COMBİ BOİLERS & DİFFERENT APPLİCATİONS

tanklessman01

One quick reminder; when it comes to combi boilers you have to remember they're tankless units. Also on demand, meaning they adjust the BTU as needed. Therefore, they give you nice even temperature without much fluctuations in the space temperature thus heat everything slowly and evenly in the living space, not just the air.

Since there's very little water in the COMBİ it heats the water in the unit very fast. Misconception; "raise the temperature so it stays ON longer" NO! ,... All it does is reach to limit temperature faster and shutdown.

165-170 heating setting with 185 limit if you can adjust (some are preset) it..

You have to install a circulator pump on the supply side, down stream from the expansion tank and Air scoop but all the piping methods are pretty much the same for all the combi boilers, find the one easiest to follow and use it.

If you're using Air handler with hydronic coils you have to install a temperature control on the coil with a differential setting, usually 150 F to activate the blower and 50 F differential so blower removes heat from the coil. If you don't like the cool air coming out of the air vents set the differential lower till you find the temperature you like.

Domestic water side is little tricky and it gets trickier if the water pressure is low and worse if some bathrooms have smaller pipes and farther away. Water goes to where there's more flow. So, if 2 people using 2 different showers at the same time, one with less flow will experience cold shower. You need to test all that before suggesting tankless. You'll find your customers raising hot water temperature when that happens. All that will do is give highly fluctuating temperatures and chance of scolding.. That's why anti scold control is required by all manufacturers.

Key is to set the water temperature closer to shower temperature (120 F factory setting) so the COMBİ boiler or tankless water heater maintains it through out the shower without fluctuating and also shutting down due to high limit.

Recirculation loop with a small pump and temperature control works very well. Connect it on the cold water inlet with a tee near boiler. İnstall a check valve to direct water from recirculation pump to boiler only as these tankless units are activated with the water flow through the heat exchanger.

I hope this information can be helpful.

The Tanklessman

hot_rod

If you add a thermostatic mixing valve, required by 4 states, the heater needs to be set at least 10 degrees hotter than the required mixed temperature for the valve to work properly. Some valves require even more delta. Check the installation instructions of the valve