Question on heat dumping

[warno]

I'm looking to redo a bunch of plumbing this summer to get to a my plumbing to run more efficiently. But I'm wanting to keep a heat dump zone for potential boiler over fire. I know most dump zones are gravity systems for power outage. we never lose power but I have been known to over load the firebox. It doesn't happen often but if it does I would rather dump the heat then have the boiler idle.

My boiler is in a shed just outside the garage there is a FPHX that the storage water is charged through. So while boiler is batch burning the storage circ is running water to the boiler shed through underground lines then to the HX then back to storage tank.

I'm wanting to use my existing garage heating loop as my dump. I will use an aquastat to control when my boiler goes into over heat mode. If over heat situation happens the aquastat will close a relay that will simultaneously open my diverter valve to dump side, turn on my garage loop circ and my garage loop fan.

The "storage charge circ" will remain running in series with my garage loop circ to help with the added head of the garage loop.

I have a drawing of the plumbing I think will work. I'd like some feedback to see if you guys agree.

 

[Bob Rohr]

really don't want any checks on the inlet side of a circ, they tend to encourage cavitation, especially in low pressure systems.
Why a swing check? The check inside the circ would be better if you don't need gravity circulation.

 

[warno]

really don't want any checks on the inlet side of a circ, they tend to encourage cavitation, especially in low pressure systems.
Why a swing check? The check inside the circ would be better if you don't need gravity circulation.

Everything in my drawing will be on my pressurized side of the FPHX.

I was wanting a check valve in that location to prevent back feed straight into the storage tank if in "dump mode". In hopes it would drive the water up into the garage loop to shed heat. If I plumb in my dump line on the outlet side of the garage circ I was concerned it would draw too much storage tank water up through with it instead of just circulating the over heated FPHX return water. Would it be better to just remove the check valve from the drawing and just run without it?

 

[Marshy]

@warno, I don't think I fully understand your question. From what I gather you want the garage zone to turn on when your boiler goes into slumber/idle to act as a heat dump.

Do you already have the zone built and installed for the garage?

My thought is you will need some sort of smart control with logic such that the "dump" zone only actuates if the boiler enters idle mode and all other zones are satisfied.

I say that because I recall you having issues with getting the heat out of the boiler fast enough to prevent it from going into idle. And if you storage is calling for heat and the boiler goes into and out of idle while the storage is trying to charge then you don't want the garage dump zone taking heat from the boiler.

If you just hook the aquastat in parallel to the dump zone's thermostat relay so that it will mimic the zone calling for heat then it will demand heat no matter if other zones are in demand or not. That would not be ideal because priority should be to the house zones and storage first.

You need logic to do this. Something to look at the storage and the boiler.

1) Storage is in demand?
True or False

2) Boiler is in idle mode?
True or False

Only time you want the dump to run is when 1 is False and 2 is True .

 

[salecker]

From what i have read and experienced...
Your storage should act as your dump zone.
One of the fringe benefits of adding storage is that you don't need a dump zone.My boiler shuts down when my storage gets to 187F there about, allowing lots of room for any BTU's that could be made with a power outage.
But i'm just a hack with a gasifier.

 

[warno]

@Marshy

I do already have a heating zone in my garage. It is a water/air heat exchanger with a fan on it.

While replumbing everything this summer I'm going to add in my much larger FPHX so the likelihood of the dump zone running will be slim. But if I over load the firebox I don't want to boiler going into idle, I would much rather it dump the heat to the garage. Of course this will only happen if the storage is getting close to boiler temps.

I do have a dump zone now that consists of it's own water/air HX with fan. And it's on a controller tied to my supply line to the FPHX boiler side. If it's reading to high it switches the diverter to dump side and kicks on the fan to that HX. The problem is I never finished the duct work from the fan to the HX of the dump zone. I'm wanting to do away with this added plumbing and tie the diverted "heat dump" water to the current garage loop.

So basically the dump zone will run as it does now but I want it to run through the garage loop instead of it's own loop. The reason being i know the heat dump won't activate often so with it on its own loop in the garage attic the water just sits there. Unless I pile a bunch of insulation around the lines and HX it's possible it may freeze and burst at some point. With using my current garage loop that threat is eliminated. Because the garage loop will run and circulate water with a call for heat anyway.

@salecker

The storage will defiantly heat first. But if I over load for the amount of heat i needed in storage my boiler goes into idle mode. I never want that to happen. I know it comes down to proper loading and learning the boiler and wood load needed but things happen. Maybe I get carried away with adding a few pieces of hedge, or maybe the weather man was wrong on the forecast. I just want to make sure the boiler never has a chance to idle and just burns the batch down like I want it to.

 

[warno]

I've been thinking more about the dump plumbing and wondering something different now. My supply and return lines all go into 3" headers on my storage tank. If I simply wire in my controller to turn on the garage loop as it's plumbed now wouldn't it draw the "heat dump" water through basically the same as my drawing is because of the headers. I know it will draw in some storage water too but my thinning now is it will mostly draw on the heated water coming from the FPHX.

Here's a pic of my supply header. The connection nearest the wall and on bottom is the FPHX return. The center connection is my current garage loop connection.

And heres a pic of my return header. The closest connection to the wall is the FPHX supply and the last connection thats horizontal is the garage loop return.

So would it work to just not change the plumbing and simply switch on the garage loop for dumping heat?

 

[maple1]

Does your boiler idle now at times before your storage gets fully charged?

