currently being used on the coal boiler. it has a triple aquastat and looks like it's only controlling boiler temp.
i had allot of help on the piping and it seems to be working great except the electrical part. this a pic of my coal boiler aquastat, looks like the same one on the oil boiler
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:oops:

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1975gt750
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Post Wed. Mar. 19, 2008 9:01 am

yes that aquastat controls boiler temp only. it will maintain your boiler temp on the limits. so if the lo limit is set at 160 and the temp of the boiler drops it will bring it back to the high limit if it is not calling for heat. now if the house is calling for heat and the temp is between you limits it will stoke right away until it reaches the high limit temp. this will do this cycle while it is calling for heat.otherwise it will sit idle. I see you pic on the coal boiler aquasat does not have any thermostat wires going to it this will cause recovery problems a run the boiler down to a very low temp.the way you have it running now when the house calls for heat the coal boiler wont start stoking until it reaches the lo limit and by that time the temp of the boiler is dropping pretty fast.you have to remember that coal is a solid fuel and it is not instant like oil or gas there is a lag time. you really need to get a thermostat hooked up to the coal boiler. you may have to make relay box like what I did.
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stoker-man
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Post Wed. Mar. 19, 2008 11:12 am

It has the C1 and C2 terminals for the circulator, but there are no wires to them. As previously stated, it will start on the low setting and shut off on the high setting because there is no circulator or tstat attached. What you have is a unit that maintains water somewhere in between the high and low settings and nothing more. Without a circulator you must be heating by gravity if the flow control valve is manually open.

bowman
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Post Wed. Mar. 19, 2008 11:26 am

Tried to private message. I don't think they are being sent. What am I doing wrong?

gregolma
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Post Fri. Mar. 21, 2008 12:56 am

Do primary and secondary pumping and run each fuel with a separate thermostat.

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Yanche
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Post Fri. Mar. 21, 2008 10:12 am

gregolma wrote:Do primary and secondary pumping and run each fuel with a separate thermostat.
No. Primary - secondary (P-S) piping loops are one way of directing water flow. It has nothing to do with the thermostat demand for heat. P-S uses the principal that water will flow to the point of least resistance. You use a pump to create a easier flow path for water when you turn on the pump. For example a P-S loop often has closely space piping tee's. The tee outlet part has a pump in it's loop. When the pump is off water will not flow to the pump because the main loop (primary) path is easier (less resistance) to water flow. The water just flows straight through the tee's. Turn the pump on and water now has an easier flow path (because the pump reduced the resistance) through the piping going to the pump. You have changed the flow path from straight through the tee to the side of the tee. For many applications it's a better way (more flow, more reliable, cheaper) to control water flow than an motor controlled valve.

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