I have a boiler and my water is not very hot. Some of my bathrooms have somewhat hotter water but even that isn’t as hot as I would expect. I replaced the mixer valve because the water pipe out from it isn’t all that hot to the touch, and it is set to 125F. No change. The hot water is probably around 80F. The boiler temperature is set to 175 and the gauge on the front confirms the water is at this temperature. The pipe from furnace to the mixing valve is hot and so are the input and output to the circulator. I also have two kitchen sinks- one has the not so warm water. The other gets barely a trickle when the hot water is on but both have no issue with the cold water. Additionally, I cannot run a hot water load in my washing machine because it fills so slowly that the washing machine shows error lights that the hot took too long to fill. Any idea?
Hot water is not very hot
- Thread starter dspahn
- Start date
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How do you heat your water
1. A storage tank type hot water heater
2. A tankless hot water heater the tankless inside the boiler
3.what type of fuel does your system use
4.do you have your boiler serviced regularly
5.do you have a mixing valve for your domestic hot water to your fixtures
1. A storage tank type hot water heater
2. A tankless hot water heater the tankless inside the boiler
3.what type of fuel does your system use
4.do you have your boiler serviced regularly
5.do you have a mixing valve for your domestic hot water to your fixtures
It is an oil-fired boiler- it provides hot water baseboard heat and has a coil for the hot water to the fixtures.
It appears that the cold water arrives at the boiler from the well pump. This is properly maintaining the pressure (IIRC abt 45 PSI). The water comes out to the circulator for the heat and has a second outlet that goes to a whole-house mixing valve set at 125F). I’m wondering if it is something stupid, like the valve supplying the mixing valve needs to be opened further or something like that.
If you are experiencing low pressure+ lower temps every were it could be that your coul is clogging up and needs to be cleaned, 1 thing to try thou, would be cleaning your mixing valve, by soaking it in vinegar I've done that before and had success and if you know the brand you could buy a rebuild kit to have on hand
Mixing valve is two weeks old- that was exactly where I started. It’s a Honeywell. The coil does need to be cleaned, but I am getting uneven results at various fixtures- I have a bathroom where the sink is weak and the shower is strong on the other side of the wall from a kitchen that gets almost no hot water flow at all. I suspected fixtures, but I have strong fixtures a short distance downstream of weak ones. The house is old (ca. 1840) so I am still looking for weird workarounds etc. they may have used. The furnace is at most 10 years old. Here’s a possible idea- looking at the hot supply to the mixing valve, will opening that further put more hot water into the mixing valve, or will it cause water to become cooler because increasing the flow means a higher volume of water will move through the coil and get less exposure to the hot in the boiler?
What kind of piping copper, galvanized, pex????? Both hot and cold to the mixing valve should be wide open,check or replace your aerators
Copper. I have a pic, so opening the hot supply all the
i opened the hot to the mixing valve all the way- no change. I fixed an issue with one fixture- it had a rubber hose from the hot that was kinked. Now it works about as well as the other fixtures. Other than fixture connections to sinks, it is copper from the furnace all the way. I let the hot run. After 3 minutes, the water temp goes from cold to warm enough to wash hands. 3 more minutes and it gets up to about its max- 80-90 degrees. Three more
Minutes and it starts to get cool again. I would expect that 160-205f water going through a mixing valve set to 125 should produce that temperature water. The temperature setting is based on the sticky LCD thermometer that came with the mixing valve for calibration. Should I increase the temp at the valve?
Mitchell-DIY-Guy
Well-Known Member
As an FYI an oil fired furnace with hot water coil is a very costly and inefficient way to heat water. Every time you turn on your hot water you fire the entire furnace up. OK when oil was $0.30 a gallon but not at today’s prices.
Not that difficult to switch to a 50 gallon electric tank style.
Not that difficult to switch to a 50 gallon electric tank style.
It’s true for the water supply- I have a tankless propane heater and haven’t decided whether to replace the supply side with that or just use it for certain fixtures. But I can’t remove the boiler because it supplies heat as well.
Mitchell-DIY-Guy
Well-Known Member
Say good bye to expensive parts and maintenance labor
Mitchell-DIY-Guy
Well-Known Member
Right. Very few of these oil fired beasts being installed today. Nothing complicated about an electric water heater.
