Need a little help please...low hot water pressure

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Woodyses

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I have an oil fired boiler with a coil that make hot water.
I have lost almost all pressure on the hot water side of all faucets. Cold water is fine.
Could this be an expansion tank that is faulty or more likely a prv?
Already made sure the supply valve is fully open.
What else could this be?
 

Reach4

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The coil could be limed up. Any faucets you could put a garden hose pressure gauge on to make sure where the blockage is?

You might post a photo or two of the coil and associated things into the boiler forum.
 

Dana

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I have an oil fired boiler with a coil that make hot water.
I have lost almost all pressure on the hot water side of all faucets. Cold water is fine.
Could this be an expansion tank that is faulty or more likely a prv?
Already made sure the supply valve is fully open.
What else could this be?

It's certainly NOT an expansion tank issue, and very unlikely to be a PRV issue (is there a separate PRV on the potable hot water line? Don't think so.)

Reach4 has it right- it's most likely to be lime deposits in the tankless coil. De-liming the coil with an extensive vinegar rinse may be possible. Often by the time a tankless coil needs deliming it will have developed pinhole leaks, which after the plugging lime deposits are cleared can cause the heating system pressure to slowly rise over time. But it's still worth giving deliming a shot- just pay attention to system pressures in the weeks/months thereafter.

But if the coil is really shot it's better to NOT replace it. In terms of efficiency, hot water service & longevity to abandon it (capping both ends) and install an indirect fired tank water heater operated as a zone off the boiler, and lowering the idling temp of the boiler to 140F instead of 160F (or wherever it was set to be able to deliver reasonable hot water service.)

When domestic hot water is being served by tankless coils the standby losses of the higher boiler temp are large, usually making the boiler room the warmest room in the house, increasing the heat losses of the house.
 

Sylvan

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Check your tempering valve as it may have mineral build up or needs an adjustment
 

Woodyses

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Gotcha...so heres a few photos of the coil area.
Cleaning it might be my option and see if that works due to budget at the moment.
Seems like a pretty straight forward job no?
 

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Jadnashua

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You need isolation valves or a way to isolate the coil, a pump and a means to circulate the acid (vinegar will work and it's potable) to run that solution through the coil until it has dissolved the mineral deposits...that can take a few hours at least. It's possible that you can buy a new coil...no idea of the cost or how easy that is to R&R.

Keeping a boiler hot to provide hot water via a coil 24/7 is expensive. Depending on your utility costs and availability, as said, an indirect may be a good choice, or maybe an electric WH, or possibly a gas one, but that's unlikely if you're using oil.
 

Dana

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Keeping a boiler hot to provide hot water via a coil 24/7 is expensive. Depending on your utility costs and availability, as said, an indirect may be a good choice, or maybe an electric WH, or possibly a gas one, but that's unlikely if you're using oil.

In most of NY an indirect water heater coupled with a heat purging boiler controller will be cheaper to operate than an electric water heater. See system #3 in Table 2 in this document.

With heat purge control heating hot water only, no space heating load will run about 10% below the steady state efficiency of the boiler. So after standby & distribution losses an 80-85% efficiency pretty-good older beast will run at 70% during the summer. This week the NY state average price of oil is $3.27/gallon. NY residential retail electricity is averaging 19.3 cents/kwh.

A gallon of oil has 138,000 BTU, and at 70% would be delivering 99,600 BTU/gallon into the indirect. Normalizing to $/MMBTU (million BTU) that would be 1o.35 gallons/MMBTU, which at $3.27/gallon costs $33.84.

A kwh of electricity is worth 3412 BTU. Normalizing to MMBTU that would be 293 kwh/MMBTU, which at $0.193/kwh costs $56.55/MMBTU.

Without heat purge controls summertime water heating with an indirect on an oil boiler could run as low as 38% (system #2 in the Brookhaven document), at which point the operating cost is comparable to that of an electric tank with 19-20 cent electricity.

During the heating season heating water with the indirect is at an efficiency comparable to the steady state efficiency of the boiler, since the standby losses are lower, and shared between the heating load and domestic hot water load. So even without heat purge control the annual cost of heating hot water will be cheaper with oil than with electricity.

With a heat pump/hybrid electric water heater it gets more interesting, since the water heater if placed in a basement boiler room converts summertime basement humidity into heat in the tank using 1/3-1/2 the kwh of a standard water heater, and during the winter it converts the standby losses of the boiler in the boiler room into heat inside the tank. The down side to heat pump water heaters is the slow recovery and higher up front cost, but it may be worth considering if you normally run a dehumidifier in the basement to keep the humidity low.
 

Reach4

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Slower than recirculating white vinegar is to get a water softener. The deposits should stop forming and very slowly go away.

But soft water is nicer for other reasons.
 
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