Reverse indirect hot water heater experiences, cycle times, and more

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Old 12-22-14, 05:59 PM
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Reverse indirect hot water heater experiences, cycle times, and more

Info on my system is 1.5 year old Crown Aruba 4 140k propane boiler on a 2400 sq ft ranch that was built in 1991 and it located in Northeast PA. Boiler run times are about ~4 hours/day with ~65 cycles/day. Thermostat is usually set at 70 in the evening and morning and 65 during the day and at night. I was not involved with the boiler selection as I just bought the house in May. I don't know what the average yearly cycles should be but it's at 13,179 in 1.5 years. There are currently 3 zones on zone valves at 95', 43', and 39'. I do want to split the large zone as the kitchen on the north side of the house is always cold. I want to replace the 50 gallon DWH with an indirect unit as the current water heater is ~20 years old. I also wanted to add a buffer tank but found the reverse indirect water heater and I am intrigued if anyone had any experiences with them. I was looking specifically at the Ergomax style as I like the idea of the buffer tank serving double duty heating DHW. Also is there anyway to down fire a propane boiler? I'm really just looking for longer cycle times so I can get the best efficiency out of it.
 
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Last edited by skalor; 12-22-14 at 07:41 PM.
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Old 12-23-14, 03:11 PM
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is there anyway to down fire a propane boiler?
The manufacturer should be the one to give that advice.
 
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Old 12-23-14, 04:20 PM
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I figured that would be the case, but I wasn't sure it was common or not. Thanks for replying though, I never seem to get much feedback.
 
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Old 12-23-14, 04:33 PM
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I was going to do that as a measure of last resort if the reverse indirect didn't work out. I also have a 500 sq ft. addition that is currently heated with a heat pump, so I want to add a zone for that too.
 
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Old 12-23-14, 06:33 PM
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I never seem to get much feedback.
Don't take it personal. I'm sure you see how busy this place is. And your system isn't 'broke', so we (I at least) try to get the 'broke' ones unbroke as priority. I bet if you asked your questions in the cooling season, you would get a lot more attention!

I want to add a zone for that too.
Looking at your photos, I see four what look like 3/4" zones coming off what looks like a 1" manifold. That's actually too many zones for a 1" job. If more than two zones call at a time, the velocity of flow in that manifold is going to be too high.

What you need to do is come up with a plan that will address all of the things you want to do at one time, like adding the indirect, adding the zone, etc. And this plan should probably include going to 1-1/4" manifolds at least.

You're talking about a buffer tank too... make sure that the ports on the buffer tank can support the flow that you need.

Your idea about cutting down that 96' zone into two is a good idea. Do you intend to make it two individual zones? Might not be a great idea... but I don't know the layout of your home, so can't say one way or the other. I think better to run a pipe from the farthest point and run parallel loops.
 
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Old 12-24-14, 05:53 AM
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Boiler seems pretty large for what size of house you have.

The ergomax, or similar, type of indirect is a good idea. The one drawback I have found is they tend to short cycle a lot themselves, and they require high boiler water temps. The latter is not a big problem for your CI boiler.

It can be hard for a bufffer tank to help a fixed firing rate boiler, as we all know the shoulder seasons don't require much heat output.

Having said that, I would try to find the largest well insulated storage tank I could afford. Fire the boiler into the tank using a tank mounted aquastat with a LARGE differential. As an extra measure I would install a motorized or injection style mix device and run the house off outdoor reset. That will help promote long runtimes, and a more efficient overall system.
I don't like the idea of storing energy, simply due to the cost to create the hot water. You need to gauge just how much the short cycles are costing you in terms of $$$, and wear and tear on your equiptement.
 
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Old 03-26-15, 08:59 AM
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I had a similar situation. I added a Lochnivar 80g SunSaver tank (4 ports), which serves as a buffer Tank AND as my DHW tank.

I have an external flat plate heat exchanger between the boiler & the tank, with a pump on the tank side, so the tank is fresh potible hot water.

The heating system takes heat as required from between the boiler & the flat plate heat exchanger.

My boiler burn cycles are about 1/2 hour long. When the boiler is off the heating system can draw heat back out of the tank via the flat plate heat exchanger in the reverse direction. Works Great

Alternate methods to pipe a buffer tank | 2014-10-22 | Plumbing and Mechanical
Much like figure 4

A Rheem ST120 or ST80 storage tank would work well.
 
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Old 03-26-15, 01:28 PM
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You mean figure THREE, don't you Bill? There's no HX in figure 4.
 
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Old 03-26-15, 06:53 PM
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NJT, No I mean fig4, except I added the flat plate HX just before the buffer tank so it also serves as DHW.

I haven't tried fig3 yet, perhaps on my next system. I have a new Taco 008-VDT that should work for moving the tanks water through the HX ASAP with a 5* D-T set to reverse mode.

I read a report from a guy in Europe on a Heat Pump system, that needs to keep temps as low as possible for max eff., his is like fig3 except he has a large flat plate HX (equivalent to a GEA 5x12x30plate) without the instant electric backup & he claims it works fine with tank at 50*C (122*F)

Possibly he had some way to pre-heat the cold in.
 

Last edited by Buffalobillpatr; 03-26-15 at 07:12 PM.
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