Pressure Drop Between Combi Boiler and Shower

[Peregrine]

With a pressure gauge at the plate heat exchanger outlet , I am having a significant pressure drop between the combi and first floor shower head when there is a call for DW. The combi is on the first floor.The water pressure at the outlet of combi is 65 lbs static. With the pressure gauge at the combi, when the shower is turned on, the pressure drops to 30 lbs on the first floor for both hot and cold water. Then with the first floor turned off and the second floor shower turned on, water pressure at the combi is 47-50 lbs for the second floor. There is even a greater pressure drop if the first floor shower is turned on with the dishwasher at the same time; I get a low water condition.. The taps on both floors register 52 lbs at the combi when they are on. the spout and shower cartridge Moen 1222 have been replaced . The flow at the combi is 6gpm and the flow at the tub is 2.8 gpm. The pipe size is ¾” out of the combi to the ¾” thermostatic mixing valve and ½” to the shower valve. I don’t know what the pipe size is to the dish washer. Feedback please. Thank you and have a great day.

 

[GReynolds929]

Well or city water supply? What is the pressure coming into the house? What size pipe feeds the house? If it is happening on both hot and cold it is most likely not related to the combi. Brand and model of the combi? Any pics?

 

[Peregrine]

Well or city water supply? What is the pressure coming into the house? What size pipe feeds the house? If it is happening on both hot and cold it is most likely not related to the combi. Brand and model of the combi? Any pics?

City water. 120 lbs . 1 1/2 into the. House to 3/4 before PRV set at 70 lbs. into the Lochenvar nkc150 combi . The pressure After the combi at plate HX outlet is 65 lbs up 1 floor from city water inlet. The pic in the upper right corner is the outlet After the combi plate HX where the pressure reading is.then to the mixing valve on the way to the shower. There are no leaks. Thanks for looking.

 

[Peregrine]

Well or city water supply? What is the pressure coming into the house? What size pipe feeds the house? If it is happening on both hot and cold it is most likely not related to the combi. Brand and model of the combi? Any pics?

It comes in from the street across the plate HX and out to the house. The outlet is where the pressure is read. I dont think it is to do with the combi. A 30 lb drop in pressure seems excessive? Thank you

 

[GReynolds929]

30 psi does seem excessive, especially with the size of the house feed and incoming pressure. Since it's seems to be happening on both hot and cold, First place I would check is the PRV, it could be clogged or acting up. Some have a strainer that can be cleaned.

 

[Peregrine]

30 psi does seem excessive, especially with the size of the house feed and incoming pressure. Since it's seems to be happening on both hot and cold, First place I would check is the PRV, it could be clogged or acting up. Some have a strainer that can be cleaned.

Thank you