Installing a plate heat exchanger

hot_rod

The service valves that are available for tankless water heaters are ideal for HX installation. 1" is a very common connection size on plate HX. This tankless valves include a 3/4" bushing also.

With a service valve you get a shut off, 1" union connection, flush port with hose connection, and a straight or angle connection option. The side port is typically for a pressure relief valve when used on tankless heaters.

On the domestic side piping you can easily run a de-limer. Valves and Union connections on the boiler side allow you to remove the HX for service.

In some cases it may be easier to take the HX to a radiator shop and let them flush and clean both sides to bring it back to optimum performance. Unions and valves on all 4 ports make this an easy task.

It seem there are issues with the Combis that use a shuttle valve for DHW. It is fairly simple too build a HX external. A pump, HX and flow switch to enable the DHW function on the boiler.

Plenty of options for sizing plate style HX. This one supplies the Peppermill Hotel in Reno, geothermal wells heat and supply DHW for the 1600 rooms pools, restaurants, etc.

PeteA

@hot_rod awesome info and great timing as always Bob
I may have to look into this method of getting the hot water restored to my house since its basically what goes on inside the combi but now it would be connected on the outside and easy to access and maintain. I will look at the wiring diagram for min and see where the flow switch is connected because if I can tap into that then it will get the signal through the normal circuit then if I tap into those wires with the external flow switch.
I don't imagine you would nned a big pump for this set up because right now the way the combi diverts the water through the internal HX is via the 3 way valve and internal pump so I don't believe a lot of flow would be needed to just feed the external HX since the internal pump would be circulating the heated water in the near boiler piping.

I see another project in my near future, wife is going to kill me.

dko

This is great
The shuttle valve is probably the #1 replaced component in these combi units as well.

Also, what caleffi valve is that? I don't think i've seen it before.. similar to the tankless wh isolation valves but not quite..

hot_rod

Many of the mod cons have extra S&R connections, so it is super simple to add a pump and HX.

Sika is another brand of flow switch available down to .35 gpm. This is what I have in my shop. Piped with 1/2" as it is for a hand sink and HW outside faucet.

We just added that tankless valve kit to the catalog. It is a 290 series in several configurations, including with the Anglemix