Help with a flat plate HX

John_108

I have a customer with a Raypak gas boiler with two baseboard zones and one zone with the heat exchanger for domestic hot water. The system is piped primary/secondary piping.

The Problem: Water temp fluctuates because there is no mass in the boiler. The heats up very fast then cycles off. During this time the water temp will drop down below 100 degrees. There is an aquastat strapped to the return line to try and maintain the water temp in the heat exchanger. Owner has been using it this way for about four years.

I was thinking of installing a small indirect but it would have to be very small as this system is in a closet in a hallway, or is there a better way to control the system to maintain a more constant temp. There is an anti-scaldvalve on the domestic water side. Are there any indirects out there that could be hung from the ceiling and that are small?

Any suggestions or advice would be greatly apprcciated.

hot_rod

some of those

Raypaks were available with modulating gas valves. That helps match the output to the load, and smooths out the short cycles Check with the raypak rep to see if it coulf br changed to the modulating valve.

How closely to the load is the boiler output? Could the boiler be oversized by a bit?

Keep an eye on the HX in those boilers when they short cycle, like that. The HX needs to get up above dewpoint before it cycles off or condensation and sooting may occur.

hr