Isotherm Basic water heater issue

I have an Isotherm Basic (Webasto) water heater that worked great last season. This year when I commissioned the boat the water output ( heater running off shore power overnight) was around 105F, yet the temperature of the brass fitting where temperature adjustment is located is around 140F (infrared reading). Also, today when I brought boat to mooring the engine coolant temp was 175F but out put from sinks and shower only 105F.

Any suggestions would be appreciated as we’re heading out on a 1 year trip and leaving next Saturday, June 9.

Thanks in advance fir your suggestions.

captcarp said:

I have an Isotherm Basic (Webasto) water heater that worked great last season. This year when I commissioned the boat the water output ( heater running off shore power overnight) was around 105F, yet the temperature of the brass fitting where temperature adjustment is located is around 140F (infrared reading). Also, today when I brought boat to mooring the engine coolant temp was 175F but out put from sinks and shower only 105F.

Any suggestions would be appreciated as we’re heading out on a 1 year trip and leaving next Saturday, June 9.

Thanks in advance fir your suggestions.

Click to expand...

I have one of those, if it looks like this.
It sounds like you might be in for a gunk flush. By which I mean disconnecting the circuit that goes from engine coolant to heater and back, and connecting a flushing hose to it, and pushing water at some pressure through it. You might get a surprise at the algae type gunk that comes out. The performance should improve dramatically after that.

Is there a tempering valve in the system that limits the hot water to 105 deg by blending with cold? These can be adjusted.


David

djmarchand said:

Is there a tempering valve in the system that limits the hot water to 105 deg by blending with cold? These can be adjusted.

David

Click to expand...

Or do you have out side shower? If the hot and cold valves are open, with the head is shut off, it will act as a tempering valve.

djmarchand said:

Is there a tempering valve in the system that limits the hot water to 105 deg by blending with cold? These can be adjusted.


David

Click to expand...

this....if the tank temp is really 140 degrees based on the outlet fitting.

Larry has a good point with recircing shower units....

Thanks for responses. First of all I mistakenly stated that water heater was an Isotherm, it’s an Isotemp.
Peter B - good idea, I will attempt to flush engine feed/return
djmarchand - there is a tempering valve and it is cranked hard over to “hot”
Larry M - there is an outside shower and during commissioning I opened both hot and cold and and pressed shower end to get flowing but I never closed the hot and cold valves. I will try this as soon as I get back on board, this would be a nice easy fix if it works ?. I’ll let you know.

Again, thanks to all. What a great forum and resource!

Attached are a couple of pics of water heater

Can't imagine it can be anything but the tempering valve if the inside is 140 degrees and the water downstream is much less.....may be a faulty valve.


Can you take it out of the system to troubleshoot?

Isn't the black valve on the left side of the the photo a tempering valve?

rochepoint said:

Isn't the black valve on the left side of the the photo a tempering valve?

Click to expand...

Yes. I have a similar model and the black valve identified is the "tempering" valve. It's job is to mix some cold water with the water coming out of the water heater to give you the hot water temp that you want. If your hot water at the faucet is too cool then try adjusting that valve first. (It may simply have been inadvertently turned during winterizing)

Ken

Tempering valves are great , but not as safe as an anti scald valve.

If there is not enough cold warer for the temperature desired the tempering valve will still pass scalding water.

An anti scald valve will simply shut off all the hot water.

For a retrofit using an engine coolant coil, try to purchase the anti scald valve.

Hi All,

Well got out to boat today and put the TF suggestions to work. First tried shutting off cockpit shower. IT WORKED! Temperature of water out of all faucets was 130 F. Also contacted Isotemp earlier this week, great response from them, and ordered a tempering valve which I’ll put with my spares.

Thanks to all for the great suggestions and again what a great resource this forum.