R-21EC Heater By-pass

[Sheepdog012]

HI folks,

Has anyone installed a by-pass valve on the heater hoses to reroute the coolant back to the engine instead of through the heater core? I have noticed that core throws quite a bit of heat during the summer and would like to keep the cabin cooler if possible. I'm wondering if that would create unforeseen problems such as expansion, higher engine temps etc... Any ideas are appreciated!

-Sheepdog

 

[bob daily]

You did not say which motor you have on your boat. If you look at the parts catalog for the yanmar fig-14 cooling (fresh water pump) you will notice it comes with two plugs for the heater kit. All you would have to do is cut the hose on the supply line and install a valve to isolate the cabin heater from the system. Your thermostat will handle the engine cooling fine. This is a common modification to engines with heaters used in hot summer weather. Good luck on the modification and stay cool! Bob

 

[Sheepdog012]

Thanks Bob! I have the Volvo-Penta D1-30F in my R21. I appreciate your insights, I'm thinking I will explore setting it up this way.

Be well!

-Sheepdog

 

[Newf]

Thanks Bob! I have the Volvo-Penta D1-30F in my R21. I appreciate your insights, I'm thinking I will explore setting it up this way.

Do you have a temperature gauge tied to your engine? I would be curious to know if you see any temperature change on your gauge after you make the modification. Probably not but it would be nice to know as I have the D1-30 as well.

 

[Sheepdog012]

Newf, I do have a temp gauge and will be getting her in the water over the next few weeks. I will see what temp she is running at and then see after I put in the by-pass. That might be a while though as I have been doing upgrades most of the winter and may take a break for a few weeks. But for now I will start figuring out what valves to use. I'll report back on how it turns out.

-Sheepdog

 

[bob daily]

If the heater ports are looped (bypassed) then the water pump output is just looping back without doing any cooling! Most auto heaters are set up to not circulate the radiator coolant unless heat is called for, that to me is the same as having the supply port plugged. If you notice on your engine the water pump there are 4 ports - coolant in, coolant out and heater in and heater out, for use on a boat without heat the heater ports are plugged. A lot of information on the pros and cons of this is discussed on the internet. Basically all you need to do is splice a valve into the supply line to the heater, open when you want to use the heater or close during those hot summer runs. Just make sure the valve is able to take the heat from the engine coolant. Hope this helps. Bob

 

[Newf]

Hi Bob, I have the same engine as Sheepdog and it's not set up with 4 ports as you describe. It has 3 ports and one of them goes to the coolant tank. The pump outlet goes to the inlet (coolant) side of the heat exchanger. A hose from the back of the heat exchanger assembly then runs directly to the heater with the return from the heater going to the top of the pump.

To "test" to see if the concept would help reduce heat in the cabin without installing a valve, fittings etc, I would just disconnect the two heater hoses (one on the top of the pump and the one behind the heat exchanger assembly) and cap them. Then just run a short hose from the top of the pump to the back of the exchanger to complete the loop. If it works, just installed valves to make it work as you want and if it doesn't help just remove the short hose and reinstall your original two hoses from the heater. A quick and easy check if you've got about 3ft of heater hose.

 

[bob daily]

Newf, sorry after looking at the correct water pump for your volvo I see it only has 3 ports! The manual lists one port on the top of the pump as the hot water port. I would think the supply line would be from the water pump and the return line would mix with the coolant at the back of your heat exchanger. But what do I know? Anyway good luck and hope I did not confuse you two to much.
Bob

 

[Sheepdog012]

Newf, Great idea. I have some extra heater hose and will try that one I get her in the water. Thanks!

 

[Newf]

Newf, sorry after looking at the correct water pump for your volvo I see it only has 3 ports! The manual lists one port on the top of the pump as the hot water port. I would think the supply line would be from the water pump and the return line would mix with the coolant at the back of your heat exchanger. But what do I know? Anyway good luck and hope I did not confuse you two to much.
Bob

No confusion Bob. Just different engines. Also the pipe routing on my boat may not be exactly as it is on another D!-30. My boat sits just outside my door so its always easy to go and check on things. I always appreciate your input on posts about our little Tugs.

Newf.