Help me get my DHW working

[Rockey]

Ok, so we moved into this house about 3 months ago and I recently found out that the DHW is not working. Here is what I understand. The circuit is there, with a B&G pump (third circuit from the left in the pic) but the pump has never been wired up ( fresh tin on the wires and no conduit run) The heat exchanger is in place and the Bradford White water heater has been in the house since day 1 (14 years) I dont know why they went through all the trouble to do this but never wire the pump up and run thermostatically control it??? Furthermore, once the circuit is working then how does the water in the water heater tank then circulate through the HX? Does it really on convective flow? Im confused on this, so Im hoping there are a few guys here that can help me understand what I need to do to get this working correctly. Ive asked a lot of hvac guys but none that are familiar with boilers and DHW.

 

[STIHLY DAN]

Not enough pics to tell you what exactly to do. That is a tube in tube heat exchanger. There should be 2 pumps running for this to work. 1 pump for the boiler circuit of the tube in tube and the other for the heat exchanger in the tank.

 

[Mike Fromme]

The heat exchanger can work on convection or as Dan said use a second pump to circulate the DHW. The second pump would not need to be very big. But it would have to be stainless.

It doesn't look like there is a second pump though?

Again hard to tell from the pics but I don't think you would get much or any convection through the heat exchanger the way it is plumbed.

 

[Mike Fromme]

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[Rockey]

Thanks guys. I see what you mean now. I beleive my Hx needs to be reconfigured so that it can setup a convective flow of water. I'll see about getting a plumber to get this done.

 

[maple1]

If you're getting some replumbing done anyway, I might also ask the guy (if he's any good at the hydronic stuff) about getting rid of all those circulators in favor of a single variable speed one (Alpha). We can't see what else is going on there & it might be pointless - but shouldn't hurt to ask. Would likely require adding zone valves.

 

[Rockey]

If you're getting some replumbing done anyway, I might also ask the guy (if he's any good at the hydronic stuff) about getting rid of all those circulators in favor of a single variable speed one (Alpha). We can't see what else is going on there & it might be pointless - but shouldn't hurt to ask. Would likely require adding zone valves.

Interesting. Ill see how much he knows about hydronic systems. I assume your talking about the Grundfos Alpha series.

 

[maple1]

Yes.

Those are curious pics. Is that other big red thing another circulator? And looks like 3 of the other ones are valved off? Looks like something that could be tidied up by someone who knows their stuff - maybe.

 

[Rockey]

Correct, there is a 1/2hp circulating pump that brings the water from the boiler, then each circuit from there has its own pump and valve. Im curious if each circuit needs a valve since the circuit pump controls the flow.

 

[woodsmaster]

Yes a side arm ex changer can work with convective flow on the domestic side but not sure yours will being partially above the water heater. Mine works with a convective flow just fine ,but a pump on the domestic side will help with recovery time especially on a smaller water heater with a large demand.

 

[woodsmaster]

the less elbows and restrictions the better when trying to heat your DHW without the additional pump.

 

[BHetrick10]

I dont like seeing zones plumbed that way. You usually end up with ghost flow issues. As mentioned above could easily be converted ans save on electricity. The zone valve would also eliminate Ghost flow. I have plumbed side arms in a few different ways. One way is a circ on both sides ran off a sensor. Could use lower T stat on WH if always going to be heating DHW with wood. I hook up a lot of OWB that need the water always moving through them to not get hot/cold spots, on those we plumb the primary loop from the Boiler in through the sidearm and let the water from the WH thermosyphon through the side are with a mixing valve on the domestic side. Quite a few other ways..... I do not like to use a circ on the WH side just more electicity used, however if you have storage and a primary loop that isnt always moving water this wont work. If you do go with a circ on both sides I do not like to use a side arm, Not as much heat transfer area as a plate exchanger.

 

[maple1]

I dont like seeing zones plumbed that way. You usually end up with ghost flow issues. As mentioned above could easily be converted ans save on electricity. The zone valve would also eliminate Ghost flow. I have plumbed side arms in a few different ways. One way is a circ on both sides ran off a sensor. Could use lower T stat on WH if always going to be heating DHW with wood. I hook up a lot of OWB that need the water always moving through them to not get hot/cold spots, on those we plumb the primary loop from the Boiler in through the sidearm and let the water from the WH thermosyphon through the side are with a mixing valve on the domestic side. Quite a few other ways..... I do not like to use a circ on the WH side just more electicity used, however if you have storage and a primary loop that isnt always moving water this wont work. If you do go with a circ on both sides I do not like to use a side arm, Not as much heat transfer area as a plate exchanger.

Yep. I started out with just a sidearm. That didn't work well at all when trying to heat DHW from storage when not heating, stratification disappeared in short order.

The Ecocirc I have on the DHW side uses next to no electricity, is super compact and has variable speed so you can dial it in pretty good. It's the E3 series, I think model 4v/btxyz. With just the sidearm & no pumped DHW I could only go maybe 2 days between burns, adding the FPHX, Ecocirc & swapping the 15-58 for an Alpha on the boiler side I could go 7 days. Sidearms work well and with great simplicity with a constant hot (160+?) supply - but without that, a pumped FPHX is the way to go.

 

[woodsmaster]

I've been running a side arm for a couple of years and have 6 people taking showers in a row, sometimes. it works good, but I have water flowing threw the boiler side of it 20 Hrs. a day. Its a 80 gallon WH. I can run my storage down to 130 and still have hot water, but it has plenty of time to recover before our showers. I dont usually need real hot water for heating so stratification isn't a huge deal for me.

 

[Rockey]

You guys that are using a sidearm, do you have a circulating pump on the domestic side?

 

[maple1]

I didn't at first, and it worked great in the heating season when the boiler side was regularly hot. You need to get it situated right though. Mount as low as possible, and with as little horizontal piping run as possible on the dhw side.

 

[woodsmaster]

No, no pump on domestic side. works fine, family of 6

 

[woodsmaster]

Replumb yours like the video shows and it will work fine. Only way it will work as plumbed is with a pump on domestic side.

 

[velvetfoot]

I'm curious, what's the boiler setup? Wood? Storage? If gas, why bother since the water heater is gas?
edit: stupid observation, but it looks like that pump is valved off.

 

[Rockey]

I'm curious, what's the boiler setup? Wood? Storage? If gas, why bother since the water heater is gas?
edit: stupid observation, but it looks like that pump is valved off.

Its a wood boiler, no storage. Im going to have it connected like the video suggests for better convective flow. Ill update when its finished.