DHW on its own pump and aquastat

[taxidermist]

I would like to install pump for the DHW sidearm, I am replumbing my system this year and am looking for a way to have my DHW "zone" pump turn on and off as needed. Where is the best spot to measure temp on my water heater?



My secondary loop pump ran all the time thru my HX and DHX but caused a lot of mixing in my tanks. I want to wire my system so the secondary pump only runs when there is a call for heat.(know how to do this already)

I also want my DHW sidearm pump to do the same thing.

Thank you,
Rob

 

[webie]

need more imformation where do you pull the water from and where does your hot go in ?

 

[taxidermist]

need more imformation where do you pull the water from and where does your hot go in ?

Not getting what your looking for? Are you talking on the dhw heater? or storage?

 

[ewdudley]

I would like to install pump for the DHW sidearm, I am replumbing my system this year and am looking for a way to have my DHW "zone" pump turn on and off as needed. Where is the best spot to measure temp on my water heater?

Rob

It sounds like you'll have a separate circulator for DHW drawing from storage though the sidearm and back to storage independent from the house HX. If this is the case I think you might consider quite a small circ with 1/2" pipe to the sidearm, maybe even 3/8" since the proper flow might be rather small.

For the the temperature measurement you could look at a differential thermostat with two sensors, one at the top of storage and another fastened to the sidearm at some point down from the top of the sidearm. The pump would run when the sidearm temperature drops X degrees below the temperature at the top of storage and would turn off when the temperature rises to X degrees plus a few. You'd also need an aquastat or some component serving the function of an aquastat to disable the DHW circ when storage isn't hot enough.

--ewd

 

[taxidermist]

I would like to install pump for the DHW sidearm, I am replumbing my system this year and am looking for a way to have my DHW "zone" pump turn on and off as needed. Where is the best spot to measure temp on my water heater?

Rob

It sounds like you'll have a separate circulator for DHW drawing from storage though the sidearm and back to storage independent from the house HX. If this is the case I think you might consider quite a small circ with 1/2" pipe to the sidearm, maybe even 3/8" since the proper flow might be rather small.

For the the temperature measurement you could look at a differential thermostat with two sensors, one at the top of storage and another fastened to the sidearm at some point down from the top of the sidearm. The pump would run when the sidearm temperature drops X degrees below the temperature at the top of storage and would turn off when the temperature rises to X degrees plus a few. You'd also need an aquastat or some component serving the function of an aquastat to disable the DHW circ when storage isn't hot enough.

--ewd

Yes I will have a small pump drawing from storage thru the sidearm back to storage. Not really worried about the control of it when storage is not hot enough.

 

[ewdudley]

...

Where is the best spot to measure temp on my water heater?

Rob

...

For the the temperature measurement you could look at a differential thermostat with two sensors, one at the top of storage and another fastened to the sidearm at some point down from the top of the sidearm. The pump would run when the sidearm temperature drops X degrees below the temperature at the top of storage and would turn off when the temperature rises to X degrees plus a few.

You'd also need an aquastat or some component serving the function of an aquastat to disable the DHW circ when storage isn't hot enough.

--ewd

Yes I will have a small pump drawing from storage thru the sidearm back to storage. Not really worried about the control of it when storage is not hot enough.

Right. The aquastat is a refinement to avoid pulling heat from the water heater back to storage. You can simply disable the circuit manually when storage is not hot enough.

For controlling the pump cycle itself the differential thermostat is nice because storage temperature can vary a lot and with a differential thermostat the subsystem only runs when it has something to offer.

For a single sensor system, I would try simply fastening the sensor to the outside of the sidearm, halfway down or so and well insulated.

If that didn't work well enough you would need to get under the insulation against the side of the tank. Electric water heaters generally have a panels for the elements that will give access, but for a gas heater you might have to cut your own access panel.

--ewd

 

[wantstoburnwood]

I hooked up a circ pump to the thermostat in the electric water heater altough you should disconnect the water heater wires as they are uually 220 .

 

[webie]

need more imformation where do you pull the water from and where does your hot go in ?

Not getting what your looking for? Are you talking on the dhw heater? or storage?

