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sarlaud 02-01-2010 08:38 AM

Flow switch use in Hydronic Heating System
I have a Taco ZVC405 Zone Valve Control on a hot water boiler. I want to incorporate a flow switch in a loop that involves a flat plate heat exchanger with a dedicated circulator. I want the flow switch to activate the boiler when flow is detected on the other loop thru the heat exchanger that has the liquid to be heated. I was going to wire the switch in series to the extra dry contacts. If I run wires from the end switch contacts in the zone control to the boiler, will this activate the boiler when the flow switch activates the circulator?

beenthere 02-01-2010 09:08 AM

It won't heat unless the zone panel gets a call for heat that way.

sarlaud 02-01-2010 09:14 AM

how would I get this to work? Will the circulator come on when flow is sensed? If so I could just let the boiler activate as temp drops? Any other suggestions on how to do this?

sarlaud 02-01-2010 09:21 AM

so my liquid to heat is potable water..... should i use a temp switch or let boiler just come on?

beenthere 02-01-2010 09:24 AM

Is there going to be a zone valve on the boiler side of the heat exchanger?

If you want the flow switch to activate the boiler. You would wire it up parallel with the end switch that currently runs the boiler.

beenthere 02-01-2010 09:33 AM


Originally Posted by sarlaud (Post 392679)
so my liquid to heat is potable water..... should i use a temp switch or let boiler just come on?

The potable water will need a tempering valve to prevent scalding.

If its potable water. You'll need to maintain a boiler temp. Or you will be waiting a long long time for your hot water in summer. And could lose it in winter when one or 2 heating zones open at the same time.

Although more expensive upfront. An Indirect water heater would save a lot on fuel for domestic/potable water heating.

sarlaud 02-01-2010 09:35 AM

I guess I need guidance on best way to do this! I have no set plans yet. I am in design stage. Maybe I should gve back ground info. I have a slantfin libery 30 hot water boiler with domestic coil. I have 4 zones of heat currently. I have a spare zone in the control. I want increase hot water supply to house using the flat plate exchanger as additional hotwater volume. I was thinking using flat plate in series or paralel and increasing my hot water supply to 3/4" from existing 1/2" with my honeywell mixing valve to limit and control temp. I was thinking that if the boiler came on when flow was sensed by the flow switch, I wouldnt have lag until boiler came on by temp decrease. What is your thoughts on this?

sarlaud 02-01-2010 09:41 AM

yes that was my first thought, the indirect heater. I was just throwing out another option if it would work. My original thought was the indirect and then turn on my beckett heat manager to let the manager control the boiler output. Then in summer the manager could contol firings and lower my cost and not have to have boiler maintain high temps. right now i have it turned off because to much lag time for hot water and it wont give enough water temp at point of use.

beenthere 02-01-2010 09:49 AM

You will increase your hot water supply by a little. How much depends on the BTU size of the boiler. And what our current tankless coil is rated at.

A 200,000 BTU input 80% efficient boiler(160,000 BTUs output). Can heat 4 gallons a minute at an 80F temp rise. Or 3.2 gallons a minute at a 100F temp rise.
This would require your boiler temp to be at 200F for the tankless coil to do this.
With a plate heat exchanger in parallel. it may only require the boiler to be at a temp of 160F.
With the majority of the water going through the plate heat exchanger.

But, your still limited to the boilers BTU output restrictions.

Another semi economical way to increase hot water supply volume is to use an aquastore tank.

It can be a regular electric water heater. just connected to that it uses the boiler to provide the hot water.
Then its thermostat turns a bronze circulator on. And circs water through the tankless coil to keep hot water in the tank. It can be piped that a " line feeds it, and the tankless coil. So that you have increased volume.

sarlaud 02-01-2010 09:59 AM

aquastore sounds like a good way to go or the indirect. Do you have schematics for the aquastore or can I get it online by searching aquastore? Thank you for your help. I follow alot of your threads to other problems for ideas. Thanks again! if you got schematic that would be great!

beenthere 02-01-2010 10:04 AM

I don't have any for an aquastore.

I might be able to draw one up later today though. And have it show both the piping and electric hook up.

beenthere 02-01-2010 07:02 PM

1 Attachment(s)
Here is one method of piping.

sarlaud 02-02-2010 06:12 AM

Thanks for the schematic! How is the circulator controlled? Is it constant running and temp controlled by mixing valve?

beenthere 02-02-2010 06:58 AM

1 Attachment(s)
If you use a regular water heater. Just use the lower thermostat to control the circulator.

Instead of connecting 240 volts to the water heater.
You just supply 120 to it, and bypass the upper thermostat, and bypass the lower element.

Here is how I do it.

sarlaud 02-02-2010 07:03 AM

Thanks beenthere! I am all set now!:thumbup::whistling2::yes:

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