Installing my Plate HX for domestic Hot water

[Buzz Saw]

Howdy,

I'm going to be installing my Plate HX for my domestic very soon,but I'm unsure of exactly how to go about installing it the way I want it to work. Currently I have a domestic hot water loop in my house. It's a small circulation pump that circulates my DHW throughout the entire house so I don't have to wait to use hot water.(we really like this feature, especially in the winter).

I would like to use the PHX to preheat my water AND for the DHW loop to circulate through the plate HX to bring the water up to set temp. Thing is I'm not sure how to do this. What components would I need? How do they get plumped?

Another option is to not pre heat the water and run the DHW loop through the plate HX. I think I know how this would work, but how much longer would it take the water to get up to temp. Would I see saving using this method?

Another option I just considered would be to run two plate HX's, one for preheating and one for the loop.

Does anyone have any experience with hooking up DHW with a DHW loop? Any advice on things to look out for when doing the install?

Components that work better than others?

What do you think is the best option for the money?


I'll post a couple diagrams of what I'm thinking from my phone

 

[Buzz Saw]

This might help.

Sent from my SM-G950U using Tapatalk

 

[maple1]

I would likely put a tank between the hx and the loop. Plate only needs to keep tank warm, loop can do what it wants. If you use an electric water heater for the tank then you're covered when not burning wood.

 

[Buzz Saw]

@maple1 are you saying to have a plate loop & a DHW loop?

Sent from my SM-G950U using Tapatalk

 

[maple1]

I think so. Heat the tank with the plate, tie the tank to your existing dhw setup. What were you planning to do for dhw when not burning?

 

[maple1]

Wasnt sure exactly what that heater is in your diagram.

 

[Buzz Saw]

It's an electric water heater.

I think I would like to have two loops, but use one pump(if it's cheaper).

If I used a solenoid 3 way valve to switch between circulating the loop or circulating and heating water.

I'll try drawing the idea, but unsure of what parts are needed to do it

Sent from my SM-G950U using Tapatalk

 

[jrod770]

I have your similar set up. My dhw circulating loop comes back to the pump, then the flat plate, and then back into the bottom of an 80 gallon storage tank. My dhw circ. loop runs 24-7, when the tank cools down, it turns on the circulating pump from the boiler , and then brings the tank up to temp. Simple design and I never have to wait for hot water. The 80 gallon storage tank is an electric water heater that I un-hooked the elements on and use the bottom thermostat to kick on the circ. from the boiler. I have a 50 gallon propane power vent water heater that we use in the warm months.

 

[maple1]

That sounds ok too.

 

[dogwood]

Buzz Saw, I'm not sure how you could get away with only one pump, not to say you couldn't.

I have a small Laing recirc pump on my DHW loop. It's activated by an aquastat off the tank's drain outlet. From that same shared outlet the Laing circulates DHW needing to be heated through a twenty plate Bell & Gosset heat exchanger. The heated DHW subsequently circulates back into the DHW tank through an inlet shared with the pressure relief valve .

The second loop is simply a circ.controlled zone which circulates hot water from the boiler to the other side of the flat plate. My circ is a 3 speed Grundfos I think set on low, activated by the same aquastat controlling the Laing. The DHW reheats very quickly.

Following are some suggestions gleaned mainly off this site. Use good quality flex pipes to connect the hx on the DHW side to facilitate removal of either the flat plate or the DHW tank. Different tanks locate their hot and cold fittings in different locations. If you ever have to replace your tank you'll be so glad to have flex fittings in place.Stupidly I didn't at first, but now do.

I also plumbed Webstone isolation valves onto the flat plate's DHW side, right before and right after the DHW fittings. The Webstone's have hose fittings to enable you to flush liquids through the flat plate to clean out hard water deposits or other grunge without having to disassemble the plumbing. I think that was Bob Rohr's idea. At Jebatty's suggestion I similarly plumbed in two temperature gauges to keep tabs on whether the flat plates were in need of cleaning, judged by a decrease in the flat plates DHW input-output temperature differential.