Your DHW Is what I was wondering ,On where you draw the cool water from and where do you return it into your water heater again after it is heated.

 

[taxidermist]

need more imformation where do you pull the water from and where does your hot go in ?

Not getting what your looking for? Are you talking on the dhw heater? or storage?

Your DHW Is what I was wondering ,On where you draw the cool water from and where do you return it into your water heater again after it is heated.

My side arm is plumbed in the top where the PRV goes into the tank and at the bottom at the drain. I have my hot water from storage going in the top port of sidearm and cool out the bottom returning to storage.

My water heater is a lp unit with cold water dip tube supply and hot water both exit out the top of the unit.

Rob

 

[webie]

I would like to install pump for the DHW sidearm, I am replumbing my system this year and am looking for a way to have my DHW "zone" pump turn on and off as needed. Where is the best spot to measure temp on my water heater?



My secondary loop pump ran all the time thru my HX and DHX but caused a lot of mixing in my tanks. I want to wire my system so the secondary pump only runs when there is a call for heat.(know how to do this already)

I also want my DHW sidearm pump to do the same thing.

Thank you,
Rob

Ok just trying to get a handle on this . Let me know if I am incorrect . What I am getting from your posts is you currently have a side arm to heat your DHW in your LP water heater . You have a primary loop with storage and then secondary loops for your zones . One zone but not really a zone is your sidearm but that runs all the time , thus causeing alot of mixing for you in your storage tank .
What I am gettting from what you want to do is basically make your side arm a controlled zone for your DHW , and you want to install a pump to cycle you DHW thru your HX rather than Gravity heat .
I hope this is all correct
What you will need is an aquastat to control your DHW pump and also turn on your DHW zone . The ideal spot for an aquastat would be about 6-12 inches off the bottom of your LP water heater to avoid short cycleing . But since this is not possible You will have to do the next best thing and measure the cold water out from your water heater to be heated. You will need to do this with an aguastat and you want to use a aquastat with a large differential to avoid short cycles because of cool downs .
Just out of couriosity is your side arm capable of suppling on demand DHW , because if it is we could get this to work a different way .

 

[dogwood]

Webie, what would you be setting the aquastat's differential at in the set-up you describe above, assuming a 30 degree range was available. So happens I'm setting mine up just as you described, except using a flat plate instead of a sidearm, and hadn't figured that differential setting out yet.

Mike

 

[webie]

Webie, what would you be setting the aquastat differential at in the set-up you describe above, assuming a 30 degree range was available. So happens I'm setting mine up just as you described, except using a flat plate instead of a sidearm, and hadn't figured that differential setting out yet.

Mike

If I talk in circles here its because of lack of sleep , I worked all night ( so excuse me )

I was looking on the net earlier what I was looking at was if it would be possible to use a remote aquastat and if you were to try and get the sender up behind the insulation next to the tank wall in your water heater say about 8-12 inches from the bottom .

This would be a much better option than on the pipe coming from the drain . I am worried about a short cycle any time someone cracks the hot water .
There is another problem too is how he has it plumbed it is inherent to stratify terribly .
You need to use your water heater as it was intended you heat it from the bottom up . This is not a storage tank for your heating system . You want your water all the same temp .
If you can pull from the drain and return to the cold will work the best this will help with short cycle .
You can then actually make your aquastat work the same as a thermostat on your water heater , infact you probably would not even need a mixer
If you have it set up like this then I would start with probably 5-10 degree differential , and go from there to suit your taste and needs .
If you are plumbed drawing from the drain back through where your pop it valve is. ( This way works I just dont care for it )
I think what will happen in this design will be if there are only small amounts of hot water drawn when ever the heated water is comeing into the tank it is coming in say at 180 degrees to the top of the tank and it has to push down to the bottom to say lets use 130 degree aquastat setting . More or less your tank will be mostly at 180 on top till near the bottom .
You might as well use a 30 degree differential .

