Delay of boiler firing?
There an easy way to delay the start fire cycle of a mod/con combi when thermostat calls for heat?
I need the pumps to come on for maybe 15-30? seconds to circulate the loop, as there's a heat exchanger and likely already hot water from an outdoor boiler... so the gas "backup" boiler wouldn't need to fire.
Comments
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It depends on how the system and boiler is being controlled. Generally there is a work around but it depends on how involved you want to get and whether its worth the investment.
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30 secs is a lot.
3-5 sounds more reasonable0 -
seems like an aquastat on the wood boiler that opens t-t to the gas boiler would be the way to go.
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This would work, but…
it strictly time. It doesn't know what the load is. It would be nice to work off temperature. Can you explain or show the wiring?
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Yes but hooked to what?
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Thermostat goes to a control, that sends signal to secondary looppump and the boiler. Boiler has primary loop pump integrated, like most little combi boilers I think.
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Not doing this would constantly short cycle the boiler I'd imagine..
Boiler needs to be kept in the loop as a backup. It doesn't see hot water after 15 seconds, it fires.
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normally you'd pipe both boilers primary-secondary so the firing boiler would not heat the non-firing boiler.
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Why does the gas boiler need to have a call for heat at all if the outdoor wood boiler is already firing? Are you firing the wood boiler without dissipating the heat somewhere? Your query seems to assume that there is a thermostat that is calling for heat on a zone (or the entire system) indicating that the call for heat is somehow off at times. Now that begs the question that you have a hand fired boiler that is generating heat with a circulator pump to a HX that is somehow off. That wood boiler will then be generating heat with no way to get rid of that heat. That sounds wasteful to fuel a hand fired boiler and not use that heat that is generated by the fuel.
I would propose that you learn to feed the wood boiler in such a way where any heat generated will be put into the home or the zone as it is generated. That way you will have a hotter home and adapt the amount of fuel you feed to the wood boiler based on how much or how little the home or zone overheats. That is how the folks used hand fired boilers in their basements before oil heat and gas heat became the norm. After 1920 you might live in a home where the winter indoor temperature was 85° inside with the windows open. (read about the Spanish Flu and how it affected heating system design) Even before that in the 1800s coal fired boilers in homes were hand fired and the only regulator was the dampers that controlled how much air flowed thru the coal fire, and how much coal you shoveled into the fire box.
However if there is a system that is hand fired, and you are using that heat elsewhere, and you want to draw some extra heat to heat a zone based on a thermostatic input from that room, there can be a circuit that can be designed to accommodate the room temperature thermostat calling for a circulator to operate to draw heat from the Wood Stove and preventing the gas from firing on the boiler if there is already enough heat available from the boiler even though it may take some time to reach the rooms.
If there is a need to have one thermostat in that room, then I can design a logical set of relays and temperature sensors to accomplish your needs. Please explain what components are in the system and how they are interconnected with the piping from the wood boiler, to the pumps, and the heat exchanger, and any other system accessories. For example: is the wood boiler’s heat being used any place other than the home or zone you want to heat in the original query, or is the wood boiler only to heat that zone or home?
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 Outdoor boiler is a used oil boiler, not wood, but same setup as far as the piping.
It's outside in a connex. 1 thermostat controls everything. It's a wifi unit with multiple area sensors.
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Gas boiler is ready to run in case the oil boiler doesn't come online. Can't risk the place freezing.
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@nate379 this is what I do here! Just ask anybody!
The outside boiler being a waste oil boiler is a whole different thing. That outside boiler needs a control to turn it on, and that can be done with controls that start with the room thermostat. I assumed that the outside boiler would be what one of my former customers was using. I have also worked on waste oil boilers that were installed inside the commercial building. I can understand why you may not want something like that installed inside your home. And your waste oil storage is also something I would not want inside my home. This makes a lot more sense now.
With this info and the fact that waste oil burning can sometimes be problematic in extreme cold weather, I would love to help you design a control system that will do just what you need. Can I trouble you for the model number of the waste oil boiler/system?
With that info, I can do some logic that might work like this
- Call for heat from the room thermostat
- Primary heat source = waste oil boiler
- Gas boiler will stay off for at least the time it takes to fire up the oil boiler and get heat to the radiators (and/or the domestic hot water tank if you have one.)
- After a sufficient amount of time has passed, if the oil boiler does not heat the home, the gas boiler will be added to the heating system to generate whatever heat can not be completed by the oil boiler.
- When operating on gas heat only, the delays can be manually disabled with a Gas/Oil switch.
- Maybe even have a way to stage both heaters when it becomes apparent that the oil boiler will not operate as a result of a flame failure in order to make the gas boiler the primary source until the oil boiler failure is resolved.
With that model number from the oil boiler and the model number info about the ModCon Gas boiler the control system will be easy to design.
Also what is the thermostat brand and model number?
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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…unless you meant "second hand #2 heating oil boiler", or "previously owned", or a "regular oil boiler that was used in a different location".
I may have jumped to a conclusion about your term: USED OIL boiler and you really ment …used OIL BOILER. Either way, that control system is still easy to design. What is the oil boiler make and model number?
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
0
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