Re. your last post, I think you are talking about doing away with the diverter setup? If so I think I agree. Usually the lowest temp water you can send back to the boiler is at the bottom of storage. So if the storage isn't full charged, and you're diverting thru your dump circuit (say when boiler is really pumping the heat out), then you would actually be sending warmer water back to the boiler than if it was coming from bottom of storage since the dT thru the dump circuit might not be that big relatively speaking. Does the dump circuit have its own circulator?

Something else some people have done, is simply plumb in a second circulator between the HX & storage, parallel with the one that is there now, (or could likely be done in series too - parallel would likely need check valves), that gets called when temps get up to your high point. Then you've upped your HX to storage flow considerably, which should move more BTUs to storage. That second circ could maybe be controlled by your boiler temps? If you do that, and have the dump zone on its own circ that gets called say when storage return temps get up to a certain point (and do away with the diverter stuff) - that should handle everything? There is likely multiple ways to skin this cat.

 

[warno]

@maple1

Right now, yes the boiler idles a bunch when the storage approaches 170s. But, going back to my other thread, my current FPHX is a tiny 20 plate and I'm stepping up to a larger 90 plate. So the bigger FPHX accompanied by the more efficient plumbing I'm going to redo this summer should help a ton with the boiler idle problem.

I understand what you're saying with the lowest storage water being coolest and the delta T of the garage loop is only around 30°F so it probably wouldn't cool as fast as I would like. Thats what got me thinking about simply letting the storage circ run like normal and just switch on the garage loop to draw heat from storage if heat dump is needed.

I have actually done that in the past. when my boiler would hit idle, I would run out to the garage and crank the thermostat. It takes a little bit but it does draw the heat down and gets the boiler up and running again.

I think I understand what you're saying about a second circ to move more gpm. I'll draw up what i think you mean and post it in a bit.

 

[BoiledOver]

@maple1

Right now, yes the boiler idles a bunch when the storage approaches 170s.

This is typical behavior for gassers. After a full season with your new plumbing, you will find that you have adapted to a sweet spot in charging your storage. Meaning, you will know what it takes and load the firebox accordingly. When nearing the end of a burn, the Eko will idle a bit. In the firebox at the point of idling is just a bed of coals which in my opinion is harmless.

 

[warno]

This is typical behavior for gassers. After a full season with your new plumbing, you will find that you have adapted to a sweet spot in charging your storage. Meaning, you will know what it takes and load the firebox accordingly. When nearing the end of a burn, the Eko will idle a bit. In the firebox at the point of idling is just a bed of coals which in my opinion is harmless.

That's how mine ran when it was running good before my issues started this season. I had it down how much i needed to load for Said amount of heat. But then everything went haywire with the pump issues i started having.

 

[warno]

@maple1 is this what you were saying about a second circ? I believe this would be considered parallel?

 

[maple1]

Yes. Each would have a check valve, either the built in one or one added.

The added benefit is you always have one on standby. If one goes down the other one will carry on until you get it fixed. Although I don't think I've ever had one go down. 15-58's are pretty reasonably priced.

Be nice to have more input from those who have done this - I'm kind of winging it based on reads on here.

 

[warno]

I guess my only concern with the added gpm is my 1" underground lines. I can only stuff so many gallons through there.

 

[BoiledOver]

That's how mine ran when it was running good before my issues started this season. I had it down how much i needed to load for Said amount of heat. But then everything went haywire with the pump issues i started having.

Could be overthinking this issue. Your thermal storage, as previously stated, is a very good dump zone when power is active. Some folks have an interest in dealing with an overheated boiler due to power outage. For this scenario, a gravity dump zone is desired, or backup power.

 

[warno]

Yeah we never lose power. My dump zone plan was only for boiler over heat because of over loading.

 

[warno]

The more I think about it I may just be concerned about nothing like you guys have said. I'm so used to running this tiny FPHX that doesn't pull btus from the boiler like I need it to. With the new 90 plate I'm going to put in it should run the storage closer to the boiler temp instead of letting the boiler pull away like it does now. I guess I'll just run it after the replumb and see how things operate this summer. If I think it may need the heat dump I'll get that figured out before next winter.

I'm going to draw up a, hopefully, final draft of my plumbing lay out tomorrow. I'll post it up and if possible have you guys review it and give any opinions.

 

[Marshy]

I want to go back to your cavitation thread and look at how you have your storage tanks set up. Did you have a good pic of them? Dont have have 2 or three tanks horizontally mounted?

 

[maple1]

I guess my only concern with the added gpm is my 1" underground lines. I can only stuff so many gallons through there.

I guess I forgot you were planning on putting the hx with the boiler.

 

[warno]

I want to go back to your cavitation thread and look at how you have your storage tanks set up. Did you have a good pic of them? Dont have have 2 or three tanks horizontally mounted?

Yes the storage is 3) 250 gallon tanks stacked horizontal.

 

[Marshy]

Yes the storage is 3) 250 gallon tanks stacked horizontal.

View attachment 224327

And where does the hot water go into the tanks at when recharging, bottom or top tank?

 

[maple1]

Top.

Should be a good stratifying setup.

 

[Marshy]

Top.

Should be a good stratifying setup.

That's why I want to verify. Something like that would cause him issues if not plumber properly. I don't recall him mentioning that in the cavitation thread. It's kind of irrelevant to this original post in this thread but none the less important.

 

[warno]

The water is pulled from the bottom and sent back to the top during recharging.