 

[feelingasi]

my DHW is set up as a zone in my system and is only allowed to run if the house isn't calling for heat. i dont have a fancy controller or anything that resembles one. i built my controlls out of "scrapable" ice cube relays and RIBS. i turn my sidearm on with a surface mount aquastat "pipe mounted previously" also a salvage item, installed next to the top element/tstat on my existing elec tank. all i did was use a putty knife to loosen up the insulation (turn power OFF) wrapped around the tank and slipped the heat sensing plate from the aquastat in. it works pretty good and keeps my DHW at about 150 dg. i also installed a timer for the elec side of things in case i get lazy with the fire and obviosly a tempering valve. the setting on the aq is at 160-170 only because the outer layer of the tank is not a true representation of internal water temp. i used a meat therm at the faucet prior to the installation of the tempering valve in determining the setting at which the DHW aquastat needed to be set. 65gal elec tank = endless hot water. i have a three person jacuzzi tub, and can fill it then go take a 10 min shower if i want.

 

[dogwood]

Thanks Webie. I am going to draw the water from the drain opening and back up through the prv ("pop") opening as you described. I'll go with the 30 degree setting you suggested and put the aquastat as close to the drain opening as possible' It's only a few inches off the bottom of the tank. Since the aquastat and fitting is paid for, I don't want to switch plans at this point. We'll see how it works. If it's lacking I'll try a sensor instead. Appreciate your advice..

Mike

 

[taxidermist]

I would like to install pump for the DHW sidearm, I am replumbing my system this year and am looking for a way to have my DHW "zone" pump turn on and off as needed. Where is the best spot to measure temp on my water heater?



My secondary loop pump ran all the time thru my HX and DHX but caused a lot of mixing in my tanks. I want to wire my system so the secondary pump only runs when there is a call for heat.(know how to do this already)

I also want my DHW sidearm pump to do the same thing.

Thank you,
Rob

Ok just trying to get a handle on this . Let me know if I am incorrect . What I am getting from your posts is you currently have a side arm to heat your DHW in your LP water heater . You have a primary loop with storage and then secondary loops for your zones . One zone but not really a zone is your sidearm but that runs all the time , thus causeing alot of mixing for you in your storage tank .
What I am gettting from what you want to do is basically make your side arm a controlled zone for your DHW , and you want to install a pump to cycle you DHW thru your HX rather than Gravity heat .
I hope this is all correct
What you will need is an aquastat to control your DHW pump and also turn on your DHW zone . The ideal spot for an aquastat would be about 6-12 inches off the bottom of your LP water heater to avoid short cycleing . But since this is not possible You will have to do the next best thing and measure the cold water out from your water heater to be heated. You will need to do this with an aguastat and you want to use a aquastat with a large differential to avoid short cycles because of cool downs .
Just out of couriosity is your side arm capable of suppling on demand DHW , because if it is we could get this to work a different way .

Kinda what I am after...I just want to cycle water from storage to sidearm to keep the water hot in my DHW heater. I am not looking to pump my DHW still want gravity heat. My problem was when I set my secondary loop pump to turn on and off when the thermostat calls for heat I loose my heat for my DHW. Are you saying I should change the way I have my sidearm plumbed???

 

[rkusek]

[/quote] Kinda what I am after...I just want to cycle water from storage to sidearm to keep the water hot in my DHW heater. I am not looking to pump my DHW still want gravity heat. My problem was when I set my secondary loop pump to turn on and off when the thermostat calls for heat I loose my heat for my DHW. Are you saying I should change the way I have my sidearm plumbed???[/quote]

Rob is your boiler, storage, and primary loop all located in the same area (basement)? If so, does your primary loop have a spare set of tees or could you add a set for your DHW. I think that is what you are asking. The primary/secondary setups use pumps instead of zone valves basically. Zone valves seem to cost more than the Grundfos 15-58s that I have bought but then you end up with more pumps running. Hopefully with the right controls they are only running when necessary.

