Best Of
Re: Am I crazy? Chimney company says you can reduce the flu.
These guys are on top of it. I would add to spec. a smoothwall ss liner so you do not have to de-rate it 20% for corrugated. Once done, perform combustion analysis to ensure proper function. If you get it fired up to 'steady state', whatever that means, take a draft pressure reading then shut off the gas quickly. If the draft rises stronger, the liner is undersized.
Make sure they put arrows on those passive MUA grilles so the air knows which way to go. Air is dumb and will observe pressure gradients. For instance, operating an open hearth fireplace could backdraft a borderline boiler.
Most fireplaces were built with undersized flues. To reline one, you need to remove the flue tile then install the properly sized insulated liner for a 2,100F rated installation. You are not required to insulate heater flues but consider whether its a cold exterior chimney vs. warm interior one. FYI, the sizing tables in the code are for interior chimneys only.
Re: Delay of boiler firing?
I usually put a strap-on aquastat on the outdoor boiler supply line and use it to interrupt the call to the gas boiler. As long as it senses that the outdoor boiler is hot, the gas won't fire. You may need a switching relay as well if you don't already have one- the gas boiler would not run the pump(s) without a thermostat call.
GroundUp
Re: Mitsubishi MUZ-FH12NAH evaporator doesn't get cold
For anyone who might be having a similar issue here is an excerpt from the service manual, indicating they know the EEV can come off. It happened to me because I transported the condenser without the original box which i guess dampens vibrations when you're going over bumpy roads with the condenser in the back of the vehicle.
Symptoms are very similar to low refrigerant. Inexperienced techs might add refrigerant overcharging the system which isn't cheap to fix if you're going to do it properly by recovering the entire charge and weighing in the right amount.
sixplex
Re: Am I crazy? Chimney company says you can reduce the flu.
@2x_Tom, you mentioned that you have a "255k net". the word NET is important, because that means something in boiler sizing. Input can be as high as 350,000 input. and there is no way a boiler with that much gas input can be vented in a 5" diameter flue pipe.
There are several BTU ratings on every gas fired boiler. there is the input. That number is how you size the gas pipe and the vent system. If you look at the PFG-6 boiler above, you can see that it has a 305k input number. Now look all the way over to the Net I=B=R rating of 215k. That is the Net number you are talking about if you are using the correct terminology. That boiler is slightly smaller than the 225 NET you stated in your original post. If you look at the last column on the ratings, that heater requires an 8” vent. So unless your chimney is over 50 feet tall, that 5” liner will not be able to properly vent that heating appliance.
If you can get the manufacturer's specifications on your customer's boiler, then you can show the customer where the chimney company is mistaken. Then you can let them deal with the problem. You gave them the proper info and you deserve to be paid for that information. The chimney Company is now responsible for getting the heater to vent properly with the work that they did and probably got paid for by now. If the customer used a credit card, they may have some recourse. Otherwise that chimney company will just walk away with the failed repair and keep the money.
I stopped recommending chimney professionals and just told the customers to just look in the yellow pages for chimney repairs. (Yellow Pages must be translated into Internet for today’s customers)
Re: Delay of boiler firing?
It depends on how the system and boiler is being controlled. Generally there is a work around but it depends on how involved you want to get and whether its worth the investment.
pedmec
Re: Trying To Estimate Heat Pump kWh Usage
Just to be clear, this spreadsheet is the brain child of @DCContrarian - he deserves all of the credit :-)
JustinS
Re: Trying To Estimate Heat Pump kWh Usage
@Jamie Hall : "The COP of a heat pump varies with source air (or water) temperature. Therefore any calculation of power usage by the heat pump must take into account that variation. The relationship of COP to source temperature varies for different types of heat pump, so you need to be looking at specific makes and models for the calculations to make any sense at all."
If you look at the spreadsheet he linked to, that's exactly what he's doing. There's a row for each degree with estimates for heating load at that temperature, annual hours at that temperature, and heat pump COP at that temperature.
The COP is going to depend upon both temperature and percent of capacity, variable speed heat pumps have higher COP at lower utilization, at least until they start short-cycling. So it also depends upon how the system is sized to the house.
Re: Trying To Estimate Heat Pump kWh Usage
It's epidemic in the industry that installers don't trust the Manual J process and put their thumb on the scale to drive the result they want. With combustion appliances it wasn't a big deal, oversizing doesn't really impact efficiency and undersizing is a big problem. With a heat pump you want to size accurately.
Are your ceilings really only R19?
