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A standard circulator, like a Grundfos UPS15-58, is what’s used for the injection pump. The mixing control (usually a Tekmar’s 356) controls the speed of the pump.

With the return sensor added, the control provides boiler protection as well as ODR.

As hot_rod mentioned, Buderus boilers are made from a specially formulated cast iron that’s actually flexible. They can withstand return water temperatures as low as 106* without damage from thermal shock. However, you don’t want to continually run it that low because of flue gas condensation. A constant temp of 140* should be sufficient. You don’t need 180* unless it’s being vented into an over sized masonry chimney or when the indirect needs quick recovery.

OP may want to consider while tearing up the kitchen taking that radiator out, sandblasting and repainting. It is a very nice radiator. I personally have never been a fan of the white paint since it shows dust an dirt so much…

@amaiale , take a pic from the end of the radiator so we can see what type and capacity are the sections it uses. Also how tall is it?

perfect application of a Thermostatic radiator valve. Turn up or down as you need or as your cat prefers. Just swap the valve, much easier than a new radiator.

Edit: Except that’s not the problem you are trying to solve! Less radiator not just less heat.
🤣

if the original installation was not designed properly, lack of adequate loops or well for example.
Maybe the load is larger than anticipated?

Or the installation was botched?

new replacement or repairs may not get what you expect

I would do some number crunching. A load calc as step 1

The 26-99 would easily support 3x what you have and is grossly oversized (though would modulate). Even the 15-58 will do nearly double what you have without issue. The Alpha 15-58 and two 3/4" Sentry zone valves would do a heck of a job here but if cost is of any concern, one UPS15-58 on each zone would be a great fit as well.

I typically run my loops 250ft in residential homes and use 32% glycol, and a single 15-58 starts to max out at about 14-15 loops. I do typically use the Alpha 26-99 with zone valves and/or actuators when it's 3 or more zones and 15+ loops, but something like yours would be two UPS 15-58 (if a budget build) or an Alpha 15-58 with two zone valves.

find a different contractor