If your DHWX is currently plumbed after your W-A HX (which it surely is) you might be able to use two 3 way valves (about $120 each) at the sidearm to accomplish what you are trying to do without changing your plumbing a great deal. Maybe someone that has done this before can add more insight. I've only envisioned this on paper but I would think if both valves where wired together to open or close simultaneously you could bypass your DHW sidearm on your existing HX loop. This would not allow for burning through warm months for DHW if you would decide to do that. Also, I imagine if you used a lot of DHW when the house was not calling for heat that would be a problem. This is kind of the reason I went with a P-S setup plus the fact that the circs where cheaper than the zone valves too.

 

[taxidermist]

If I plumbed it into my primary loop I could only heat the DHW when the boiler was running. I think I know how I want it plumbed but thought someone might have temp sensors installed some where to take the guess work out of where I should place them.


Rob

 

[webie]

If you are heating your DHW by gravity via a side arm that is supplied by heat from a secondary loop via a pump, I am not sure how you would control this . Gravity heating is slow . Your pump on your storage loop will still have to run quite a bit . So Your sure going to have alot of mixing yet . I thought from your original posts you were planning on installing a pump .

 

[taxidermist]

If you are heating your DHW by gravity via a side arm that is supplied by heat from a secondary loop via a pump, I am not sure how you would control this . Gravity heating is slow . Your pump on your storage loop will still have to run quite a bit . So Your sure going to have alot of mixing yet . I thought from your original posts you were planning on installing a pump .

I did say I wanted to ad a pump to circulate water from storage to sidearm. Think of it as pumping to a zone.

1 pump from storage to forced air HX controled by thermostat that turns the blower on.

1 pump to pump fro storage to sidearm controled by a differential control.

I know I can not eliminate all mixing but I know I can make it way less by not running 170 water thru HX that are not calling for heat like I am now.



Rob

 

[ewdudley]

If you are heating your DHW by gravity via a side arm that is supplied by heat from a secondary loop via a pump, I am not sure how you would control this . Gravity heating is slow . Your pump on your storage loop will still have to run quite a bit . So Your sure going to have alot of mixing yet . I thought from your original posts you were planning on installing a pump .

I did say I wanted to ad a pump to circulate water from storage to sidearm. Think of it as pumping to a zone.

1 pump from storage to forced air HX controled by thermostat that turns the blower on.

1 pump to pump fro storage to sidearm controled by a differential control.

I know I can not eliminate all mixing but I know I can make it way less by not running 170 water thru HX that are not calling for heat like I am now.

Rob,

Like webie says gravity heating makes for slow flow on the water heater side of the side arm.

You could use stainless steel circ pump on the water heater side, and a tiny circ pump coming from storage to the storage side of the sidearm. Your sensor would then go against the wall of the water heater tank near the bottom, or anywhere on the pipe coming from the heater to the sidearm and both pumps would run together.

Unnecessary mixing would be prevented by insuring that the pump from storage is small enough. If you wanted to get real fancy you could us a variable speed pump with setpoint control that would adjust the pump speed to insure a return temperature that isn't too high.

If you don't want two pumps you could move the sidearm over above your storage tank as high as you can get it, and use gravity to supply hot water to the sidearm and use a stainless steel circ to move DHW from the bottom of the heater tank over to the sidearm and back. With the sidearm above the storage tank the increased difference in elevation would cause much greater gravity flow, but return water from the sidearm would not fall into the storage tank until it was sufficiently dense and cool enough.

--ewd

 

[webie]

If you don't want two pumps you could move the sidearm over above your storage tank as high as you can get it, and use gravity to supply hot water to the sidearm and use a stainless steel circ to move DHW from the bottom of the heater tank over to the sidearm and back. With the sidearm above the storage tank the increased difference in elevation would cause much greater gravity flow, but return water from the sidearm would not fall into the storage tank until it was sufficiently dense and cool enough.

--ewd[/quote]


+1
Infact depending on your side arm size this could work as a direct water heater .

 

[twofer]

What about just throwing a SSR on the pump and a 1-Wire sensor on the DHW and then let the Arduino control when the pump turns on? That's what I plan on doing with mine.

 

[taxidermist]

What about just throwing a SSR on the pump and a 1-Wire sensor on the DHW and then let the Arduino control when the pump turns on? That's what I plan on doing with mine.

Yeah I know you and I were talking about doing it that way I was just looking for some other ways too.