Good options here but I still need to solve the problem. Here is some new info- I ran the hot water at one of my sinks for 5 minutes. The water reached a peak temperature of 87 degrees F. I left the water running and opened the mixing valve. The valve is 70-145f. I measured the temperature of the pipes. The furnace has a thermometer that read 160. The hot from the furnace to the mixing valve read 136. The mixing valve showed 90 coming out. The cold input was below 70. This is a new mixing valve, and is the same model as the previous mixing valve that I replaced because it was doing the same thing. Any idea what I need to adjust to get the mixing valve to deliver the right temperature? Perhaps partly closing the cold supply valve?
I think you need to have your hot water coil cleaned, you said yo also had reduced pressure , low temp and reduced pressure are 2 signs of a clogging coil, the scale is insulating the copper from the inside stealing the heat and reducing pressure you can cut tees into the cold going into the coil and hot going out with valves before the mixing valve you can pump vinegar thru it or the is a liquid made for this.
I read up on this. It looks like the way to go (if it shows improvement, I could always have someone come in and do the full acid flush, but vinegar seems like a benign way to start). What I read said you could connect washing machine hoses and pump 5 gallons of vinegar through over a course of a couple of hours. Couple of questions:
- what kind of pump- what flow rate, etc. ?
- Is there a more concentrated vinegar than the gallon containers in the baking aisle that should be used?
-does this process seem reasonable:
— close the valves on either side of the coil
— open the connection going out from the coil into a bucket
—Open the cold water in to the coil
—use compressed air to chase any remaining water through the coil
—pump vinegar in until it drains out and close the coil connections
—wait about 3 hours
—Open the coil and start pumping 5 gallons of vinegar through the coil.
--disconnect the pump and reconnect the cold supply. Open the cold valve and flush through with about 10 gallons of water
Reconnect the coil out, open the out valve, and resume using the system as normal
Does that process make sense?
Mitchell-DIY-Guy
Well-Known Member
Out of curiosity, when was the last time the entire oil burner (which includes the water coil) was serviced and cleaned? If any HVAC system of any kind needs regular maintenance, this is it.
Oil burners are really dirty, messy things which is why they are really not being installed new anymore except in retrofits. Oil is absurdly expensive in which to heat a home, you need to deal with the tank the mess, etc. It's archaic.
You may even have minor leaks in your hot water coil. If it were MINE, and I was dead-set to keep this, I'd have a pro pull out the coil and inspect it, and maybe clean it and test it outside of the burner. While it's out the entire burner firebox etc. should be cleaned and serviced. I bet there are some YouTube how to videos to assist.
Not that this has ANY bearing on your situation, but one of my earliest memories as a child was when my father converted our former gas furnace/forced hot air system in our NY ranch house of the 1950s (this was probably about 1960 when he did it) to an oil burner and hot water hydronic radiators. My mother (then a young mother with three young kids) was overly concerned with having gas in the home, so she wanted it OUT. When relatively new, the hot water coil failed somehow and we had to drive out to the manufacturer (Edwards Engineering) in New Jersey to pick up a replacement. It was an adventure--even if only 90 minutes away. We had to go over NY's big bridges and through tunnels. Fun for a kid.
Oil burners are really dirty, messy things which is why they are really not being installed new anymore except in retrofits. Oil is absurdly expensive in which to heat a home, you need to deal with the tank the mess, etc. It's archaic.
You may even have minor leaks in your hot water coil. If it were MINE, and I was dead-set to keep this, I'd have a pro pull out the coil and inspect it, and maybe clean it and test it outside of the burner. While it's out the entire burner firebox etc. should be cleaned and serviced. I bet there are some YouTube how to videos to assist.
Not that this has ANY bearing on your situation, but one of my earliest memories as a child was when my father converted our former gas furnace/forced hot air system in our NY ranch house of the 1950s (this was probably about 1960 when he did it) to an oil burner and hot water hydronic radiators. My mother (then a young mother with three young kids) was overly concerned with having gas in the home, so she wanted it OUT. When relatively new, the hot water coil failed somehow and we had to drive out to the manufacturer (Edwards Engineering) in New Jersey to pick up a replacement. It was an adventure--even if only 90 minutes away. We had to go over NY's big bridges and through tunnels. Fun for a kid.
Way back in my 2nd post I asked about service, especially oil should be serviced yearly oil is dirty.
He did, I seeeeeeen it.
Mitchell-DIY-Guy
Well-Known Member
Yes you did ask about cleaning. 
The OP indicated the furnace was 10 years old. He also indicated that “the coil needs cleaning”
No indication that any of this oil burner service was actually done however.
The OP indicated the furnace was 10 years old. He also indicated that “the coil needs cleaning”
No indication that any of this oil burner service was actually done however.