Plumb a wye stainer before the flat plate's boiler water input to keep any grunge for getting into and clogging that side of the flat plate. I followed another of Bob's suggestions and put a shutoff with a hose fitting at the end of the wye strainer to faciitate draining it's strainer.

I also have a mixing valve on the hot water tanks output. You can then heat your DHW hotter, giving you extra capacity in your tank, at the same time gaining insurance against Legionnaires disease by having a higher tank temp. The mixing valve's output can be set to give you a nice, safe hot water temperature the tap.

This setup has worked like a charm into it's third heating season now.

Good luck,

Mike

 

[maple1]

Buzz Saw, I'm not sure how you could get away with only one pump, not to say you couldn't.

I have a small Laing recirc pump on my DHW loop. It's activated by an aquastat off the tank's drain outlet. From that same shared outlet the Laing circulates DHW needing to be heated through a twenty plate Bell & Gosset heat exchanger. The heated DHW subsequently circulates back into the DHW tank through an inlet shared with the pressure relief valve .

The second loop is simply a circ.controlled zone which circulates hot water from the boiler to the other side of the flat plate. My circ is a 3 speed Grundfos I think set on low, activated by the same aquastat controlling the Laing. The DHW reheats very quickly.

Following are some suggestions gleaned mainly off this site. Use good quality flex pipes to connect the hx on the DHW side to facilitate removal of either the flat plate or the DHW tank. Different tanks locate their hot and cold fittings in different locations. If you ever have to replace your tank you'll be so glad to have flex fittings in place.Stupidly I didn't at first, but now do.

I also plumbed Webstone isolation valves onto the flat plate's DHW side, right before and right after the DHW fittings. The Webstone's have hose fittings to enable you to flush liquids through the flat plate to clean out hard water deposits or other grunge without having to disassemble the plumbing. I think that was Bob Rohr's idea. At Jebatty's suggestion I similarly plumbed in two temperature gauges to keep tabs on whether the flat plates were in need of cleaning, judged by a decrease in the flat plates DHW input-output temperature differential.

Plumb a wye stainer before the flat plate's boiler water input to keep any grunge for getting into and clogging that side of the flat plate. I followed another of Bob's suggestions and put a shutoff with a hose fitting at the end of the wye strainer to faciitate draining it's strainer.

I also have a mixing valve on the hot water tanks output. You can then heat your DHW hotter, giving you extra capacity in your tank, at the same time gaining insurance against Legionnaires disease by having a higher tank temp. The mixing valve's output can be set to give you a nice, safe hot water temperature the tap.

This setup has worked like a charm into it's third heating season now.

Good luck,

Mike

So yours only has one circ on the DHW side of the HX? Did I get that right? I think that is what Buzz Saw had in mind?

If that little recirc pump is running 24/7, it should be able to heat the tank OK too - with a call for heat from the tank activating the boiler side of the HX. As long as the tank is big enough for reserve for when hot water is being used. If you use a lot of hot water at once and empty the tank, that little recirc pump would then not be able to keep up with the demand and would take a little while to replenish it. Not sure how much those small recirc pumps can flow with all the head factored in? Would be quite a bit of small pipe in a DHW loop, plus the HX pressure drop. I have a little B&G Ecocirc on the DHW side of my HX but it doesn't do a loop - just circulates between HX and the tank right beside it. It does very well.

 

[Buzz Saw]

Yes one pump on the domestic side of the HX is what I'm thinking.....however I never considered the head pressure & GPM of the little loop pump.





Sent from my SM-G950U using Tapatalk

 

[Buzz Saw]

Buzz Saw, I'm not sure how you could get away with only one pump, not to say you couldn't.

I have a small Laing recirc pump on my DHW loop. It's activated by an aquastat off the tank's drain outlet. From that same shared outlet the Laing circulates DHW needing to be heated through a twenty plate Bell & Gosset heat exchanger. The heated DHW subsequently circulates back into the DHW tank through an inlet shared with the pressure relief valve .

The second loop is simply a circ.controlled zone which circulates hot water from the boiler to the other side of the flat plate. My circ is a 3 speed Grundfos I think set on low, activated by the same aquastat controlling the Laing. The DHW reheats very quickly.

