Hot Water Priority

[Rickard]

I know that is a good idea to make hot water a priority in a normal boiler system but, does it make sense to make and indirect hot water tank a priority zone in a wood boiler system being that there is a lage amount of storage?

Dean

 

[Eric Johnson]

If you never want to hear the words: "Honey, there's no hot water," then you will make DHW a priority in any system.

 

[EricV]

If you never want to hear the words: "Honey, there's no hot water," then you will make DHW a priority in any system.

Amen to that

Try it, be ready to put it back to priority. "sorry honey, minor glitch, it will back to normal in a minute"

 

[ken999]

+3...

I can just imagine the azz pealing I will get if the better half runs out of hot water mid-shower after spending all this money on a new OWB....no thanks...

 

[chuck172]

azz pealing?
Been there, got that, No matter how well the heating system has been running, I keep hearing about the time she ran out of Hot water.

 

[ken999]

LOL...amazing what sticks and what doesn't eh?

 

[Rickard]

Thanks guys. I'm leaving it alone then.

 

[WoodNotOil]

That was how I got her to agree to let me build the storage tank. I just told she won't run out of free hot water anymore... sold!

 

[Rick Stanley]

I'm gonna have underground pex coming through the cellar floor from a Garn, going through a flatplate hx, then back to the Garn. The other side of the hx will be

pressurized and piped to the heat zones.

I want to add an indirect water heater and circulator. To make dhw a priority, it sounds like I should tee into the supply pipe coming from the Garn BEFORE it reaches the hx.

Does that sound right?

Thanks

 

[Nofossil]

I'm gonna have underground pex coming through the cellar floor from a Garn, going through a flatplate hx, then back to the Garn. The other side of the hx will be

pressurized and piped to the heat zones.

I want to add an indirect water heater and circulator. To make dhw a priority, it sounds like I should tee into the supply pipe coming from the Garn BEFORE it reaches the hx.

Does that sound right?

Thanks

I'm not sure that's absolutely necessary. I'd just be sure that the DHW gets first dibs on hot water as an ordinary zone.

What I do to ensure hot water and domestic tranquility is superheat my DHW tank (to 160 degrees) and use mixing valves to deliver constant / safe water temps (120 degrees) to the house. My boiler has been out since midnight, and both resident females took showers this morning. My 40 gallon DHW tank is still at 153 degrees.

 

[Jim K in PA]

I'm gonna have underground pex coming through the cellar floor from a Garn, going through a flatplate hx, then back to the Garn. The other side of the hx will be

pressurized and piped to the heat zones.

I want to add an indirect water heater and circulator. To make dhw a priority, it sounds like I should tee into the supply pipe coming from the Garn BEFORE it reaches the hx.

Does that sound right?

Thanks

Rick - that is not necessary, and not what DHW priority means. HW priority on a zoned system means that the DHW demand will be satisfied before any other demand is supplied. This can be accomplished a number of ways. I am using a TACO ZVC-406 with priority. It is a zone valve controller with the 6th zone set up for (optional) priority. The valve (or pumps) for zones 1-5 will not energize if zone 6 is energized. Once Zone 6 is satisfied, then the other zones will energize (on a heat call, of course). The TACO SRCs will do the same thing with their priority on the last relay.

 

[Rick Stanley]

So, in other words, it's better to wait for heat for 5-10 minutes, which you may not even notice, than to end up in the shower waiting for HW. Got it.

Thank You

 

[shoeboxlen]

If you never want to hear the words: "Honey, there's no hot water," then you will make DHW a priority in any system.

totally aggree unless you want the toilet flushed every time your in the shower take care of the wife because if she aint happy you ant happy and if she isnt happy long enough you will be unhappy with half your stuff......... that being said I use our wood boiler to heat DHW as well as heat the house and it has been great no issues with running out of hot watter however I do suggest a larger domestic hot water tank to store it up as it takes a bit longer to warm it back up so its best to just not run out.

 

[Rickard]

I changed my mind. I am going to experiment with this one. With heat and hot water being separate secondaries on a primary/secondary system, being fed mainly by a large storage of hot water, I think that the draw of heat and hot water at the same time will have a minimal effect.

