Noritz W/H as boiler and pumping

Mark Custis

a pump is a pump. Never tried heating with a Noritz but have used them for many DHW applications.

I have several trinity boilers in service and they are very clear on pipe and pump sizing. Flow and head laws must be obeyed.

You can not cram three pounds of BTUH in a one pound can.

Big Will

I have done it before and will not do it again

For a list of reasons but getting enough flow through the water heater is the biggest. In this case we take Noritz warranty calls in my area and this is a GC who did it him self. He had a grundfoss 15-58 running his boiler loop less than ten feet of 3/4 pipe and 11 90s. It was showing a flow of .5 GPM. I know this is not enough pump for this set up but that seamed a bit low. I switched to a 26-99 and the flow went up to 1.1 GPM. Barring a defect in the flow sensor in the water heater what would cause this. If you look at the charts for the Noritz and the pump in high speed I should get 3-4 GPM.

Note; I did check the inlet filter and we did back flush the heater.

Big Will

Check my math 1.1 Gpm = 9.2Lb per. minute. so one hour at 25 deg rise is =(9.2X60X25)13,800 Btu per hour at 1.1 gallons per minute . Thats assuming the flow meter is accurate. Like I said I have used Noritz water heaters before as boilers and this is the only failure in the water heater I have had so far. I don't think that it likes the funk that can travel through a hydronic closed loop system. The 26-99 should be able to move about 4 GPM considering the high head of the tankless and the piping on the primary loop. This would give me 49,800 BTU at the same delta T. I need to do a load caulc for the house.

tim smith

?? stuck check valve on pump. Just a thought, we have had

them hang up on us. Also you mention some pipe and fittings but what about the type of heat x and pd on it?? Tim

Big Will

about 20 feet of head at 4 gpm through the Noritz 631. The head loss of the pipe on the main loop is 1.5 feet of head at 4 gpm. I need to go back and check the flow sensor but even 4 gpm keeps the btu movement very low. I was thinking about having him pump in series to increase the head. He has my 26-99 in now I wonder what it would do if he put the 15-58 in with it. I know two 26-99 pumps would almost double the head but would a 15-58 just be in the way?

Big Will

Sorry Tim

I forgot to answer the check valve was removed from the 26-99.

Big Will

Did my heat loss

Love the Slant Finn program. Came up with just under 40 KBTU for design day (32deg). So 4 GPM carries almost 50 KBTU.