DHW. Control

[huffdawg]

Whats the most simple inexpensive way to control an indirect . I have my smart 40 all plumbed and ready , I will be controling it manually for the time being.

 

[RobC]

Your set up is SWEET !
My Superstor is it's own zone. When the thermostat on tank calls for heat the zone opens and a RIB relay turns on the circulator. This is powered by it's own transformer.
With the buffer tank your thinking, no zone valve and circulator with check valve is all you need ?
If that's the case, you could have transformer to DHW thermostat to RIB relay to control circulator.
Rob

 

[ewdudley]

Whats the most simple inexpensive way to control an indirect .

With those three meter ceilings, the most simple and inexpensive would be to hang the indirect tank sideways from the ceiling and thermo-siphon self regulating flow from the buffer tank.

--ewd

 

[huffdawg]

Whats the most simple inexpensive way to control an indirect .

With those three meter ceilings, the most simple and inexpensive would be to hang the indirect tank sideways from the ceiling and thermo-siphon self regulating flow from the buffer tank.

--ewd

Its 9' just to the top of the buffer tank..Would it not get to HOt Elliot ,

 

[ewdudley]

Its 9' just to the top of the buffer tank. Would it not get to HOT?

I was kinda half serious.

Then again it might could work. But not on its side, I thought it was a coil-in-tank with all connections on the top, but now I see it's a tank-in-tank with the heating water connections on the side, so with the air vent and support issues it would probably be best to stick with the intended orientation.

Just need to raise the tank to get the heating water inlet up as high as can be done conveniently and run the return down to the bottom and it just might perform quite well considering there's no flow resistance inside the tank.

As for getting too hot, going strictly by the book, even if the pump or zone valve was thermostatically controlled in a conventional configuration, prudence and many code enforcers would require a DHW supply tempering valve for safety and peace of mind.

 

[jebatty]

You might consider a differential controller (Tekmar, Steca, etc.) to turn on the circulator for the DHW tank only when DHW is cooler than supply temperature. You don't want the circulator on when DHW is hotter than supply temperature. Many such controllers also have a maximum setting, or use a separate aquasta, which you could use to limit the DHW tank temperature to a safe temperature (120F), or let DHW get up to as hot as you want and then use a mixing valve for DHW supply to your house. You will need a cold water supply for this. Unless you use a DHW recirculation loop you might have short bursts of very hot or cool water at the faucets until the mixing valve adjusts to its setting. Insulate all of your DHW pipes as much as you can.

 

[maple1]

Does that tank have a thermostat built in?

I would try to get the tank as high as possible, and plumb it so that it heats by simple convection, as ewdudley was getting at. But throw a small circ in that circuit (non-checked), so that if convection flow can't keep up, or there's a big demand, it will kick in when the temp drops to the calling point. Put a mixer on the DHW out in case the tank gets hotter than comfortable - all the bases should be covered?

 

[ewdudley]

Does that tank have a thermostat built in?

I would try to get the tank as high as possible, and plumb it so that it heats by simple convection, as ewdudley was getting at. But throw a small circ in that circuit (non-checked), so that if convection flow can't keep up, or there's a big demand, it will kick in when the temp drops to the calling point. Put a mixer on the DHW out in case the tank gets hotter than comfortable - all the bases should be covered?

Yeah, the TriangleTube Smart Tank has a conventional adjustable snap-disc aquastat, so can't get much simpler than a normal zone relay controlled by the indirect tank's existing aquastat, since the pump and plumbing are all in place.

Add a mixer on the output for safety and to have consistent DHW temperature. Also a mixer would allow the indirect tank to be maintained at a higher temperature for more reserve capacity.

Some scheme would be desirable to guarantee that the buffer is hotter than the DHW tank setpoint, either a differential control or a simple aquastat, so that the pump won't run if water in the buffer tank is not hot enough.

But if you're in a mood for experimenting, the elevated tank scheme could possibly eliminate the need for any controls or pumping.