I'll try it for a week or two and post my findings. My wife and I are on good terms with the heat and DHW so I have a little marrital capital to spend!

Dean

 

[Rick Stanley]

I'm gonna have underground pex coming through the cellar floor from a Garn, going through a flatplate hx, then back to the Garn. The other side of the hx will be

pressurized and piped to the heat zones.

I want to add an indirect water heater and circulator. To make dhw a priority, it sounds like I should tee into the supply pipe coming from the Garn BEFORE it reaches the hx.

Does that sound right?

Thanks

Rick - that is not necessary, and not what DHW priority means. HW priority on a zoned system means that the DHW demand will be satisfied before any other demand is supplied. This can be accomplished a number of ways. I am using a TACO ZVC-406 with priority. It is a zone valve controller with the 6th zone set up for (optional) priority. The valve (or pumps) for zones 1-5 will not energize if zone 6 is energized. Once Zone 6 is satisfied, then the other zones will energize (on a heat call, of course). The TACO SRCs will do the same thing with their priority on the last relay.

What do you guys think of this?

I already have an insulated 40 gallon dhw tank that is piped to a coil in my oil boiler with a circulator/aquastat set-up. It works great. Provides plenty of hw for two families. Could it be as simple as adding a flat plate hx for dhw and have the existing circulator push water through that, when I'm burning wood, and through the existing coil when burning oil? What would be possible drawbacks to that? Maybe couldn't keep up with heavy demands as good as the oil burner does? I don't know. Any thought?

Thanks!! ps- possibly, maybe, the priority thing is already handled with that little dhw circulator being wired with priorty? How could I check?

 

[Rick Stanley]

I'm gonna have underground pex coming through the cellar floor from a Garn, going through a flatplate hx, then back to the Garn. The other side of the hx will be

pressurized and piped to the heat zones.

I want to add an indirect water heater and circulator. To make dhw a priority, it sounds like I should tee into the supply pipe coming from the Garn BEFORE it reaches the hx.

Does that sound right?

Thanks

Rick - that is not necessary, and not what DHW priority means. HW priority on a zoned system means that the DHW demand will be satisfied before any other demand is supplied. This can be accomplished a number of ways. I am using a TACO ZVC-406 with priority. It is a zone valve controller with the 6th zone set up for (optional) priority. The valve (or pumps) for zones 1-5 will not energize if zone 6 is energized. Once Zone 6 is satisfied, then the other zones will energize (on a heat call, of course). The TACO SRCs will do the same thing with their priority on the last relay.

What do you guys think of this?

I already have an insulated 40 gallon dhw tank that is piped to a coil in my oil boiler with a circulator/aquastat set-up. It works great. Provides plenty of hw for two families. Could it be as simple as adding a flat plate hx for dhw and have the existing circulator push water through that, when I'm burning wood, and through the existing coil when burning oil? What would be possible drawbacks to that? Maybe couldn't keep up with heavy demands as good as the oil burner does? I don't know. Any thought?

Thanks!! ps- possibly, maybe, the priority thing is already handled with that little dhw circulator being wired with priorty? How could I check?

bump

 

[Jim K in PA]

What do you guys think of this?

I already have an insulated 40 gallon dhw tank that is piped to a coil in my oil boiler with a circulator/aquastat set-up. It works great. Provides plenty of hw for two families. Could it be as simple as adding a flat plate hx for dhw and have the existing circulator push water through that, when I'm burning wood, and through the existing coil when burning oil? What would be possible drawbacks to that? Maybe couldn't keep up with heavy demands as good as the oil burner does? I don't know. Any thought?

Thanks!! ps- possibly, maybe, the priority thing is already handled with that little dhw circulator being wired with priorty? How could I check?

Not sure I am following you here Rick. Are you saying you have an indirect WH heated off of a zone on the oil furnace? Or are you using the 40 gallon tank just for storage of HW? Sorry I am just being dense here.

The easiest way to meet the HW demand is to use an indirect tank and supply it as you would any other zone, except it uses an aquastat and a zone valve, or aquastat and a circ. You can wire either the ZV or the circ as priority with the correct controller.

If you are using an HX between your GARN and the furnace, there is no need for another. If you are running your oil furnace in series with the GARN. most codes will require an HX to act as another barrier between potable and boiler water (Failure of the coil in the indirect AND the HX required for contamination - not likely).

