Burner Controls

[ejhills]

Can the burner contacts on my Honeywell be attatched to a pump? It seems that the aquastat could just as easily call for the pump to turn on as the Beckett.

Any thoughts?

Ed

 

[__dan]

Just kidding but if you want to start designing your own controls, start with your Christmas lights and leave the burner controls to the boiler manufacturer.

The boiler circ and the burner will not cycle exactly in lockstep. There will be a few more parameters which will mean one is on when the other is off.

For a cast iron boiler, you have thermal shock concerns. Short cycling the burner is OK but the circ stays on. For steel or cast iron boilers you have flue gas condensation and heat scavenging concerns. The manufacturer determines when flow is required through the heat exchanger, and it is not only exactly with the burner.

What you want to do is consult the boiler manufacturer and run the near boiler circs exactly in the manner they prescribe.

 

[ejhills]

I dont need the burner control. I need the same aquastat to trigger a circ pump.

 

[ewdudley]

Can the burner contacts on my Honeywell be attatched to a pump? It seems that the aquastat could just as easily call for the pump to turn on as the Beckett.

Any thoughts?

Ed

If you mean disconnect the burner and use the same contacts to operate a circulator to pump heat into the boiler, then by all means should be no problem. Honeywell aquastats have have some pretty stout contacts that stand up to inductive loads on that scale, and the circ voltage is the same.


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[__dan]

Electrically, adding the circ load is within the rating of the switch.

If it is right or not, if you will get some of the negligent damage listed above, I have no clue.

Code also requires you to follow the manufacturer's instructions. Not doing so makes the work illegal.

Pretty frequently the local farmer plumber electricians, my friends, show me what they have done and it scares me. Then they want me involved to offload the liability onto my name.

Did I mention what you propose may be illegal and scares me ?

 

[maple1]

When I re-did my system, I moved my old aquastat that used to turn the oil burner on, into a fitting in my supply header, and wired the old wire that used to hook to the burner onto a relay - the other side which I ran low voltage wire to the thermostat contacts on my new electric boiler. So what once fired up my oil boiler, now turns on my backup electric boiler.

Moving all controls from my old boiler over to my new system pretty well intact turned out to work pretty good for me - I'd likely still be figuring out what I needed to get to do what.

We still don't have the whole picture of what you're wanting to do though - so I'm claiming the same disclaimer posted above.

 

[ejhills]

The oil and wood boiler are plumber supply to supply and return to return. I have installed an exchange coil and storage tank between the 2 of them on the supply line. My challenge is to get the BTU out of the storage and into the oil boiler before it enters the house. I think another pump between the return and the exchange coil should do the job.
All wood all the time.

 

[ejhills]

OK a new approach.... I've got the plumbing figured but electrically I'm not sure.
Will this picture work electrically? And the pump is supposed to be P! and P2....

 

[__dan]

I hope you take this as an honest answer even if it's not the answer you want.

Yes, electrically there is some way to put the wood aquastat in parallel with the oil aquastat as you describe. I do not know the P1 P2, B1 B2 details but if you know wiring circuits, it will be in the unit wiring diagrams. I believe you should not touch the B terminals as those will be the burner and not the circ. Paralleling the B terms with the wood aquastat will fire the oil burner regardless any attached safeties. you will have bypassed all the safeties, except for the pressure relief valve (do not stand it front of it when it blows).

Still unknown, and maybe something you don't know that you need to know, is if this will give the proper operation or if you will get misoperation and a variety of bad to worse consequences mentioned earlier.

If you're intentionally trying to pull the wood boiler water through the oil boiler, I would say you do not have the plumbing figured out. I would advise starting with design. The various adverse consequences you could cause yourself are beyond most people. Determine what you want to happen them go through the various standardized plumbing layouts available. Once you have a plumbing design and install, you can wire it.

Trying to do the job in the reverse order and wiring something that may not be plumbed right is just asking for trouble.

Try to not let your trial and error disasters get so large that they injure yourself or others. If negligent, take the blame and don't go spreading it around.

Post a few pictures of what you have done so far and the crowd will be sure to tell you if you have to stop, or if you are showing some forward progress.