Following are some suggestions gleaned mainly off this site. Use good quality flex pipes to connect the hx on the DHW side to facilitate removal of either the flat plate or the DHW tank. Different tanks locate their hot and cold fittings in different locations. If you ever have to replace your tank you'll be so glad to have flex fittings in place.Stupidly I didn't at first, but now do.

I also plumbed Webstone isolation valves onto the flat plate's DHW side, right before and right after the DHW fittings. The Webstone's have hose fittings to enable you to flush liquids through the flat plate to clean out hard water deposits or other grunge without having to disassemble the plumbing. I think that was Bob Rohr's idea. At Jebatty's suggestion I similarly plumbed in two temperature gauges to keep tabs on whether the flat plates were in need of cleaning, judged by a decrease in the flat plates DHW input-output temperature differential.

Plumb a wye stainer before the flat plate's boiler water input to keep any grunge for getting into and clogging that side of the flat plate. I followed another of Bob's suggestions and put a shutoff with a hose fitting at the end of the wye strainer to faciitate draining it's strainer.

I also have a mixing valve on the hot water tanks output. You can then heat your DHW hotter, giving you extra capacity in your tank, at the same time gaining insurance against Legionnaires disease by having a higher tank temp. The mixing valve's output can be set to give you a nice, safe hot water temperature the tap.

This setup has worked like a charm into it's third heating season now.

Good luck,

Mike

I like this idea alot...but I only have a 40 gallon tank.

Sent from my SM-G950U using Tapatalk

 

[maple1]

I don't know anything about Laing circs - but sounds like dogwoods setup heats his tank well, at the same time as it is recircing the loop. I think if you go with your Option 1 diagram above, and get the controls right on the boiler side, you would be OK. When hot water is being used, the incoming cold should be first going thru the HX. As long as it can't go backwards through the loop - which may or may not need a check valve. And if the HX is sized adequately/generously, and the boiler side is controlled to start circulating the boiler side as soon as it senses a temp drop on the DHW-out side of the HX, it should function as an on-demand heater fairly well. Or should let you use a lot of hot water before you run out, by preheating a lot. Then when hot water is not being used and the recirc circ is running, that same control would also serve to keep the DHW tank charged.

 

[dogwood]

Buzz Saw, my DHW tank is only 40 gallons, like yours. It's propane fired during the summer, and I turn off the propane to it during the heating season. If I had electric like yours I suppose I'd leave it on with the tanks thermostat turned down a bit so it wouldn't kick on at the same time as you're pumping to the flat plate

Maple1, maybe I'm using the term "loop" incorrectly. My set-up with the Laing recirc pump is exactly the same as yours with the Ecocirc. It's located immediately next to the DHW tank with only a few feet of pipe involved. The Laing circulates the cooled off water from the from the bottom of the DHW tank to the flat plate hx located right above the DHW tank, then back into the DHW tank inlet shared with the pressure relief valve.

The boiler water that goes to the flat plate through the Grundfos circ involves only a few feet of 3/4 inch pipe too. That line is teed off from the 1-1/2 inch supply line from the boiler to the w/a hx above my furnace. The boiler water returns from the flat plate into the 1-1/2 return line from the w/a hx heading back to the wood boiier.

I don't recall how much head is involved for the Laing but it wasn't much. I don't recalll the gpm output of the Laing either, but I did figure it out at the time to coordinate with the capacity of the flat plate. Bell and Gosset had tables on their site to figure this out. Here's a thread that addressed sizing the pump: https://www.hearth.com/talk/threads/any-suggestions-on-small-circ-pump.36575/#post-36575 The Laing and Grundfos only run when the the DHW is being reheated, and at least 140 degree boiler water is available to do the job, not 24/7. And the 40 gallon DHW tank does reheat quickly. We've never had to wait for hot water.

