Moen shower valve--replaced cartridge, still no hot water

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The Moen shower valve is now working fine. After the hot water tank was replaced, the main water valve was turn off and on which caused the calcium clog on the hot water side line to be flushed out and in effect the hot water side water flow became stronger and hot water now comes out normally.
Thank you all for all your input and suggestions.

The new hot water tank installed in our house is the Bradford White Corp., Defender Safety System, Energy Saver, Model # CSW2TW50T10FBN-457, Type: Combi, Cap. 45.0/37.5 (U.S./Imp. Gal.) Rec 56.8. Added to the 3 holes on top, there are two holes on one side of the tank. One labelled supply to heating system and the other return from heating system. The furnace we have uses hot water with blower used to blow warm air via pvc pipes throughout the house. Right now the furnace share the hot water supplied to the hot water line to the house coming out from the top of the tank. The problem with this is when the furnace is running, there is no hot water left for the shower and other taps in the house. We have to shut down the furnace before we can use the shower. My question is: Can the furnace be connected to the hot water supplied on the side of the tank so it is in effect separate from the hot water line of the house. Maybe we can use hot water on the furnace, shower and faucet at the same time.

I gotta see some pictures of this. What brand and model is the furnace? And is the furnace heating the water, or is the water tank heating the water? Please post some pics of your epuiptment, as there are many different types.

Sorry I got back only now. I got busy and had to look for a camera.
Attached are the pixs. Like I said, the Furnace is sharing with the hot water being supplied to the house. The furnace does not heat the water. When the furnace turns on it takes over and only a little is left for the hot water line for the showers and faucets. We have to turn off the furnace before we can use hot water for the shower and faucets. There is it looks like a metal radiator inside the furnace and the blower blows the warm air throughout the house. The air coming out is not really hot, just warm.

Attached Images

	PixCombiCombiWaterHeater1.pdf (689.5 KB, 30 views)
	PixCombiWaterHeater2.pdf (713.8 KB, 24 views)
	PixCombiWaterHeater3.pdf (676.0 KB, 20 views)

You surely could hook the furnace supply and return to the side of the water heater, but Im not so sure it will make any difference. The real problem is that you dont have enough btu's to keep up with the furnace and domestic hot water demand. Give the side ports a try, and see if things improve, just dont hold your breath.

Couple questions. What size and btu was the old water heater? And when you say no hot water to other fixtures when furnace is running, do you mean no flow out of hot water taps, or just no hot water (cold instead with good flow)? With what I see in your pics, you should still have good flow at the fixtures, just not hot water due undersized water heater.

Cold water is coming out instead of hot or warm. The previous water tank was 80,000 BTU. I am not sure about the new one installed by the contractor. He said he had a hard time looking for the correct tank because of the sharing of the hot water with the furnace. It actually is a big job separating the connection. Plastic or is it pvc pipes are currently used.

The new tank is rated between 60300 and 67000 btu all depending on your elevation, according to the tag in the pic. So lets say you are above 2000ft elevation wise in your location. This means you just lost 20000 btu with the new water heater. This could be just enough to cause your issue. Time to get the plumber back in and size the heater correctly, or maybe add another water heater or boiler for the heating equiptment. Sounds like they just hoped the new water heater would do the job of the old one, which apparently it isnt. Wish I had an easy cheap fix for you, but there just isnt one out there (that I can think of anyway). Wishing you the best of luck, and please do keep us posted on what the outcome is.

Actually, even on the old tank we had the same problem of turning off the furnace to be able to get hot water on the water taps and shower heads. I thought, fortunately, the old tank leaked so it gave me the chance to buy my own instead of renting. When I saw the new tank and the two holes on the side, I thought maybe if the furnace is connected separately on the side of the water tank and the house hot water supply line is connected on the top of the tank source of hot water, maybe it will fix our problem of shutting off the furnace in order to get hot water.

Hey, I still think its worth hooking the furnace lines to the side ports. It may iimprove the situation. Im more than a little surprised that the installer didnt do that to begin with. The plastic pipe you have between the water heater and the furnace is called wirsbo pex and has wirsbo fittings and rings. Good quality stuff (imo). Just need the correct tool to install it. Really shouldnt be too big a job for a plumber, and well worth a shot. But, like I said, it really comes down to lack of btus to keep up with domestic hot water and furnace demands all at the same time. There is something a person could do, but it would cost a bit, and it may not even work correctly. If a plumber were to turn the temp of the water heater all the way up, it would give you a better chance of the furnace heating better, and also could leave enough hot water for domestic use. However, in this case, a tempering device would have to be installed on the domestic hot to keep from scalding temperatures, and tempering devices arent cheap. Have you considered adding a seperate heating device for the furnace? Any way you look at it, its probably gonna cost more than you would like to spend, but its hard to put a price on comfort and reliability. Contact some pluming companys, have them come out and give you some suggestions and quotes and see if they wont work out a payment plan. As you know by now, this settup was done incorrectly from the day it was originally installed. I wouldnt put too much blame on the recent installer, as it sounds like they were just trying to replace water heater and get you up and running. I would, however, suggest trying a different company, one that will look further into the complete system and come up with a true sollution. Just keep in mind, this may run into some $$$. Good luck, and please let me know what you decide.