 

[Nofossil]

A plumbing diagram goes a long way. I've read a lot of descriptions, but I'll understand a picture way more reliably. Even a cell phone photo of a sketch on a napkin.......

 

[maple1]

What they say about pictures being worth lots of words? It's a true story.

 

[ejhills]

The Plumbing, less the expansion tanks.

 

[__dan]

From what the drawing shows, you should stop were you are and hire an experienced professional.

I would ignore that drawing and start with a blank page. If you bought the boiler recently, maybe the dealer can recommend someone in your area to help with your install.

The other question you asked, the wood aquastat has nothing to do with the oil boiler circ. Do not interconnect.

 

[ejhills]

Ok, that was negative.
The wood boiler charges the oil boiler. The oil boiler feeds the house. Simple. The Aquastat on the wood boiler runs the charging pump. The thermostat runs the main circ pump. Since I am not burning oil.... I want to use the honeywell controller burner contacts to help drive the logic for the charging pump.

Why am I at this place? Because I don't have 10-20k to rip out 150 year old plumbing and asbestos. Suggestions please!
Help me keep my family warm.

 

[ewdudley]

The Plumbing, less the expansion tanks.

Getting there. Supply to supply, return to return is called a figure eight, which is the best way to go when connecting to an existing system without changing any of the load side of the existing system.

Using boiler aquastat to maintain boiler jacket temperature by pumping in heated water should work correctly, same as using boiler aquastat to maintain boiler jacket temperature by running burner. But it's not clear at all what you're up to with the "wood aquastat".

What kind of storage? Pressurized? Can't tell what you're up to there.

(You may find you can get better drawings faster with pencil and paper.)

 

[Nofossil]

It might help to spend a few minutes studying the two stickies at the top of this forum that discuss plumbing configurations. There are two basic approaches with a ton of variations, but getting anything to work well with storage takes a bit of planning.

There are a bunch of questions:

1. Does your DHW come from a coil in the oil boiler?
2. Will the oil boiler act as a backup heat source?
3. What are the details of the storage - pressurized? Internal HX coil(s)? How big?

Answers to these questions lead to a second round of questions. You're not far from the supply-return manifold configuration described in the 'simplest pressurized storage' approach, but there's a lot of detail to be worked out.

 

[maple1]

The Plumbing, less the expansion tanks.

Echo EW - what kind of storage is that?

That drawing (I think) has the water being drawn through the oil boiler when you're charging storage. Which might keep your oil boiler on the warm side as you get your storage hot, but it will also keep it cool until you get your storage hot. I think you need to do some re-thinking on that - or else your drawing isn't painting a clear picture.

And I have to ask - if you're not using the oil boiler to burn oil (correct?), why keep it there?

 

[Nofossil]

EW - that's an awesome disclaimer! I think that should be implicitly assumed as a ground rule for any forum or conversation anywhere, any time.

 

[ewdudley]

That drawing (I think) has the water being drawn through the oil boiler when you're charging storage. Which might keep your oil boiler on the warm side as you get your storage hot, but it will also keep it cool until you get your storage hot. I think you need to do some re-thinking on that - or else your drawing isn't painting a clear picture.

And I have to ask - if you're not using the oil boiler to burn oil (correct?), why keep it there?

I think he's got supply to supply, return to return, which in effect turns the old boiler into a hydraulic separator. Although it appears to be merely expedient, it's actually an excellent configuration for decoupling the load side from the supply side. If intended to be a permanent field expedient just need to block off the flue, add some insulation, and send a photo off to 'There, I fixed it!'.

Supply hot water from wood system arrives at top of old boiler. If excess supply flow then some flow goes to load and the rest flows backwards through boiler, mixes with system return on the return side of boiler and then returns to wood system. If load flow exceeds wood system supply flow then load gets all of wood system hot water and recycles some load return flow forward through old boiler. If wood flow gets ahead of load flow, or If load flow stops, supply from wood system fills old boiler from top down and break-on-rise aquastat stops flow from wood system.

