# Burkay recirculation setup.



## jim285pro (Sep 3, 2020)

Don’t see many systems like this in my area. Recently got a new customer with several Gyms in town. Was looking over one of the systems. two Ao Smith Burkays feeding a 250 gallon storage tank. There is no aquastat on the tank to control the temp. The recirc just runs constantly and the boilers fire pretty steady and run in short bursts. Couple questions, Do the boilers just heat until the stat on the boiler is satisfied? Is this an acceptable setup? Getting some mild water hammer out of one unit, The expansion tank is bad but I’m not sure if that’s the cause of the hammering. Everything is piped correctly according to AO Smith drawings but the lack of a stat on the tank had me concerned. Thoughts?


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## skoronesa (Oct 27, 2015)

You don't need a t-stat on the water heater as it will just reach up to 180f, the same as the boiler. Yes, the boiler burner fires when the aquastat temp in the boiler drops, it gives power to the burner control. The burner runs until the aquastat is satisfied. The aquastat will have a differential you can adjust, I think the usual swing is around 5f.

The water heaters can safely be at 180f because there is certainly tempering valves installed to limit the hot water temp.

I'm not an HVAC guy, this is just what I happened to know from having to check this stuff out sometimes, and fix my own stuff.


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## Sstratton6175 (Jan 10, 2021)

We work on plenty of these systems typically with this set up you’d set the control on the boiler to 140°-150°ish and mix down the water coming out of the tanks to 120°-130°. With the pump running constantly it will keep the tank within the desired temp. You can also run the pump off of an aqua stat in the tank set at 140° and run the boiler at 180°. IMO this is a better/more efficient way to run the system but a lot of installers set it up that way yours is set up because it’s easier/cheaper to set it up that way. Also replacing the expansion tank should help with the hammering.


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## jim285pro (Sep 3, 2020)

Thanks. Every piping diagram I saw called for the tstat in the tank to regulate when the boilers and pump would run to heat up. In my mind it seems like your temp would fluctuate a lot more just reading the boiler temps rather than the storage tank but I could be wrong. Yes there is a mixing valve to temper it down to 120 but it’s in need of a rebuild. Prob gonna be a good customer but I’m weeding through all the hack work they’ve had for the last 20 years.


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## skoronesa (Oct 27, 2015)

Sstratton6175 said:


> We work on plenty of these systems typically with this set up you’d set the control on the boiler to 140°-150°ish and mix down the water coming out of the tanks to 120°-130°. With the pump running constantly it will keep the tank within the desired temp. You can also run the pump off of an aqua stat in the tank set at 140° and run the boiler at 180°. IMO this is a better/more efficient way to run the system but a lot of installers set it up that way yours is set up because it’s easier/cheaper to set it up that way. Also replacing the expansion tank should help with the hammering.


Keeping the boiler at 180f instead of say 140f is less efficient for a couple reasons. The boiler itself will radiate more heat into the room, which if it isn't winter will have to be made up for by the air conditioning. Also, as the boiler temp rises the burner flame will transfer less heat into the firebox wall, not sure how much less but it will be less. You'll have a higher flue temp, more heat just going up the chimney.

And yes, you'll have more fluctuation without an aquastat on the water heater itself but if they've gone 20years without an issue the fluctuation must be acceptable.


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## Toli (Nov 7, 2015)

The pump running 24/7 is the old school way of way of thought- Get the heat out of the boiler and into the tank where it can be used. This can cause short cycling of the boilers and fluctuating storage tank temps. But if the hot water is all tempered, the fluctuating tank temps might not be noticed.

Thee should be an aqua stat in the storage tank. This is the brain of the system. Aqstat calls for heat, pump starts, makes flow switch (if present), pilot, burner, Aqstat ends call for heat, boiler shuts down, thermal balancer runs pump for a bit then shuts it off. Fairly simple system.


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