Indirect water heater check valves

[jrc2905]

I am looking for some input on the placement of flow check valves on an indirect water heater when used on a boiler system with zone valves.
I was on a service call the other day and the indirect water heater was returning water to the boiler return and also sending heated water to the heating loops because the zone valves were open on a call for heat. The circulator was on the return. There was a check valve on the feed to the indirect water heater. I was thinking that the one inch return should also have a check valve to prevent water flow to the heating loops, is this really needed and what would be the recommended type of valve. Is this overkill?
I have seen many indirect heaters with no check valves at all. Thanks.

[simpleman]

Most time when you have zone valves on your supply there is no need for a check valve on the returns..

However I have seen some returns thermal cycle when they return above the boiler.

In your case it sound more like you need to add a relay that will de-energize the zone valves when ever there a call for the indirect.

I could only assume that the call came in as,the tstat are
over riding and we seem to not have enough hot water in the
winter months.

[jrc2905]

The call was no heat due to a blocked nozzle, the boiler was cold and I noticed on start up the indirect was calling for heat. I put my hand on the return from the heating loops and it was hot but the supply to the zones was cold.

[Panama]

Originally posted by simpleman

... I have seen some returns thermal cycle when they return above the boiler.

The return from the indirect must drop a foot or two below the supply. Then if there is a check valve on the supply to the indirect you won't have any problems.

[tinknocker service tech]

if the water heater was calling for heat and the bolier was not working but the circulator was and all zone valves were open the hot water you were feeling was from the heater as the supply was beeing fed into the tank and picking up heat from the hot water in the tank and coming out hot. as the tank cooled down the return would also
inderect should be on its own circulator with check valve.
since mine is on zone vzlves and works fine i shouldnt say much heheh

[jrc2905]

I spoke to the factory tech line and they said no one has brought this issue up before and not to worry about it a check valve on the indirect return is all that is needed.

[nutshell]

Prioritize the hot water demand.

[jrc2905]

It is.

[GradyWhite244]

Are you sure the hot returns were not simply due to conducted heat?

[beenthere]

Sounds like the indirect is being used as a buffer tank, and the returns were as grady said, being heated by conduction.

[jrc2905]

Not conduction, the heat was too hot and had traveled too fast.