 

[Nofossil]

Yeah - that's pretty much the way I read it. The storage plumbing needs some clarification, and I'm a much bigger fan of using storage as a hydraulic separator than keeping an oil boiler hanging around for that purpose.

 

[ejhills]

Good Morning All,

The wood aquastat runs the charging pump.
The storage is open with an exchange coil. I can get the BTU'S into the tank but getting them out is difficult as the wood boiler can become a heat sink.
DHW is completely separate.
The Oil Boiler is used as a distribution point. I am not using oil, or the burner. Re-configuring the load side would require a sledgehammer, and an asbestos clean up crew. Not happening this year.

Are there suggestions on getting the BTU's out of storage via plumbing or or electrical control.

My 2 thoughts were to put my spare 007 pump between the supply/return just before the storage tank and use the aquatstat for the oil burner. The description in the manual describes the logic perfect. A call for heat from the TT closes the burner until the aquastat is satisfied. But that would mean there could be 3 pumps asking or return water at the same time. That seems instinctively seems problematic although I don't know why.

The other thought was to leave the plumbing as is and wire the two aquastats together in some way, like a three way switch, to run the charging pump.

Or a third option, but I don't see it right now.

Thank you for the discussion.

Ed

 

[ewdudley]

Yeah - that's pretty much the way I read it. The storage plumbing needs some clarification, and I'm a much bigger fan of using storage as a hydraulic separator than keeping an oil boiler hanging around for that purpose.

Except that using a separate system hydraulic separator gives control of return-to-storage temperature. Whenever return side of hydraulic separator (or old boiler, in this case) is too hot, suspend flow from storage until it's cooled off some. I've got my return-to-storage temperature set to 90 degF this time of year, have to take it up to 120 degF in dead of winter, which maintains maximum stratification for conditions.

 

[maple1]

So - you've just got the one heat exchanger? That is being used to both charge storage via wood, and draw from it via the oil side? And when charging, the flow goes wood-coil-oil-return to wood?

I don't see an issue with adding another circulator, say between the coil and oil-supply. You should be able to move the wires that were hooked to your oil burner, right to that circ pump - the circ would run when it would have run the oil burner before. That's the kind of thing I did when I replaced my oil boiler with an electric boiler & to control that. The circ pump takes 120v, same as the oil boiler does.

However, I'm not sure what you have for boiler protection at the bottom of your bypass T. That might close up before your storage gets to your desired low & dead-head your circ. And is there a means in your controls to shut off the circ if storage temp drops below that desired low? You might need to add on another strap-on stat, or something like a Johnson A-419.

 

[__dan]

You may consult the local asbestos removal company about removing only enough of the pipe insulation to expose it so you may connect without going through the oil boiler. You are saying you know the old oil boiler is coming out.

The abatement company will give you instructions if you are allowed to touch any of it. They can advise you if you as the homeowner can remove any of it and place it in the disposal bags, double bagged with duct tape seals.

There are different types of asbestos. Some types make a fine dust that spreads through the air when disturbed. Some types are a more solid form with less dust. But it is heavily regulated by EPA with stiff fines. The abatement company will be able to tell you how much of the work you as the homeowner can do yourself.

 

[Nofossil]

Asbestos is one of those areas where dosage gets lost in the discussion. It's pretty clear that long-term exposure to large amounts of certain types of asbestos causes nasty problems. It's much less clear that there's any reason to treat it like high-level radioactive waste. Pretty near every commercial building used tons of it in the day for ceiling tiles as well as heating system insulation, and it was even used for cigarette filters(!). Seems likely that intermittent exposure to smaller amounts isn't as risky as the regulations imply. However, lawyers have gotten involved so everything has gotten way more complicated and expensive - huge costs for tiny risk reduction. It would be great if there were common-sense guidelines that balanced risk with cost so that people could make reasonable tradeoffs for themselves.

The indirect cost of regulations can be a big issue. Some states require ASME certified boilers, or require licensed plumbers and electricians to do all work. That means that if cost is an issue (and it always is) then people end up with a much worse solution since the cost is too great to make improvements. I'd much rather help people figure out how to be more self-sufficient and able to make their lives better......