Trouble with new electric water heater install.

DudeAbides

Hi knowledgeable plumbers, first timer here collecting bruises on the way to eventually having a clue (hopefully).

I'm trying to install a new electric water heater in series with an inadequate oil boiler. I've got it in place and connected to the water system, but get no flow when I try to use the hot water in any faucet (cold still works fine). At first I thought the tank just hadn't filled up and was taking forever, so I let it continue to fill overnight (with the faucets open on hot), and still no flow this morning.

I've tried releasing the internal pressure via the TP valve, I've tried clearing air lock in the pipes, no improvement. If I turn the cold water on with one faucet, the other (with the hot turned on) will flow then cease to flow when I turn the cold off.

I really don't understand where the block is... there are no signs of leaking anywhere and my building water pressure is quite high (haven't measured it personally but the water company said it should be ~100 psi).

Here is a pic of the install: https://i.imgur.com/PcAqIE8.jpg

Thanks for any advice!

heathead

Question is the tempering valve installed in the right direction? It has a check valve and if it the wrong way no flow? I would see if you have flow out tank drain first. If yes then move to the tempering valve. Did the water heater have flow checks that you installed?

STEVEusaPA

First, post the pic on this site.

Second, you need a bronze or stainless steel circulator from the coil to the storage tank. If you are only drawing from the tank, get rid of the mixing valve on the boiler.

Here's your mess, I mean work.

Ironman

Why two tempering valves and what’s smeared on the fitting of the one on the boiler?

You should only have one on the boiler.

DudeAbides

heathead said:

Question is the tempering valve installed in the right direction? It has a check valve and if it the wrong way no flow? I would see if you have flow out tank drain first. If yes then move to the tempering valve. Did the water heater have flow checks that you installed?

I just double checked and it is installed correctly. The input/output stems came pre-installed on the tank.

Yes, it is most definitely a mess- at least I can only lay claim to a portion of it
I think you are right and I should just cut the boiler out entirely... I guess I was concerned that if the boiler was on but the domestic water function of it was not hooked up with flowing water that it might damage it somehow. I can't get a plumber here for weeks and I'm trying to get my tenants a satisfying shower (the boiler wasn't producing sufficient hot water for more than a 3 minute shower) so I was hoping this would give them that until a more refined solution could be applied. When I finally get the service done on the boiler (which the previous owner probably hadn't had done in a decade) and it turns out there was some issue dramatically reducing it's capacity for hot water production, I can switch it back over and I'll have a spare hot water heater to replace the aging one that services my shower upstairs

Ironman

The hot water coil in the boiler may be plugged, but you also need to eliminate the tempering valve on the tank; it’s unnecessary and won’t function with two sources of hot water feeding it.

EdTheHeaterMan

There are several ways to pipe two hot water sources so one will assist or supplement the other. I posted this as MY BEST WAY. so you can alternate which water heater is the primary and which is the secondary. By using this valve set up you don't lock yourself into what the best idea TODAY is. As times change and energy rates change you have options in the future.

https://forum.heatinghelp.com/discussion/comment/1693154#Comment_1693154

The arrangements shone in the diagram are on two tank type water heaters, but you can substitute your tankless coil as one of the DHW sources.

Have you had the tankless coil maintained regularly? If not, then it is probably fouled up inside the boiler. A good cleaning and flushing may solve your issue.

mattmia2

Since you are only sending hot water from the boiler to the mixing valve in the water heater it is probably shutting down because it can't get cold water to produce a safe temp mix.

Like others asked, do you get flow from the drain valve of the water heater? Also turn off the electrical until you get it figured out so you don't heat the elements in the water heater dry and burn them out.

Larry Weingarten

Hi, @DudeAbides , Do let us know what steps you take. Also, we can certainly help you with a sequence for troubleshooting and finding the flow problem/s.

I like the idea of bypassing the boiler as it likely needs work. If the hourly hot water usage is covered by the size of the new heater, than you shouldn't need that mixing valve at the tank. It would help with a small tank, holding water that's much too hot to use directly.

Yours, Larry

EdTheHeaterMan

mattmia2 said:

Since you are only sending hot water from the boiler to the mixing valve in the water heater it is probably shutting down because it can't get cold water to produce a safe temp mix.

