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Hot water boiler

Looking for a manual on honeywell hot water boiler for a house

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Re: hot water boiler

Contact honeywell with right model no. and they should be able to help or try online on honeywell website.

Posted on Dec 12, 2007

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My Honeywell ST 6400C won't heat the hot water the light comes on but pump doesn't run or boiler fire. But does work on C/Heating.I can get hot water only by running the C/H and manually opening the hot...

it sounds like the motor in the motorised valve is not working on some models you can just change the head /motor , check cylinderstat (hot water stat) is working

Dec 14, 2010 | Honeywell Heaters


The extra benefit of a Modulating Boiler

You're looking to install a new hot water boiler or replace your existing boiler. You come across something called a "modulating" boiler. You wonder what on earth that means. I will attempt to explain some of the features of a modulating boiler.

How nice would it be if you could have your boiler make just enough heat to keep your house warm and nothing more? Your thermostat tells your boiler that you need heat in the house. The boiler starts up and heats the water that runs through the pipes to heat your house. The water does not heat up to temperatures that are more than just warm. But you notice that the temperature in your house is staying right where you want it to be.
This boiler is no ordinary boiler. It knows what the temperature is outside and varies your water temperature to make just the heat needed to keep you comfortable. The modulating boiler also runs much more then a normal boiler would but you can see by your gas bill that you are getting great efficiency from this thing.

The feature that makes this wonder so great is that it has the ability to vary the fire that heats the water up and down so that the water temperature stays precisely where the computer brain in the boiler wants it to be. This temperature is figured by measuring the outdoor temperature and changing the water temperature based on that. The colder the weather is outside, the hotter the water is going through your system.

With a system like this you will notice that your heat will run longer and still not cost anymore money. This makes you more comfortable. The modulating boiler will give you just enough heat to keep you warm without wasting much of the heat that a normal boiler would. This type of furnace will give you the most efficient heating possible on any given day.

Before buying a new heating system or replacing your old hot water boiler make sure that you check into a system that will modulate the fire and also vary your heating water temperatures according to the outdoor temperatures. This will save you money and give you a very comfortable heating system.

on Dec 08, 2009 | Heaters


Boiler Aquastat - How to set it

It is the coldest day of the year and your boiler is chugging along. However you notice that your house is slowly cooling off even though the boiler is running. Then you notice that the boiler is shutting down even though your house is not up to the thermostat temperature setting.

You look into the situation farther and notice that you boiler temperature is below say 180F. What is shutting the boiler off? The device that controls the temperature of your boiler is called an aquastat. This device senses the temperature of the water in your boiler, and then fires the burners to keep the water at the temperature call for by the aquastat.


The other role that this device may play is to keep the boiler from getting too hot and making steam. However for this time we will concentrate on the lower side and the heat of the water. If you have a house that has barely enough baseboard or radiators for that really cold day then you need your water to be very hot or around 200F. This will give the water enough BTU's to carry around the piping to give off to keep your house warm. The downside is that it also makes your boiler less efficient when it needs to heat the water this hot.

So, now you know that if you need more heat you can turn the aquastat up higher to get more heat and turn it lower on the milder days to save energy. Another way to do this is to buy and install a smart control that will do that automatically for you. These are called an outdoor reset control and will vary your boiler temperature according to the outdoor temperature, saving you money and keeping you warm all at the same time.

Now, the one thing you need to know yet. The aquastat is usually a gray box with a screw driver slot in a little wheel that has numbers on it. It is often hidden pretty well and may take some looking to find it. Some of the newer boilers may have a digital one that is in a bigger gray box. Read the instructions to learn to change the temperatures.

Setting your aquastat correctly can save a lot of money and it can be the difference between keeping you warm or not.

on Dec 08, 2009 | Heaters

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My honeywell timer for the back boiler heating is blank

need to contact the people who worked on it yesterday to come back and look at it again because it sounds like you have no power to now.

Jan 29, 2010 | Honeywell CT3600 7 Day Electronic...

1 Answer


Hi, It sounds to me that you have a floor furnace that is working, but you have hot water set-up for the rest of the house. You say the water stays hot for about 10 minutes only? Is it on a hot water heater or small boiler with a circulating pump? If this is how it is set up, It sounds as though what ever is heating the water to the rest of the house is shutting off to soon, or if you have a pump, it may have failed. If you do have a pump that has failed, they are set - up to shut the heating system down if it were to fail. Please check to see what set-up you have and get back to me asap, so that I can solve this for you. Check these things out I have Mentioned to you and let me know.

Nov 28, 2009 | Honeywell CT87B ROUND HEATING&COOLING...

1 Answer

Ravenheat he85aaa combi boiler running fault

sounds like low water pressure, check pressure guage, get unit serviced

Nov 27, 2009 | Honeywell CT87B ROUND HEATING&COOLING...

1 Answer

I have oil heat hot water boiler. i set thermostat to 60 and the temp goes to 80 using up alot of oil and very hot in house. any suggestions?

You may have either a bad thermostat, shorted wire to the thermostat, a stuck relay or a bad gas valve. You will need to test the thermostat using a multimeter to make sure it is working correctly. If that is good, start checking the aquastat relay.

Nov 10, 2009 | Honeywell Heaters

1 Answer

Need to wire a honeywell RTH7400D thermostat to 3 wire hot water

Just mark the old wires on the old thermnostat...R , W etc...and put them on the same terminals on the new 1.....also there should be some adjustment ire : switch on the back or under the cover to adjust for Hot water heating or electric heat...either is the setting you should have it on....also you shouldn't setback the thermostat at night or when away very much....2 degrees is fine , as the boiler will run along time to raise the temperature in the morning and may not get there by the set time

Oct 18, 2009 | Honeywell Electronic Programmable...

1 Answer

When i turn heating or hot water on fuse board trips

it was a faulty heating pump. replaced, all ok now.

Jan 03, 2009 | Honeywell Electronic Programmable...

1 Answer

No heat in zone with Honeywell rth230B

It is not your thermostat, it is an airbound zone. The gurgly noise you heard was that water and air flowing through the radiator. The zone needs to be purged either at the boiler, or through vents on the radiator. Hope this helps

Nov 01, 2008 | Honeywell Electronic Programmable...

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