I hope I am not confusing you, or myself.

 

[Rick Stanley]

Jim,

Thanks for replying. I guess it's confusing partly because I jumped in on a "Hot Water Priority" thread and started asking "what if this and what if that" questions and partly because I started out asking about indirect water heaters and ended up asking about flat plate hx's. I guess I should start new threads with each area of questions, since I seem to have so many :-/ ..............I'm trying to consider all options....thanks for bearing with me

Anyway, you and nofossil have straightened me out already on indirect water heaters being piped up like any heating zone and controlled with priority. Got that. Thank you.

Now, in considering other options, I looked at what I already have in place and that is this: There's an oil boiler with a dhw coil in it. Sitting 2 ft away is a 40 gallon tank, piped into the coil, with a circulator in the loop. I look at that and think that there must be a simple way to use a second smaller dhw flat plate hx to replace to coil in the boiler and then I could let the oil boiler go cold when I'm burning wood and make use of the tank and circulator that's already in place.

Does any of this make sense?

 

[Jim K in PA]

Now, in considering other options, I looked at what I already have in place and that is this: There's an oil boiler with a dhw coil in it. Sitting 2 ft away is a 40 gallon tank, piped into the coil, with a circulator in the loop. I look at that and think that there must be a simple way to use a second smaller dhw flat plate hx to replace to coil in the boiler and then I could let the oil boiler go cold when I'm burning wood and make use of the tank and circulator that's already in place.

Does any of this make sense?

OK - From your description above, it sounds like you have an indirect tank already. The circ is pumping water in a closed loop between the coil in the boiler (where it is being heated) and the coil in the 40 gallon tank. If I am wrong, then please straighten me out. There should be some means for expansion on that circuit as well. I have not seen a setup like that before.

Now, how are you going to keep water from passing through your furnace? If you are putting an HX on the return leg of the zone manifold before it gets to the boiler, then are you adding a bypass circuit to send the heated water to the supply leg of the zone manifold? If so, then the boiler will go cold, and you cannot heat the DHW via the coil in the boiler.

However, rather than buying another small HX, why not just pipe the circ you are already using on the DHW loop to circulate the heated water from the supply leg and then back to the return leg (before the HX)? The extra piping is going to be cheaper than the HX, and the amount of work is probably the same or less than adding another HX.

BTW - if you completely bypass the oil boiler as above, how are you going to handel backup situations? Unless you are using motorized isolation valves, you will have to manually open the circuits to allow flow through the oil furnace again. You will also have to shut down the oil furnace electrically, too.

 

[Rick Stanley]

Now, in considering other options, I looked at what I already have in place and that is this: There's an oil boiler with a dhw coil in it. Sitting 2 ft away is a 40 gallon tank, piped into the coil, with a circulator in the loop. I look at that and think that there must be a simple way to use a second smaller dhw flat plate hx to replace to coil in the boiler and then I could let the oil boiler go cold when I'm burning wood and make use of the tank and circulator that's already in place.

Does any of this make sense?

OK - From your description above, it sounds like you have an indirect tank already. The circ is pumping water in a closed loop between the coil in the boiler (where it is being heated) and the coil in the 40 gallon tank. If I am wrong, then please straighten me out. There should be some means for expansion on that circuit as well. I have not seen a setup like that before.

Now, how are you going to keep water from passing through your furnace? If you are putting an HX on the return leg of the zone manifold before it gets to the boiler, then are you adding a bypass circuit to send the heated water to the supply leg of the zone manifold? If so, then the boiler will go cold, and you cannot heat the DHW via the coil in the boiler.

However, rather than buying another small HX, why not just pipe the circ you are already using on the DHW loop to circulate the heated water from the supply leg and then back to the return leg (before the HX)? The extra piping is going to be cheaper than the HX, and the amount of work is probably the same or less than adding another HX.

BTW - if you completely bypass the oil boiler as above, how are you going to handel backup situations? Unless you are using motorized isolation valves, you will have to manually open the circuits to allow flow through the oil furnace again. You will also have to shut down the oil furnace electrically, too.