Like others asked, do you get flow from the drain valve of the water heater? Also turn off the electrical until you get it figured out so you don't heat the elements in the water heater dry and burn them out.

This may be correct. Here is a way to pipe the system with my "BEST WAY" using only one mixing valve.

Mr.Ed

Ironman

I don’t think that will work, Ed. You’re feeding two hot lines to the mixing valve on the tank and in this scenario, the one feeding the “cold” inlet to the valve would actually be warmer than the one feeding the “hot” inlet.

Those mixing valves are designed to have at least 40* cooler water at the “cold” inlet - if memory serves me correctly.

kcopp

Ditch the boiler mix valve. Two mix valves in series will not work. (ask me how I know) You are prob best to by pass the boiler period but if you want to get a little boost you can try that...
Set the water temp in the tank to 140F then mix down.

DudeAbides

Hi everyone- thanks for all the input! It was a busy day, but I finally got it working. At first I was convinced it was airlocked, but after several tries at burping various faucets in different orders I just cut the boiler out entirely and now it's working just fine. I suspect the mixing valve was going bad which was probably also causing the poor performance of the boiler... hopefully that will be confirmed when I have it serviced in a couple weeks and I can have the option to put it back in use if I wish... then I'd have a spare electric tank to replace the aging one currently servicing the upstairs!

DudeAbides

Ironman said:

Why two tempering valves and what’s smeared on the fitting of the one on the boiler?

You should only have one on the boiler.

Yeah I guess I didn't need the second one if my original plan was to keep the boiler in the system... but it worked out having the second in the end. ...and that's discoloration caused by a leaking dishwasher hose above that was giving the whole boiler system a nice shower whenever it was used. The previous owner was an absentee landlord... and it shows everywhere. But hey, improvements one job at a time!

mattmia2

DudeAbides said:

At first I was convinced it was airlocked, but after several tries at burping various faucets in different orders I just cut the boiler out entirely and now it's working just fine.

A potable water system can't be airlocked, there is more than enough pressure to push the water through in a residential height building.

Was there flow of hot water but it wasn't hot enough before or was the flow low without the water heater? I still think the lack of cold water to the mixing valve on the water heater was putting it in scald protection lockout.

DudeAbides

mattmia2 said:

A potable water system can't be airlocked, there is more than enough pressure to push the water through in a residential height building.

Was there flow of hot water but it wasn't hot enough before or was the flow low without the water heater? I still think the lack of cold water to the mixing valve on the water heater was putting it in scald protection lockout.

There was plenty of flow before I added the electric tank, the problem was the duration of hot water... it was nice and hot for about 3 minutes then a pretty quick slide down to tepid. I should note that the red pex going into the system in that picture is misleading- I used red because I assumed the boiler would be running and putting hot water out to the tank; however, It wouldn't work even when the boiler was off and the water moving through it was all cold.

EdTheHeaterMan

@DudeAbides...Now that you have a separate hot water source, Did you tell the heating boiler to stop makin. g hot water? Sounds like a dumb question, BUT the electrical controls are why the boiler knows to make hot water. If you purchased that boiler with no tankless coil, the controls would not tell the boiler to make hot water.

This is the difference between Cold Start Boilers (heating only from oil burner) and boilers that maintain a minimum temperature in order to supply heat to the Tankless Coil (heat and hot water from same oil burner). If you don't tell the oil burner that you are not making hot water for that coil, the burner is going to keep trying to make hot water that you can never use (because the pipes are not connected)

Ask me how to do this.

hot_rod

The mix valve on the water heater may be the issue. Depending on the listing number on the valve, is it a ASSE 1070?
Those valves will fail if there is a pressure imbalance, which happens a lot with tankless coils, when they start to plug up. The first mix valve is adding to the flow issue. They will also fail off on loss of cold. Probably a 20- 27° differential between hot inlet and mixed outlet required.

Basically they can fail off with pressure or temperature imbalance, you may have both

A 1017 behaves differently, but some manufacturers are dual listing, so the 1070 requirements, which is a fail safe requirement still applies to point of distribution applications like that.

There is also a time requirement on the fail safe mode, sometimes you get a trickle until the sensor inside can respond.

DudeAbides

Ed- I have not yet changed over to cold start mode, and I'd love a how to on that!