 

[Gasifier]

Huff,

Don't know how far along you are on hook up of DHW, and I am no expert. I will just tell you what I have and what my experience with my T.T. Indirect DHW heater is.

If there are times when you have a lot of hot water demand, like I have, I would simply have the indirect on it's own zone with a circ pump controlled by the indirect itself. This is how my Triangle Tube is set up and it gives us endless hot water. No worries. I love this hot water tank. Worked great with my oil boiler. And now it works great with the Wood Gun heating it. The only downside I guess there is to them is that they are expensive. But I have had mine running for about 8 years now and not one problem. Would do it again in a heart beat. Later.

Oh, we found we had to turn the thermostat dial almost all the way down on the T.T. itself in the very beginning. Water was too hot. Be careful at first if you do not have mixing valve on the outlet. Someone could get burned.

 

[huffdawg]

Thanx for all the help guys.
I was thinking about elevating the tank but had my head set around that the supply had to come from the top of the buffer tank. That is something I will eventually do in the future as it will also give me more space in the boiler room. But for now I have all plumbed and its ready to go. just needs controlling. I have an anti scald valve in the shower. I will see how the it goes without the mixing valve on the domestic side ,maybe add one later.

Huff.

 

[huffdawg]

[quote
Yeah, the TriangleTube Smart Tank has a conventional adjustable snap-disc aquastat, so can't get much simpler than a normal zone relay controlled by the indirect tank's existing aquastat, since the pump and plumbing are all in place.


Some scheme would be desirable to guarantee that the buffer is hotter than the DHW tank setpoint, either a differential control or a simple aquastat, so that the pump won't run if water in the buffer tank is not hot enough.

Any way you can do a diagram for me Eliot . I'm good at doing the work part but not design. I have three aquastat wells in the buffer tank , high middle and low.


But if you're in a mood for experimenting, the elevated tank scheme could possibly eliminate the need for any controls or pumping.[/quote]

I like experimenting but right now My daughter wants to get in the suite I've just finished building above the shop!

Last night I tried the DHW . tank and it heated up to 140 °F in roughly 15 mins. Pretty happy with that.

Huff

 

[ewdudley]

Yeah, the TriangleTube Smart Tank has a conventional adjustable snap-disc aquastat, so can't get much simpler than a normal zone relay controlled by the indirect tank's existing aquastat, since the pump and plumbing are all in place.

Some scheme would be desirable to guarantee that the buffer is hotter than the DHW tank setpoint, either a differential control or a simple aquastat, so that the pump won't run if water in the buffer tank is not hot enough.

Any way you can do a diagram for me Eliot . I'm good at doing the work part but not design. I have three aquastat wells in the buffer tank , high middle and low.

The DHW indirect tank aquastat hooks to your zone relay control box as shown in the TriangleTube installation documentation, as do the lines to the circulator.

As far as adding something fancy to disable the DHW circulator if the buffer tank is too cool; if your buffer tank is in fact too cool then the DHW circulator running constantly would probably be the least of your worries, so probably no need to fool with that feature until you're sure it's worth doing.

 

[jebatty]

Good point on constantly running circulator; still by doing so I would not want my DHW to backfeed my storage/system through the hx and cool down because DHW is at a higher temp than storage. A differential controller will prevent this.

 

[ewdudley]

Good point on constantly running circulator; still by doing so I would not want my DHW to backfeed my storage/system through the hx and cool down because DHW is at a higher temp than storage. A differential controller will prevent this.

Yes, agree completely, my comment was in the context of the OP trying to get operational soon, so I was letting him know lack of a differential control shouldn't stand in the way for the time being. Ultimately it would certainly be better to be able to offer a full tank of hot water to mitigate a lack of heat!

 

[huffdawg]

Gasifier ,do you have an expansion tank on the domestic side of your "smart 40" . the reason I ask is my pressure on the domestic side raises to over 70 psi. when I recharge.

Huff