Point of use water heater for washing machine

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Old 11-08-20, 07:26 PM
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Point of use water heater for washing machine

We use a whole house gas tankless water heater. However, with this system there is an initial amount of cold water that results in our washing machine not drawing (any) hot water, resulting in cold washes, even on hot cycles. (It does not have an internal water heater). Would you recommend a point of use water heater to overcome this problem, and if so any particular or specs??

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Old 11-09-20, 05:43 AM
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Is the washer not cleaning properly?
 
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Old 11-09-20, 06:35 AM
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It seems fine, however, I am under impression warm water will wash better, esp. if clothes very soiled.
 
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Old 11-09-20, 09:36 AM
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Yes, generally warm or hot water is better for washing. But, if you don't have complaints about the wash then you'll have to decide if it's worth investing the money to make hot water available to the machine.

Your washer is no different than any fixture in the home. Just like at a sink when you have to let the water run to get hot water it's the same for your washer. If that's a problem one solution is a hot water circulation system. A pump continuously circulates the hot water so it is more quickly available around the house. It's bad for energy efficiency since your paying to run a pump 24/7 and all you hot water pipes become radiators loosing heat so you water heater will have to run more frequently to keep the temperature up, even when you are not using hot water.

Or, you could do as you suggest. A point of use water heater could be installed right at the washer. Of course you'll have to have gas or sufficient electricity available to power it but it would spare the energy wastage of a hot water circulation system.
 
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Old 11-09-20, 10:25 AM
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Thanks, kind of what I thought. I was curious as to what specs such a device should have, in particular minimum flow rate of heated water to machine, to prevent it from alarming “inadequate hot water supply” or something like that......
 
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Old 11-09-20, 10:47 AM
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Trying to pick a water heater can be a problem. Most point-of-use water heaters are designed to be connected to the cold water line. That means connecting it to the hot water line could cause it to run too hot/overheat once the hot water arrived. Technically you'd need a water heater booster.

That's going to take some looking into.
 
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Old 11-10-20, 07:05 PM
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FWIW: Many newer washing machines have "green" operating strategies that prevent (or greatly reduce the amount of) hot water being used during the wash, including the fill cycle. See for example:

https://products.geappliances.com/ap...ontentId=22225
 
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Old 11-10-20, 10:35 PM
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Hot water is only used in the first filling. Cold is used for rinse regardless of temperature setting.
 
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Old 11-11-20, 11:11 AM
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The incoming hot water has to warm up the pipe on the way to the washing machine and also warm up the interior of the machine. Particularly for those machines that use smaller mounts of water per fill, the final temperature of the water at the start of the wash cycle can be severely compromised.

Older top loading machines take about 15 gallons per fill, often getting water up to 140 degrees F and are less affected by the water temperature drop compared with modern front loading machines that might take just 7 gallons per fill at up to 120 F...
 
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Old 11-11-20, 12:40 PM
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Thank you all for the input. Looking at AllanJ’s comments, a “water heater booster” seems like what may be needed. My previous machine (Bosch), had built in water heater, so this was not an issue.
 
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Old 11-11-20, 02:54 PM
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You might also consider buying a 6 or 10 gallon 1,500W 120V electric water heater (20A circuit req'd), connecting its CW inlet to the existing HW, setting for 140F and putting it on a time clock set for the time(s) of day you do wash. The heater's thermostat will automatically deactivate the element when setpoint is reached, whether from incoming HW temperature (if it's higher than 140F) or the heater's element, so you'll have plenty of "float" until the HW gets there.
 
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Old 11-11-20, 07:24 PM
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Good idea as long as you have room for that size tank.
 
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Old 12-06-20, 03:52 PM
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Following up on this thread, I am reconsidering using a hot water recirculating system. This will solve my issue of getting hot water fast enough to my washing machine, but also the significant lag time of the showers on our 2nd floor. I have a few questions:

1. Can I place such recirculating pump on a “smart outlet” that can be controlled with wifi and app on mobile phone? Easy to call up hot water before showers / laundry.

2. My tankless water heater is a Takagi (natural gas). I assume these type of units utilize temp sensors on the incoming (now heated) returning water recirculated, and adjust burners accordingly?

3. Is it OK for the pump to run while water is being used?

4. Is there any point in using more than one bypass (“shunt” ), or just one at the furthest point away from the water heater?


Thanks!
Jan
 
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Old 12-06-20, 11:09 PM
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I assume these type of units utilize temp sensors on the incoming (now heated) returning water recirculated, and adjust burners accordingly?
That needs to be confirmed with manufacturer.
As mentioned previously.....usually only cold water can be sent into a tankless water heater.
 
 

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