Hi Jim,

No, it's just a storage tank. I think it's an electric water heater that's not wired up. Instead, it's contents are circulated through a coil in the oil boiler. So, I just was wondering, that if I did decide to let the oil boiler go cold, if a second flat plate may be a good option.

I'm really torn, still, about all of the options and go back and forth a lot.. Right now, I'm pondering the Eric Johnson approach. He shuts his fossil fuel boiler off, plugs up the flue and BURNS WOOD, period, during the winter. Because of the way it's piped he does keep his propane boiler hot with Eko water, but he has to change over manually if he's away or something. I could live with that, I'm here all of the time anyway. I think he built a side-arm hx for hw.

Anyway, thanks for helping me try to figure out whatever it is that I'm trying to figure out :lol: I can just picture people reading my questions and wanting to help but end up shaking their head saying "I can't tell what he wants to know"

 

[Jim K in PA]

Hi Jim,

No, it's just a storage tank. I think it's an electric water heater that's not wired up. Instead, it's contents are circulated through a coil in the oil boiler. So, I just was wondering, that if I did decide to let the oil boiler go cold, if a second flat plate may be a good option.

So does the cold supply go through the coil, then into the storage tank, and then get distributed to the house? If so, then I am not sure how you are getting much HW, as it will be diluted by the cooler water in the tank. If, on the other hand, it is piped with the supply going into the tank, then into the coil, then to the rest of the house, you may be pre-heating it in the storage tank. I am not sure what the circulator is actually doing. A diagram, pics, or both would help. How many pipes are connected to the water tank?

If your boiler goes cold, a small (10 or 20 plate) HX could be used to supply DHW, but the flow rate will need to be pretty high to meet demand. DHW consumes a lot of heat in a short period of time. You will need something equivalent to 100k+ Btuh in heat transfer. An indirect will do the same thing, but perhaps more expensively(?). Perhaps a seperate post on this solution is in order.

I'm really torn, still, about all of the options and go back and forth a lot. Right now, I'm pondering the Eric Johnson approach. He shuts his fossil fuel boiler off, plugs up the flue and BURNS WOOD, period, during the winter. Because of the way it's piped he does keep his propane boiler hot with Eko water, but he has to change over manually if he's away or something. I could live with that, I'm here all of the time anyway. I think he built a side-arm hx for hw.

If you are comfortable with that, then it would be a more efficient setup to do so. No standby losses throught the flue, etc. I very much look forward to the day that I no longer need the oil burner. I will have my propane backup done before next heating season. Then the old oil furnace will be savd for another remote outbuilding that is too far away from the GARN.

Anyway, thanks for helping me try to figure out whatever it is that I'm trying to figure out :lol: I can just picture people reading my questions and wanting to help but end up shaking their head saying "I can't tell what he wants to know"

Heck, this is fun.

 

[Rick Stanley]

"I am not sure what the circulator is actually doing. "

I don't know either, but I'm going to find out, (along with all the other pumps and controls I have) and let you know.

I've become confident enough with my basic plumbing scheme, because of help from you and the others, that I ordered about $1800 worth of parts and pieces over the weekend. Now, there are a bunch of control issues to tackle. I already have a good idea of the ways of having a system behave and I need to figure out (control wise) what's most practical. I need to educate myself on available components and their applications because I really know very little about it. But first, or at least along the way, I need to learn what control capabilities I already have.

Like, for instance, it seems I already have a boiler loop or bypass loop that circulates water out of the supply header over to the return header. There's a taco 007 on that loop that creates flow through the boiler. I did not know that, until last night at about 10pm. That could be handy, I would think...............................

Another for instance would be that this "oil boiler" that I've been referring to is actually a multi-fuel oil/wood boiler and it already has the capability to switch automatically back and forth between wood and oil. Also handy once I figure out how it's wired and controlled..............

So, I'm glad it's fun for you because every time I get an answer, there are about thirteen more questions that come with it. Stay tuned

 

[Rickard]

I have determinded that for my system Hot Water Priority is not necessary. This is a system with 1000 gallons of pressurized storage and primary/secondary loops for plumbing. If there is enough heat getting to the primary loop (ie:the tanks are charged) then the energy can be distributed to the heat zones and the hot water zone with a neglegible effect on each other. It will just pull the energy out of the storage tanks faster.

Dean