I purchased the Laing SM-303 model because it was a little less pricey than the Ecocirc. It's plumbed into 3/4 inch pipe. Here's a thread on sizing your flat plate hx: https://www.hearth.com/talk/threads/how-do-i-size-a-flat-plat-exchanger-to-heat-dhw.40748/#post-519482



Mike

 

[maple1]

OK that might make a difference. Buzz Saw wants to incorporate his DHW recirc loop - so maybe head loss numbers should be run to get an idea of GPMs it would be able to do. Just quick thoughts out loud - I don't have a DHW loop but if I did I am guessing it would be maybe 100' of 3/4" copper. Not sure how much head that presents. Plus a lot of els & Ts. Actually I would likely need more than one loop to reach all my taps. A pump upsize would likely cover it, if needed. My Ecocirc is I think set at or around the middle position on its speed dial, and it can turn over and heat up my 80 gallon tank in something like half an hour. I could also get away with a smaller tank I am quite sure - when I put it in I wanted max capacity. It won't be replaced with one that big again whenever that time comes, our household has since downsized significantly.

 

[Buzz Saw]

I have your similar set up. My dhw circulating loop comes back to the pump, then the flat plate, and then back into the bottom of an 80 gallon storage tank. My dhw circ. loop runs 24-7, when the tank cools down, it turns on the circulating pump from the boiler , and then brings the tank up to temp. Simple design and I never have to wait for hot water. The 80 gallon storage tank is an electric water heater that I un-hooked the elements on and use the bottom thermostat to kick on the circ. from the boiler. I have a 50 gallon propane power vent water heater that we use in the warm months.

How big of a plate do you have in your setup?

Sent from my SM-G950U using Tapatalk

 

[dogwood]

Buzz Saw, I added a couple of links above on sizing the pump and flat plate.

Mike

 

[Buzz Saw]

Buss Saw, I added a couple of links above on sizing the pump and flat plate.

Mike

Thanks, I didn't even notice you made a post when asked.

Sent from my SM-G950U using Tapatalk

 

[Bob Rohr]

Thanks, I didn't even notice you made a post when asked.

Sent from my SM-G950U using Tapatalk

What controls the temperature in the tank. If the tank can run to boiler temperature you need a mixing valve.

What is the summer time back up?

 

[Buzz Saw]

Bob, I have not determined what will control water temp. I was thinking maybe an aqua-stat to turn on the boiler side pump. But I'm completely open to ideas at the moment. No decision had been made because I'm not sure how I want to go about heating the water..

Do you have any recommendations?

Summer time hot water I will use the electric elements.




Sent from my SM-G950U using Tapatalk

 

[Buzz Saw]

The HX is a 5"x12" with 20 plates.

Sent from my SM-G950U using Tapatalk

 

[dogwood]

An aquastat (or two) at the bottom of the tank can turn circs to both sides of the flat plate on, when heat is needed, and off, when the desired temp in the tank is reached. A mixing valve at the top of the tank keeps the water from getting too hot at the taps, no matter what the temp is inside the DHW tank near its upper reaches. That's where the tank's output originates, where tank temps are highest due to stratification, and also in my set-up where hot water flows in from the flat plate at high temps. Correct me if I'm wrong Bob. You know way more about this stuff than I ever will. Anyway, that's how I visualized and installed my set-up.

Mike

 

[jrod770]

How big of a plate do you have in your setup?

Sent from my SM-G950U using Tapatalk

I have a 26 plate. Provides plenty of hot water and best of all, it was free. One of the benefits of the family plumbing biz.

 

[Bob Rohr]

How fancy do you want to get?

This Taco smart plug is a clever way to control the recirc pump. I think most any pump can connect to it. No need to run that pump once the loop is up to temperature. In that Taco drawing there needs to be a thermal expansion tank on the cold after that check valve.

Usually a very small pump for the recirc, it only needs to move a few GPM, just enough to overcome the heat loss of the loop.

For the plate HX a solar differential control would work great. Sensor 1 on the boiler side of the HX, sensor 2 tab tank bottom. So that pump only runs when there is heat available, if the stove goes out, pump stops. You can also put a limit on it, say 150F.

With a single sensor aqua stat that pump would run until it hit setpoint, it would not know when there was no fire.